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Landslide Up Close

Sculpting Tropical Peaks - Mon, 06/16/2014 - 12:31

By Max Cunningham
June 9, 2014

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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.

Chiseling Away

Sculpting Tropical Peaks - Fri, 06/13/2014 - 10:52

By Max Cunningham
June 8

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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.


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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.


Climbing Mount Chirripó

Sculpting Tropical Peaks - Thu, 06/12/2014 - 15:09

By Max Cunningham
June 7

After arriving in the town of San Gerrardo de Rivas, Mike Kaplan and I immediately started gearing up for our trek to Mount Chirripó.

Our arrival here was somewhat hectic. After landing in San Jose around 10:30 a.m., we hopped a bus to San Isidro de el General, a town just west of Chirripó National Park.  Winding through the rugged mountains of the Talamanca Range, we were treated to spectacular views of central Costa Rica’s countryside. Max 2a

Once in San Isidro de el General, we navigated our way to the local office of Ministerio de Ambiente y Energia de Costa Rica, the government agency that provides research permits for Chirripó National Park. Our contact, Marisol Rodríguez Pacheco, showed remarkable patience with our broken Spanish and helped us pull together some final requirements for the permit.

By 5 p.m., the two of us made base camp at the Cloudbridge Reserve, above the San Gerrardo de Rivas. Founded in 2002, the Cloudbridge Reserve supports researchers in Costa Rica and works towards sustainable forest management. Volunteers at the Cloudbridge Reserve provided us with a beautiful working space and a warm place to sleep.

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The clouds rolled in early, by 9 a.m., on their way from San Isidro de el General in the distance.

The weather here can be erratic.  During the early morning hours the sun is intense and the sky is blue; by 1 p.m. clouds roll in. You can anticipate heavy rain from 4 to 6 every day, and nights are cold.

After taking a day to gather food supplies and find porters to help us carry heavy packs up to Mount Chirripó, Mike and I set off around 4:30 a.m. to make our way to the top of Mount Chirripó before the afternoon rain.

Travelers and locals alike warned us that the hike would be strenuous, and indeed they were correct. The trail leading to Mount Chirripó is steep and rugged (although pristinely maintained), and we gained nearly 5,000 feet in elevation over nine miles of trail.

The trail leading up to Mount Chirripó around 8,000 feet is densely vegetated and humid.

The trail leading up to Mount Chirripó around 8,000 feet is densely vegetated and humid.

One especially difficult aspect of our climb was the dramatic change in climate with elevation. Below 10,000 feet, we trekked through a humid, dense rain forest, but once above about 9,500 feet, the vegetation became sparse and the temperature dropped. At the summit of Chirripó, we rarely experienced temperatures warmer than 60°F.

In terms of Earth surface processes, this dramatic change in environment invokes thoughts about difference in landscape evolution: How does change in altitude, and associated changes in climate, affect erosion processes in the long term? This is just one question we hope our research can eventually inform.

Above 10,000 feet, the climate is extremely different, and so is the terrain.  At high elevations we see broad U-shaped valleys, and cold conditions inhibit dense vegetation growth.

Above 10,000 feet, the climate is extremely different, and so is the terrain. At high elevations we see broad U-shaped valleys, and cold conditions inhibit dense vegetation growth.

After an 8.5 hour hike, we finally reached Talari Valley, a lowland about 500 feet below Mount Chirripó. We made camp at the Crestones Base Camp, a meticulously maintained hostel in the Talari Valley, near Cerro Chirripó. The Crestones Base Camp is home to many travelers seeking the thrill of climbing Mount Chirripó. Impressively, many of the hikers we encountered wake up around 2:30 a.m. to hike the remaining 5,000 feet to the peak of Cerro Chirripo to watch the sunrise over this beautiful mountain. Mike and I made no such plans, and instead rested for a busy week of fieldwork.

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From Crestones Base Camp, you can pick out our hostel with the green roof in this expansive view of Talari Valley.


Mount Chirripó: Shaped by Glaciers or Tectonic Forces?

Sculpting Tropical Peaks - Fri, 06/06/2014 - 14:38

By Max Cunningham

Max Cunningham

Max Cunningham

I’m a graduate student at the Lamont-Doherty Earth Observatory and work in Colin Stark’s Earth Surface Processes Group. My research focuses on the role that climate plays in molding Earth’s surface, and how we can use clues carved into landscapes to learn more about climate and climate change in the past.

Since arriving at Lamont-Doherty, I’ve focused my attention on glacial valleys responding to climate change. I want to learn more about erosion in landscapes undergoing a transition from cold, frozen conditions to warm conditions. Questions about the timing of glacial retreat in the past and the erosional processes that occur as landscapes unfreeze are particularly relevant today, as glaciers around the world shrink in response to a warming global climate. max 1

Specifically, I want to learn about the history of glacial erosion in tropical mountains. Features on many tropical peaks around the world suggest that glaciers once persisted at low latitudes, but nearly all of these places are far too warm to sustain glaciers today.

Google Earth images of glacial thumbprints at Mount Chirripo, Costa Rica (left) and Mount Wilhelm, Papua New Guinea (right).  Both mountains are located within 10° latitude of the equator.

Google Earth images of glacial thumbprints at Mount Chirripo, Costa Rica (left) and Mount Wilhelm, Papua New Guinea (right). Both mountains are located within 10° latitude of the equator.

Glaciers are a crucial link between climate and erosion: They form only under very specific climatic conditions and leave very distinctive marks after they retreat. During a glacier’s lifetime, snow accumulates at high elevation and compacts into hard ice that flows downslope; at lower elevations warmer temperatures melt away layers of snow, allowing ice deeper within the glacier to move toward the surface. The total effect of compacting ice above and disappearing ice below is a “scooping” motion, and rocks caught in this “ice scoop” wear away bedrock. A combination of this rock-on-rock wear and other processes produces features unique to glacial erosion, such as circular valleys called cirques. In map view glacially sculpted valleys look like thumbprints in clay.

A somewhat startling realization is that these glacial thumbprints can be found on mountains in hot, tropical places like Costa Rica, Uganda, Kenya and Papua New Guinea. Some major questions arise: How long ago did glaciers carve out valleys in the tropics? How far down mountainsides did glaciers persist in these perennially warm regions? To start honing in on these questions, I’ll be traveling to Costa Rica’s tallest peak, Mount Chirripó, in Chirripó National Park for the month of June.

On Mount Chirripó, which rises to 12,530 feet, glacial thumbprints are clustered a few hundred feet below the summit. River profiles have a distinctive shape, exiting U-shaped valleys along gentle gradients and then breaking suddenly into a steep slope at about 6,500 feet. Waterfalls, or more technically “knickpoints,” form at this steep slope change.

Scientists have studied the unusual glacial thumbprints and clustering of knickpoints at Mount Chirripó. In 2000, researchers at the University of Tennessee identified a series of lakes that formed as a result of glacial erosion. They extracted sediment cores from the lakes and noticed a sharp transition from granular, glacially-produced sediment to organic material with depth in the core. Using 14C radiometric dating, they found that the transition occurred between 12,000 and 9,800 years ago.

Why is that important? Between 20,000 and 10,000 years ago the world was thawing out of an ice age. The 14C dates imply that glaciers persisted at about 12,000 feet at Mount Chirripó as recently as 9,800 years ago. By comparison, North America’s Laurentide ice sheet, which once extended south of New York City, retreated into Canada well before 9,800 years ago.

A 2012 study looked at Mount Chirripó from a different lens. The collision of tectonic plates in the tropical Pacific Ocean pushed Mount Chirripó to its modern elevation, but the timing of this uplift remains unclear. The 2012 study suggested that the clustering of knickpoints could reveal when tectonic uplift began.

Rapid tectonic uplift provides rivers with potential energy that expresses itself in steep slopes that slowly creep up mountainsides, creating a “wave” of erosion that travels up hillslopes. By assuming a “vertical” erosion rate, these researchers estimate that knickpoints at 6,500 feet signify tectonic upheaval that began about 2 million years ago.

The conclusions reached by these independent studies present a major conflict. On the one hand, valleys atop Mount Chirripó may have been carved by glaciers. If this is the case, the landscape must be “young,” as glacial erosion would have occurred during the last 2.5 million years. On the other hand, the valleys at high elevations at Mount Chirripó may represent a landscape that existed before 2 million years ago and rode a pulse of uplift to 12,500 feet.

In other words, two competing hypotheses have emerged: Is Mount Chirripó a sculpture of glacial erosion, or an ancient landscape perched at high elevations by tectonic forces?

My colleague Mike Kaplan and I plan to analyze evidence of past glaciation on Mount Chirripó in an attempt to test these two competing hypotheses. Using a geochemical technique called surface exposure age dating, which will allow us to measure how long rocks at the summit of Mount Chirripó have been exposed to the atmosphere, we will attempt to test how “old” the landscape is—is it relatively young, around 9,800 years old? Or does it predate a massive shift in tectonic uplift that began 2 million years ago?

Clock Is Ticking in West Antarctic

Melting Glaciers-Tracking Their Path - Fri, 05/23/2014 - 12:54
Pine Island Glacier, Antarctica

The leading edge of the floating ice tongue of the Pine Island Glacier, Antarctica. Photo: M. Wolovick

Reports that a portion of the West Antarctic Ice Sheet has begun to irretrievably collapse, threatening a 4-foot rise in sea levels over the next couple of centuries, surged through the news media last week. But many are asking if even this dramatic news will alter the policy conversation over what to do about climate change.

Glaciers like the ones that were the focus of two new studies move at, well, a glacial pace. Researchers are used to contemplating changes that happen over many thousands of years.

This time, however, we’re talking hundreds of years, perhaps — something that can be understood in comparison to recent history, a timescale of several human generations. In that time, the papers’ authors suggest, melting ice could raise sea levels enough to inundate or at least threaten the shorelines where tens of millions of people live.

“The high-resolution records that we’re getting and the high-resolution models we’re able to make now are sort of moving the questions a little bit closer into human, understandable time frames,” said Kirsty Tinto, a researcher from Lamont-Doherty Earth Observatory who has spent a decade studying the Antarctic.

“We’re still not saying things are going to happen this year or next year. But it’s easier to grasp [a couple of hundred years] than the time scales we’re used to looking at.”

The authors of two papers published last week looked at a set of glaciers that slide down into the Amundsen Sea from a huge ice sheet in West Antarctica, which researchers for years have suspected may be nearing an “unstable” state that would lead to its collapse. The West Antarctic Ice Sheet is mostly grounded on land that is below sea level (the much larger ice sheet covering East Antarctica sits mostly on land above sea level).

Advances in radar and other scanning technologies have allowed researchers to build a detailed picture of the topography underlying these glaciers, and to better understand the dynamics of how the ice behaves. Where the forward, bottom edge of the ice meets the land is called the grounding line. Friction between the ice and the land holds back the glacier, slowing its progress to the ocean. Beyond that line, however, the ice floats on the sea surface, where it is exposed to warmer ocean water that melts and thins these shelves of ice. As the ice shelves thin and lose mass, they have less ability to hold back the glacier.

What researchers are finding now is that some of these enormous glaciers have become unhinged from the land – ice has melted back from earlier grounding lines and into deeper basins, losing its anchor on the bottom, exposing more ice to the warmer ocean water and accelerating the melting.

In their paper published in Geophysical Research Letters, Eric Rignot and colleagues from the University of California, Irvine, and NASA’s Jet Propulsion Laboratory in Pasadena, Calif., described the “rapid retreat” of several major glaciers over the past two decades, including the Pine Island, Thwaites, Haynes, Smith and Kohler glaciers.

“We find no major bed obstacle upstream of the 2011 grounding lines that would prevent further retreat of the grounding lines farther south,” they write. “We conclude that this sector of West Antarctica is undergoing a marine ice sheet instability that will significantly contribute to sea level rise in decades to come.”

The region studied holds enough ice to raise sea levels by about 4 feet (Pine Island Glacier alone covers about 62,000 square miles, larger than Florida). If the whole West Antarctic Ice Sheet were to melt, it could raise the oceans about 16 feet.

 Eric Rignot

The glaciers studied by Rignot’s research team. Red indicates areas where flow speeds have increased over the past 40 years. The darker the color, the greater the increase. The increases in flow speeds extend hundreds of miles inland. Image: Eric Rignot

In the second paper, Ian Joughlin and colleagues from the University of Washington used models to investigate whether the Thwaites and Haynes glaciers, which together are a major contributor to sea level change, were indeed on their way to collapsing. “The simulations indicate that early-stage collapse has begun,” they said. How long that would take varies with different simulations – from 200 to 900 years.

“All of our simulations show it will retreat at less than a millimeter of sea level rise per year for a couple of hundred years, and then, boom, it just starts to really go,” Joughin said in a news release from the University of Washington.

Many scientists who’ve been studying the region were already braced for the storm.

“It’s gone over the tipping point, and there’s no coming back,” said Jim Cochran, another Lamont researcher with experience in the Antarctic. “This … confirms what we’ve been thinking for quite a while.”

Cochran is principal lead investigator for Columbia University in Ice Bridge, the NASA-directed program that sends scientists to Antarctica and Greenland to study ice sheets, ice shelves and sea ice using airborne surveys. Much of the data used in the new papers came from the Ice Bridge project.

Tinto, also an Ice Bridge veteran, agreed. “I thought it was pretty exciting, because we’ve all been working on this area for a long time, and that potential for the West Antarctic Ice Sheet to behave in this way, we’ve been aware of it for a long time,” she said. “[It] made me want to get in there and look at the rest of the area, what else is going on.”

And there are still many questions about what’s going on: How fast the ocean that swirls around Antarctica is warming, how those ocean currents shift, and to what extent that is influenced by global warming.

“I have a problem with the widespread implication (in the popular press) that the West Antarctic collapse can be attributed to anthropogenic climate change,” said Mike Wolovik, a graduate researcher at Lamont-Doherty who studies ice sheet dynamics. “The marine ice sheet instability is an inherent part of ice sheet dynamics that doesn’t require any human forcing to operate. When the papers say that collapse is underway, and likely to last for several hundred years, that’s a reasonable and plausible conclusion.”

But, he said, the link between CO2 levels and the loss of ice in West Antarctica “is pretty tenuous.” The upwelling of warmer waters that melt the ice has been tied to stronger westerly winds around Antarctica, which have been linked to a stronger air pressure difference between the polar latitudes and the mid-latitudes, which have in turn been linked to global warming.

“I’m not an atmospheric scientist, so I can’t evaluate the strength of all of those linkages,” Wolovik said. “However, it’s a lot of linkages.” And that leaves a lot of room for uncertainty about what’s actually causing the collapse of the glaciers, he said.

Researchers have been discussing the theory of how marine ice sheets become unstable for many years, said Stan Jacobs, an oceanographer at Lamont-Doherty who has studied ocean currents and their impact on ice shelves for several decades.

“Some of us are a bit wary of indications that substantial new ground has been broken” by the two new papers, Jacobs said. While ocean temperatures seem to be the main cause of the West Antarctic ice retreat, there’s a lot of variability in how heat is transported around the ocean in the region, and it’s unclear what’s driving that, he said. And, he’s skeptical that modeling the system at this point can accurately predict the timing of the ice’s retreat.

But, he added, “this is one more message indicating that a substantial sea level rise from continued melting of the West Antarctic Ice Sheet could occur in the foreseeable future. In the absence of serious near-term greenhouse gas mitigation efforts, such as an escalating tax on carbon, they may well be right.”

“It starts bringing it a little closer to home,” said Tinto. “It’s a significant amount of change, but something we can start planning for. Hopefully [this will] make people stop procrastinating and start planning for it.”

Cochran agreed: The papers’ message is “that … over the next couple hundred years, there’s going to be a significant rise in sea level, and at this point we can’t stop it.” But, he added, “it doesn’t say give up on trying to cut emissions. … [Just] don’t buy land in Florida.”


For further details on what’s going on in West Antarctica, check out these resources:

The two papers in question:

Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith and Kohler glaciers, West Antarctica from 1992 to 2011, E. Rignot, J. Mouginot, M. Morlighem, H. Seroussi, B. Scheuchl, Geophysical Research Letters (2014)

Marine Ice Sheet Collapse Potentially Underway for the Thwaites Glacier Basin, West Antarctica, Ian Joughin, Benjamin E. Smith, Brooke Medley, Science (2014)

Armin Van Buuren, Ancient Wood, and Ghengis Khan: This is not your father’s field research in Mongolia

We never expected this. Enkhbat had us hovering at warp speed along the Millennium Road in the northern shadows of the Khangai Mountains. Armin Van Buuren’s A State of Trance filling our rig. We were starting a new project to study the interaction between climate, fire, and forest history in the land of Chinggis Khaan and a silky voice was lifting us higher, “and if you only knew, just how much the Sun needs you, to help him light the sky, you’d be surprised. Do…do…”. We were exhilarated. The Sun was shining. This was not exactly Chinggis’ steppe. But little did we know, we would eventually be chasing his ghost.



Byarbaatar & Amy in front of Khorgo, unknowingly about to meet Chinggis’s ghost. Photo credit: Enkhbat.

After about a day’s travel we started passing the Khorgo lava field. Amy asked, “What’s that?” Neil had forgotten about this landmark despite having walked upon it 10 years prior. It is a ~30 km2 lava field with old trees on it. Gordon Jacoby, Nicole Davi, Baatarbileg Nachin, and others had sampled in the early aughts and put together a ca 700 yr long drought record from Siberian larch. Neil relayed this information to Amy and she said that we should sample on it knowing that a 2,000 yr long record in the American Southwest had been produced on a similar landscape feature. We had a tight schedule, but as we drove out to the western edge of the Khangai’s, sampled sites, witnessed a sheep in the dying throes of a brain worm infection, got snowed on, and then sweated in much warmer temperatures, we decided it was worth the time to see what was out there. Little did we know.

By the time we arrived to start sampling, Neil was getting sick (we learned days later that Neil was coming down with tonsillitis) and we were on fumes from some bone-challenging swings in the weather. Amy pushed on during the first day with Byarbaatar and Balginnyam. The found a pile of dead horse bones and couldn’t get the chainsaw running stopping them from acquiring samples from downed, dead trees. It felt almost hopeless.

We summoned our strength the next day and explored a new section of the lava field. Soon after getting out there we starting seeing Siberian pine, a tree Neil hadn’t seen on his first visit and hadn’t been sampled previously at this site. We decided that after our fire history collection we would sample some pine trees just to see what They might have to say.



The Logo Tree: The Siberian pine that clued us into the possibility that there might be something extraordinary on the Khorgo lava field. Photo credit: Amy Hessl

As this collection wasn’t priority, these samples sat until late January of the following year. Here is the first email of the discovery (partially redacted for some sensitive language).


The sample “locked in and said the inner ring i measured was 1235…whoa! that was cool b/c i started a good bit from the pith…. i race back to me scope and measuring stage…..make mistakes. going too fast. fix the mistakes…..the PITH is 1142!!!!

yes, i can see the yr Chinggis was born. i can see the yr he died. i can see the yrs Mongolia rose to rule Asia!

this has been our Holy Chinggis during the entire Mongolian project.

this is totally hot censored.


ps – i guess we are going back to Khorgo, huh?”



KLP0010a – the first sample of Siberian pine from the 2010 Khorgo lava collection to break the 1200s. The pith is 1142 CE (Common Era). Photo credit: Neil Pederson

We secured funding and we went back to Khorgo in 2012 with a bigger crew and one goal in mind – collect more wood.

We cannot believe what we have found.

For centuries, common wisdom held that the Mongols were driven to conquest because of harsh conditions – drought. Our new record, dating back with confidence to 900 CE (Common Era), indicates the opposite. After the unification of the Mongols, Chinggis Khan, you know him as Ghengis Khan, led his army from Northern China in 1211 to the Caspian Sea in 1224 CE. Our new record in PNAS indicates that it was consistently wet from 1211-1225, a period we are calling the Mongol Pluvial (look for an open access version of this paper here or contact Amy or me). No years during this period were below the long-term average, which is a singular rare run of moisture conditions in our 1,100 year long record. Independent tree-ring records over extra tropical Asia also indicate that this period was warm.

On the cool semi-arid steppe of Central Asia, water is life and in those days, water was energy. The Mongol diet is heavily based on the meat of grazers. Their mode of transportation was the short, but Pheidippidic horse. So, for food and for travel, grass is life. Grass is energy. An abundance of moisture would seem to provide the horsepower for the rapidly growing Mongol Empire. The Mongol soldier had five steed at their disposal. With a large army, that quickly translates into a huge herd and a huge need for grass.

Our tree-ring record suggests that the grasslands of central Mongolia were likely productive. They strongly agree with satellite estimates of grassland productivity. Going back in time, then, the trees would suggest the Mongol Empire during its rapid expansion was sitting in a sea of grass, a sea of energy, a potential abundance of life.

That is our hypothesis, anyhow, and something we will test in the coming years with historical documents, environmental records from lake sediments, more tree rings, and ecological modeling experiments.

While this record speaks to a rapid transformation of Eurasian culture during the 13th century, it also speaks about an abrupt transformation in Mongol culture today. Towards the end of our tree-ring record we see a prolonged drought from the end of the 20th century into the beginning of the 21st century. This drought followed the wettest century of the last 11 and occurred during the warmest period of the last 1,100 years in Asia. The abrupt transition in the environmental conditions, a transition that saw hundreds of lakes and wetlands disappear from the landscape, occurs during the transition from a more agriculturally-based economy to a more urban-based economy. These severe conditions, in combination with some harsh winters, killed millions of livestock and are thought to be one trigger of a mass migration of Mongols from the countryside into the capital of Ulaanbaatar.



Ulaanbaatar in 2006. The homes on the far hills likely reflect climatic and economic refugees moving from the countryside into the city. Photo credit: N. Pederson

Though we cannot connect this heat drought to climate change (though maybe we kind of can), warming temperatures have stacked the deck towards higher evaporative demand, so even if the amount of precipitation remains the same, high temperatures will generate a more intense drought. That’s what we observed in the early 21st century and based on past moisture variation in Mongolia and future predictions of warming, we would expect to see similar events in the future.

From Armin Van Buuren to Chinggis Khaan to Armin Van Buuren again. We had no clue of how Summer 2010 would light the sky.*




* this post was requested by a media outlet so they could have the ‘author’s voice’ on this discovery. That version was ultimately sanitized for your protection. Here it is unadultered.



Categories: TRL

Long lines and lots of instruments

Sugar - Tue, 03/25/2014 - 11:38
If you want to image the Earth’s crust and upper mantle with seismic data, you need to record the arrival of seismic waves that have propagated down to, in our case, depths of up to ~30 km.  These deep-diving phases travel quickly through the denser, higher velocity rocks of the lower crust and upper mantle, and they arrive back at the surface ahead of shallower phases at long source-receiver offsets (see video below).  

To record these lower-crustal and upper-mantle phases as “first arrivals”, where they are not obscured by the arrival of energy from shallow paths, we use long lines.  Long lines mean lots of receivers and lots of driving to deploy and recover these instruments.  We could have used lots of sources instead, but the blasts we used to get seismic energy into the lower crust and upper mantle in this experiment take a lot of time and money to setup.  Receivers are much cheaper, so we used a lot of them.  (For similar wide-angle/long-offset work at sea, airgun sources are cheaper than putting seismometers on the seafloor, so we use many shots and a smaller number of receivers out there.)

This time-lapse video shows Team 13 of 14 recovering 89 of the 1200 total short-period seismograph stations from where our line crossed Fort Benning, near the northwestern end of the line.

Nathan Miller, LDEO

Deploy in the rain, recover in the sunshine…

Sugar - Tue, 03/25/2014 - 00:32

Weather map during deployment.
When the time came to install our 1200 small seismographs across Georgia at the flagged positions, the rains came….   A lot of rain.  During our first deployment day, we received 1-2 inches of rain, and another wave of rain clouds came through on Day 2 (check out map). Roads that used to be easily passable became mudholes or were flooded with water. All-wheel-drive vehicles and drill rigs alike got stuck, and a few station locations could only be reached on foot. Our hard-working field crew labored in the rain digging holes and deploying seismometers.  Vehicles, equipment and people were covered in the famous Georgia red clay (and other muds and sands of Georgia and northernmost Florida). Adding insult to injury, problems with the programming of some of the instruments meant that we actually had to pick up and redeploy many of them. It was a mudbath.  Nonetheless, our field crew managed to deploy 1200 seismometers across Georgia by Tuesday at sundown. It was an impressive show of endurance, and an inspiring display of positivity given the number of people that were still smiling and upbeat at the end of it all. 
A couple of days later, after our seismic shots, it was already time to pick up the instruments, and the weather changed completely.  The sun shined on SW Georgia, and we picked up almost every last seismometer in just one day under blue skies….  
Donna Shillington, LDEO

Random Pictures from the Road (and otherwise)

Sugar - Wed, 03/19/2014 - 13:43
As a follow follow up to Chastity's post, I thought a few random pictures from the road would be entertaining. I have been part of group 5 and as such responsible for the part of the line that spans from Hahira in the south to just north of Adel.

 South-central part of the seismic line. The yellow line is team 5's section.  We have been in a relatively rural part of Georgia and as a result have not encountered many locals save a few who have stopped to ask if we are ok. However, we have seen quite a few interesting things that are quite out of the ordinary (to me at least).

Friendly Muscovy duck.Rocks in a stream bed with associated pink spongy material (?)
Spanish moss.Linguoid (current) ripples on a washed out road. We have also seen quite a few old abandoned farm houses in various stages of aging...

At least 10-15 dogs were standing guard at this house, including about 8 puppies.

Caroline making some new friends.
All said we have dug 122 holes in team 5's stretch. We have also helped deploy instruments in other sections as well and while doing so have seen others hard at work.

Meghan and Nate getting it done!Along the way the cars have taken quite a beating and have actually held up pretty well. Although there have been a few instances where people got stuck, I think that the people with the toughest job will be the guys that have to detail the cars upon their return...

A more appropriate vehicle (?)And lastly here's a couple more random pictures that I thought were interesting.

The large disparity in fuel grade gas prices.
A ~perfectly leveled geophone (it's harder than you'd think).Hopefully this random selection of pictures was entertaining. Up next we will post about last night's "shots." In the meantime, I can say that they were all successful with varying degrees of excitement. The most important thing is that all of our hard work is being realized as the instruments are recording refractions from buried geology that will help us unravel some of the mystery that surrounds events that happened in this area long ago.

James Gibson, LDEO

Rain, geophones, and animals … Oh my!

Sugar - Tue, 03/18/2014 - 17:15

Chastity Aiken
Georgia Institute of Technology

Flags, Flags, and More Flags - Locating the sites for 1200 instruments

Sugar - Sat, 03/15/2014 - 23:14
Many of the SUGAR field team arrived in Americus, GA on Wednesday to start helping with the massive charge of deploying 1200 seismic instruments along the SUGAR seismic line.  The seismic line spans 200 miles from northwest Georgia to just past the Georgia-Florida border; a 4+ hour car drive from end to end!  Everyone gathered early Thursday morning on the idyllic Georgia Southwestern State campus to meet with the chief scientists and learn about the proper techniques for identifying installation sites for the seismographs (just the first step in installing the instruments).  With neon orange safety jackets, numerous maps, GPS devices, packets of official permitting documents, and heads full of safety precautions the field team split into seven two-person pairs each equipped with their own squeaky clean rental car (though they didn’t stay clean for very long!).  
The fleet of SUGAR rental cars looking clean and shiny before being driven
into the field where they undoubtedly got a little mud on their tires.
Each pair of field assistants was given a segment of the seismic line to drive and flag locations for instrument installation deemed safe both from the seismograph (i.e. dry, firm soil) and the install team (i.e. a safe distance from the road).  Given the shear distance of the seismic line, teams found themselves amid diverse backdrops from rolling farmland with overly friendly cows to buzzing residential neighborhoods to sandy stretches flanked by towering groves of Ponderosa Pine trees. 
Antonio placing a flag and using a GPS device to note the location where a
seismograph will be installed amid the sandy surroundings of a Ponderosa Pine farm.
Every team was able to flag all their sites within just two days leaving us the luxury of a sunny Saturday morning free for exploring more of our beautiful Georgia surroundings.  Next up is the actual task of installing the 1200 seismographs which will involve twice the people, six more (temporarily clean) vehicles, and of course countless exciting adventures from the field.  Happy (almost) St. Patrick’s Day from Americus!
A picturesque county road near Jasper, FL along which instruments will be deployed.
-- Natalie Accardo, LDEO

A day with the seismic source team in photos

Sugar - Fri, 03/14/2014 - 23:43
The source of sound waves for the SUGAR experiment will be a series of controlled blasts along the profile.  For each of these, we drill a 60-100 ft deep hole, place emulsion explosives with boosters and caps at the base of the hole, and fill in the rest of the hole with dirt and gravel.  Each seismic source location requires a substantial amount of work by drillers and the UTEP seismic source team.  Below, Adrian Gutierrez shows a day in the life of the source team with pictures (Donna Shillington, 13 March 2014)

Adrian Gutierrez, 13 March 14
7:30 am: Leave Georgia Southwestern State University, where we are staying, and head to the site8:20 am: Arrive at site 8:30 am: Start drilling and take geological samples every 5 ft.

9:00 am: Dyno Nobel truck arrives; load emulsion into cut PVC pipe sections that serve as a holders for emulsion.
9:30 am: Surprise visit from other scientists on the project9.50 am: Setting up the booster in the emulsion.11.20 am: Loading the explosives into the drill hole12.00 pm: Drill crew starts removing their equipment12.45 pm: Tagging the charges and plugging the hole3.15 pm: Move onto the next drill site.Nighttime: Finally back to the dorm.

Arrival of the seismic equipment!

Sugar - Tue, 03/11/2014 - 19:57
Boxes with seismographs and other equipment
During this project, we will deploy 1200 small seismographs along a 200-mile-long (300-km-long) profile across Georgia.  All of these seismographs were shipped to Georgia from Socorro, New Mexico. This is the headquarters of the Incorporated Research Institutions for Seismology (IRIS) Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL), a facility that provides seismic instrumentation to US researchers.  It takes a lot of boxes to hold all 1200 seismographs and the associated equipment and tools.  There are 15 seismographs per box, so that's 80 boxes alone without counting boxes for geophones, etc. 

Fortunately, we have a lot of space! Our field headquarters is located in a historic gym on the campus of Georgia Southwestern State University in Americus, GA.  Faculty and staff at GSW have been extraordinarily generous with their time and expertise. They are allowing us to use the Florrie Chappel gym as our base of operations, and they have helped us enormously with Georgia geology and logistics coordination, handling our huge shipment of equipment and supplies, housing on the campus (many of us are staying in one of the dorms!), setting up the gym with internet access, power, and tables, and much, much more. Today, they moved all of the boxes with our seismic equipment from the shipping warehouse to our field headquarters in the gym. I can sense that all of our seismic instruments are itching to be deployed....
Pallets waiting outside the Florrie Chappell gym
Donna Shillington
11 March 2014

More preparations: mini seismic experiments

Sugar - Mon, 03/10/2014 - 11:31
A geophone in grass, awaiting sound waves.

To prepare for our big seismic experiment, we have collected a couple of miniature seismic datasets.  The shallow geology varies substantially along our profile and is very important for planning the depth of drilling and size of our seismic sources. In particular, we need to determine the depth to a limestone layer in a few places.   The same seismic method that we will use to understand the deep geological structures beneath Georgia can also be used at a smaller scale to examine layering in the upper ~100 ft (~30 m) beneath the surface. We recorded the data on 24 geophones attached to a 230-ft-long (70-m-long) cable.  The source was a modified shot gun that looks like a pogo stick.  We drilled small holes in the ground, loaded the gun and stuck it in the hole. To limit the kickback, we weighted the gun down with a metal plate topped by two heavy jugs filled with sand. Hit the plate with a mallet and – BANG – a seismic source! Not a bad way to spend a sunny Sunday!

Check out Dan firing the seismic source...

Donna Shillington
9 March 14

Laying the groundwork

Sugar - Wed, 03/05/2014 - 22:56

We have just arrived in sunny Americus, GA from the cold north to ramp up for the SUGAR project. The peaceful, pastoral landscapes of southern Georgia mask geological structures created by a series of dramatic events that were central to the formation of the North American continent.  During SUGAR, we will use sound waves to image these geological structures.   Less than 2 weeks from now, we’ll deploy 1200 small seismographs along a 200-mile-long line that extends from north of Columbus to south of Valdosta with the help of a cadre of students from across Georgia and beyond. These instruments will record sound waves generated by a series of controlled blasts in deep drill holes.

Spanish moss lined trees along our transect south of Valdosta
Collecting these data will involve a week of intense work by >30 people. However, just laying the groundwork for this effort has already required a long list of (sometimes novel) tasks.  When we conceived of this project, we drew a couple of straight lines on a map that would enable us to capture the geological features that we wish to study: the South Georgia Basin, the Suwanne Suture, and frozen magmas from the huge Central Atlantic Magmatic Province.  In reality, we must create this line by knitting together a patchwork of roads.  During a couple of planning trips, we bumped along on dirt roads, cruised county lanes, and zoomed down state highways mapping out the best route. 

Dan and Steve scouting our route. Our seismometers will line county and state roads across southwestern Georgia, and both seismometers and seismic sources will cross private properties. Identifying private landowners to request permission has transformed us into detectives. In most cases, the name and address of the owner are easily found on the tax assessor's website for each county.  But actually getting in touch with people is not so easy! We mailed letters. We put flyers directly into people’s mailboxes. We searched for phone numbers online and left messages (sometimes multiple messages…). We found websites and email addresses for companies, and sometimes wrote to people about our project through website forms (including those for a bank, a dentist's office and a website selling organic beef!).  Happily, once we made contact, individuals and companies have been very welcoming and graciously granted us permission – southern hospitality in action!  A litany of other preparations have already been completed or are currently underway. Drilling of the holes for seismic sources has just begun, and the seismometers will arrive very soon. We are definitely ready for the transition from preparing to doing....
Donna Shillington
5 March 2014

The Story at the Bottom of the South China Sea

Opening the South China Sea - Mon, 02/10/2014 - 10:17

We have drilled 2,600 feet below the sea floor and in another 500 feet, will reach the crystalline igneous basalt of the ocean crust. Though finding the age of the basalt is our main aim, the thick sediments that overly the crust also have a story to tell. As the sediments build up over time, they record the geological and climate history of the region.

There are the muds, silts, and sands, shaken loose from shallower depths and transported by gravity down-slope to the deep basin, where our first drill site is located. Ultimately, these sediments come from erosion of the surrounding land, and in this tectonically active part of the world, there is a lot of erosion going on. The island of Taiwan, for example, is being tectonically uplifted at a rate of about 0.2 inches per year, and is being eroded at about the same rate. This may not sound like much uplift, but imagine a world without erosion, Taiwan would stand 12 miles high after 4 million years. All that eroded rock ends up on the seabed, and some of it may find its way to our site.

There are the tiny shells of foraminifera and coccolithophores (familiar to us as chalk, in their pure rock form). They form a continual rain from the sea surface, and build up slowly but steadily on the seabed. The overturn of marker species shows us the age of the sediments, and their chemistry carries a record of ocean temperatures in the past.

Finally, there are volcanic sediments – from thin ash layers from distant volcanoes, to thick beds containing coarse chunks of rock exploded from nearby volcanoes. The close volcanoes are no longer active, and some have sunk beneath the sea to become seamounts. We will know from the depth of these beds in the sediment succession when the volcanoes erupted and for how long they were active.

This diversity means there is always something new and interesting to see in each 33-foot-long core that comes up from the sea bed, each another chapter in the geological history of the South China Sea. Among the 32 scientists on board, we have specialists in sedimentology, micropaleontology, volcanology and other fields. We are an international group; about half of us hail from China, a quarter from the U.S, and the rest from Australia, Brazil, France, Switzerland, Japan, Taiwan, and the Philippines (so there’s a good mix of music in the core laboratory – very nice). And that’s just the science party – the ship’s crew is almost as diverse.

Drilling Deep into the South China Sea’s Past

Opening the South China Sea - Tue, 02/04/2014 - 10:56

SCS mapFive days after leaving Hong Kong, the JOIDES Resolution is on site and drilling into the muds and silts of the South China Sea. The expedition’s main objectives are tectonic in nature, and I’m not really a tectonicist (I’m on board for the borehole logging), so for me this cruise is a crash course in the geological history of this area.

The origin of the ocean crust under the South China Sea is enigmatic, and there is ongoing scientific debate about which tectonic forces pulled apart the crust here to form the basin. In one hypothesis, the collision of India into Asia that built the Himalayas and pushed out Indochina to the southeast had the collateral effect of causing extension to form the South China Sea. The leading rival hypothesis says that the extension resulted from slab-pull from subduction at the southern edge of the basin (Borneo and Padawan). Of course, there are theories that mix the two, as well as minor-party candidates (plumes!).

The expedition aims to test the competing hypotheses by dating the earliest ocean crust (at the northern edge of the basin) and the youngest ocean crust (close to the now-inactive spreading center). If the age interval of sea floor spreading matches the age of the extrusion of Indochina (lets say 35 to 16 million years ago), then the Indochina extrusion hypothesis gains support; but if we find different ages, other hypotheses will move up the leader board. The debate and this expedition add to our understanding of the basic forces that shape the Earth’s surface.

Until now, the dating and interpretations rely on magnetic sea floor anomalies and other geophysical surveys. We will date the rocks directly for the first time, by argon-argon dating of the basalt that forms the ocean crust, and by the age of the sediments sitting on the basalt. The tricky part is that the basalt lies under 950 meters of sediments at the first site, and under 1850 meters at the second. To drill to this depth and bring back 100 meters of basalt is challenging to say the least, but there is a highly experienced drilling crew on board, so we are in with a shot. I’ll let you know how we get on!

Explore the Arctic Ocean With ‘IceTracker’

American Geophysical Union Fall Meeting - Tue, 12/10/2013 - 19:46

pfirman icetrackerBy Stephanie Pfirman

This week, we are launching a test of “IceTracker”—a tool that allows users to see the trajectories of Arctic sea ice forward or backward from any day between 1981 and 2012, as well as other data including sea-ice speed, air temperature, water depth and the age of the sea ice along the track. We think IceTracker will be useful not only for Arctic research and policy, but for bringing the Arctic sea ice alive for students and the general public.

Researchers interested in climate and arctic dynamics will be able to assess the origin and melt location of sea ice, and seasonal and year-to-year variations in drift trajectories from specific locations. They will also be able to look into the transport of sediment or contaminants on or in the ice; this might for instance shed light on potential trajectories of oil spilled in ice-covered waters, or habitat changes that might affect the foraging patterns of polar bears or other creatures.

The IceTracker might eventually be used to consider future management options in the Arctic. Among these: projecting where declining sea ice is likely to persist, providing future potential refuge for threatened arctic creatures (an idea that got a lot of attention at AGU in 2010). It can even be used to recreate historical events; we used it to figure out where Fridtjof Nansen and his crew would have drifted had they frozen their ship into the ice today, rather than during their famous 1893-1896 trans-Arctic drift.

IceTracker is an excellent inquiry-driven research environment for any student with access to a computer. Teachers can use the IceTracker in guided exercises, or let students work on their own to learn about ice dynamics, interannual variability and climate change. For instance, we have set up team competitions where students can vie to be the first to reach the North Pole by drifting with the ice, or to make it out alive through Fram Strait. By exploring the Arctic in this way, the IceTracker lets students do their own sampling of a real-world non-linear system. They can see how diminished ice cover has changed ice speed, and demonstrate for themselves how initial conditions can affect ice movements much farther down the line.

Others might use IceTracker to consider historical conditions in planning adventure expeditions, or to visualize changing conditions for Arctic wildlife.

We will present IceTracker at AGU on Friday, Dec. 13, at the Moscone South poster hall (look for abstract number C15A-0490). You can also try running trajectories yourself at our beta testing web site: We would appreciate ideas on how to make it better. Send feedback to:

The project has received funding from the U.S. Office of Naval Research and the U.S. National Science Foundation.

Some further resources:

Fowler, C. and M. Tschudi. 2003. Polar Pathfinder Daily 25 km EASE-Grid Sea Ice Motion

Vectors. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center.

Pfirman, S., G.G.Campbell,B. Tremblay, R. Newton, W. Meier. New IceTracker Tool Depicts Forward and Backward Arctic Sea Ice Trajectories AGU San Francisco, December 2013. C51A-0490.

Pfirman, S., C. Fowler, B. Tremblay, R. Newton, 2009a. The Last Arctic Sea Ice Refuge. The Circle, 4:6-8.

Pfirman, S., B. Tremblay, C. Fowler, 2009b. Going with the Floe: An analysis of the epic expeditions of Fridtjof Nansen and Sir Ernest Shackleton. American Scientist, 97: 484-493.

Stephanie Pfirman is Hirschorn professor of environmental science at Barnard College, and an adjunct senior scientist at Lamont-Doherty Earth Observatory.

Explore the Arctic Ocean With ‘IceTracker’

pfirman icetrackerThis week, we are launching a test of “IceTracker”—a tool that allows users to see the trajectories of Arctic sea ice forward or backward from any day between 1981 and 2012, as well as sea-ice speed, air temperature, water depth and the age of the sea ice.

AGU 2013: Social Science Perspectives on Natural Hazards

American Geophysical Union Fall Meeting - Mon, 12/09/2013 - 14:16

Courtesy Erik


Are you attending the American Geophysical Union (AGU) meeting this week in San Francisco? Are you interested in hearing from social scientists about Natural Hazards? The Center for Research on Environmental Decisions (CRED) will be there to answer your questions. Below is a schedule of sessions that CRED researchers are speaking at or convening.

We hope to see you there. If you can’t be at AGU in person we encourage you to livestream the sessions here. 


Katherine Thompson, CRED PhD candidate, “The Problem with Probability: Why rare hazards feel even rarer”

Thompson_bioTuesday December 10, 1:55-2:10 PM PST, 2000 (Moscone West)
Session: Why Should We Talk About What We Don’t Know? Implications of Communicating Scientific Uncertainty II
How is probability of natural hazards events actually used by decision makers? The presentation will make recommendations on presenting probabilistic information to best take advantage of people’s tendencies to either amplify risk or ignore it, as well as recent findings that may shed light on ways that the negative effects of uncertainty can be mitigated.



David H. Krantz, CRED co-director, “Coordination of Individual and Organizational Planning for Natural Hazards”
krantz_bioThursday December 12, 1:40-1:55 PM PST, 3002 (Moscone West)
Session: Climate Change Effects on Natural Hazards: Science, Communication and Policy I
Dave Krantz will explore the four different kinds of decision aids needed to improve natural hazard planning: mechanisms that support horizontal dissemination of plans, mechanisms that support vertical dissemination, mechanisms for examining goal conflicts and reducing these through plans that take others’ goals into account, and mechanisms for examining belief conflicts.


Poster session, “Climate Change Effects on Natural Hazards: Science, Communication and Policy II Posters 
8:00 AM – 12:20 PM PST; Hall A-C (Moscone South)
Convener(s): Kelly Klima (Carnegie Mellon University) and Courtney St John (CRED, Columbia Earth Institute)



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