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Eruptions that ripped apart continents in the Triassic also caused mass extinctions, says a new study co-authored by Lamont-Doherty scientists Paul Olsen and Dennis Kent.

More than 200 million years ago, toothy crocodile-like creatures stalked a hot, dry mega-continent while squid-like mollusks with spiral shells drifted in the surrounding ocean.

Quotes LDEO director Sean Solomon.

"People have been running up and down the river for hundreds of years. Now there's all sorts of stuff down there," said Lamont’s Robin Bell. N.Y.

Coming decades could see delays in summer monsoon rains in the U.S. Southwest and northwestern Mexico that water crops for 20 million people, according to a new study by Lamont-Doherty scientists Benjamin Cook and Richard Seager.

Lamont-Doherty's Klaus Jacob, a professor specializing in climate-change adaption, on the sorts of planning that might help prepare for an era of rising seas.

The science is yet unclear as to whether climate change influenced Hurricane Sandy, says Lamont-Doherty scientist Adam Sobel.

Did humans start altering the climate by farming, long before industrialization? Lamont-Doherty climate scientist Wally Broecker is one of the skeptics.

By Daniel D. Douglas

“Are you using this idea for your thesis research?”

I heard this as I stood in front of a classroom full of old-growth forest ecology students. The question had come from Neil Pederson, who was sitting directly in front of me. He was asking this question because I had just spent the past 12 minutes discussing the intricacies of land snail biology and ecology that would make them great organisms to use for ecological modeling in regards to disturbance. Things such as their lack of mobility, susceptibility to desiccation and sudden change that would occur because of major disturbance make their preferences for habitat similar to the defining characteristics of old-growth. Neil looked at me with the excitement of a small child on Christmas morning because he knew that I could potentially be on to something.

So, you can imagine his dismay when I answered his question with “No, I hadn’t really given it any thought.” I know I winced (at least on the inside, if not physically) after I answered because I had suddenly realized that I could be passing up a golden opportunity. I remember walking back to my apartment that night, thinking about what had just happened. I thought about it another hour or so after I arrived home and then emailed Neil to discuss the potential that my presentation had for being used as a master’s research project. Long story short, we developed a research plan of attack with the help of David Brown, my co-advisor, to study how anthropogenic disturbance* can shape land snail communities.

Microsnails on the Honest Abe – can you find the 28 microsnails? Image: D. Douglas

Not many people study land snail ecology. I had the fortune of working under someone that did, Ron Caldwell, while I was an undergraduate at Lincoln Memorial University. I had become deeply interested in these ignored and overlooked organisms. So, as I entered graduate school in biological sciences at Eastern Kentucky University, I had a fairly strong background in “snailology”, aka malacology. I had been unsuccessful in finding a graduate program where I could continue to work with land snails and was wandering the halls of EKU uncertain about what I was going to do for a graduate research project.

What happened in Neil’s class that semester was really fate telling me this is what I should be doing. A year and a half later, I found myself sitting on my back porch sifting through leaf litter samples, picking out micro-snails, excitedly thinking “I’ve got something here.” It was clear that these organisms could be indicators of past human disturbance.

This research took me to some of the most memorable places that I’ve ever been. Since the availability of old-growth in Kentucky is sparse, my sampling sites were limited. The first place I sampled, Floracliff Nature Sanctuary, was just a few miles north in the Bluegrass Region of Kentucky and, oddly enough, a few miles outside of Lexington. It’s crazy to think that a place with trees hundreds of years old exists right outside a fairly large municipal area, but it does.

The EpiCenter, a relatively dense cluster of 300-400 year old chinkapin oak, in Floracliff Nature Sanctuary. Photo: B. James

Floracliff rests on the Kentucky River Palisades in a very rugged, deeply dissected network of gorges cut by streams over eons of geologic time. It also has some of the most spectacular examples of old-growth trees you’ll find in Kentucky, including the oldest known tree in Kentucky to date: a 400+ year old Chinqaupin Oak.

Though this wasn’t true old-growth, it gave me some of the best results I got for the entire study: there was a clear separation of the land snail communities between old and young forest sites. In fact, abundance, richness, and species diversity, were all greater in the older sites. This is also the site where I found the most new county records (i.e. never documented from that county). These results only whet my appetite for more data from different forests.

The next stop was EKU Natural Areas‘ Lilley Cornett Woods Appalachian Ecological Research Station, a small patch of prime mesophytic old-growth forest in Letcher County. It’s bizarre to think that forests like this exists in the Cumberland Plateau portion of Kentucky, due to the fact that our countries insatiable thirst for natural resources has left the region in one kind of an ecological ruin. I was deeply impressed by this forest as wandered around. The snails at LCW did not disappoint either. I saw the same patterns as in Floracliff: old-growth forest had greater abundance, richness, and diversity. The highest species richness for the entire study came from LCW as well, which is something that I did not expect. The evidence was beginning to stack up.

Big Everidge Hollow, old-growth forest goodness, in in Lilley Cornett Woods. Photo: D. Douglas

My final study site was Blanton Forest State Nature Preserve. This preserve is over 1200 hectares and contains the largest tract of old-growth forest in Kentucky. Dominated mostly by oak and hemlock, the forest is very rugged and it had more rhododendron than I care to remember.  Nevertheless, it is impressive. Comparing Blanton to a nearby young forest didn’t necessarily give me the same exact results, statistically speaking, but I still saw the same trend of higher abundance, richness, and diversity of microsnails in old-growth forest.

A phatt, old-growth white oak in Blanton Forest, Bob posing, Merril coring. Photo: N. Pederson

You may be asking, “What does this all mean” or, “Well, he found that there is better habitat for these organisms in undisturbed forests. That’s doesn’t really seem novel.” In reality, this is novel. Better, it is important.

First, I documented that a minimum of several decades, if not more than a century, is needed for land snail populations to recover to a point that resembles what their assemblages looked like before human disturbance. As an important part of forested ecosystems in terms of nutrient cycling, organic material decomposition, calcium sequestration, and food sources for many other animals, it is vital that we know things like this so that we can better manage our forests for everything that lives there, starting from the ground up. Second, all of you must know that everything in an ecosystem is interconnected and, once one thing is removed, it can have cascading effects throughout the ecosystem. Better management practices will help us maintain ecological integrity of forests. Third, my findings also indicate the need for locating and protecting remnants of old-growth forests. As I have shown, old forests, whether true old-growth or lightly logged by humans a century or more ago, are biodiversity hotspots and therefore deserve protection beyond their representation of how complex forests are at great ages. And finally, my findings also indicate that land snails have great potential for being used as indicators of old-growth. This is something that many scientists, especially citizen scientists, have been chasing after for decades.

For myself personally? This means that I have a lot more work to do. Despite the fact that there are people out there that study land snails, they remain poorly understood. I feel as if it is my job to bridge that gap in the knowledge. I also hope that what I have accomplished with this research will open the door for future studies on not just land snails, but other non-charismatic fauna. I also hope that my work enables people to look at more than just the trees in old-growth forests. The trees are wonderful, and we are lucky to still have them, but there is a lot going on underneath those trees that we don’t know much about.

 

* = the linked article is open access and free for downloading – download away!

[UPDATE]

Earthwise picked up this study for their radio series on our changing environment. Hear their piece on land snails and old-growth forests here.

_________

Daniel Douglas earned his master’s degree in biological science from Eastern Kentucky University in 2011 studying terrestrial snails, important, but less charismatic creatures.

Big droughts have hit New York City's watershed in the past 500 years. More research from scientists at Lamont-Doherty suggest it could happen again.

Lamont-Doherty seismologists Paul Richards and Won-Young Kim discuss their analysis of North Korea's nuclear test in this video piece.

Women washing, clothes, their children and themselves at the foot of the embankment at Sirajganj. Suring the summer, the water reaches almost to the top.

Prior to the late 1700s, the Brahmaputra River flowed farther east by up to 100 km.  It then switched, or avulsed, into a straight north-south route, possibly triggered by an earthquake in 1787.  The small river whose course it usurped was called the Jamuna River.  Now, below the avulsion point where what is now the Old Brahmaputra deviates from the present course, the Brahmaputra is called the Jamuna.  The last two days were upstream of that location.  Now we are downstream of it and thus on the Jamuna River.   Our first stop was Sirajganj.  This town is protected by a stone embankment.  The river has been migrating to the west, threatening the town.  As a result, the embankment now protrudes into the river.  When I was here in 2011 I saw several collapses along the embankment and my class

Meredith and Chris buying snacks and fruit for lunch.

saw them repairing it in 2012.  They now have a lot more riprap at the base to protect it.

We drove along the embankment, a nice promenade, to the ghat and got a fast boat.  Chris had picked out an area with a lot of diversity, so we could efficiently do our sampling.  We checked our notes and found the char that had joined to the very large stable island was not the one we visited in 2005.  That char was now a thin sliver.  We stopped at the head of Katanga Char, only 2 years old, where the high ground was stabilized by grasses and people were growing peanuts and rice on the flanks.  We then crossed a channel to the tail of the next char to the north.  Here, what had been a grass-covered highland had been

Meredith taking notes with our sporty boat in the background.

ravaged by the river.  Tufts of grass that had help on were surrounded by large scours over a meter deep.  The little remnants had the same teardrop shape as the larger chars.  Here and on another small char, we were able to collect all the samples we needed.  We headed for the ghat and our hotel with an outside chance of taking their boat to the char I visited with my students last year.  However, before arriving, we finally found green coconuts for sale.  We had been searching for days for green coconuts. The seller cuts off the top with a machete, inserts a straw and you drink the refreshing coconut water.  Afterwards, he splits it and you can eat the coconut jelly, not yet matured into the coconut meat.  To add to our enjoyment,

All that was left of a vegetated char were mounds anchored by grass that had resisted the flood surrounded by large scours. The teardrop shape was a miniature of the larger chars.

Chris also found a shop selling the wasabi potato chips he had been searching for.  With the extra stop and the slow check-in process, we abandoned visiting the char, but it was still early, so we went into Tangail for some shopping, although we found most shops closed as it was Friday.

For our last stop in the field, we continued south to the confluence, where the Jamuna meets the Ganges to form the Padma River. There are ghats for crossing the Padma and for crossing the Jamuna.  We went to the later, which is smaller now that there is a bridge over the Jamuna.  As the chars shift, so does the ghat.  We had to walk for the last ½ km to the rental boats as Babu’s van could not go.  We started at the southern end of Shivayala Char, a large char at least 30-40 years

I am still drinking the green coconut water while Humayun is already eating the jelly inside the split coconut.

old.  However, the southern end had been eroded and then grew back.  Where we were was only few years old.  From there we went to the next, newer char for examining and sampling as it showed a lot of variety on the satellite imagery.  That done, our next stop was a piece of fluviotourism, the confluence or actual meeting point of the Brahmaputra and Ganges Rivers.  We stopped upstream and walked down the long narrow char.  There were huge scour pits from the turbulence of the two rivers meeting during the monsoon.  The point where the tow rivers met wasn’t as clearly defined as in 2005, but we waded around and found it our final group photo.  Our work was done and it was time to return to Dhaka for some final meetings and a last hartal, and then home.  As usual here, many things did

Boatman at Sirajganj watches Chris load a data point into his GPS. The white wind-blown sand is starting to cover the dry channel behind them.

not go as planned, but with some adjustments, everything we planned got done.

People leaving a crowded ferry at Aricha, by the confluence.

The scours pits formed by swirling eddies of water where the two rivers met during the monsoon.

Lunch on the boat.

The four of us standing a the confluence of the Brahmaputra (left) and Ganges (right) rivers.

Chris walking cross the shallow dry season Tista River. During the monsoon, it will be filled to the opposite bank in the distance.

We left the pleasant house in Kushtia to resume our nomadic existence.  We spent a full day driving to northern Bangladesh. We will now work our way downstream stopping at multiple places along the Brahmaputra River.  Finding little traffic, we drove past Rangpur, where we will be staying to the Tista River, a tributary of the Brahmaputra.  While it is a large river during the summer monsoon, today it was a shallow stream with exposed sandbanks and people growing crops in the middle of the channel.   Chris decided the hour we had before sunset was enough time, so we climbed down the embankment and hired a boat to cross the river.  It was shallow enough that we saw children wading across and Chris got out and walked the rest of the way, followed by the chidren.  Water diversion projects upstream means

Humayun standing near the eroding bank of the Brahmaputra at Chilmari. The cracks show the next places to fall off the cliff.

there is little water here in the winter.  Some exploration, some sampling, some photos and we were done.

We were up early for the long drive to the Brahmaputra.  We hadn’t planned on coming this far north, so we didn’t have maps of this years arrangement of the river.  I found two possible places for boat hires and ended up choosing Chilmari as the place easiest to get a boat.  When we got the to river agound 11am, we found a cliff.  Apparently ~1 mile of the coast had eroded here.  An old woman chastised us that we should either prevent the bank erosion or give them money so they could move.  We learned the boats were a few hundred meters upstream where you could walk down to the water’s edge.  Along the way we

Meredith examining the bedforms on the bottom of what was a channel during the monsoon season.

passed a group digging up the topsoil along the cliff to sell before it toppled into the river.  We could see the cracks where the next pieces of land would be lost.

We bought some snacks for lunch and hired a boat.  The fist char (sandy island) was unnamed, but 5 families from Bazradiarkhata Char had settled the north end and started farming, growing squash, wheat and dal.  The char was only 5-6 years old.  The families still returned to the larger char in the summer and New Bazradiarkhata Char, as we called it, was chest deep in water during the summer.  We continued north to Kachkol Char.  This char was 8-10 years old.  However, it was now attached to Bazradiarkhata Char.  The corn, wheat, dal, etc. growing was being farmed by

The villagers brought us a bench so we could sit in the shade and not get sunburnt.

people from Bazradiarkhata Char.  The village we visited were people who only moved there 6 months ago when their village and land on a char was claimed by the river.  They were working a paid laborers and did not have their own land to farm.  They were concerned that Meredith be careful of the sun so she wouldn’t get burned.  They also suggested that if she moved to the char, she could get dark like them. We then went downstream to Bazradiarkhata Char itself.  This char was formed during the major 1988 flood when 2/3 of Bangladesh was submerged. Now, 25 years later it had lots of trees homes, crops, an elementary school and an adult education center.  We were surrounded by children, particularly Meredith.  She could get the girls to pose for her,

Eroded cut banks on the side of the channel revealed the successive layers of sedimentation that built the char.

but I could not.  On the side of the village, there were great sedimentary features and Meredith and I measured a channel for some flow calculations.  At all of there sites Chris sampled and documented the sediments and vegetation cover.  By now it was getting late, so we left and circled the downstream end of New Bazradiarkhata Char.  Newer and still unpopulated, the cut banks showed amazing patterns of crossbedding from the migration of the sand waves that built the char during high water. We explored this end of the char as the sun set over the right bank of the Brahmaputra.

Today, February 21st, is Language Day commemorating the 1952 martyrdom of students protesting Pakistan’s law making “Urdu and only

School children in Rangpur march to the local Language day memorial to pay their respects.

Urdu the language of Pakistan” when the Pakistan army opened fire.  The ultimately successful language movement in the 1950s marked the beginning of the path toward independence.   On our drive to Gaibanda, we saw numerous troups of school children heading to their local Shahid Minar, language day memorial, to pay their respects and drop off flowers.   In Dhaka people laid numerous fantastic decorations made of flowers.

Gaibanda was the opposite of Chilamari.  Here the coastline has grown outward and we had to walk out to the docks.  We later discovered that the new land filled in what was the channel we crossed to reach Rosulpur Char in 2005.  It is now attached to the mainland.  The embayment by the coast is all that is left of the channel.  Humayun again hired

Mr. Uddin explains to us the history of Manikkor Char and how he received the land his grandfather farmed when it reemerged from the river.

a boat and we went south to an area where Chris could see numerous color variations on the satellite image.  We found the land has changed substantially from the image of early January.  The channel we wanted was too shallow for the boat, so we had a very long walk. A new Landsat image to be acquired tomorrow should be close to what we saw. Where we stopped was Manikkor Char, only 6 years old.  The tree covered area to the north was Kashkhali Char, which is 13 years old. We walked towards it and met a farmer. He told us that there was a town and bazaar here 30-40 years ago, but it was lost to the river.  When it returned he received land because his grandfather had owned land here.  Such is life on the ephemeral chars.   We continued walking towards Kashkhali, but wanted to cross to another area. Only Chris

The farmer we met brought Chris samples of the muddy crusts on the sandy sediments.

and I walked through the muddy shallow waters of the embayment.  In this area, which we called New Kashkhali Char, we met another farmer, but had no translator.  Still, he helped us sample.

After finishing sampling, we went north to Rosulpur char that we visited in 2005.  We showed the people photos on my iPad, but found that most of our photos were of people who resided there only temporarily due to their land being lost.  They now lived across the channel to the east.  Still we were welcomed and follow by lots of children and a few people remembered us from 2005.  The teacher remembered Chris, but wasn’t sure about me. Overall, the village seems to be doing well with lots of corn growing on the char.  We ended early, but then had a long drive to Bogra for our hotel.

Meredith walks through the street of Rosulpur followed by the village’s children.

Me standing with the kids and women that came out to see us in Rosulpur.

View from the ghat (dock) looking towards Rosulpur. All this land is where the channel was when I was last here in 2005.

 

Sea surface temperatures in the Pacific Ocean have historically helped define climate variation in the American Southwest but as climate warms the region will become drier overall, says Lamont-Doherty scientist Richard Seager.

Humayun interviewing farmers about the history of shrimp and rice farming in the area.

We got to Khulna about 5 pm and met up with Chris Small, who was brought from the boat with all the Vanderbilt University people by Bachchu.  This is the last segment of my trip. The next day, we went to an area near the compaction site.  Chris had analyzed 10 years of MODIS satellite images and just west of the compaction site was an area that stood out for having increasing vegetation over that time.  We drove to the site and then continued on the small dirt road that followed the small creek.  We went around a bend and followed the road as far as we could with Chris snapping photos the whole way.  We talked to locals at two places and the second one had the answer.  Most of the rice fields were still fallow, but one area had a pump watering some fields.  We walked over and immediately

Downloading the GPS data from the compaction site in the Islam family home.

became a center of conversation.   This area had previously been converted to shrimp farming. About 15 years ago the BWDB built and embankment, which was the road we were on.  This stopped the tidal flooding of the land inside the embankment.  The shrimp company pulled out and as the land was cleared of its salt by successive monsoons, everyone switched to rice farming.  That started about 8 years ago and the land has become more productive with time.  This is what caused the long-term trend.

On our way out, we stopped at the compaction site.  The Scotts had done everything but download the GPS data. Only the mother and youngest son were home. We were welcomed warmly and served cookies and pakan-pitha, a

The house of Humayun’s aunt in Kushtia where we stayed for 3 nights.

pastry filled with a dal paste.  Then I downloaded the data and visited the wells.  We were invited for lunch and told that Mr. Islam would be upset if he knew we left without lunch, but we were already behind schedule.  We had to go on to Kushtia near the Ganges.  During the long drive, we found out that there was a hartal called for Monday.  We had to rework our plans since we had a lot of driving to do that day.  It was dark when we got to Kushtia, Humayun’s hometown.  We were surprised to find we were staying in his aunt’s house.  Only the caretaker was there and we split the 3 bedrooms.  Staying in a home reinforced the plan we had come up with.  We would need to stay here three nights. An added plus is we’re close enough to hear the protesters singing every night.

We gathered in the rain for a photo to commemorate reaching the Ganges for the first stop on our river survey.

For our new plan, we went to the Ganges downstream of Rajshahi and back so we can go locally at Kushtia during the hartal.  During the long drive it started raining.  We also had trouble finding a ghat (dock) to rent a boat.  We ended up driving to the river and then walking out on a semi-attached char (sandy island).  The mud was incredibly slippery in the rain, but I only fell once.  Chris sampled along the riverbank and then the two of us waded over to the char to sample some more.  Chris will measure the spectra of these samples back home to calibrate his satellite analysis. He will be able to distinguish the percentage of different sediment types for each pixel of the satellite image, which we will then use to better understand the changes in the rivers.  The chars move around, appear and disappear

Chris prepares to take his first sediment samples along the Ganges in the rain at Charghat.

every year during the monsoon.  Meanwhile, we were getting soaked and called it quits.  Good thing we didn’t go out on a boat for hours.

Today, is another hartal (general strike), however, we were able to walk to the Gorai River here in Kushtia.  We went to a park where a lot of boats come to take people on rides, but none were here this early.  Still, we managed to flag one down and hire it for the day.  We went up the Gorai into the Ganges and headed upstream to Ranakor Char.  We spent the day visiting three chars (sandy islands), stopping at multiple sites on each.  The cold overcast day brightened as it went on.  We did sampling and a lot of walking around examining the bedforms and varied sediment deposits.  We could see 5 different scales of bedforms from the

We spent our first day on the water using a local boat to visit several chars.

chars themselves to the tiny ripples in the lows of larger waves.  This area by Kushtia now has numerous chars and they are much more accessible than the ones we tried and failed to visit yesterday.  When we returned in the late afternoon the empty park was filled with people.

Humayun and Meredith discussing the bedforms they see on one of the chars.

 

After dinner, we walked over to the nightly peaceful protests calling for the death penalty for the convicted rajakers, collaborators with the Pakistani army during the 1971 liberation war. The one on the left was given a life sentence for complicity in ~380 murders prompting the popular protests.

Lamont-Doherty seismologist Paul Richards quoted in a story about North Korea's nuclear ambitions.

Data from a seismic station in China confirms that North Korea is getting a lot better at building nuclear bombs. The good news: they can't hide their tests from seismologists. Lamont-Doherty seismologists Paul Richards and Won-Young Kim weigh in.

February 13th was the first day of Spring in the Bengali calendar and many women (and some men) were dressed in orange and red with flowers in their hair to celebrate.

We passed protesters marching to Shahbagh Square, the site of huge rallies every night since the hartal.

After the resistivity, I was supposed to go to Khulna to join Scott and Scott on repairing the compaction meters.  We have two places with sets of wells where we installed optical fibers.  A local person uses a device to measure the length of the fibers each week by shining a laser through the fiber.  Unfortunately several on the fibers have broken since we installed them.  The Scotts will be repairing them, as well as the usual yearly measurements and data collecting.  They went to the northern site first – we saw them heading north while the conclave group was heading south.  I was going to join them for the southern site, but their work went so much faster than expected that they finished while I was doing resistivity.  Thus there was no need for me to go to Khulna before meeting Chris Small for the river work.  I spent the two extra days in Dhaka.  I had plenty of people to look up that I didn’t expect to have time to meet.

On the first day, Humayun and I went to the US Embassy to meet with people who couldn’t make it to the conclave due to the hartal.  Even the US Ambassador was going to meet us when he took guests to a resort in Sylhet.  As Humayun and I passed through several layers of security, we ran into the Ambassador on his way out.  We chatted for a few minutes and then went on to our meeting.  After making it back to the university for lunch, we went to the Geological Survey of Bangladesh, where my main contact has been promoted to Director General.  I showed him our results and we discussed collaborations, particularly on GPS.  All around the university women were dressed on yellow, orange and red

Banners hanging from buildings at Shahbagh Square. They are calling for the execution of the collaborators during the 1971 revolution. It is a huge popular response to the hartals calling for their release. It has been going on for the last 10 days.

saris for the first day of Bangla spring. Finally back to the Ambala Inn where I met up with the Scotts and Doug and all of us went to dinner with Chowdhury, my collaborator from the Bangladesh Water Development Board (BWDB).  He has gotten us a huge dataset on the water levels in the rivers and in groundwater wells.  Well over a million individual measurement.  Water is so central to life in Bangladesh that there is an excellent monitoring system in place that we use to determine the amount of water impounded in Bangladesh during the monsoon.  It is over 100 billion tons of water.

The next day, we went to BITWA to try to obtain more detailed information about the tide gauges for examining sea level changes.  Tide gauges measure the height of the water relative to the land, but here the land is sinking.  We put 2 GPS

Babu, our legendary driver, in his van. This time he managed to get us into the last spot on the fast ferry across the Padma River saving us two hours.

to monitor the land subsidence next to tide gauges.  That will let us separate the sea level rise from the subsidence.  The combined effect has Bangladesh worried about land loss and water salinification.  We went meet with the wrong person twice before we finally found the correct person, a woman whose sister had been a student of Humayun’s.  It will now be straightforward to get the detailed data.  The afternoon was spent working with one of the students from the resistivity training.  Sojon wanted to go through everything in detail so he knows how to run the system.  Fayaz would have joined us, but he was out filming archeological sites with Doug.  The two of them have taken the initiative to be leaders among the group.  The 10-minute ride back to the Ambala Inn took an hour.  An area just north of the

The semi-chaotic process of loading vehicles onto the ferries was particularly bad this time after a 3 hour wait. There were several fender-benders as everyone tried to force their way in.

university has been blocked off because of the peaceful protests against the razakers, the groups that collaborated with the Pakistani army during the revolution and helped them in their killings.  The Islamist party’s hartals for the release of their leader has lead to a larger movement wanting the death sentence for him and others.  It is Occupy Dhaka.  It was very strange to see women dressing in colorful clothing yesterday with headbands calling for death for the razakers.  Finally, I arrived and waited for Meredith, the last of our party to arrive from NY for the river work.  The bad traffic meant she arrived very late.  Doug and I had a last dinner together at 11 pm in a local packed restaurant.

Today I am finally on my way to Khulna with Meredith and Humayun, with Babu as our driver, of

Meredith Reitz on the Mawa ferry on her first full day in Bangladesh.

course.  I am stuck waiting to get on the ferry across the Padma River, formed by the merger of the Ganges and Brahmaputra.  Once across, we will be in the more leisurely and relaxing south to meet up with Chris in Khulna.

The resistivity cable and electrodes laid out along the fields with the Lalmai anticline of Comilla in the distance.

After returning from Sylhet, I left Dhaka the next morning for Comilla for 4 days to train a group of Dhaka University students and graduates on operating our resistivity imaging system.  Many of the conclave people headed out to the Padma River, formed by the joining of the Ganges and Brahmaputra to do sampling for a remote sensing study of the rivers.  I will be doing this later in the trip, but had other plans now.  The transects of wells that we are drilling provide detailed vertical records of the sediments, but how do we connect the dots when the wells are 3-4 km apart?  It turns out we can do it with electricity.  Clay and mud has much lower electrical resistivity (or higher conductivity) than sands.  The basic technique it to pound two pairs of electrodes (stainless steel rods) into the ground. We then use a car battery to

Sojon and Fuad coiling up the cables at the end of the day. It is important to collect the electrodes first or you cannot find them after the cable is gone.

send a current between one pair and measure the voltage at another pair.  The voltage depends on the rock type between the 4 electrodes.  For our system, we have 84 electrodes that can be spaced up to 9 m apart and a long cable in 12 sections to connect them.  A sophisticated resistivity device then sends current to one pair and measures the voltage at up to 8 other pairs at a time.  The device is programed to do measurements with thousands of different combinations.  The result is similar to doing and electrical catscan of the earth showing the distribution of sand and mud.

I came to Comilla with 6 trainees, Fayaz, Sojon, Jia, Rabi, Fuad and Paval.  During the 4 days, they will work with me to learn to use the system

Fuad standing over the resistivity meter monitoring as the measurements come in.

well enough to be able to carry out these surveys on their own.  For the training site, we came to Comilla where to work around the Lamai anticline. It is the westernmost hill sticking up out of the floodplain.  To help interpret the structure creating the anticlines, we need to know the dip, or slope, of the folded beds.  This has been roughly done from topography, but the exposed topography is partly eroded.  We want to image the boundary between the older Pleistocene sediments of the anticline and the younger Holocene sediments that cover them.  Both sediments are similar, but the surface exposed during the last glacial period when sea level was 120 m lower has been altered to clay.  This should show up as a dipping layer of low resistivity. We will do 4 lines, two on each side of the anticline to image the dipping beds.

Jia, Sojon, Pavel Babu, Rabi (cut off) and Fayaz having dinner at BARD cafeteria. We ate Bangladeshi style with our hands. The food line can be seen in the background.

Our first day was short because of the time it took to get here.  We laid out a short line with 56 electrodes a short distance south of one of the wells that was drilled on the east side of the anticline.  The car batteries we took along were not fully charged, so we hooked up Babu’s van to provide more power.  That worked well and decided to use the car to run the equipmet the rest of the days.  However, that meant the lines had to be where a car could go.  Humayun did not join us because his wife has been ill.  That meant we didn’t have a GPS to record positions or track where we were. We managed to use the GPS in my camera to get the positions of the line. We moved to our home for the next few days, the Bangladesh Academy for Rural Development or BARD.

Sojon downloading the data to a laptop after completing a line.

The next day we shifted to the west side the next day.  Google Earth became our tool for finding sites.  With a USB modem we had slow, but continuous internet.  We found a set of fields close to the one of our drill sites.  We navigated to it by recognizing buildings, mostly gas stations from Google Earth.  The fields were fallow, so we could cut across them. Everything was going smoothly.  We finished early and I was able to spend the late afternoon teaching the students.  That evening we processed the data for both lines.  The first one showed the boundary we were looking for to be very shallow.  A river had eroded part of the anticline.  Thus we were on top of it and not on the flank.  Good data, but it didn’t provide us with a slope.  The other line had noise problems from a power line, but clearly showed the layer we wanted dipping ~3° to the west.  The system was providing hard data.

Farmers planting rice in the fields. These muddy fields were too wet for us to use for the resistivity line, so we had to use the roadside.

We still needed a line on the east.  We tried our first site, but Babu’s van could not drive to the line location. On to plan B, a country road on the west side.  We drove our electrodes into the fields at the base of the road being careful not to disturb the growing vegetables. The data was marred by some power lines, but showed our layer for part of the line. It lined up well with the previous day’s results. For our final day, we need a good line on the east.  I picked several candidates on Google Earth.  The first was inaccessible, but I quickly found another road and we did it there.  Because they were planting rice, the side of the elevated road was not useable.  The top turned to not be that good a place.  The data was much worse quality than any of the other sites.  Still, it gave reasonable results.  Humayun and Doug came out, so we interspersed working on the resistivity line with filming.  That line competed our work here and the training and we all headed back to Dhaka. The students were trained and we learned how to select good sites.

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