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The Thrill to Drill in the Chill Julie Brigham-Grette, Martin Melles, Pavel Minyuk and Christian Koeberl EARTH Vol. 55 (No. 7), p. 48

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ATHE AMERICGAN GEOLOGIICAL INSTITUTE akd y h ylo sa. lsa s o h es, cos the seas. across Chukchi and Bering east, the to is Alaska star. yellow the by is marked drilled team the where Russia, Chukotka, in location The in the The 48 best-preserved impact cratersbest-preserved impact 

EARTH July 2010 Chill Thrill to Probing oneofEarth’s Drill to learnsecrets of Arctic change Arctic N The crater The about change. Arctic region to drill into these sediments to see what we could learn the last 3.6 million years. Last year, we traveled to this remote best stratigraphic records of high-latitude climate change over the of one provide may impact the since the lake that of bottom in collected that sediments The water. with filled then Koeberl Melles, PavelJulie Brigham-Grette, Martin Minyuk andchristian Continued on page 50 page on Continued ally through the ground, compressing the volcanic rocks and mostly splashedoutside the crater rim. A shock wave material spread out radi- melted The world. whole the of arsenal nuclear combined the than larger magnitude of orders was the top layers of rock. The energy released during this impact volcanic rocks, almost instantaneously melting and vaporizing 30 to 15 Cretaceous-agedthe surfaceof the secondhit kilometersper about at traveling diameter in kilometer 1 asteroid about an El’gygytgyn, of case the In minutes. few a just in over is events of sequence main the — process geological environment. delicate a in event with other planets), but also about the effects of a large impact about shocked volcanic rocks (which is useful for comparison informationunique gain to us allows only not thus study Its cra- impact ter known on only Earth that has the formed in siliceous alsovolcanic rocks. is It sediments. lake buried underneath still currently is which center, the in portion raised location. geographic crater’sstrategic the and of age because principally potential scientific untapped holds El’gygytgyn Lake but world, thethroughout uncommon not are systems lake deep Large, change. climate past and processes impact El’gygytgynuniqueaboutopportunitymorelearnoffers a to road. by cessible inac- is — El’gygytgyn Lake now — Crater ghee-git-gin) el the Arctic Ocean and the Bering Sea, El’gygytgyn (pronounced Circle in central Chukotka, on the continental divide Arctic between the of north kilometers 100 At location: remote its of on the planet. But the crater has hardly been studied because it left behind one of the best-preserved large impact structures The formation of an impact crater is a surprisingly rapid rapid surprisingly a is crater impact an of formation The a with crater impact “complex” classic a is structure The u bcue t s o eoe n wl-rsre, Lake well-preserved, and remote so is it because But The impact occurred in a region of rolling, low mountains; n 8klmtrwd hl i te rud that ground the in hole 18-kilometer-wide an formed impact the minutes, Within Russia. ern northeast- today is what asteroidin Earth into large slammed a ago, years million 3.6 early www.earthmagazine.org

All: El’gygytgyn International Science Crew Above: Panorama of the drill site in February 2009. Bottom: Schematic sequence of the formation of a complex impact crater like El’gygytgyn.

• Moment of impact: As the asteroid hits the ground Projectile with a velocity of several tens of kilometers per second, a shock wave is generated that penetrates Shock wave radially into the ground and compresses the rocks.

• A few seconds after the impact: The shock wave Contact/compression stage proceeds into the ground and a release wave moves back toward the surface, causing material to flow downward and outward, which leads to the excava- Vapor Ejecta curtain tion of the crater. Early in the impact phase, both the projectile and some rocks are vaporized and melted, lining the cavity of the crater. Melt • A few tens of seconds after the impact: The maximum crater depth is reached. Shocked, broken (brecciated) Excavation stage Material flow and melted rocks are thrown into the air. Some of Shock wave these ejecta are deposited outside the crater, some fall back into the crater. The crater floor starts to rebound, leading to a central uplift formation.

• A few minutes after the impact: The central uplift Transient cavity has formed and is being buried by the cooling melt rocks and breccias that are falling back to Earth. The steep crater rim starts to collapse and slide into the End excavation stage/ crater, leading to a wider and shallower crater. The start modification stage formation of the crater structure is over after just a few minutes. Breccia and debris continue to fall back into the crater for a few hours. Ejecta Uplift of crater • A few years after the impact: The crater floor is now floor covered by melt rocks and fallback breccia (dark red), and rain and groundwater have formed an early crater lake (blue), and some early lake sediment Modification stage deposition has begun. The crater rim has completed its collapse.

Collapse Ejecta layer zone Central uplift

Final structure

Right: Today, El’gygytgyn Crater is filled

Diagram: Christian Koeberl, University of ; right: NASA image created by Jesse Allen, using data from NASA/GSFC/METI/ERSDAC/JAROS, and the U.S./Japan ASTER Science Team ASTER Science and the U.S./Japan NASA/GSFC/METI/ERSDAC/JAROS, from using data Jesse Allen, by right: NASA image created Vienna; of University Christian Koeberl, Diagram: with water and called Lake El’gygytgyn.

www.earthmagazine.org EARTH July 2010  49 Top right: Truck at the drilling platform. Middle: In these remote work areas, self-reliance and a good set of tools are mandatory. All of the tools were labeled in Russian and English. Bottom: Flags lined the road from camp to the drill site.

”The Thrill to Drill” continued from page 48 causing irreversible changes in the structure of the minerals in those rocks. Shocked minerals, high-pressure minerals and melted rocks from this shock wave are still preserved at the impact site today. As a result of the shock wave, the layers of rocks in the main crater were broken, melted and thrown many tens of kilometers in the air. Some of the material fell back into the crater — even as the bottom of the crater rebounded from the impact to form what’s known as a central uplift. Within tens of seconds, a mountain of rock about 1.5 kilometers in height and several kilometers in diameter was uplifted. As the rocks that were thrown into the sky rained back down, they buried the central uplift and formed a layer of different types of rocks (called suevites), including some impact melt or glass inclusions, that is hundreds of meters thick, maybe even a kilometer or two. For a few thousand years after the violent impact, heat from the event fueled hot springs and hydrothermal waters that circulated in the fractured rocks. Only after the fractured rocks from the impact, called breccia, cooled was the impact phase over, giving way to a calmer post-impact history, when a lake formed on the crater floor and sediments were deposited over the next few million years, perfectly preserving the Arctic’s climatic history.

Continued on page 53

Below: Lake El’gygytgyn today. Bottom: Boya Lake in British Columbia; around the time the impact struck 3.6 million years ago, the landscape surrounding El’gygytgyn may have looked more like this. Bottom left: Kenna Wilkie; rest: El’gygytgyn International Science Crew El’gygytgyn Wilkie; rest: left:Bottom Kenna

50  EARTH July 2010 www.earthmagazine.org Both: El’gygytgyn International Science Crew www.earthmagazine.org one wanted was for a 100-metric-ton drilling system to end up lake ice that was monitored by ice engineers. The last thing any- thickened artificially of meters 2.3 of pad drill a on place took world. the remoteof areasmost the of one in site drill the to — tundrafrozen basically and snow over dragged was equipment our kilometers 90 last the over — assistance) more than 350 kilometers over snow-covered “roads” bulldozer (with driven and trucks onto loaded and inspected Pevek, In containers the Sea. were Siberian East coastthe the of BeringStraitthePevek,viato small villageRussia, locateda on equipment delivered by Siberian Rail, were transported by barge shipping containers, as well as two more containers of scientific and intoimported Russia by way Utah, of Vladivostok. City,These 6-meter-long Lake Salt from containers 16 in shipped were parts spare and mud casing, of supplies and rig drill GLAD-800 shifts. 12-hour two in inventory core and operations drilling both sustain to shore of the lake that could house and feed 40 people, enough D process logistical arduous An international funding.international with planning of years took It undertaking. logistical massive Then there was the actual drilling. Heavy drilling operations operations drilling Heavy drilling. Then there actual was the anotherchallenge.suppliesDOSECCwasourImportingOur h frt tp a t st p fed ap n h western the on camp field a up set to was step first The — in Beringia, north of the Arctic Circle in Russia — was a was — Russia Circle in Arctic the of north Beringia, in — Chukotka of center the in lake deep broad, a into rilling recordEl’gygytgyn.Lake from rewarded with the successful recovery of a complete sediment coresforresults.immediatefull the on properties physical of number a measure to us allowed have would that — projects drilling such in routine — source tion we were not allowed by Russian Customs to import a small radia- sediment cores with undue shaking and possible spillage. Also, in centralwould have Chukotka jeopardized of the the quality core halves. Moreover, the rough overland transportation issues delicatethe remotenessand naturethe drilling openthe of of initially able to open the sediment cores in the field because of calving.forseasonal Celsius in early May, when the regional caribou herds gathered degrees 4 as high as to account) into factor chill wind the ing tak- (without winter in Celsius degrees 40 minus about from about minus 30 degrees Celsius. Temperature extremes ranged at temperatures air with windy and cold Russia: northeastern for expect might you what was 2009 May to 2008 November perseveranceteam. forof the test proveda crane be to light of February by means of three languages and one Russian on the floor of the lake! And constructing the drill rig in the dim bv:“an tet a te ap Ist Te em received Pevek,Russia. from support helicopter team The Inset: camp. the at Street” “Main Above: But the challenges didn’t end with the drilling. We weren’tWe drilling. the with end didn’t challenges the But Eventually, however, our hard work and tenacious spirits were from operations during El’gygytgyn Lake at weather The EARTH

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EARTH July 2010 the tents at the drilling platform. drilling the at tents the of One Below: core. Sample Left: Christian Koeberl with a section of an impactite core. impactite an of Bottom: section a with Koeberl Christian N.C. Greensboro, in grade 8th teaches Martin rations. PolarTREC The core. the collabo- field in researcherstogether and teachers programputs cutting expedition, this on Teacher PolarTREC Foundation Science National the Martin, Tim Middle: breccias and suevites — tell us about the impact itself. impact the about us tell — suevitesbreccias and the rocks beneath the sediment — impact formations such as mation about the climate record over the last 3.6 million years, the center of the lake. While the sediment cores provide infor- region.entireArctic the in unprecedented therefore are record climate this of significance geologic and length temporal The Greenland. in drilled that than longer times 30 than more time in back record the extending further, even concept the took 2009, coreicerecords.Greenland the of portions oldest the 300,000 years — roughly three times longer back in time than record, as they contain climate data that extend back in time climate a as cores these of importance the demonstrating concept, of proof provided 2003, and 1998 in taken cores, A results Early with such clarity in an Arctic terrestrial setting.terrestrial Arctic an in clarity such with of Northern Hemisphere glacial cycles seen for the first time onset and style the on information exciting and new duce sediments. the in recorded field Earth’smagnetic the of stratigraphy paleomagneticinitial the reversalusing impact the of age much younger pilot cores. Furthermore, we confirmed the years, we see warm and cold cycles like those we saw in the at dioxideforcing. carbon foranalogue fascinatingpossible a as future climate todue especially is recovery. interval percent This 100 nearly with Pliocenemiddle warm the in lake the of history earliest the meters.207 of interval depth overrock)a melted with (breccia suevites and breccias impact various collected also we sediments lake the Beneath materials. these for sources glacial unexpected suggest units coarser of coarse sand and gravel interbedded with lake mud. These ago, albeit with lower recovery due to sequences surprising below the lake floor to the time of impact at meters 3.6 million 315 years to 100 from cores sediment collected also We ered sediments that cover roughly the last 2.6 million years. the data we had collected so far.so collected had wedata the www.icdp-online.org/front_content.php?idart=2265 . Overall, the record so far suggests that the cores will pro- million 2.6 last the covering cores the in Interestingly, A weekly of diary all drilling operations is available online We recovered sediment and rock from three holes drilled in May to 2008 November from drilled cores, main Our pilot initial Our cores. of types several drilled had We Equally exciting is that we recovered roughly 40 meters of From these three holes, at a depth of 130 meters, we recov- until early next year, our team met in May to review all review to May in met year,team next our early until published be to begin won’t results final our lthough www.earthmagazine.org Julie Brigham-Grette Brigham-Grette Julie

All: El’gygytgyn International Science Crew Both: El’gygytgyn International Science Crew Julie Brigham-Grette and Pavel Minyuk at the drill site. drill the Pavelat and Minyuk Brigham-Grette Julie Melles, Martin right: Bottom data. precipitation and perature Top right: This meteorological records station in Chukotka tem- crater impact Bosumtwi the at studies crater Recent formation. impact of understanding our refine us help will also crater the Studying Mars. on targets similar with Earth on craters impact compare to scientists allow will it impact. an by shocked are behavethey rockswhen the cores give us a unique opportunity to study how such crater on Earth that formed in silica-rich volcanic rocks, so crater.impact only the the El’gygytgyn, isof El’gygytgyn sidebar). (see cores the examine to beginning just are we labs, shared our into and Russia of out cores the getting process arduous an 2009. After May kind. this of craters of formation the and provide new insights into the climate evolution of the Arctic will cores these We hope breccias. impact and lake sediments containing cores of meters of hundreds recover to El’gygytgyn Lake at operations drilling scientific staged tists from the United States, Germany, Russia and , international partnerships, an international team of scien- of development the and planning logistical of challenging years After project. our for impetus major provided learn to hope we What weit. wantedwhy study to Hemisphere. Northern the of tion the asteroid’s impact and the onset of the first major glacia- present form. In its fact, nearly in a million years exist passed between not did Sheet Ice Greenland the and winter), the in briefly over frozen have may surface the (though Ocean was many degrees warmer, lacking summer sea ice degrees Celsius warmer than today. Meanwhile, the Arctic larch. and pines of fir,types several by coniferous forests, complete with alder, birch, hemlock, largely blanketed coasts, northernmost the to way the all forested were borderlands the Arctic instead, permafrost; the today.wastelandsnow-covered it resembles not It was of free was Russia northeastern ago, years million 3.6 change. climate past of record terrestrial since the time of impact should chronicle a long, unbroken throughout time. As a consequence, sediments accumulated glaciation continental-scale widespread, escaped have to the in Arctic landscape contiguous largest the — Beringia Pliocene the in El’gygytgyn Lake Drill”50 to Thrillpage from”The continued www.earthmagazine.org Oneaspect of the project focuses on our understanding We began drilling in November 2008 and ended in early It has seen a lot of changes since then, which is precisely When the impact occurred in the warm middle Pliocene This This has implications for . For example, continuous so is record sediment this that fact The 14 to 10 probably were temperatures annual Mean of center the in nearly located is El’gygytgyn Lake EARTH

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EARTH July 2010 and refreezing.and flooding repeated by meters two to thickened was pad the Celsius, temperatures of minus 40 degrees At section. snow-cleared a onto water lake pumped engineers ice cleared of snow by bulldozer. Then first wasfootball field a of size the about area an operations, ment equip- heavy and rig drilling the lake ice strong enough to support the on platform drill a create To causing remarkable alterations in snow cover, glacial retreat retreat cover,glacial snow in alterations remarkable causing are changes summer. These in warming moderate only with dramatically,warming been have winters decades, recent in Arctic the of much Across system. a as Earth modulate that feedbacks and forces complex the evaluating for datasets unprecedented with scientists provides — moorings ocean satellite measurements, ocean buoy networks and subsurface high latitudes — including land-based meteorological stations, change. The observational instrumentation available across the Today seas. and of rates the remarkable is undergoing Arctic to discern the rates and timing of changes to the Arctic’s land us allowing change, climate Arctic of evolution the explore delicate the ecosystem. Arctic wecourse, in are how interested such a huge impact affected temperature of the melt and many other parameters. And, of maximum the component, meteoritic a of presence possible the rocks, target the in saturation water the of influence the El’gygytgyn’sing present),we(ifmelt impact determine can shaping impact craters than previously thought. By investigat- in has rocks the playedtarget a role in much more important water of presence the that indicate West Africa in Ghana in interglacial.presentsummer, the in today during looks it as El’gygytgynLake inset: ago. Bottom years 21,000 glaciation peak Top inset: Lake El’gygytgyn as it might have looked during the last Earth’s orbit around the sun caused the ice ages of the last few region. high-latitude this in change millennial-scale and glacial-interglacial of ics dynam- and mechanisms the of information new reflecting perspective, terrestrial Arctic an time, first the for will provide, El’gygytgyn Lake from studying now are we record during the mid- to late Pliocene. The continuous depositional ago years million 3 and million 2 between sometime system eco- permafrost cold a into ecosystem warmforested a from is determining why and how the Arctic climate system evolved fidelity.and length this of recordspaleoclimate entire the in wedo nowhere Arctic have because context this in important thus is El’gygytgyn Lake planet. the cooling be solar insolation due to changes in Earth’s orbit, which should in decline long-term natural a of face the in dioxide carbon atmospheric by driven being is change modern that likely the for climate’swarming.natural of instances past to comparison reaction of point a offer cores El’gygytgyn The one: this like studies paleoclimate from come only can gases versus the climate system’s response to increased greenhouse variability natural of result the are today’s changes of much Teasing how loop. out feedback a in warmsfaster region the sun’sthe of less reflect radiation, ice and snow coveredwith longer no are that sea and land of areas As reflectivity: ing chang- like effects to due planet the of rest the than warmer example, when Earth warms, the Arctic gets three to four times in the context of polar amplification and albedo feedbacks. For ecosystems. terrestrial and rates, summer sea-ice extent and the migration of both marine But more than anything, the El’gygytgyn cores will help us Such studies are especially important, given that it seems it that given important, especially are studies Such h crs il lo lrf hw ytmtc hne in changes systematic how clarify also will cores The Among the many challenges facing the scientific community These short-term changes are important to grasp, especially www.earthmagazine.org

All: El’gygytgyn International Science Crew Both: El’gygytgyn International Science Crew History Museum. History the naturalvienna of director and austria of in viennaversity Uni- the at geochemist a is Koeberl russia. Magadan, in tute insti- research Scientific interdisciplinary northeastern the at director of paleomagnetics University the is the Minyuk Germany. at in geologist cologne a is Melles amherst. in setts Massachu- of University the at geologist a is Brigham-Grette future? the in there happen over?will What freeze to start they did why and How warmso past? the in the ultimate puzzle of the poles: Why were the solvepolar regions us help could together that record merged spatially a create us help will Antarctic the in drilling ongoing the and 2004, in drilled was which Ocean, Arctic the in Ridge cores from other scientific drill sites, such as the Lomonosov should not be studied in isolation. Comparing these cores to feedbacks. interrelated of in this transition, and Arctic how it the may be of a responder or driverrole the about more learn us help will cores tion of Earth’s axis of rotation) and tilt. We hope that these orienta- (the precession of combination some or sun) the long cycle of eccentricity (the shape of Earth’s orbit around Earth’sof cycle 100,000-year-the by dominated one to tilt million a years roughly ago from a world dominated by transitioned the 41,000-year-long Earth how about remain questions fundamental many particular, In years. million www.earthmagazine.org Stay tuned. Results will be coming soon. soon. coming be will Results tuned. Stay cores sediment these that note to important it’sFinally, University of Minnesota handled corehandledcuration. Minnesota of University Arctic operations was developed by DOSECC Inc., and LacCore- for system drilling deep The Institute. Research Antarctic and Arctic Roshydromet’s and Institute, Geological East Far the Institute, Research Scientific Interdisciplinary Northeastern the for Science and Research. The leading Russian institutions include Branch, Russian East Foundation for Basic Research, Far and the Austrian Sciences Ministry of Academy Russian the Potsdam, and Research, Alfred Wegener Institute, GeoForschungsZentrum- Education for Ministry Federal German the Programs, Polar of National Science Foundation Earth Sciences Division and Office funded by the International Continental Drilling Program, the U.S. support and Funding The drilling team. Above: Drilling platform. Drilling Above:team. drilling The The The Lake El’gygytgyn Drilling Project is an international effort EARTH

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