Geohazards in Bangladesh
With the scouting done, we just that the installation of the final two GPS sites to do. Since we started drilling the hole for the antenna rod at Kalenga, we went there first to finish the installation. This time, the new road surface had dried enough for us to go over it. We arrived and went to work, becoming an experienced team for the installation. As promised, they had built us a ladder, a rickety one, but functional. After competing the job, we were surrounded by kids when we returned to the ground from the installation. We once again
handed out chocolates to all the students and teachers, had tea and went on our way.
It was still afternoon, so we drove to Chunarughat where the seismic team had just finished installing a station in the college where we reoccupied. We all had tea, some fresh pineapple, snacks and caught up. They went off to another site, while we went to scout two sites farther along that were on tea plantations. We had had problems
getting permissions as some were large corporations with headquarters in Dhaka. We headed to the first one, the Chundeecherra Tea Estate. We found the office and explained the situation. As first we were dismissed, but Sanju persisted, making friends with the assistant, who called the manager back and we were invited to his bungalow. We went there and discussed the project, and had tea and snacks. The Tea Garden and bungalow – a term meaning a house in the Bengali style – date from 1876. He
needed to confirm with his higher ups in Dhaka, but had been won over to allowing our deployment. In fact, later we received approval to place seismometers in any Tea Garden belonging to the National Tea Company.
He directed us to the next Tea Garden, although we got lost before finding the right place. While we call these places Tea Gardens, they can be miles of tea plants in every direction, major operations to run. We had trouble
finding the correct entrance. We again showed up at the manager’s house and were welcomed with tea and snacks. Sanju did his magic again, making friends and persuading him to allow us to install the seismometer at his bungalow. This tea company is privately held and the manager gave approval pending confirmation with the owner, his uncle. A productive day.
The next day we went back to install the last GPS station, again bringing chocolates for the students. The drilling was slow as the concrete was hard and the batteries didn’t last. We sent our driver to recharge them at the nearest town with electricity.
He went with the principal on his motorcycle. After finishing the job we took our last group photos and had tea and cookies with the teachers.
Again we went to stop at a Tea Garden for permission. This was at Finley’s a large multinational company. We were turned away at the gate. Sanju did not give up. He persisted and argued with them for a long time, although it seemed fruitless. He then tried going above them calling the local chief of police and elected representatives. He would not give up. Eventually the assistant manager came out and spoke to us. We explained our situation. He had previously spoken with the scouting team. He agreed that we needed to speak to the Chief
Operating Officer of Finlay. He would be in the next morning at 9. We had succeeded in getting out foot in the door thanks to Sanju’s determination. And with all of the GPS stations completed, we could turn our full attention to scouting the seismic stations for the one day before Keith leaves to return to the U.S.
The next morning we arrived and were let through the gate. We drove to the COO’s office and waited until he was free. Again we explained what we were doing, reassured him, as the others that the seismometers only listen to earthquakes from around the world. They do not interfere with anything or cause earthquakes. His concern was not being able
to provide security to watch the instruments, but we reassured him that we usually left them unattended. He tentatively agreed pending some paperwork. We headed to the offices of the managers of the individual Tea Gardens we would be installing in. We drove past miles of tea to the first. When we showed the manager to location, he pointed out that it was not in Finlay’s but another Tea Garden beyond their property.
We headed off farther into the hill. The roads got progressively worse, although the road cuts showed some good geology. Finally, we hit a rut we could not drive through and walked the last mile. After waiting for him in the gazebo to finish his shower, we again had tea and snacks. We got an agreement and chose a site in his yard next to the satellite dishes (after reassuring him it would not affect reception). Another site successfully done. We walked back and then got a ride the last part of the way
from his jeep, carrying the head of another tea company. We drove to the other site on Finlay’s property, but the manager was not home. He would be back in 2 hours at 4. We left and went to pick up some gift bags of tea that Sanju’s father had left for us. It was on top of the next anticline. After several wrong turns, and more cups of tea, we got our packages. It had only taken an hour and a half to get there. On the way back, we got a call from the manager, he would meet the COO tonight to discuss the seismometers, so no need to come today. We had done what we could today. This part of the trip was a success.
After the drive yesterday, it was clear the car needed fixing. No need to rush out early in the morning and I got some much needed sleep for my jetlag and my cold. After a later, for us, breakfast, Bulbul, our driver took the car to be fixed. We took an autorickshaw to the first site to add the chain and lock security system and see the sky view without the trees. This time we had neither a ladder nor a truck to climb on. Keith and Sanju scaled the building, but I was still shaky from the cold and stayed
below. I worked on my blog until I ended up showing a group of kids my photos. That was where I was when they found me after completing the short job. My choice to stay down was reinforce by learning that Sanju had fallen on the way down. A pice of the concrete roof had broken off in his hand and he fell backwards onto the cut down tree. Luckily he was OK. His glasses frame was broken, his elbow banged up and had a some scratches from thorns, only minor injuries. With the car still being repaired,
we had some enforced free time. We went to a famous shop outside of Srimongal past a rubber tree plantation, where they serve 7-layer tea. In fact, this was where it was created. Carefully pouring (I presume) they float 7 distinct layers of different colored teas on each other. Refreshed, we headed back to wait for the car, and Keith repaired Sanju’s glasses.
It was too late for an installation that was
an hour drive away, so we turned out attention westward. We were reoccupying a site at a College (high school) in Chunarughat, but we also had one more place to scout. This one was to be co-located with a seismic site, B4. The advance team found a home, but it would require constructing a monument. We went to see for ourselves if it would work for us, passing one of the two seismic teams joining us in Srimongal – Nano, Céline, Alissa and Karim. A few minutes of greetings and
we were both back on our way. Driving across the rice fields, with a few wrong turns, we found the direct road had a bamboo bridge we could not cross. We had to double back and take a longer more roundabout route ending with bumpy dirt roads that were not meant for cars. Finally, we hit another bamboo bridge less than a kilometer from the site. We walked there and met the owner of the house. It would be usable
for seismometers, but there was no open sky view for us. We walked another kilometer farther, but this time we had no luck. The school was surrounded by trees. We were told that there was another school at a place called Kalenga with no trees. By now it was dark, so we headed to the dinner with the seismic team. They were having a more difficult time. Permissions were not finalized and appeared to be harder to get.
The next day we went to Chunarughat to do the reinstallation. I have been here a few times since the initial visit in 2007. The last time, I saw the antenna, it was loose and assumed it was a problem with the mount. Instead, it was more serious. The rod itself was loose and had rotated. 2 silver threads on the rod were visible
beneath the green weathered ones. Looking at my photos we pieced together that the antenna cable came loose and the straightening of the loops to relieve tension had rotated the antenna 1.5 times so the north end was pointing south. The unscrewing created a 3.5 mm increase in the height of the rod. I will have to look at the data carefully to see if we can figure out when it happened and correct it. Keith then carefully unscrewed it, added a really strong epoxy and screwed it back to its original level. Sanju and I took rickshaws into
town to buy more electrical wire for the solar panel and for grounding. After a while, Chunarughat was up and running again.
After some tea and snacks, it was time for the last task – finding the final GPS site. We went off in search of the now mythical Kalenga. I didn’t understand why everyone we asked seemed to know the direction to Kalenga until I realized there was a Forest Reserve of the same
name. We continued along progressively worse roads until the colorful school at Kalenga appeared. It was indeed open, surrounded on two sides by rice fields. Although it was on the anticlines, the rivers eroding it had created valleys suitable for rice will into the anticline. The school principal quickly agreed to the installation. We didn’t have more equipment with us, but we had the drill. That would save us some time tomorrow, so we drilled until the power ran out of the batteries. None of these schools had power, so instead of the large drill, we had to use the smaller battery powered
one. We had been needing to recharge the batteries to do all the drilling, but with this early start, perhaps we would not. In any case, sites for all the GPS had been located and arranged. All that was left was the mechanics of the actual installation for the last two sites.
We headed to the next area. One of Humayun’s students scouted for a location and found a reinforced concrete building, but it was not on the anticline as I wanted. It was farther west on the flatter land adjacent to the hill. It was on the wrong side of the rice/tea transition. We met the owner of the property and he accompanied us as we searched for another place. We could see why he stopped. Farther on the driving was more difficult and the houses were all thatch and tin. Walking around, we were shown a reinforced concrete building
under construction, but it wouldn’t be finished for 2 years. We kept hunting and then we found it. There, in a clearing, was a brightly colored primary school. Again, the headmaster quickly agreed to let us install the GPS on the roof. I even was presented to the classes. The students are a mixture of Bengali, Khasi and Garo. The later two are groups that are mainly in the eastern and western Shillong Plateau (Meghalaya). We are finding that many of the villages in the hills are part of the 2% of the non-Bengali population of Bangladesh. The Bengalis like the plains and rice farming, the others are hill people growing other crops. The Khasi here are Christian, we passed a church on our way in. Later we met their tribal leader.
This time a short ladder was found, allowing us to climb to the ledge over the window and then onto the roof. Much easier going up than going down
with the roof overhang. We again went to work, drilling holes in their roof and mounting the antenna, the solar panels and chaining the receiver box down for security. They had no electricity so we had to use the cordless drill until it ran out of power. Then we had to send our driver to the closest village to recharge them. Meanwhile, they served us tea and cookies on the roof. We couldn’t quite get the antenna rod as far in as I like, but plenty for stability.
The next day we had another site in a building that was too far from the hill. Again we went forward into the hills. This time, however, there was no local school. One of the Khasi villagers showed us around, but even the open fields had too many tall trees around. The best we could find was the corner of the rice of our guide. He would sell us the little plot of land we need, but it would be expensive since it would permanently removed it from productive rice farming. Sanju pointed out that there were some
Manipuri villages to the south, so we went back to the main road to try them. We discovered the maps of the area were not accurate; we failed to get to Islampur. We tried some other roads farther south. Our car could not make the direct route, so we took a detour that led us into dirt roads through a tea estate. It led us off in the wrong direction and our van was sounding worse and worse. It sounded like the CV joint was failing. We circled back to the main road on an unmapped road. We picked up someone who would show us how to
drive to Kolabonpara, our last option to the south. Beyond that is India. Again, there were no local concrete buildings. The best we could find was a newly planted field of tea. Since the tea is kept waist high, we could put the monument in the middle of the field. However, the only way to get to it was over a bamboo bridge. It would be very difficult to get a welder and generator over that. We took the name and phone number of the
manager, who was away in Dhaka, and headed off. On the way back north, we decided to make one last try by going to a village north of where we started. We got most of the way there and found a newly rebuild section of dirt road. It was too soft for the van, so we walked the final ½ hour to the village. We went passed the rice fields in through the beautiful woods next to the first high hill. Finally at the end, we saw it, the land opened up and there in the clearing was another brightly colored reinforced
concrete school. Since it was Friday, it was closed, but we got the name, address and phone number of the headmaster and went off to meet him. He turned out, not only to be Manipuri, but to also be Sanju’s “uncle”. Our hotel. With permission in hand, we headed back to our hotel. Scouting had taken the entire day, but we now had a location for the next GPS.
Unlike the GPS in your car or phone that gets a location to about 10 feet, the much more expensive systems we are putting in will get daily position estimates to about 2 millimeters. To do that, they need a clear view of the sky in all directions. We have two options for mounting the GPS antennas. If we can locate solid reinforced concrete buildings, we have cement a stainless steel rod into one of the columns. If not, we can build a braced monument out of vertical and diagonal stainless steel rods driven into the ground and welded
together to make a solid base. We came prepared for either. The first can be done in a day, but the second will need at least two days and finding a local welder. This part of Bangladesh has the sediments folded up into linear hills where they grow tea and broad flat valleys where they grow rice. We will put 6 GPS on different parts of multiple hills and valleys.
Walking through the grounds of Lemon
Garden in the morning fog, there were no appropriate buildings and no sufficiently open space. We did find their grove of lemon trees (actually limes). We considered a hill nearby, but there was a tree at the top. As we saw later, the slopes are planted with pineapples that were being harvested. If fact, the hills here are either heavily forested or covered in tea. The tea plants are kept short for ease of picking leaves, but trees are scattered among them. We headed over to my backup for this area, a village
nearby where perhaps there will be some homes, government buildings or schools that are suitable. As soon as we got to the village, we saw the local school. It is the only reinforced concrete building in the village. It seems promising, but there are some trees around it that block the view. We met with the school officials and amazingly they agreed to cut down the trees. However, we needed final permission from the Upazila (county) Education Minister. We drove down to Srimongal, and got our permissions, along with cups of tea and cookies. It is amazing how accommodating the Bangladeshis are to us.
Our next hurdle was a ladder to the roof. When none was found, used the truck as our ladder, climbing onto its roof and then the building’s. It was now the afternoon, so we quickly went to
work, drilling an 18” hole in the roof and epoxying in the rod for the antenna, assembling the solar panel frame and attaching it to the roof, and finally setting up the waterproof box that will hold the GPS, the batteries, and the modem that will send the data to UNAVCO in Colorado. While we were working, the woodcutter arrived. Sanju is an ethnic Manipuri from the others side of this hill or anticline. He used his contacts to find a woodcutter, who arrived along with his uncle and younger brother. His tools
were a machete and a rope. Because we needed two trees cut down and he needed to avoid a nearby home, he raised his price. In the end, it cost us 1400 Taka, almost $17, a tiny fraction of the cost in the U.S. Part of the tree falling killed a lemon tree, so we will have to pay the owner for the loss. Sanju is still negotiating the terms. As is almost always the case, it was dark before we finished the last part, installing the grounding rod for lightning protection.
The next day, we traveled two and a half hours to our farthest site. This is a reinstallation of one be installed in 2007. The GPS, borrowed from UNAVCO had to be returned in late 2016. That makes this a simpler installation as the rod and cables are already in place. It is in a medical clinic with the equipment box located in the birthing room. The people I had met in 2007 have moved and there is a new doctor and his family living in the clinic. Since 2007, a number of trees have grown up. We again need to have trees cut down. Sanju negotiated with
the neighbor and she agreed to cut the tree for a fee, which she will sell for the wood. The branches of another tree will be cut back once the boroi fruit, like miniature apples are collected. Lunch was again tea and snacks. Two days and two sites installed. After delays of a few more days, the seismic group finally got their equipment and started testing them as we finished the second site. Things are going well for us.
I am back in Bangladesh to start the deployment of equipment for a large new project. Results from our last project showed there is a large earthquake hazard here. We demonstrated that the Sumatra subduction zone, where India plunges beneath Asia, continues to the north under Bangladesh. The subduction down at Sumatra caused the 2004 earthquake and tsunami that killed over 230,000 people. Even though the plate boundary comes onshore, unusual for subduction zones, is it still active with the world’s largest pile of sediments, the Ganges-Brahmaputra Delta, entering it. We have designed an experiment to investigate this plate boundary across 3 countries: Bangladesh, India and Myanmar.
Our first step is to install 29 seismometers and 6 GPS receivers in Bangladesh. To do this, we have a team of 11 people. Most of us will be here for three and a half weeks. There are five of us from Lamont, two engineers from PASSCAL and UNAVCO, organizations that provide support and equipment to NSF projects like ours, and four from Dhaka University. Ahead of us, we shipped over 2 tons of seismic equipment and carried over 300 lbs. with us on the plane. Thanks to a 2 hr. delay due to fog in Dhaka, our flights lasted a full 24 hours, longer for the two engineers coming from Colorado and New Mexico. We then spent the next several at the airport getting all our luggage, getting them through the huge backup at customs from all the delayed flights, changing money and getting local phone numbers.
At a lunch stop, 4 members of our team who have never been here before tasted their first Bangla food. So far, they are all enjoying it. We then arrived at the Dhaka University of Engineering and Technology (DUET), north of that city to set up our base.
When we arrived we found out that the seismic equipment is being help up by customs. Since the packing list mentions antennas, the GPS antenna that gets exact time for the seismometers,
customs referred it to the Telecommunications Regulatory Commission. Humayun went back to Dhaka and spent the day there dealing with it, while Alissa and I tried to find the documents he needed to show the antennas only receive signals and do not cause not interference. The paperwork is slowly going through the bureaucracy and we hope it will be released tomorrow. Meanwhile, we spent the time running around Joydebpur shopping for the materials we need. The seismologists need to build underground vaults to hold
the instruments, while the GPS team needed grounding rods and wire. Most of seismic supplies bought or ordered, so they should be ready to move out ahead of schedule even with the delay, if they get it tomorrow. The GPS team finished our shopping so tomorrow we will pack up, hopefully be able to fit everything in one van and take off. It will be Keith from UNAVCO, Sanju from Dhaka University and myself. When they are done shopping and testing, the seismic team will split into two 4-person groups for the installations, starting with the dense central line of stations. We will hopefully
see one of them by the end of the week when they arrive in the Srimongol area, where we are going. The other team will initially work from here at DUET. These are the two ends of the dense lines in Bangladesh and they will spend the following week deploying towards each other.
Of course we had too much stuff for the van, so the truck will come with us to carry our equipment than then return to
DUET. He had the mandatory meet and greet with the president of DUET. In the end our leaving first thing in the morning stretched to 12:30. We had hoped to stop at one of the sites on the way, but instead we went straight to the Lemon Garden Resort in the hills near Srimongal. The hills in Sylhet, the NE part of Bangladesh are covered in tea estates. There are a growing number of resorts in the hills as well. Lemon Gardens has beautiful grounds and tomorrow we will see if there is a good spot for a GPS.
From Khulna in the SW, we are heading to Rajshahi on the Ganges River, but first we are stopping at Kushtia, Humayun’s home town. Because the road on the more direct route is supposed to have bad road conditions, we took a longer route, way longer. It wiped out any chance to get to Rajshahi in time for some fieldwork, but it did my districts (states) of Bangladesh visited to 40 out of 64. After many hours on the road, we reached Kushtia and out goal – jordibaja, a fried noodle snack that is only available here. Chris bought ten 500 gram bags, about 11 lbs, at the bakery that makes
the best, of course. We then had a late lunch and continued to Rajshahi where we were once again joined by a police escort. Different teams stayed with us until we left the area. After finding our hotel, we all had our first hot water shower since we left Dhaka. Living on boats is great, except for the complete lack of hot water. Once cleaned up, we went to Humayun’s sister for a delicious dinner. After dinner, the commissioner of police, a former student of Humayun’s stopped by. He suggested we visit some of the chars (sandy river islands) close to Rajshahi rather than the places we went
to other years, an hour or more drive away. Chris and Dan checked their satellite images and found that the nearby chars would work, probably dsaving 2-3 hrs of driving.
The next morning, we headed off with out new escort, that included two policewoman. However, that had to switch off when we crossed from one precinct to another. Renting a country boat we crossed the Ganges to the chars. While Dan and Chris (with Humayun) made salinity, moisture and spectroscopic measurements, Liz and I
scouted for the proper sediment samples for her OSL needs. After wandering about the island we found what she wanted and collected a sample. Until now, her studies of the delta did not have any samples from the Ganges itself. For Dan and Chris to get the observations they wanted, we visited several chars before ending up back at the first one for them to study the transition from sandy sediments to rice fields. As soon as the chars have deposits of the right kind of sediments, people start planting crops. If the char continues
to grow and stabilize, they will move there as well. They are great places to live 9 months of the year, but a struggle during the high water of the monsoon season. The islands with migrate, eroding from one side while sediment deposits on the other. The char people have to move frequently as the chars move out from under their homes. Liz and I wandered off and found another place to sample. Now she have both a sand and a silt samples from the Ganges. It only took a few hours to accomplish the more specific tasks of this field program. When we first started visiting chars 12 years ago, we explored then from the morning
until dusk. We needed to see and explore all aspects of this new environment for us. Now, we are building on our work with much more focused activities.
Off the river by early afternoon, we drove across country to Bogra near the Jamuna River, as this part of the Brahmaputra is known. We were able to arrive around sunset, avoiding the sometimes frightening driving in the dark. For old times sake, we skipped the new hotel that was booked and stayed at the colorful Parjartan Hotel that we first used
in 2005. It is literally painted the colors of the rainbow, as well as having more character, even if everything is not quite working. This was the hotel where my room once had electric outlets of 4 different shapes, requiring every adapter I had to recharge my equipment. Now I always bring an outlet strip so I only need one adapter.
We had planned to go north to Gaibandha, but a new satellite overpass showed that we could get all the data we needed farther south at Sirajganj. We could cut out a day. As it turns out, this was fortuitious. I have a family
emergency and have to return to the U.S. From Sirajganj we could return to Dhaka, rather than stay at Tangail. Chris and the others can do the rest of the field work as day trips from Dhaka. It is more driving for them, but will enable be to catch the evening flight back to the U.S. We packed up and headed to the embankment at Sirajganj, which protects the city from the shifts in the Jamuna River. We walked down the embankment (the river level is about 7 m or 23 feet higher during the summer monsoon season). We headed for a large char that
we first visited in 2005. It has grown and become attached to other chars. It also has much more agriculture, they are growing rice, peanuts, lentils, corn and more. The complex history of changes in the char provides lots of different sediment types for Chris and Dan and plent of cut bank surfaces for Liz to get a good silt sample. A few hours of exploring, sampling, measuring and we were done. Since it is Friday, the Muslim holy day and the weekend here, traffic is light until we reach Dhaka. Near the university and our hotel, the streets are packed with people and rickshaws. Still we manage to get to the university to drop off equipment and for me to get 7
GPS receivers that finally have to be returned to UNAVCO after 10 years. This is the last of the 11 we were lent in 2007 by them. They provide geodetic data and services for NSF and allowed us multiple extensions that enabled us to get this much needed data for so long. It is the basis for our paper on the potential earthquake hazard in Bangladesh as we can see the slow motion of the surface (0-17 mm/y) that indicates the buildup of strain in the earth. Then back to our hotel to meet Dhiman and have a final dinner together before an Uber takes me to the airport. It is sad to leave early, but I
am needed at home and they can carry on without me for the last few days. They will visit the confluence of the Ganges and Brahmaputra Rivers, and the Padma, as the combined river is called. For me, my critical goals for this trip were accomplished.
My critical equipment repairs were now done. Chris and Dan still had several days of work in the area, but Humayun and I were interested in traveling to Hiron Point near the coast in the Sundarban Mangrove Forest. We want to take advantage of being so close to We hoped we could do it in a day, with the tides and broad open channel to the south, it would take two, too much for Chris to spare. We worked out that Humayun, Liz and I could take Bachchu’s smaller boat, the M.B. Mowali. Mowali are the honey collectors in the Sundarban and Bawali are the wood cutters.
Before we leave, we have one day with Chris and the others. After, Matt and Tanjil, our forest guide from 2015 who stayed with us for a day, departed, I went out with them to Polders 32 and 31 for their afternoon run. They are making soil salinity measurements to see if it is possible to determine soil salinity from satellite imagery. Saline soils are a large problem in this part of Bangladesh. We took the country boat to shore and scouted for the appropriate place. At each one Chris and Dan laid out a grid of probes to measure salinity and moisture
content. Kingston and Zahan did similar measurements at the surface and at the root level. As always, we attracted a crowd of onlookers curious as to what these foreigners were doing.
Later, after dinner, the M.B. Mowali arrived and our group split once again. We traveled to the edge of the Sundarbans that night, to pick up our guide and our armed guard for the tigers. The Mowali is much smaller. I
haven’t seen her since she was renovated. Now there is one cabin, which Liz got, and a larger room for Humayun, myself and our guide. In the early morning we headed south. Once the fog lifted and we entered smaller channels, we started seeing deer and monkeys on the banks and in the forest. We stopped in a small side channel and had lunch before crossing the over 10-km wide estuary in our speed boat, a 40-min ride. I could see that a lot on fresh land had grown at the mouth of the channel with the forest station and our GPS since the
last time I was here, two years ago.
We brought along lots of extra equipment in case anything had broken down. Humayun and I worked on downloading the GPS data while Liz and the guide went for a walk and climbed the observation tower. They got to see deer, wild boar and a monitor lizard, while Humayun and I sat in a dark room. As usual, we struggled to remember how to connect and download data exacerbated my unfamiliarity with the Windows OS on the PC we were using.
Eventually, we got it right and were happy to see that the system was working perfectly, data files for every day since I last visited. Obviously, because we had brought all the equipment along, we didn’t need it. We downloaded all the data and then changed the SIM card in the modem. We had set up cellular communications when we installed the station, but the signal was too weak to every collect any data. Now there is a good signal here from a different cell phone company. When we get back we will have UNAVCO check to see if it works. In any case, we now have enough data to measure the subsidence here. The sinking of the land exacerbates the impact of rising sea level. Only the vast sediment supply of the delta counters it to maintain the land. And that is at risk from human intervention.
We had tea and cookies with the forest ranger and then headed back before low tide trapped us in the channel. As things went well, we stopped on the newly emerged char land and Liz and I walked around examining the sediments, surprisingly sandy for a tidal estuary. Back in the speed boat, we crossed the broad channel and then paused to watch the sunset on the water. Once on the Mowali, we sailed to where we would spend the night in the Mangrove Forest and now I got to see deer and boar on
the way before darkness descended. There was even a herd of 9 or 10 just across from where we rejoined the Mowali.
In the morning, we started heading north. Because it was very foggy, we stayed in smaller channels for a few hours before entering the main channel of the Pussur River. I spent the early morning before breakfast watching the forest go by and spotted a few more
deer. By noon we were out of the Sundarbans and ready to drop off our guard. I actually hadn’t seen him for the entire trip. We continued past the Rampal power plant. This a coal-fired plant being built less than 20 km from the Sundarbans. Most of the coal for it will likely be transported up the Pussur River through the Sundarbans. It is the subject of a lot of protests, including the hartal we had last week, but they are not likely to stop it from being built. A short time later we met up with the Bawali and
moved back across. Then, work here being done, both ships sailed up to Khulna for the night. Tomorrow morning we disembark for the next phase of the trip.
After a night in Dhaka, our group temporarily split up. Chris and Dan headed to Khulna in the SW at 4 am to avoid the hartal (general strike) that was planned for 6am-2pm. Liz and I stayed in Dhaka for a day. I spent it mostly editing material for a new project. The next day Liz, Humayun, my partner from Dhaka University, and I followed the others to Khulna, crossing the Padma (combined Ganges and Brahmaputra) River by ferry at Mawa. After waiting an hour, Humayun used a connection from a former student to get us on the next
ferry, a fast one. It is impressive how much the river has silted up since the last time I crossed here. Another few hours and we arrived at our compaction meter site SE of Khulna. We picked up one of the 4 sons from the family that takes care of the site. Mofizur, the second son, now a student at Chittagong University, is returning home for the first time in 6 months. Making the weekly measurements has been passed along from the oldest to youngest sons. It made for a great welcoming by the Islam family when we arrived mid-afternoon.
The last time I was here, the river adjacent to the site was being dredge and widened. It had gone from 200 m wide to just a few and was now too small for boats except at high tide. The widening cut into the bank that held our instruments. While the engineer tried to leave us enough room, it clearly didn’t work. The pillar that holds the GPS antenna is tilting badly towards the stream. They have secured it with ropes to keep it from completely falling over. We got hold of a ladder and removed the unusable antenna. Mofizur climbed up, afraid that I weighed too much for the fragile system. Next, Humayun and I surveyed the monuments for the compaction meter wells. We had to dig out the sediments
covering the base. Liz measured the thicknesses, which were 4-7 inches. We could clearly see the finely layered sediments deposited from before the river was enlarged to the thick muds that accumulated afterwards. The sedimentation rate had clearly increased due to the river widening. The survey will give us the relative heights of the wells. When we get back we will compare it to earlier measurement to see if the wells have shifted, too. Without the GPS we cannot determine the absolute elevations. Our last task was to measure the lengths of the optical fibers in the wells. We brought along a new laptop to work with the electronic distance meter (EDM), but we found the recharger was still in Dhaka. We had forgotten it. With a dead battery and no way to recharge it, the measurements will have to wait until Humayun can send the recharger.
While we were there, we were served lunch, a huge banquet. Three finds of fish, chicken, rice, vegetables, two desserts. The three of us sat a table outside in the yard, while the family plied us with the delicious home-cooked Bangladeshi food. The more important the guests, the more food and were were suitably overwhelmed. And since it was after 3 pm, we were famished and did our best make a dent in it. Since the GPS is no longer usable, we left them the battery and solar panel that was powering it, doubling their electricity supply. Before we installed the
equipment in 2011, they did not have electricity at all. After some heartfelt farewells, we headed to Khulna to meet up with Chris, Dan and Matt Winters, my TA from the class I taught in 2015. Fluent in Bangla, he has been working with Chris on field observations for his Master’s thesis at Columbia. He and some of his assistants will join us for a few days. The three of them had a dinner meeting, so my group headed to the M.B. Bawali, our home for the next 4 days. Smaller than the M.B. Kokilmoni, it is a perfect size for our group.
The next morning, we headed for Polder 32, the embanked island we have been studying. Humayun and I will visit the GPS station we set up there in 2012. It has a cellular modem so data can be downloaded remotely every day, but stopped working in November. It seemed that the receiver was not recording satellites, so we brought along replacement antennas, cables and lightning protectors. Another GPS station had a similar problem and there the cable had to be replaced. When we arrived at the school, we found the receiver was tracking satellites. We didn’t
have to track down a break in the system. But why wasn’t it recording data. The best we could ascertain was the modem had hung up; rebooting it fixed the problem. It was working, but I don’t understand what happened enough to be sure it won’t happen again. Hopefully, now that it is working, the engineers at UNAVCO can log in an work on it. When we doublechecked everything, we found that the grounding wire was missing. This is unsafe. If there is a lightning strike, the lightning protector blows the connection
to the equipment inside and shunts the electricity down the grounding wire. We cannot put a school full of children at risk. The only wires we had were the coaxial antenna cables. We stripped the ends off a partial cable and wired it between the cut ends on the roof and near the ground. We made a visit to the Hindu goddess of education and headed back to the ship having done all the repairs we could, and satisfied that the school was safe.
It has been over a year since I was in Bangladesh after coming here twice a year for the previous five years. This will be a packed trip doing many different things, collecting samples, fixing equipment, visiting rivers and hopefully meeting with the public and government officials about the earthquake hazard. My paper last year showed that there is the potential for an earthquake of at least Mw8.2 here, an area with ~140,000,000 people. However, with no knowledge of when the last megaquake was or how often that comes, we don’t know when it might occur, in years or centuries. The article received widespread coverage in the press and caused a panic in the region. Now I feel an obligation to help steer things towards better preparation and building construction.
Our first task is related to a past earthquake. The last time we were here, Céline and I collected samples from an abandoned river that shifted ~20 km to the west. We think the shift was caused by an earthquake, but we don’t know if it
was a moderate M7 or a large M8.5. Either one could be pretty destructive to people living on the soft delta sediments. We now have dates for the samples. The 3 ages we got for the last sediments deposited before the shift, or avulsion, were 3800, 3800 and 3600 years ago. The method we used was OSL, optically stimulated luminescence, dating. It measures electrons trapped in quartz crystals. The electrons are so weakly trapped, that sunlight can set them free. Thus we date how long it has been since the sediment has seen the sun. The one
hitch is the possibility that when the sediment was transported down the river, not all the electrons were freed. This is known as incomplete bleaching and would result in too old an age. Our solution is to collect samples from the modern river to see if there is any residual age that would shift our estimate for the earthquake.
Four of us arrived together, Chris Small and Dan Sousa, who use remote sensing to study the changes in the delta: rivers, coastline, vegetation, Liz Chamberlain, a graduate student specializing in OSL and
myself. On arrival, we were met by Saddam Hossain and headed NE towards the Kushiara and Meghna Rivers. We stayed the first night in a “resort” in the folded hills of Sylhet where tea is grown. As a result of the attack on the Holey Artisan Bakery last year, the country is taking precautions. When we entered the Sylhet Division, we were met with a police escort. They stayed with us all through the nigh and their relief through the next day until we left the Division on our way to Dhaka. This is a new experience for me. It did have the
advantage of being able to drive without stopping for tolls and the police used their siren to help with passing cars. Still we only got to our room around midnight, a long drive after two long flights.
Our first stop was the Kushiara River, a bit upstream of the river avulsion, but above the lake that forms every summer during the monsoon. My concern is that the lake decants the sands so the sediments upstream and downstream of the lake are different. Thus we will sample both. We drove to the small town
of Sherpur and the police facilitated renting a small boat. Sailing along the river, we spotted a good spot where the bank was eroding and we could easily collect samples. This was as simple as cleaning a spot and then hammering an iron tube into the deposits. The main precaution is that the sample must not be exposed to light or it will lose all its electrons. We then decided to collect a sample from the river bottom from the boat. This proved more challenging and it took several tries to get the boat into the
correct depth of water and collect a sample with the sampler at the end of a several meter long augur. We found we had to work fast as the boat would drift in the strong current. By noon, we had our two samples and headed to the Meghna River on the way back towards Dhaka.
The much larger and more industrialized Meghna River was a bit more challenging. We need an area undisturbed by people. We rented a country boat at the ghat (dock) near the Bhairab Bazaar Bridge over the river and sailed off. After almost an hour on the river, we found it. The nose of a large island and an eroding cut bank nearby. The point of the island was protected by sand bars, so Liz and I got out and sampled the bottom with the augur. Not movement to worry about when the boat is aground. Then we headed to the cut back exposure and took our 4th and final sample. The set of samples is different then I envisioned, but with Liz’s guidance, they will fit the bill well. By the time we got back to the ghat it was dusk. Time for a slow and traffic filled drive to Dhaka. We got in just in time to rush off to our favorite restaurant for a celebratory dinner at our favorite restaurant before it closed. This trip is off to a great start.
A new film takes viewers from the eastern highlands of India to the booming lowland metropolis of Dhaka, the capital of Bangladesh–and explores an ever-more detailed picture of catastrophic earthquake threat that scientists are discovering under the region.
Scientists from Columbia University’s Lamont-Doherty Earth Observatory, the University of Dhaka and other institutions have been working for more than a decade to understand deeply buried geologic structures that could produce earthquakes here, one of the most densely populated places on earth. No one can predict when the next quake will strike, or how big it will be–but clearly there is potential for a very large one. “Some of this have long suspected this hazard, but we didn’t have the data and a model,” says Lamont-Doherty geophysicist Michael Steckler, leader of a recently published study outlining the threat.
Under Bangladesh, India and neighboring Myanmar, the scientists have found signs of a megathrust–the meeting of two gigantic moving tectonic plates, with one diving under the other. But the plates don’t seem to be moving right now; they are locked, and strain is building. The researchers say that when–not if–the plates do slip, destruction and casualties could be massive. Some 140 million people might be affected.
The hazard has been hard to assess up to now, because most of the region’s underlying geology is covered by the world’s largest river delta–miles-deep layers of sediment carried down from the Himalayas and built up over millennia. The team has deployed seismometers, GPS instruments, satellite imagery and other technology to draw up a picture of what is going on down below.
The region is unprepared. Not only are many people too poor to build earthquake-resistant structures. “From history, there’s been a lot of destructive earthquakes in this area, but there hasn’t been one in recent years, so people tend to forget,” said Lamont-Doherty geologist Leonardo Seeber. Geologist Humayun Akhter of the University of Dhaka, said, “Our cities are not built in a planned way, and this cannot be changed in a few years. So we have to work within this system, and teach our people how to cope.”
The movie was made by filmmakers Douglas Prose and Diane LaMacchia with support from the U.S. National Science Foundation. The NSF also funded the research.
The weather is miserable, but there is no let up in the forecast. However, we seem to be in a local area of less rain, and more importantly no lightning. The worst weather is in northern Louisiana. They are getting 15-20”. While waiting for a break in the weather, we assembled some of the wooden planks into walkway sections. As the rain let up a little, we finally decided to go for it and head to the site. We loaded up the mudboat and Don and Keith took a load over to lay down the walkway. Don is the technician
for the fiber optic system and Keith is a UNAVCO GPS engineer. Tim is a professor specializing in geodetics, while I have experience with subsidence on a variety of scales, including our GPS and compaction meters in Bangladesh. When they returned, we followed with more of the supplies. The wooden walkway allowed us to only sink up to our ankles instead of our knees in the mud. Carrying the supplies out, we started construction
on the structure that will hold most of the equipment – solar panels, GPS receivers, batteries, modem. Sinking the six 4×4 columns into the mud was tough, but less so than we envisioned. After that, we managed to get most of the structure built while Don worked on the compaction meters. We were completely soaked, but got a satisfying amount done. Returning to camp, we spent the rest of the day planning, buying more supplies, and dinner. Our biggest question mark is how to attach a GPS antenna to the reference rod that goes
down 37 meters to the bottom of hole 1. The size of the rod and the standard thread size for GPS equipment do not match. Adapters are not readily available. Tim and I wanted to install GPS antennas on both the reference rod and the upper casing, but it is not clear whether the two antennas will interfere. We decided against putting two on the same well, but may add it later if feasible.
The next day, the weather remains lousy, but we are still in a pocket of less rainfall
than much of Louisiana. We started out soon after sunrise. All the rain meant that the planks sank farther into the loose mud than the day before. By now, walking in thigh high muddy water all the time is usual. We split into different tasks. Tim and I mounted the solar panels, Keith set up the GPS antenna mounts and Don redid the compaction meter electronics. Later Keith and I set up the receivers and batteries while Tim and Don redid the conduit connecting the compaction meters to our control platform. Tor Tornqvist and a John, a
graduate student from Tulane University, visited us in the morning and went back to the camp via a pirogue, a small Cajun boat. As time went on, the rain lessened. Best weather we’ve had. We are working well together. Hardship makes for good bonding. By 2pm, we had finished all we could do today and called for Mark to take us back.
We decided we needed a machine shop to make the adapter, which needs to be stainless steel. That is not possible until Monday morning. The rest of our needs we could get at a hardware store. After
lots of discussion about the plans, Tim delayed his flight home. Don will decide at 10 am tomorrow morning if he needs to delay his flight. The aim is for everything but the reference rod to be done by midday tomorrow. If so, Don can leave. Keith will stay to the end, to set up he reference rod. Since so little is left that needs manpower, now that the major construction is done, I will leave as scheduled tomorrow morning. We are approaching completion of the site. While I hate leaving before it is completed, I have other commitments and this group can easily do the work without me. We will shortly have two extremely sensitive compaction meters and three GPS receivers to monitor ground subsidence and sediment compaction. If we can get more funding we will install another optical fiber in the middle depth hole and another GPS. Meanwhile we have the world’s best compaction meter in one of the world’s worst sites for fieldwork and solid ground.
P.S. Don delayed his flight and Sunday and Monday the group finished everything. A machine shop built the missing parts on Monday and Keith, as the only one remaining, will install it Tuesday. Success, despite the weather.
This summer I am visiting a different delta. I am in the Mississippi Delta in Louisiana rather than the Ganges-Brahmaputa Delta in Bangladesh. We are installing several GPS as part of a system of instruments to measure sediment compaction. In Bangladesh, we have installed two sets of wells drilled from 20-300 meters deep with stretched optical fiber strainmeters. We measure the length of the fiber every week and have been watching as they shorten when the sediments compact. Now, a group of us has been able to get
funding to put an improved system in the Mississippi Delta near where land subsidence and deposition is already being measured.The effort started a few years ago at a meeting on coastal subsidence in New Orleans, which worsens the problems of sea level rise. A group of us combined to propose a “supersite” where we could apply multiple methods to measure subsidence and compaction. Mean Allison and Tor Tornqvist were finally able
to raise enough money from the Army Core of Engineers to drill 3 wells and install new generation optical fiber strainmeters in them. These provide continuous measurements accurate to better than a millionth of a meter. The wells were drilled in January and are 37, 90 and 128 feet deep. Mark Zumberge’s team installed strainmeters in the shallowest and deepest wells in July. Now I am here in Myrtle Grove, Louisiana with Tim Dixon, Don Elliott and Keith Williams to install 3 GPS receivers at the site, two
attached to the casing and the tops of wells and on a rod that goes all the way to the bottom of the deepest well. These will give us the absolute elevations of the tops and, in one case, the bottom of the wells. We will also build a new platform to host the receivers, batteries, solar panels, and all the electronics, including the modem to transmit the data. Then all the gear will be separate from the wells.
After arriving and meeting up over dinner, we drove to the “camp”, house we are renting at the Myrtle Grove Marina near the site. It is usually used as a vacation home and for duck hunting. The site itself is only accessible by boat. It is only a 10 minute ride by mud boat, a flat bottomed skill that
can travel over almost no water. An air conditioning breakdown upstairs left us all sleeping downstairs on the couches and the floor. More importantly, the weather has been rain and thunderstorms for days. In the morning it was still raining pretty hard, but no lightning. After a lot of discussion on possible ways to do the installation, we were able to take advantage of a break, or at least lessening of the weather, to visit the site. Mark Brockhoeft took us out on a mudboat into the marsh. After working there with rain from above and mud and water below, we sailed back with a plan of how to proceed. Mark leant me better gear for working in the rain and mud, which were much worse than I expected. Later in the day, Don and Keith got the supplies we need and we started preparing to head out tomorrow to start construction, weather permitting.
We finished our work at the river transect. Now we had one more sample to collect. It was to the north where the abandoned valley is still flooded at the site of the tube well that started this idea. It is well BNGB013 along one of the transects that was done for the BanglaPIRE project. It was done along the side of a major “highway”, so will be accessible and it not far out of our way home. Alamgir had a contact in a nearby village and arranged, and rearranged a driller. We were glad to be heading back
to Dhaka. The hotel we stayed in was the best in Brahmanbaria, but it had bedbugs. In this moderate sized town, the choice of restaurants was limited.
The drillers arrived at our meeting place late. There was a fight between two villages the night before and some people were stabbed. They own a plot of land along the main road in the other village. Those villagers wanted them to swap it for land perpendicular to the road, but they refused. The land along the road is valuable for shops. The result was a fight until the police broke it up, but several people ended up injured. They came without their equipment so
they could sneak quickly through the other town. They got what they needed at the store where we met about 2 km west of the well site. I went ahead and located the exact place we wanted to sample.
Since the well had already been logged and sampled, we only needed to drill down to the sands, making sure the stratigraphy agreed. Relooking at the logs of the well, I realized that we barely had enough extension rods to make it to the sampling depth. Luckily we hit the sands with a couple of feet to spare. We
got our sample and headed for Dhaka. Of course, we hit terrible traffic and were late to dinner with other scientists from our project that just arrived from the U.S. Over dinner I learned that Kazi Matin Ahmed, one of the Dhaka University professors we work with was from a town right near our sampling. He said that growing up he would go to school by boat during the monsoon. The next day was packing up at the university and making copies of everything. We also had to pack up a number of GPS and seismic recorders that need to be returned to the U.S. for repairs. Unsalvageable was one from Madhupur that was destroyed in a fire. This trip was very successful; we achieved all our goals, although as usual, there were a lot of changes of plans on the fly. In Bangladesh, nothing goes as planned, but we always get everything
done. Bangladesh is a country of resilient people who know how to get things done.
We planned to drill four or five tube wells across the abandoned channel and pick one for OSL dating samples. With the success of yesterday’s tube well drilling, we were optimistic that we could actually do the sampling. We met the drillers in the morning and headed to the next site. Since only two or three people are needed for logging the well, we left Céline and Basu and the rest of us headed off to do a short resistivity line near the first drill site. We scouted it during the drilling of the first well. On the way to the resistivity
site, we selected locations for three more wells. Depending on time, we will either drill two and then the sampling well or just three stratigraphic wells. Since it will be only 2 meter spacing between the electrodes, it will be quicker to set up despite less people. We are only trying to image the channel, so we don’t need a larger spacing. The site was also drier than the first two resistivity lines. We laid it out and started collecting data. My only concern was that the route was used as a path for local farmers collecting hay. I didn’t want them to knock off the electrode connections or to have them
shocked by the pulses of electricity we sent through the electrodes.
Once the line was running, I headed back to the drill site. They once again found a think mud layer over sand. They continued drilling deeper and found the silt clay that marks the boundary between the Holocene and Pleistocene, when sea level rose following the end of the last ice age. This was a bonus and confirmed that we were on line with the Lalmai anticline farther south. We shifted to the next line, a more difficult location next to a pond, but they managed. I headed back to the resistivity line and found them starting to pack up the equipment. When I went to take a look at the instrument, I found it hadn’t finished. It had run out of memory for recording line and stopped. We quickly reinstalled the electrodes that had been
pulled that we still needed. I deleted some older files that had already been downloaded and restarted acquisition. We had only lost four of 584 command lines.
By the time the second well and the resistivity line were done, it was questionable as to whether we could do the sampling well, which will take longer. The drillers going off for a lunch break settled it. We would do a third tube well today. During the drilling, the skies that had been threatening all day opened up.
The drillers and loggers got completely soaked, but kept going and we completed our five-well transect of the river valley. In the evening we compiled all the logs and discussed a sampling plan. Rather than take four samples in one well, we decided to take two, one above and one below the sand-mud transition in two different wells.
The OSL sample is over 2” wide and the wells we drilled were 1.5” wide. The driller decided it was best to drill a 1.5” well to the depth of the first sample, a few feet above the transition, and then overcore it to 3.5”. Then 3” wide PVC pipe
was lowered to keep the well from collapsing. Finally, we put the sampler on the auger rods and lowered it to the bottom of the well. We, actually people younger and stronger than me, pounded the sampler 30 cm into the bottom. Then we all had to pull up on it to get it out. The next step was to extrude the sample in its liner into a thick PVC pipe casing. The sample must be kept in the dark, so this was done inside a black plastic bag. Then the entire sample is wrapped in the black plastic bag and taped securely. The ends and outside of the sample will be discarded and only the core of the sample will be used for dating. Later, sample preparation will all have to be done in a darkroom. I helped sample on my last trip, but the was the first time I was in charge of the procedure. It went well. After the first sample, the drillers drilled to 1 ft. past the contact, overcored to the same depth, added the PVC liner and we sampled again. We
repeated everything for the second well and we had four OSL samples. We celebrated with green coconuts.
The next day we went out again for resistivity and augering. Céline picked out two alternative sites that might be drier. We drove through the abandoned valley to the site. We took the direct route and found the local road to be in a terrible state of disrepair. The vans could barely make it through. Then we hit a spot where slumping off each side of the road narrowed it too much. The villagers helped make a temporary road with bricks and wood, but it was still too narrow. Then they filled a sandbag and together with the bricks, wood and other
handy items we got across. It turned out that since the Upazila (county) voted for the opposition party, they have not had their roads repaired for over a decade. This level of politicization of everything in Bangladesh really hurts the country. When we reached the location of the line, we found that ponds between the road and the fields limited our access. We walked around and found a site next to a brick factory. The line was along an irrigation ditch. Fine to walk on either side, but submerged to mid-shin if you
stepped in the middle. The data looked very good after processing. We may have found the top of the Pleistocene as relatively shallow depths consistent with the site being the top of a buried anticline (folded hill).
The delays from the bad road, site searching, and a longer distance to lug the equipment meant that we couldn’t do augering. We came to the conclusion that we have to alternate days of resistivity and drilling. Not enough time in a day to do both properly. That meant
the next day was for augering. We went back to the soccer field site, officially BNGTi1, and started augering with all six of us. We hurried past the section we had already described. To minimize hole collapse, we switched between two augers and tried to work quickly on the descriptions. It took all of us all morning to make it to 4.8 meters. The mud was too hard. We needed to go to plan B. We would drill tube wells and sample inside the wells. Alamgir and Basu went off to the village to find a driller. The rest of us
cleaned off the equipment and ourselves at a nearby pond and well and had lunch. After several attempts, they found a driller, but he couldn’t come until 3 p.m. I like to use all the available time I have here, but we now had a few hours break.
The three-person drill team arrived right at 3, unusual in this part of the world. I have seen the drilling technique before, but never the initial set up. In 20 minutes they set two vertical bamboo poles in the ground, tied on the cross piece to make a large H, attached a lever arm and the drill pipe, dug a mud pit for water and a
channel to the actual well location. Then they started drilling. It was so much faster and easier than augering! In 10-20 minutes they were past the depth we reached. We don’t get continuous samples described every 10 cm (4 in.), but the lithology averaged every 5 ft. Muds come up as solid cylinders that we collect, sands as a slurry that we decant. We subdivide the 5 ft. sections if there is a lithology change. The driller caught on quickly to what we wanted and kept us informed of all changes in sediment type, which he could easily feel. Céline and Basu, an experienced logger of tube wells, did most of the sediment work,
with some help from the rest of us. As expected, the section was primarily mud with some silt. We reached the sands from the abandoned channel at 42 ft., a little deeper than I expected but reasonable. It was still early enough for us to do another. Alamgir and I scouted a second location as they finished and packed up the equipment. We completed that one, with the sands at only 20 ft. North of our transect looks like there was an island splitting the channel in two. Here would have been downstream of the island, so we
expected it to be shallow. Finally, things were going well. Using tubewells, we should have plenty of time to drill several stratigraphic wells and then pick one for sampling. We celebrated with dinner at the local Chinese restaurant.
Six of us headed out on Oct. 8 for Brahmanbaria, northeast of Dhaka. Our target is a large winding abandoned river valley that we believe used to be the course of the Meghna River. Currently, the much smaller Titas River flows northward in the channel. Why would a river in the world’s largest delta flow the wrong way? We think that an earthquake uplifted the Comilla District area to the south. That caused the Meghna River to shift westward to its present channel and the Titas to flow up the old channel. A well drilled in the channel in 2012 shows a layer of muds overlying coarser sands.
We think the sands represent sediments from the old Meghna and the muds are sediments filling up the channel. We will be using resistivity to image the channel and an auger to first sample and describe the sediments and then to collect samples for dating.
Finding organic matter to date by carbon 14 is rare, so we plan to use a technique called OSL dating. OSL stands for Optically Stimulated Luminescence. Electrons from the radioactivity of all rocks get trapped in defects in quartz grains. However, they
are so weakly trapped that sunlight can release them. When traveling down the river, the electrons are released and then start accumulating when they are buried. By measuring the light released by the sample when optically stimulated, we can calculate the time since the sample last was exposed to light. By sampling the top of the sands and the bottom of the muds, we can date the time the river switches, or avulsed. The details of the procedure to get an OSL age are pretty complicated, but if this works, we
will date the earthquake that caused the river avulsion.
This technique is new to me. I helped with some sampling the last time I was here, but I have not been in charge of doing it. I am also more comfortable with the quantitative data from the resistivity than the qualitative geologic descriptions we will make of the sediments. Luckily I have a good team with me, Céline, my postdoc, Matt, my former teaching assistant, and Alamgir, Atik and Basu from Dhaka University. I have spent time in the field with Alamgir and
Atik before. Alamgir has conducted his own resistivity surveys. Basu was recommended to me as someone with a lot of experience in describing sediments.
We set out early in the morning for the four-hour drive. However, when we reached the river valley, we found it was almost completely flooded. We walked out on an elevated road and there was pani—the Bangla word for water—everywhere. The abandoned valley is still slightly lower in elevation than the surrounding land. Even that land has the rice fields flooded with shallow water, although the
boundaries between the fields are above water. But our main target is submerged! In the winter this will be dry land, but we are a month and a half too early. A number of scheduling issues required me to come now, although I knew it was too soon after the monsoon, but I didn’t expect so much of the land to still be flooded. Time to come up with an alternative plan.
For the resistivity, we need long straight stretches of dry land. We decided to
do it west of the valley to try to image the thickness of the entire Holocene (last 10,000 years) section. It should vary because of the folding of the strata from the tectonics. Mapping the thickness will help us to map the position of the buried fold. For augering, we only need a small patch of land to stand on. To find it we headed south towards where the valley was uplifted more and might be drier. Not as ideal as the original location, but possible. The next morning we headed farther south and crossed the river valley. It was drier and we noted some potential augering sites. We continued to a location for resistivity. The six of us set up the >350 m long resistivity line, then Céline, Basu and I headed back to try augering while the resistivity data was collected. The augering proved very difficult. We were very slow describing the core that the auger brought up, and while we were doing it the hole would start to collapse. The muddy sediment was very stiff, and we had to hammer the auger in. We only got to 2.7 m when we stopped, nowhere near the depth we needed. Things were pretty discouraging.
I am heading back to Bangladesh, but this time I am stopping in New Delhi before heading to Bengal (West Bengal and Bangladesh). It is the first time that I will be in a part of India that is not adjacent to Bangladesh. Several of us are meeting there to plan for a new project that will span Bangladesh to India to Myanmar. I arrived a few hours before Nano Seeber and Paul Betka and used the time to get a new Indian SIM for my phone. After meeting up, we headed to the guesthouse of the Ministry of Earth Sciences, where we will be staying. If only the U.S. had a cabinet level department for earth sciences. It was difficult to find at night without a Hindi speaker, but we managed.
Over the next few days we had meetings about the project, but also some time for sightseeing, while
discussing the project in the car. Most of our meals were vegetarian, and Gandhi’s birthday, which occurred while we were there, is celebrated by eating vegetarian. When two more scientists arrived from Singapore, we started the day by visiting the Qutub Minar, dating back to the 1200s and the arrival of the Muslim Delhi Sultanate, followed by the Mughal Empire in the 1500s. In the Quwwat-ul-Islam mosque, there is the famous Iron Pillar originally erected by Chandragupta in the 4th century, probably at Patna, and brought here much later. Near the beginning of the inscription it says: “in battle with the Vanga countries, he kneaded (and turned) back with (his) breast the enemies who, uniting together came against (him).” Vanga is Bengal, now split into West Bengal in India and Bangladesh.
After mostly finishing discussions, the others decided to take a day trip to Agra to see the Taj Mahal. I was able to change my flight to Kolkata to the following morning and joined them, continuing to talk science on the 4-hour drive. We had to buy the expensive tickets at 750 rupees rather than the 10 rupees the Indians were paying. However, the premium ticket lets us bypass the long lines. The Taj Mahal is the tomb of Mumtaz Mahal,
the beloved wife of Shah Jahan, the Mughal Emperor. It was built over 17 years from 1631-1648. She died in childbirth of her 14th child. He was buried there as well when he died in 1668, after being overthrown by his son. I have seen many pictures but was not expecting how enormous the structure is. The entire place is beautiful and enormous with flanking buildings, gardens and gateways. I kept wondering about the cost of building it and how many man-years of India’s peasants financed it. Perhaps this excess was why this was the peak of the Mughal Empire. Within a 100 years, the British were
taking over. Afterwards we went to Agra Fort, which is similarly gigantic, and another seat of the Mughals. There are palaces and a throne inside the red fort with views of the Taj. There are 30 buildings left, the rest having been leveled by the British to erect barracks for their troops. We didn’t get back to our hotel until 11.
I left early the next morning for Kolkata, the British Indian capital until 1911, when they moved it to Delhi. It was done to punish the Bengalis for opposing the
splitting of the Bengal Presidency into more manageable size, which would have cut Bengal in two. I spent the day at Calcutta University then headed back to the airport to fly to Dhaka. At my usual hotel, I met up with Jenn Pickering, a student at Vanderbilt University, and Céline Grall, my postdoc. They were teaching a short course at Dhaka University. I spent the next few days in multiple meetings and making arrangements for a week of fieldwork. It will be good to get out into the countryside.
We had a smooth trip to Kolkata with our two taxis amazingly staying together through the traffic. After checking in and freshing up, we went out for dinner and found a great Bengali Restaurant filled mostly with Bangladeshis around the corner. Our hotel turned out to be next to an area where Bangladeshis frequently stay, including Humayun previously. In the morning, he and I went for an early morning walk through the park and saw the Queen Victoria Memorial. Circling back past all the cricket players, we passed Fort William, the original British fort here, and joined Doug and Diane for breakfast. Our car arrived and before heading to the Sundarbans, we drove around to get shots of the Hooghly River. Before the 1600s, this was the main course of the Ganges, but since
then it shifted to it present course into Bangladesh. We got some shots from the new bridge before being chased off. Then we headed to the Strand to get close to the river. While we were filming, a funeral procession arrived to scatter ashes of the deceased into the river. Once the Holy Ganges, always the Holy Ganges. We couldn’t have planned it better.
Then, off to the Sundarbans. Where we were going was a lot farther than implied. This is because of a difference in naming. In Bangladesh, the Sundarbans is the National Mangrove Forest. The cultivated areas that previously were forest are not considered the Sundarbans. In India, they are. Thus we entered the Sundarbans after 2.5 hrs, but still had that long to go to meet our boat.
Admittedly, some of the cultivated areas in India still maintain mangroves outside of the embankments, which is not the case in Bangladesh. Continuing on, we reached literally the end of the road and carried our luggage (including a 50 lb. bag of rock samples) down to a ferry that took us to Gosaba. There, we first got a hand rickshaw to get the luggage across the town, then got two motorized rickshaw trucks to cross to the other side of the island. Finally, we were met by a boat that took us across the river to the eco-lodge where we would stay. After a late (4 pm) lunch we went on a sunset boat ride through some tidal channels. The saw and heard lots of bird and at times the channel became so narrow that we had to push branches away to fit through. The
trees here overhang the channels more than in Bangladesh. We would see further differences tomorrow. After finally showering off, we met other people staying at the eco-lodge, started by 4 cousins including Ajoy, who is leading our trip. The lodge is solar powered, so electricity is limited,but the water was refreshingly cool, not cold. We all heard a performance of Bengali Baul music, recognizing some songs from similar experiences across the border. After dinner, we all went for some local rice wine and then a boat ride to see bioluminescent plankton in a small channel. If you wave your hand in the water dots of light flash.
In the morning, we started at 6 am to have enough time before I had to head for the airport. We picked
up food and a cook and permits and a guide and finally were ready to enter the forest. In India, no one is allowed off the boat to step on the forest, nor to stay overnight in the forest, even on a boat. Thus many hotels and lodges have sprung up outside the forest for tourists. Many come simply to party and drink. We are very glad to be using an eco-lodge that is more respectful of the land and the local population.
At 8, we finally entered the national forest. Among the differences from the Bangladesh side we noted were the shorter height of the trees in the more saline water, the lack of sediment in the water, and the extent of bank erosion. Where the eastern Sundarbans is fresher with ample sediment carried by the tides due to its proximity to the Ganges-
Brahmaputra-Meghna River mouth, the western, Indian Sundarbans is more saline and lacks new sediment. Between subsidence and sea level, it is loosing ground. More land is being lost than gained. With the higher salinity, there is also less wildlife. However, there was a tiger sighting this morning. We sailed to the spot, but it was too late, we missed it. Still, we spent 4 hours sailing through tidal channels of different size, eating, and filming. Doug captured the beauty of the Sundarbans and I was interviewed with a great backdrop.
After completing our work, we briefly visited an observation post, we took a short cut through an interior channel in Gosaba Island, dropped off our guide, and crossed the channel to our car. Three hours later, I arrived here at the airport to start my journey home. It was an intense, yet calm 48 hours in West Bengal, the third leg of three very different pieces of this trip.
Humayun Akhter, my main collaborator in Bangladesh, joined me at the airport and we flew together to Kolkata. We spent the night at a nondescript hotel near the airport. The next morning, we met up with film makers Doug Prose and Diane LaMacchia in the airport and all flew together to Aizawl, the capital of Mizoram state in NE India. Doug and Diane have funding from NSF to expand the 5-min YouTube video they made about our project two years ago (https://www.youtube.com/watch?v=WTETuqJPygs) to a ½ hour TV special. Their previous films have been shown on PBS.
The Sumatra subduction zone, source of the 2004 earthquake and tsunami, continues to the north where it encounters the Ganges-Brahmaputra Delta. The 15-20 kilometer thick delta sediments are folded and faulted as they enter the subduction zone. Because of the huge amounts of sediments, this is the only subduction zone whose front is subaerial – entirely exposed on land. In Bangladesh we can see the beginning of this process. Here in Mizoram, farther east, the former delta sediments are folded up into a very hilly terrain. The steep slopes are subject to frequent landslides. One that started last October has moved again and blocks the main road from the airport to the city of Aizawl. As a result, we had to take a longer, slower, bumpier and dustier road to get to the city.
We met up with Nano Seeber and Paul Betka from Lamont at breakfast. They have been doing geologic mapping the region and returned to Aizawl late the night before. We spent the day circling the city and visiting outcrops, many ones I had seen my last time here. We had several interesting discussions on differences of interpretation of the strata. I had visited most of these outcrops before, but it was the first time for Humayun. At the end of the day we were joined by
Vineet Gahalaut from the mainland, as the rest of India is considered here. The people here look Asian and the Mizo language is a tonal language in the Tibeto-Burmese family. Plus, almost all Mizo are Christian. Mizoram is part of India, but also distinct, like many of the other states in NE India. Part of the sense of separation is that the 7 NE states are only connected to the rest of India by the narrow 23 km (14 mi.) Siliguri Corridor between Bangladesh and Nepal – the chicken neck. We spent the evening talking with Vineet about future joint projects in this region.
The next day we were joined by Victor Ralte, our partner from Mizoram University, who became a proud father of a fourth daughter last week. We all headed north, visiting geological sites and filming
beautiful vistas, dropping Vineet off at the airport and continuing on to Kolasib, a small town about 70 km north as the crow flies, but probably twice that on the windy roads of Mizoram. We stayed in Hotel Cloud 9. I had been told since I was a child that I was always off on Cloud 9 and now I was actually here. However, the electricity wasn’t for the first few hours, so showers were cold, but the dinner was hot.
The next day we headed still farther north to see some complex faulting associated with the growth of the anticlines – the hills of folded strata. As we examined each outcrop, it was also clear that we were passing through several kilometers of rocks in which the environment that were deposited in shallowed from the inner continental shelf (10s of
meters water depth) to the tidal zone to estuaries like the present Sundarbans to fully fluvial (river). This represents the ancient Brahmaputra Delta passing across this area as it grew southwards. That several kilometers of sediments were deposited while the environment only shallowed by 10s of meters indicates that there was a lot of subsidence to make space for the sediments. I will have to model this when I return.
Stopping for a beautiful sunset over the hills, we finished heading back to Aizawl for a last dinner together. In my room as it turned out since the restaurant closed for some repairs. The six of us ate a mixture of American, Indian, Chinese and Mizo food with plates dishes and ourselves filling all available surfaces. Today, a quick stop at Mizoram University and then back to Kolkata for my last leg before home.
For our last morning, we did a dawn silent boat ride up a tidal channel. Since the students did one the day before, a few sat out. The ones that remained stayed silent to increase our chance of sighting animals. We saw many birds: kingfishers, kites, egrets and others. There were numerous mud skippers – fish that come out of the water to avoid predators – and a wild boar. The highlight was sets of fresh tiger tracks. The first set came down one bank and up the other. Tanjil, our guide, estimated that they were 5-6 hours old. After returning to the ship, we headed north through the Sundarbans towards Dhaka, a day and a half journey.
Along the way, we had a quick stop at a small village along the Baleshwari River. Chris Small had noticed that the width of the villages in this area had doubled between 1989 and 2010. We wanted to find out why. A small party went ashore to talk to the villagers. Unlike Polder 32, the water here is fresh and it shows. Lots of trees and a more prosperous and happier population. Boys jumping
into the creek from the top of the sluice gate. The trees included betel nut, papaya and other fruit trees and well as trees for wood. The local policy is that for every tree they cut down, they plan 4 new ones. This accounts for the increased size of the villages, a net switch from rice field to trees. After only a ½ hour, we had to return to the boat, drop off Carol and Saddam where a car would take them back to Khulna, and continue on our way.
We decided not to stop for visiting Barisal or swimming and thus were able to get to Dhaka the next afternoon rather than at night. Instead of spending the night on the Kokilmoni on the polluted, smelly, Shitalakshya River, we went into Dhaka and back to the Ambala Inn. More importantly for the students, we arrived with time to
shop. After checking in, we formed groups of 2 US and 1 Bangladeshi and sent them off by foot and rickshaw to New Market for shopping. The lack of shopping opportunities was the main complaint about the trip. They made up for it with clothes for themselves and presents for friends and family. That accomplished, we gathered for a final dinner in Bangladesh at Voot, one of our favorite restaurants. The slow service with cooking for 22 allowed plenty of time for socializing and picture taking. The students showed off their new Bangladeshi togs and a good time was had by all.
The next morning was our chance to see Dhaka. We met our counterparts the university and headed to Old Dhaka. We stopped at the 800-year old Dhaleshwari Temple where a child was getting
her first solid food in a Hindu ceremony. Then on to the Lalbag Fort built by the Mughals in 1676, or so we thought. Sunday is its day to be closed. We decided to go to the Ahsan Manzil, known as the Pink Palace. As we drove through the narrow streets, traffic got slower and slower. Finally, we stopped and decided to walk the last quarter mile. Now we all got a true taste of Old Dhaka, dodging rickshaws, hand trucks, pedestrians, and workers balancing parcels on their head. We managed to get all of us there and toured the grounds overlooking the Buriganga River then the massive palace built by the Nawab of Dhaka in 1872.
After the chaotic walk back to the vehicles, we spent an hour going the few kilometers back to Dhaka University. When we finally got back, we
had to abandon our plans for visiting the National Museum. We went to lunch at a very Bangladesh restaurant, picked up our luggage at our hotel and headed to Aarong. It is an upscale shop that sells all Bangladeshi clothes, crafts and products. The students got their last fill of shopping. Satisfied with their gifts, we headed to the airport. They went home, while I started my next leg in Kolkata and Aizawl, India.