This week we have been exploring all the parts of the ship we have not yet discovered and were lucky enough to get shown around the engine room and the bridge. It is evident that each area of a ship (bridge, engines, science etc.) has a group of people doing those specific jobs and that the combination of everyone doing their part keeps everything running smoothly; like cogs in a massive machine.
The engine room control panel. With that many buttons no wonder it takes so much training to work in the engine room!The engine room is located in the hull of the ship and is the biggest room on board by far, taking up about 2/3rds of the bottom deck. This is obviously a very important part of the ship because without it we would not be moving anywhere! The Langseth has 2 engines leading to 2 propellers and also 1 bow-thruster. There are so many different bits of machinery down there that it can take 4 years of studying to be qualified to work in the engine room. It is very loud and warm but surprisingly clean and tidy. There are also 2 compressors which are used to pressurise the air for the air guns that we tow.
One of the very noisy compressors. It is hard to portray the size of these in a photo, they are huge!The heat from the engines is used to produce all the hot water for the ship and the engine room also has machines for desalinising our water. Fuel usage is constantly monitored and fuel moved between all the many tanks spread around the ship to ensure even weight distribution. Even though we only travel at about 4 knots whilst acquiring data we burn between 5000-6000 Gallons of fuel a day due to the massive load of the equipment we are towing behind us.
One of the two enginesThe bridge sits at the front of the ship on top of the main living quarters. From here it seems as if practically everything can be controlled. They drive the ship when we are not driving from the main science lab during acquisition, control the speed, can manage the safety aspects including all alarms and watertight doors and keep a look out for anything floating past that might get caught up in our seismic gear (so far buoys and pallets have been sighted). One very important job of the bridge is to communicate with other nearby vessels. Nobody would expect us to be towing 6km of streamers so we have to make sure we let other ships know with enough time to arrange safe passing, therefore avoiding collisions.
This is the main control panel in the bridge. There are screens for navigation and
radar as well as all the speed controls. There are two smaller control panels
on the port and starboard sides of the bridge for work that
involves careful maneuvering e.g. picking up OBS's. The last seismic line is just being finished right now and then we can get ready to begin equipment recovery. It is about 40 hours until we are back on dry land again!
Tessa GregoryUniversity of Southampton
A screen capture from the multi-beam sonar Seafloor Information System (SIS).
The image on the left shows swath coverage. The image on the right shows an active ping through the water column.Multi-beam sonar (swath seafloor mapping) data are collected, gridded (binned) to the predefined cell size, and output in two flavors. Bathymetric grids, which are essentially 3D topographic maps, and Backscatter grids, which display the reflectivity of the seafloor. The reflectivity varies due to both incidence angle of the respective beams and the density of the surface (e.g. hard rock, sediment etc). As the ship moves along at a given velocity, the multi-beam sonar sends a "ping" from the transducers (transmitters) to the seafloor and then waits until the receipt of the last return to ping again. The ping rate (Hz or 1/seconds) is a function of the depth of the ocean as well as the sound speed through water (XBT's are useful!). The swath width also scales as a function of depth. Our average depth is ~4800m (2.98 miles), which allows for an achievable swath width of ~20km (12.43 miles!).
Swath coverage display of the backscatter (reflectivity of the seafloor) collected across a swath.In order to gain insight on the density of the multi-channel seismic (MCS) data that we are collecting we use the Spectra software package. Spectra tracks the position of the ship, streamers, and air guns in real time using GPS and an acoustic network, and then bins the data accordingly within the predefined grid. The goal is to get an equal amount of seismic traces (reflected seismic waves) in each bin. The traces can then be stacked (combined), which increases the signal to noise ratio. Stacked traces within a bin are called "fold" and ideally represent traces from all offsets along the streamer in respect to the source.
A screen capture of the Spectra display. The image on the left shows active binning of the MCS data.
The image on the right shows the bins being infilled (filling holes).We are getting to the end of the "No Mores," which means we are finished on Friday!! Stay tuned for a word from our Chief Scientist along with a look at the MCS data (and our cruise pic).
When the New York Air National Guard travels to Kangerlussuaq, they toss in a few fishing poles with the baggage for whatever few hours of free time might be available. A favored pastime for this location’s summer assignments means the local lakes are well known by the crew, so when we sat down to map out the flight plan, a request for locating lakes met with an easy nod. No problem at all. It took only seconds to register that our definition of lakes might differ from theirs.
We are interested in lakes atop the ice sheet surface, places where the ice sheet melt is puddled into lakes of various sizes. It is in locations like these lakes where water, with its darker color, absorbs more heat from the sun than the surrounding white ice surface. This process can contribute to more melt, and in some instances the water finds a weak “joint” in the ice and drains right down to the bottom. Both the extent of the ponding and this process are of interest to the science community in better understanding the ice sheet.
The guard is quick to assure us, no problem, these too can be located!
It was an “optics day,” where our focus is on the cameras in IcePod. Using both our Bobcat (visible wavelength) and our (IR) infrared cameras, we will image surface lakes and the meandering meltwater channels on the ice sheet surface, and then fly over a few of the southwest fjords to image meltwater as it plumes at the calving edge of the ice sheet. This is a day that Chris Zappa, our resident oceanographer and optics expert, has been waiting patiently for. The weather is perfect, the sky crystal clear, and the instruments are humming. We are ready to go.
The surface of the ice sheet barely resembles our April visit. Large lakes, some a mile across, are printed along the ice sheet surface, as if a skipping stone has skimmed along the surface leaving pockets of water in its wake.
These ice surface lakes are viewed more cautiously than our lakes back home, as they pose a threat of suddenly emptying through a “moulin” or drainage tube. Moulins transfer water from the surface to the bottom of the ice sheet in short order, circumventing a process that could otherwise take many thousands of years. Cutting across the surface in various patterns, meandering channels carry the melting surface water into these catchment pools. On the ice sheet these channels are the equivalent of streams from our home communities. Back home they collect runoff and drain into freshwater lakes. Here they serve the same function but are more striking, as there are no plants to screen them.
The cameras work furiously. The Bobcat, is a 29-megapixel camera. The IR samples at 100 frames per second. Both cameras collect a staggering 60 gigabytes a second. Images play across the screen showing the temperature contrasts as we move over the surface features.
We move from the ice sheet to the coastline, where rugged mountains circle Greenland’s perimeter like a crown. Fjords cut through in many areas, allowing deeply stacked ice in the interior to move off the land. Today we are flying down small “arms” of Godthaab Fjord with a focus on their leading edges, where the ice meets the Atlantic water. We are interested in how the IR camera can be used to track thermal plumes at the interface of the cold glacier meltwater and the warmer ocean water. Combining both the Bobcat and the IR cameras allows sediment plumes to be tracked moving through the fjord. Sediment should warm faster than the surrounding water, and may be transferring more heat into the system. Both will tell us about circulation, mixing and transit of the glacial meltwater systems.
Flying back down the fjord we pass over a small fishing town perched on the edge of the water. There is no apparent movement below. Perhaps they have gone fishing?
For more about the IcePod project: http://www.ldeo.columbia.edu/icepod
Even the most skilled of English language lipreaders are only able to tease apart about 30 percent of the information being shared. I learned this reading a recent article (Kolb, 20131). The author, herself deaf, went on to note that in some transmissions the information capture is higher while in others there is nothing collected. An average of 30 percent information transfer…most of us seek more information, we are curious beings. I don’t know anyone who is happy to sit comfortably saying “yes we know 30 percent, that is good enough.”
I am surrounded by question posers, information seekers, hypothesis formers – scientists are an inquisitive bunch for sure – and that is how we find ourselves back in Greenland in July seeking to learn more about the information operating underneath and deep inside this changing ice sheet, and testing just what our IcePod instruments are capable of telling us. Thirty percent is well in excess of what we currently know about ice sheets and their processes, but every line flown and piece of data collected and analyzed builds upon our current understanding.
Prior to arriving at the base for the morning, flight plans were laid well in advance. Discussions threaded through the series of meetings leading up to our return to Kangerlssuaq, piecing together the right combination of flights that would focus on testing instruments and addressing the science. Instrument range, elevation, seasonal snow conditions, old radar lines all are factored in. Once in Greenland we must weave weather and instrument issues into our planning. Weather is cloudy and reports suggest an improvement during the week, so we will shelve our camera testing for the minute and focus on instruments designed to penetrate through the clouds. Today our flight will focus on tuning our Deep Ice Radar System (DICE).
Located at the crest of the ice sheet the elevation is just over 10,500 ft. and seems just the place to test our deep ice radar. Once aloft, we head for deep ice up over Summit. The weather reports are validated – the whole area is socked in with cloud cover and the pilots switch to Instrument Flight Rules (IFR). Our survey flight at Summit is 3,000 ft. above ground level (agl), but the aircraft instruments tell us we are 13,000 ft. above sea level (asl). The ice is deep and DICE is the focus of the next few hours as we survey and resurvey in the same area with dialogue, testing, refining and learning with each pass.
A question was raised — would we want to move to a second area to look at different conditions? Checking other areas of the ice sheet is tempting, but the science team vetoes this…”We learn more by doing this now,” holding our focus on one location. So we refocused our efforts, collecting more data, making more small adjustments, and consider that with each data point we are improving our lipreading of the ice sheet.
For more about IcePod: http://www.ldeo.columbia.edu/icepod.
1Kolb, Rachel, Seeing at the speed of sound, in Standford Magazine, March/April 2013 http://alumni.stanford.edu/get/page/magazine/article/?article_id=59977
After all these posts about how we live and work onboard the R/V Langseth you may just be wondering what sort of sustenance keeps us going during the long hours. Well you’re in luck! The excellent cooks serve meals with a smile promptly three times a day at 7:20 am, 11:30 am, and 5:30 pm. Breakfasts always include mountains of eggs, bacon, sausages, and pancakes and on special occasions scrumptious muffins. Lunch usually comes with toasty grilled sandwiches, soup that warms your limbs, and crunchy French fries. Dinner varies but commonly consists of a juicy steak or pork chop, rice, mashed potatoes that put even your Mom’s Thanksgiving potatoes to shame, and a delicious desert like cherry pie. The salad bar is open 24 hours a day and even this far into the cruise still contains crisp spinach, olives, tomatoes, and a variety of other vegetables.A sampling of the meals served onboard with cooked by the always smiling galley staff.
From left to right breakfast, lunch, and dinner.
In the center image the galley staff made up of June, Hervin, and Brian pose behind a lunch of pizza and soda.We are now in the home stretch of our cruise, steaming furiously down our final sail lines to complete our 3D grid. Can’t believe there’s only four more dinners until we set foot back on dry land!
I was sent to join this cruise half way through because a lot of the scientific party had to leave and nobody more qualified than me could be found at such short notice! I have never been on a cruise before and had no idea what to expect, or any idea how complex and time consuming 3D seismic acquisition is. I have learnt so much about the technical side of acquisition and a little bit about the processing side; however I have also gained a lot of non-scientific tips and tricks!
Here are my top 5 tips:
1) ‘Boring science is good science’ – If you are bored on a 6 hour watch that is a good thing because it means that everything is running smoothly and good data is being collected. Having things to do is always a bad sign! Things have been running pretty well recently and as a result I have greatly improved my crossword skills.
2) Things will break, don’t panic! – This is a hand me down ship filled with second-hand instruments from industry vessels. Because of this a lot of the equipment is temperamental and repeatedly needs to be fixed. However, I have also seen instruments that have been offline for days randomly start working again so you never know!
3) Duck tape has a million uses – There is no end to the list of things duck tape is used for on this ship: keeping weights in place on streamers, keeping your laptop on the desk during bad weather, taping your ladder to your bunk so it doesn’t bang during rough weather and keeping ropes in place on the deck to name a few. It seems like any problem can be fixed with tape.
If you don't want your office chair rolling around or you need a cable tie just use tape!
4) Hoard food – When food you like is put out in the mess then take it while you can. A few days ago a gigantic tub of mini snickers and bounty bars was put out in the mess….I have never seen chocolate disappear so fast!
5) Taking a shower is the most dangerous activity on the ship – I recommend keeping either an elbow or hand on the wall at all times so you can feel when you start to move. I think taking a shower is probably the best form of exercise on the ship because of the amount of effort and energy it takes just to balance. Also, never soap the bottom of your feet in rough seas. That is probably classified as an extreme sport!
Tessa GregoryUniversity of Southampton
Located next to the Galley we have our Library which has a lot of good books (I was reading the Che Guevara's travel book before the beginning of this part II, I really want to finish it!) and these excellent chairs...they're really comfortable, believe me. You can also find a variety of mystery, fiction and scientific books on the shelves.
The library with a wide variety of books
Yeah, but John actually I'm not a book lover ...No problem! This is what you need! A 42-inch TV screen and a big collection of movies and TV shows. Ah, and don't forget the PS3, which makes the crew's free-time fun. I have to admit something to you, I've never used the movie room, but maybe sometime I will go there to catch a movie or documentary.The movie room with seating for plentyBut if you're an athletic person, this is your place, the gym!
It's a little bit small, but if you think we're in the middle of the ocean, the luxury of having some equipment must be appreciated.
The gym ... be careful when the ship is moving!So, there is a treadmill, some free weights, etc. Be aware of the pitch, roll and heave! These are the movements made by the ship. Instead of explaining them, I'll post an image which can perfectly illustrate what I'm trying to say.
The differences between pitching, rolling, and heavingFor those who appreciate an indoor sport, we also have a ping-pong table. It's located one level below the Galley, at the Main Deck. I didn't use this table either, but I'll launch a challenge: Try to play ping-pong during rough seas! Imagine how cool a ping-pong game is inside a ship facing waves of 5 or 7m (or even higher).
The ping pong table ... this could get interesting in rough seasThank you...or should I say Obrigado?
João (John) Pedro T. Zielinski
Complutense University of Madrid/Federal University of Santa Catarina
Don't forget to check out our progress as we fill in the sail lines here
Hudson River Sewage Spills Breed Illness, Antibiotic-Resistant Bacteria - (Rockland, NY) Journal News
The back of the lab where most of the preprocessing and quality control is done.Additionally, we use this bank of terminals to monitor for the presence of critters in the water, the weather and sea conditions, and the health of the EM122 multi-beam. Sitting back from the semi-circle of computers is another set of desks where the we, the students and scientists, stake our claim. Outfitted with no-slip fabric and duck tape, we have covered the back of the room with our computers, which we use for pre-processing and quality control (QC) of the incoming data.
That about covers the main lab, they keep it pretty cold down here for the sake of the computers so I’m headed up to grab another sweatshirt before I get frost bite. Stay warm out there!
For those of you who have been following our adventure here's a comparison of the sea-state. I know that the few of us who have been out here for both halves definitely appreciate the difference, and for those joining for the second half it looks like smooth seas ahead!
Also, we have now reached 10,000 page views!! So thanks Mom (and everybody else).
James Gibson Lamont-Doherty
We started our tour of the R/V Langseth almost a month ago with a walk through of the mess hall and now with our return to the high seas are excited to pick back up where we left off. Let’s begin with our sleeping quarters.
As we all know, the most important aspect of real estate is location, location, location and the same can be said for room assignments when at sea. On first glance, you might be tempted to opt for a room on a higher floor accompanied by a nice porthole to allow full view of the spectacular sea outside. However, hold that thought! Remember that the further above sea level you are, the more you will move with each passing wave. What may feel like a peaceful sway down on the lower levels can turn into a ferocious veer strong enough to topple chairs on the top deck. Thus, if you have any inclination that you could succumb to seasickness it is probably best to pass on the picturesque vista and opt instead for a windowless cabin below. Fortunately, for many of the scientists mental struggles over room selection never occurred as cabins had been assigned to us before we walked up the gangway. Most of the students aboard are sleeping in a suite of cabins that share a common living space endearingly termed the “Snake Pit”. The origin of the room’s namesake remains mysterious, perhaps previous groups of students did some sort of battle there? Or fought snakes? Who knows, for now though it represents a comfortable room where many spend their off time reading books from the library or taking short siestas in between work.
The "Snake Pit" where students read and lounge between shifts
All of the cabins aboard share similar features such as a set of bunk beds and matching closets. Depending on the individual setup, you might find yourself lucky enough to also have a set of desks and perhaps even a small couch though these furnishings are found mostly in the higher rooms reserved for the principle scientists and the superior ship mates. Given that work continues around the clock on the Langseth, all bunk beds include an individual light for private reading and also black out drapes to both prevent any light from your bed reaching your room mate and conversely any light from your room mate reaching you. Additionally, all rooms come with either adjoining shared or private bathrooms (termed “heads”). Given the combination of rolling waves and slippery tiles, it could easily be said that the heads may be some of the most injury prone rooms aboard. Thus whenever attempting to take a shower, remember to always keep one hand on the hand rail and if the ship starts swaying don’t neglect to hold on tight otherwise you might suddenly find yourself autonomously ejected onto the cold, wet floor.
Our cozy cabin equipped with bunk beds and closets
I think that about does it for now, dinnertime is just around the corner and I can smell the ahi tuna from here. Buenas Noches!
Being at sea again allows me to look back at our extended stay in Vigo (Galicia). The port city of Vigo is a unique and beautiful place. The summer months are particularly nice as this part of the Atlantic coast is rainy most of the year. Vigo is just about 2hrs north of Porto (Port wine), which is in Portugal. The proximity to Portugal and the fact that in the past teaching the English language was not stressed within the school system leads to a population that speaks a mixture of Portuguese and Spanish, but not much English. As a result my (poor) Spanish was definitely put to the test as well as my ability to communicate using what are best described as elementary level sketches.
What Vigoites lack in English they make up in hospitality and a relaxed outlook on life. In short, the idea of a "siesta" is not lost on them. While the bars (and there are hundreds if not thousands) are usually open, the restaurants do not open until 8:30 p.m., and generally not at all on Sunday. However, we did manage to find one that is, and it happened to have very good (and cheap) Tapas. Although off the beaten path it quickly became one of our favorites.
A view down the alley to one of our favorite bar/restaurants.Vigo also has some amazing beaches! After what amounted to a 45 minute walk or a 6 Euro (~$8) cab ride from the ship we could either lay a towel down and get some sun or grab a drink at one of the bars that are literally on the sand. I was shocked to say the least in the shear number of people that were at the beach, and it seemed like there were more during the weekdays than the weekends. Must have something to do with the laid back lifestyle (?)
Playa Samil on a Tuesday.The best beach (Rodas) in the world (The Guardian, 2007) can be found on one of three islands about 45 minutes (16 Euro, ~$20) by ferry named Illas Cies. The archipelago of Cies is also a Spanish National Park. An interesting thing about these islands is that they look like an above sea analog to what we are seeing sub-seafloor in the data. That is to say that they consist of a series of faulted crustal blocks (granite). The style of faulting is termed "Normal," which means that the hanging wall moved down relative to the foot wall. This type of faulting is indicative of extension and is expected along the length of this margin.
A view of Cies from Playa Samil with faults indicated by the arrows.The part that we had been so patiently waiting for arrived after almost 3 weeks in this unique place. While I will not miss being in port, I am happy to have had the chance to see and experience this part of the world as it truly is a beautiful place.
Arrival of "La Cabeza" (the head).
Welcome back to our blog! As of yesterday morning, we are back at sea and shortly we will resume acquiring 3D data. The repairs to the engine were more difficult than originally thought. We had the Rolls Royce engineers with us for the whole time, working with our fine engineers on the ship. You may not know that Rolls Royce makes really big engines like those in the Langseth. They worked to clean out the engine, ordered a number of parts, and the parts gradually arrived in Vigo. The engine was reassembled and tested at the dock. It worked again!We sailed from Vigo at 0700 on 15 July with a partially new science team. Several people left the ship because they had conflicts with the extended cruise. They were Donna, Tim, Cesar, Mari, Brian, Steve, Luke, Marianne, Miguel, and Toby. Remaining were Dale, James, Raj, and Sarah. We could hardly do with a science team of four, so we recruited six newcomers. They are Natalie Accardo (Lamont), Milena Marjonovic (Lamont), Gaye Bayrakci (Southampton), Joao Pedro Tauscheck Zielinski (Madrid), Tessa Gregory (Southampton), and Katherine Coates (Southampton). We will try to get photos and bios up shortly.We are deploying the seismic gear now. We have two streamers out and the third almost out. We hope to begin acquisition in the morning.We are all excited about continuing our cruise and completing the 3D survey.
Dale SawyerRice University
It has been a while since we last updated this blog. The reasons are many. The primary reason for the delay is that we have had singular focus in launching our next project, a project that for many is a dream come true.
Before we launch into that and officially start the 2013 field season, let’s do a quick recap of our team’s efforts since last August.
Our academic year started with a bang: our new research project, which was an unexpected off shoot of our efforts to study climate, fire, and forest ecology, was funded by the National Science Foundation in September 2012.
Since then, our team has spent much time presenting prior results, new preliminary results and processing samples. Many, many samples.
First, kudos to Nicole Davi work improving a tree-ring based reconstruction of the Kherlen Gol in Mongolia (gol = river). Many of the chronologies used were collected between 2009 & 2011 as a part of the Climate, Fire, and Forest Ecology project. The new work, “Is eastern Mongolia drying? A long-term perspective of a multi-decadal trend” can be found here.
Second, we need to congratulate Cari Leland on persisting and publishing the first paper from her thesis: “A hydroclimatic regionalization of central Mongolia as inferred from tree rings “ – link
Cari’s effort set the stage for our second paper on the climate history of the Mongol Breadbasket: “Three centuries of shifting hydroclimatic regimes across the Mongolian Breadbasket“ – link
Finally, Tom Saladyga got a nice piece of his dissertation published with the article, “Privatization, Drought, and Fire Exclusion in the Tuul River Watershed, Mongolia“ – link
We have a few manuscripts in development from our Climate, Fire, and Forest history project, which ends in 2013. And, we are very happy that Byambaa is on the doorstep of completing her dissertation. This project is coming to a very nice completion and we are thrilled.
We are equally thrilled with the start of our new project, “Pluvials, Droughts, Energetics, and the Mongol Empire”. We’ve gotten a silly amount of press here, here, here, here, and here – it has been great. Both institutions have made nice videos and overviews of the project: here is an example of WVU‘s and here is LDEO‘s. Awareness of this project has been widespread. We meet new scholars from various parts of the world and it seems they are already familiar with the new study. Neil presented preliminary results at the PAGES meeting in Goa, India – that was hard work
Amy Hessl garnered two invites based upon our work. The first was a workshop primarily populated with historians on migration and empires across Eurasia. The setting and out-discipline experience was fantastic. The second was an archeology-based workshop on Chinggis Khaan in Jerusalem – sounds like that was equally hard work!
We are now gathering in Ulaanbaatar to launch the first season of ‘complete’ field work. By complete fieldwork, I mean that we will not only be collecting tree cores and cross-sections from dead trees, but Avery Shinneman Cook will be leading the effort in collecting lake sediments in central Mongolia to better understand long-term environmental history and the impact of the Mongol Empire on the landscape in and around the ancient capitol, Karakorum.
Prior to that, we will hold a 4-day workshop introducing ourselves to our wonderful and diverse team (a dream team? Besides Amy Hessl and Neil Pederson, team members include: Baatarbileg Nachin, Hanchin Tian, Nicola Di Cosmo, Avery Shinneman Cook, Kevin Anchukaitis, Oyunsanaa Byambasuren, and PhD students, Caroline Leland and John Quinn Burkhart) and their specific research. We will visit historical sites and lakes to begin the discussion on how to address some questions originally posed in our grant: did the rise of the Mongol Empire, driven literally by horsepower, benefit from an abundant climate and a surplus of ecosystem energy? Did the construction of the Mongol population, army, and herds of grazers significantly impact the landscape? Answers to the ful climatic context of the Mongol Empire has been a primary goal of the Mongolian-American Tree-RIng Project, (MATRIP) since the mid-1990s. We finally have the chance to address these questions. We do not know the answers yet, but stay tuned.
Brief Observations on an alternative approach to Mongolia:
This is my 9th trip to Mongolia. It is hard to believe that I have visited this far-away land so many times. But, when I smell the steppe as we enter the airport, I relax and hit a new mode that is akin to putting on old slippers. I go through customs with nary a concern knowing that Baatar will be waiting for me with a warm greeting and hug. The drive to UB is filled with the same conversation – “How are you? How is Mongolia? How are things going? How is your family? How are your students? My, Mongolia has changed“. It is wonderful.
What changed for me this year was how I got to Mongolia. I typically venture west and enter through eastern Asia. This time, I traveled east, stopping in Turkey, re-fueling in Bishkek, and then flying over western China and western Mongolia.
The sky was clear upon entering western China and the scenery was stunning. Really. I stopped my movie and just drooled out the window [akin to a dog?]. It adds a few hours of travel time at most, but I’d do it again.
Scenes of Going East to go East
A new study in the journal Nature provides fresh insight into deep-earth processes driving apart huge sections of the earth’s crust. The process, called rifting, mostly takes place on seabeds, but can be seen in a few places on land—nowhere more visibly than in the Afar region of northern Ethiopia. (See the slideshow below.) Here, earthquakes and volcanoes have rent the surface over some 30 million years, forming part of Africa’s Great Rift Valley. What causes this, and does it resemble the processes on the seafloor, as many geologists think?
The study suggests that conventional ideas may be wrong. Past calculations done by scientists predict that the solid rock under the Afar should be stretching and thinning substantially as the continent tears apart; thus molten rock should not have far to travel to the surface. Led by David Ferguson, a postdoctoral researcher at Columbia University’s Lamont-Doherty Earth Observatory, researchers analyzed the chemical makeup of lava chunks they collected from the Afar. They showed that magmas actually came from quite deep–greater than 80 kilometers, or 45 miles, within the earth’s mantle–and formed under extraordinarily high temperatures, above 1,450 degrees C, or 2,600 F.
This implies that magmas are generated by a long-lasting plume of mantle heat. It also indicates that magma must make its way up through a surprisingly thick lid of solid rock, called the lithosphere. This idea has been supported by some seismic images of the Afar subsurface.
Rifting here is fairly slow—one or two centimeters a year, or 0.4 to 0.8 inches, and this may partly explain why so much solid rock persists. As the lithosphere is pulled apart, it does stretch, crack and thin. However, because the process in this region takes so long, the base of the lithosphere has time to cool down by losing heat to the colder rock above. This keeps the relatively cold, brittle lithosphere thicker than would be expected, and counteracts stretching. Sometimes, though, magma suddenly spurts long distances to the surface, and the earth visibly cracks and pulls apart during spectacular rifting events. That includes a series of events that started in 2005, and was closely observed by scientists.
Parts of the rift have already sunk below sea level. In the distant future–maybe 10 million years from now–the process will advance so far that the Red Sea will break through and flood the region. A new sea will open up, whether or not there is anyone around to name it.
In East Africa, earth’s crust is stretching and cracking, in a process called rifting. Here in the Afar region of northern Ethiopia, hundreds of faults and fissures have formed over time. (David Ferguson)
An important force driving the rifting is magma created beneath earth’s rocky outer shell, which has forced its way upward to push apart the crust. This eruption happened in the Afar in June 2009. (David Ferguson)
This crevice opened in a matter of hours, during a sequence of very large earthquakes in September 2005. It formed in response to magma being injected into the shallow crust, and is still emitting volcanic gases. This injection of magma was the largest event of its kind to be observed by scientists. (Lorraine Field)
Fresh lava erupted onto the desert floor preserves fragile surface textures, formed as the viscous molten rock cooled and hardened. Over time, these sharp features will erode away. (David Pyle)
A remote field site within the rift. Afar is one of the hottest and most sparsely populated regions on the planet. (David Pyle)
In a region that is vast, largely roadless and dominated by armed tribes, scientists depend on helicopters to get around, and on local people to act as guides and security guards. The climate necessitates large amounts of portable drinking water. (David Ferguson)
Lavas forming the rift surface cracked apart during an earthquake in 2005 to form this fault. The horizontal boundary between the light and dark area marks the pre-2005 ground surface, and shows that the area in the foreground dropped several meters during the quake. The geology of Afar provides many clues to the tectonic and magmatic process operating beneath our feet. (David Pyle)