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Glacier Marks on Mount Chirripó

Sculpting Tropical Peaks - Wed, 07/09/2014 - 15:39

By Max Cunningham
June 12, 2014
We continued to sample boulders in Valle de Las Morrenas, Valle Talari, where the hostel sits, and several places along Mount Chirripó’s ridgeline.

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Large boulders of granodiorite line the ridge of Mount Chirripó. These are likely produced by exfoliation, a process that occurs in response to stress release associated with the melting of glacier ice.

The view from the top of Mount Chirripó is spectacular.  Looking out along the ridge I could see huge boulders of granodiorite produced by exfoliation, or the response of rock at the surface to the removal of ice.

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Striations in the meta-sandstone at the summit of Mount Chirripó point down the axis of Valle de Los Lagos, (a mechanical pencil and sample bag are included in the picture for scale, the pencil points in the direction of striations). Striae are a telltale sign of glacial coverage.

The actual summit of Chirripó, however, is a very different kind of rock.  I believe the peak is composed of a sedimentary rock that was melted and then fused back together as the magma that formed the granodiorite rocks moved toward the surface.  This metamorphosed sandstone (meta-sandstone) is extremely hard, and resistant to weathering processes.

In the meta-sandstone near the summit of Mount Chirripó, I discovered glacial striations.  These striations occur at 12,513 feet (the summit is 12,529 feet), which is a good 1,000 feet above the moraines in the upper portion of Valle de Las Morrenas.

Back to Mount Chirripó

Sculpting Tropical Peaks - Tue, 07/08/2014 - 11:14

By Max Cunningham
June 11, 2014

 Volunteers  at the Cloudbridge Reserve stay in a series of houses built in the Costa Rican rainforest.   They work towards returning mountainsides near Mount Chirripó to natural conditions.

Volunteers at the Cloudbridge Reserve are returning the hills near Mount Chirripó to natural conditions.

Mike and I hiked down 7,000 feet from Mount Chirripó to the Cloudbridge
Reserve early on the morning of June 10th to refuel and replenish supplies.

At this point, the Cloudbridge Reserve deserves a special mention.  Tucked away in the forest above San Gerardo de Rivas, volunteers at the Cloudbridge Reserve work to transform old farmland into natural forest.  After the cold ruggedness of the Mount Chirripó summit, the volunteers at Cloudbridge provided an exceptionally welcoming and engaging environment.  Mike and I were extremely lucky to have such a supportive base camp.

I kept an eye out for interesting geomorphology as I walked along the trails of the Cloudbridge Reserve.  The rivers here are particularly beautiful.  The water is clear and blue, and channel beds are floored by bedrock and boulders (all granodioritic in composition, like many of the rocks atop Mount Chirripó).  I was struck by the power of the local rivers; the erosional features carved into this hard, granodioritic rock were impressive.

The raging Chirripó River cuts through granodiorite, about 1 mile away from the Cloudbridge Reserve.

The raging Chirripó River cuts through granodiorite, about 1 mile away from the Cloudbridge Reserve.

After two days of rest and catching up on all we’d missed while isolated on Costa Rica’s highest peak, Mike and I headed back up to Mount Chirripó to continue sampling and to learn more about the processes shaping this landscape.

During our second journey, we hoped to extend our sampling range by venturing farther into glacial valleys and higher onto peaks.  We targeted Valle de Las Morrenas, a valley that we knew well from our first sampling trip and that other researchers had discussed extensively.

Earlier, we sampled boulders from moraines adjacent to large lakes.  This time, we targeted a steep drop-off (what we called a “lip) that occurs in the valley directly below the lakes.  Looking at maps and satellite images, it appeared that the lower valley was actually a remnant cirque:

A 60-foot drop-off separates the upper and lower valleys in this picture.  The lip may represent the retreat of a large glacier that once filled lower Valle de Las Morrenas.

A 60-foot drop-off separates the upper and lower valleys in this picture. The lip may represent the retreat of a large glacier that once filled lower Valle de Las Morrenas.

Our discovery of a large lateral moraine in the lower valley corroborated our hypothesis that a glacier produced the pronounced lip in Valle de Las Morrenas.  The vegetative cover increased substantially as we moved lower in the valley, which made accessing the moraine a real challenge.  After pushing through thick, woody bushes, we finally found ourselves on the crest of the moraine.

From the image it’s hard to tell, but this is actually a pretty big moraine, Max 6.4about 50-60 feet in height.  Meandering rivers cut through cobbles along the moraine’s edge, analogous to what we saw in Sabana de los Leones, only here with water raging through the channel.

Max 6.5We quickly came to realize that the boulder selection on the crest of this lower moraine was a far cry from the beautiful, large, flat boulders we saw along moraines in the upper valley.  Here, boulders seemed to be more deeply weathered, and more sparsely scattered.

While the lack of good boulders for sampling induced a bit of hand wringing (made worse by storm clouds quickly moving up the valley), the effectiveness of weathering on these boulders may add to the story of glaciation at Mount Chirripó.  Deep weathering of boulders suggests that they have been sitting around, exposed to the atmosphere, for a long time.  How long?  Glaciologists have employed relative weathering techniques for centuries to estimate exposure age, but 10-Be dating will tell us for sure.

 

 

Hudson Highlands Earthquake Prompts Questions - (Rockland, N.Y.) Journal News

Featured News - Tue, 07/08/2014 - 10:09
Lamont's John Armbruster discusses the magnitude 2.5 quake that struck Garrison on July 5.

Did Halley’s Comet Convert the Irish to Christianity? - Smithsonian Channel

Featured News - Tue, 07/08/2014 - 09:57
Lamont's Dallas Abbott and the Lamont-Doherty Core Repository appear in a new documentary linking the passing of Halley's Comet 5,000 years ago to a change in Ireland's religious beliefs.

Small Earthquake Recorded in Hudson Valley - WAMC

Featured News - Mon, 07/07/2014 - 11:00
Features Lamont-Doherty seismologist Leonardo Seeber.

Earthquake Hits Hudson Highlands - (Rockland, N.Y.) Journal News

Featured News - Sat, 07/05/2014 - 11:00
The Lamont-Doherty seismic network records a magnitude 2.5 earthquake in the Hudson Highlands, in Garrison, New York.

Nuclear Power: Worst-Case Recalibration - Capital New York

Featured News - Wed, 07/02/2014 - 13:41
Lamont-Doherty seismologist Lynn Sykes highlights the risks that were unknown at Indian Point nuclear power plant at the time it was built.

Editorial: Towns Can Avoid Fracking Future - (Rockland, N.Y,) Journal News

Featured News - Tue, 07/01/2014 - 14:40
Cites research linking disposal of waste fracking fluid to earthquakes.

Lamont-Doherty Researchers Make Their Mark on the Map - Columbia Record

Featured News - Tue, 07/01/2014 - 11:00
Feature on map features named for Lamont scientists.

Global Warming Makes Drought Come on Earlier, Faster, and Harder - Guardian

Featured News - Mon, 06/30/2014 - 11:13
A new study coauthored by Lamont's Richard Seager tries to separate natural and human influences on drought.

Australopithecene Dental Calculus

Geopoetry - Fri, 06/27/2014 - 09:36
 AG Henry, Nature, 2012.

Phytoliths — mineral particles formed by plants — found in the teeth of one of our ancient ancestors. Photo: AG Henry, Nature, 2012.

Across a mixed landscape, Au. sediba plods
Sometimes on two feet, and sometimes on four,
Munching on fruits and leguminous pods,
Nuts and some seeds … C3 foods galore!
They did have a choice (so coprolites hint);
Lush grasses, fat grazers were also around,
But in these old ancestors (destined for flint?)
New clues, new stories have just now been found.
With lasers and microscopes, old dental plaque –
Tiny, stuck phytoliths show a rich diet!
Scratched-up enamel, it all brings us back
To lives of these creatures that have long been quiet.
What wonders are learned from plaque and from feces,
History bound in compounds beneath!
So, we should say to that wonderful species:
Thanks for not brushing your teeth!

___________________________________________

Further reading:

Palaeoanthropology: The ancestral dinner table, Nature, 2012

The diet of Australopithecus sediba, Amanda G. Henry et al., Nature, 2012

This is one in a series of poems written by Katherine Allen, a researcher in geochemistry and paleoclimate at the Lamont-Doherty Earth Observatory

Ice Age Reboot: Ocean Current Shutdown Viewed as Culprit - Live Science

Featured News - Thu, 06/26/2014 - 11:00
A dramatic slowdown in deep ocean currents matches a major reset in Earth's ice ages about 1 million years ago, according to a new study by Lamont-Doherty scientists Leo Pena and Steven Goldstein.

Herbie’s Great Adventure: NUM Dendroecological Fieldweek

Kristen de Graauw and Cari Leland

Cari and Kristen here, checking in from Mongolia. This year we were invited to be instructors for the Third National Dendroecological Fieldweek, May 23-29 in Udleg, Mongolia. We arrived to Ulaanbaatar on May 20th so we were fortunate enough to have a few days to recover from some pretty terrible jetlag before beginning the fieldweek marathon. Anyone who has ever attended a fieldweek anywhere in the world knows how challenging (and rewarding!) these events can be. Our first few days of the fieldweek were spent at the NUM (National University of Mongolia) research station near Udleg, a few hours north of UB. We were so happy to see the beautiful countryside for a few days. We got to ride there in this awesome Russian vehicle, which Cari nicknamed Herbie.

 

The roads were rough but Herbie was a trooper and we arrived at the research station safely.

The roads were rough but Herbie was a trooper and we arrived at the research station safely.

We took a break at Teacher’s Pass for a nice panoramic view of the mountains before continuing on to the research station.

We took a break at Teacher’s Pass for a nice panoramic view of the mountains before continuing on to the research station.

The research station was a complex of buildings for housing, a kitchen, and lecture rooms. We shared a cozy room for two and enjoyed beautiful views of the valley and mountains surrounding us.

The NUM Forestry research station

The NUM Forestry research station

Our room from the outside...

Our room from the outside…

..and the inside.

…and the inside (Hi Cari!).

After everyone settled in, we met for the opening ceremony. Baatar gave a nice introduction of the project and the history of the CEME collaboration. There were 8 students in total, and 7 of them were female (girl power!). There was a good mix of participants; from first year undergraduates to PhD students.

Baatar giving the opening ceremony speech.

Baatar giving the opening ceremony speech.

After the opening ceremony we went out to the field. Baatar gave us a guided tour of all the current research projects at the station (there were many!) and the potential sites for the fieldweek. Then we gave a quick lecture on the basics of dendrochronology and headed back towards the research station to discuss potential fieldweek projects.

The flux tower on the research station property. It was pretty impressive.

The flux tower on the research station property. It was pretty impressive.

We noticed Gypsy moth larvae emerging from their cocoons on the ground near the forest.

We noticed Gypsy moth larvae emerging from their cocoons on the ground near the forest.

More gypsy moth larvae after emerging from their cocoons.

More gypsy moth larvae after emerging from their cocoons.

We headed back after a nice hike through the forest.

We headed back after a nice hike through the forest.

Day 2 at the research station was field sampling day. Unfortunately we woke up to a cold and rainy day but that didn’t stop our groups from heading out into the forest. After a long discussion we decided Cari would teach the Climate group and Kristen would teach the Ecology group. Cari’s group headed up the mountain in search of old larch and pine trees to core while Kristen’s group went to a portion of the forest that had been logged. The goal for the climate group was to find moisture-stressed trees and look at the relationship between tree rings and climate. The ecology group’s goal was to determine logging dates and the effects on surviving trees.

Cari’s group preparing to core a large pine near the mountain ridge.

Cari’s group preparing to core a large pine near the mountain ridge.

Kristen’s group coring a living larch near the stump graveyard.

Sundermaa coring a living larch near the stump graveyard for Kristen’s ecology group.

After one of the coldest and rainiest field days we’ve ever experienced we headed back to the field station to thaw and dry ourselves and the cores.

Cari’s group heading back from the ridge.

Cari’s group heading back from the ridge.

While we waited for the cores to dry, the students practiced skeleton plotting.

The students mounting wet cores with tape to help them dry straight.

Margad, Togii, and Badra mounting wet cores with tape to help them dry straight.

Byamba teaching Oyunna a skeleton plotting exercise.

Byambaa teaching Oyunna a skeleton plotting exercise.

The students are working hard on their skeleton plot exercises, while Kristen and Cari check their work.

The students are working hard on their skeleton plot exercises!

Everyone was very anxious to see if their skeleton plots matched!

Everyone was very anxious to see if their skeleton plots matched!

After a rainy day, we were treated with a beautiful sunset.

After a rainy day, we were treated with a beautiful sunset.

The next day we mounted the cores with glue and taught the students how to sand. They quickly learned that a well sanded core took time, patience, and persistence. At the end of the day we headed back to UB to begin laboratory methods.

Sainaa sanding her first core.

Sainaa sanding her first core.

Kristen telling the students they need to sand more! “Sand more!!”

Kristen telling the students they need to sand more…“Sand more!!”

The view from our sanding “room”. Not bad!

The view from our sanding “room”. Not bad!

Back at the university we had to hit the ground running with lab methods. The students skeleton plotted the samples from the research station one day, learned how to do the list method and measure the next day, and finally on the last day they learned how to run COFECHA and read the output files. It was challenging but everyone worked their hardest. The final day was very busy. The students were working on their presentations until the very last minute. The groups did an outstanding job presenting their projects, which made us feel so grateful for being able to teach such a bright and dedicated group of students. During the closing ceremony Baatar gave us both a really nice Mongolian tree and shrub guide book and then presented each student with a certificate of achievement. The students then gave us the most thoughtful gifts of Mongolian art and script.

Oyunna discussing the correlations between climate and pine during the climate group presentation.

Oyunna discussing the correlations between climate and pine tree growth during the climate group presentation.

Baatar presenting Margad with her certificate of achievement.

Baatar presenting Margad with her certificate of achievement.

 Cari, Margad, Togii, Sundermaa, Oyunna, Sainaa, Gerelee, Baatar, Sanaa, Kristen, M?, Byambaa, and Badra.
The whole group after an amazing fieldweek! From the left: Cari Leland*, Margad Ovgonkhuu, Togtokhbayar Erdene-Ochir, Sundermaa Sergelen, Oyunmunkh Byambaa, Sainbayar Gombo, Oyungerel Sereenen, Baatarbileg Nachin*, Oyunsanaa Byambasuren*, Kristen de Graauw*, Myagmarsuren Batdorj, Byambagerel Suran*, and Badar-Uugan Khasbaatar. ( *Instructors)

 

 


Categories: TRL

The New Environmentalism Will Lead Us to Disaster - Scientific American

Featured News - Thu, 06/19/2014 - 09:41
Lamont's Wally Broecker has proposed naming a new geologic era after the imprint modern humans have made on the planet the Anthropozoic.

A Quick Retreat from ‘Mountain Lion’ Savannah

Sculpting Tropical Peaks - Tue, 06/17/2014 - 11:03
Max 5.1

The discovery of a flat grassland leads to a morning of exploration.

By Max Cunningham
June 10, 2014

Mike, Colin and I made meticulous plans for exploring Mount Chirripó before we left New York, but on the way to the summit Mike and I saw something that made us change direction: at about 9,500 feet, a mysterious grassland beckoned beneath jagged peaks. With just one day to go before our trip back to the Cloudbridge Reserve to refuel, we decided to make an early morning trek to this unusual valley to investigate why it is so flat and devoid of vegetation.

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The dry stream bed is sharply cut but lined with angular rocks suggesting minimal erosion.

Over the course of a beautiful, sunny day Mike and I trekked over the rugged terrain from Crestones Base Camp before reaching a sudden transition from forest to grassland. A few things struck us. First, a thin river snakes through this entire shallow valley. Around bends in the river we noticed sharply cut banks where the stream has become more powerful and eroded away the banks.

Max 5.3

A stone marks the place where a lion killed someone in 1956.

Second, we were surprised to find the stream bed completely dry. From a distance, we had expected to find a powerful body of water. In another test of our geomorphology knowledge we discovered that this dry stream bed is paved mostly in cobble-sized rocks, the type you might find on a cobblestone street except these cobbles are sharp and angular instead of smooth and rounded. Mike and I spent the morning walking the Sabena de Leones valley and the more we looked, the more baffled we remained by the processes that shaped this landscape. Why is the river bed dry and its sediment load so large and angular? We hope to find more clues in the coming week.

In the early afternoon, Mike and I stumbled on a small marker along the river channel in Spanish dated 1956. Combining our Spanish skills, Mike and I deduced that the sign commemorated the unfortunate death of a man by mountain lion, and then I realized that Sabana de los Leones  translates to “Savannah of the Lions.” That’s all we needed to know before skedaddling back to the Talari Valley and the security of the Crestones Base Camp.

Landslide Up Close

Sculpting Tropical Peaks - Mon, 06/16/2014 - 11:31

By Max Cunningham
June 9, 2014

Max 4.1

The landslide below the dark rocks in the center of this photo was discovered first in satellite images.

During the last decade, scientists have noticed an apparent rise in catastrophic events in mountain valleys as glaciers retreat and permafrost thaws. Some evidence suggests that thawing glacial valleys are responsible for enormous, fast-moving landslides that can destabilize river dams and cause other damage. Last July, my colleague Colin Stark and others at Lamont identified one such landslide in Alaska.

The idea that catastrophic processes may become more frequent as glacial valleys warm globally is a frightening one, but further information is needed to assess the threat. I came to Mount Chirripó hoping to find evidence of past landslides. Before flying here, Stark and I used high-resolution satellite images to identify potential landslide features on Mount Chirripó. On our second day in the field, Kaplan and I tried to locate them on foot.

We found our first landslide in Valle de los Conejos, a cirque valley carved into Mount Chirripó’s southern side. Apparently, we walked right by it on our previous day of fieldwork; the trees and bushes growing amid the fallen boulders provide an excellent disguise.The glacial debris blends in almost perfectly with the hillside. To highlight it, I have outlined the scarp in red where the failure occurred, but even this image, taken more than a half-mile away, is deceiving. Mike and I spent what felt like hours whacking through thick bushes to get there. You can just make out some of the large boulders in the background.

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Kaplan bushwhacks to the landslide.

From a distance I thought we could scale the landslide, but the house-sized blocks were too big to scramble over.  During the slide, boulders stacked up on each other and formed crevasses and caves that are now covered in treacherous mats of vegetation. I suspect that pumas may sleep in the caves by day if they are able to withstand the altitude.

Mike and I traipsed around the landslide, stopping at various scarps to enjoy the views. The run-out distance appears to be only about a tenth of a mile, and the boulders are densely packed. Looking down, I got the impression that the landslide created a crevasse somewhere between 60 to 100 feet in depth. When did this major failure happen in relation to deglaciation?

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Quartz sampled from the landslide debris may help us discover when the event happened.

Mike and I decided to use our CRN dating tools to find out. We made our way to several boulders on the east side of the landslide, where the rock is sedimentary, unlike the granodiorite found in the Valle de las Morrenas.  Once again, Mike and I found bits of fine-grained quartz in the rocks, indicating we can measure their Beryllium-10 levels to understand how long this landslide has been exposed to cosmic rays. Mike and I think that the extent of weathering on these boulders is a clue to the age of the landslide: For the surface of these boulders to undergo alteration, they probably sat in the same place for a long period of time. Perhaps this landslide is indeed paraglacial, a result of glacier retreat and permafrost thaw. We hope our efforts to measure CRN production here will inform us.

'Jellyroll' Ice Sculptures Discovered Under Greenland Ice Sheet - LiveScience

Featured News - Mon, 06/16/2014 - 11:00
Melting and refreezing creates giant jellyroll-like ice sculptures at the bottom of Greenland's northern ice sheet, says a new study led by Lamont's Robin Bell.

Refreezing Water Causes Weird Warps in Greenland's Ice - Climate Central

Featured News - Sun, 06/15/2014 - 11:00
In a new study led by Lamont's Robin Bell, scientists discover sections of ice below the surface where meltwater has refrozen, causing layers of ice to build up.

Frozen Underworld Discovered Beneath Greenland Ice Sheet - Guardian

Featured News - Sun, 06/15/2014 - 11:00
A previously unknown landscape of jagged, soaring shapes beneath the ice are described in a new study led by Lamont-Doherty geophysicist Robin Bell.

Chiseling Away

Sculpting Tropical Peaks - Fri, 06/13/2014 - 09:52

By Max Cunningham
June 8

Max 3-4

Cunningham chisels away at this glacial moraine for a sample that will reveal when the ice last withdrew.

Our expedition has two main goals: assess glacial erosion features on Mount Chirripó and search for clues of the summit’s age. Were the broad, flat landscapes on Mount Chirripó formed by glacial erosion or a change in tectonic forces pushing the Talamanca Range up about 2.5 million years ago?

A chemical dating technique called Cosmogenic Radionuclide (CRN) Dating may lead us to the answer. This technique will help tell us how long ago the valleys flanking Mount Chirripó eroded, and therefore, whether Mount Chirripó’s high elevation landscape is older than 2.5 million years or whether it eroded into its current shape as recently as 10,000 years ago.

Earth is being constantly bombarded by high-energy protons and neutrons from beyond our solar system, and CRN dating exploits this process. The collision of high-energy particles and atoms in the atmosphere and on rock at Earth’s surface produces new atoms of different mass, or isotopes. Fortunately for many Earth scientists, the impact of cosmic rays and oxygen produces an extremely rare isotope of the element Beryllium: Beryllium-10.  Oxygen is abundant in Earth’s crust, and quartz (SiO2) is among the most common minerals found there. When cosmogenic rays react with quartz at the surface, about six atoms of Beryllium-10 are produced per gram of quartz per year.

Measuring concentrations of Berylium-10 at the surface can potentially tell us how long the rock has been exposed to the atmosphere, and quartz is a particularly convenient mineral for measuring Beryllium-10 concentrations. Mike and I sought out glacial features with quartz-bearing rocks at Mount Chirripó with the hope of understanding whether rocks here were exposed to the atmosphere after the recent retreat of ice.

Max  3-1

Glacial debris can create natural dams where lakes form.

Glacial features jumped out at us during our initial tour of Mount Chirripó. We saw broad cirque valleys, floored by large lakes likely filled during glacial retreat. We also saw striated rocks and moraine ridges scattered with cobbles and boulders. In one valley, Valle de Las Morrenas, we noticed several lakes above the boulder-strewn ridges. This fits in neatly with previous observations of lakes dammed by moraines.

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Kaplan inspects a moraine.

Because moraines are abandoned when the ice retreats, measuring concentrations of Beryllium-10 in boulders on top of moraines may give us an idea of how long ago glacial erosion happened here. After locating boulders sitting on moraines, our next step was to see what the boulders are made of.

 

Max 3-3

Chiseling exposes a fresh surface of quartz.

We discovered that many are granodioritic, an intrusive igneous rock composed of the minerals plagioclase, amphibole and our good friend quartz! Next we took samples to analyze their Beryllium-10 levels in the lab later. Collecting samples is a physically rigorous process, especially in the low-oxygen, rainy conditions at 10,000 feet on Mount Chirripó. With a hammer and a chisel, and a bandanna to protect our faces from shattering rock fragments, we chipped away at the surface of the boulder, hoping to come away with about two pounds of rock to analyze.

We collected samples from boulders on two moraine crests. After months of processing, we hope to be able to describe how long ago glacial ice retreated from different parts of the valley. Calling the day a success, we hiked back through the afternoon rain to Crestones Base Camp.

 

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