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December 09, 2013

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Huge underwater cliff may hold clues to dinos’ fate

Dec. 9, 2013
Courtesy of Mon­te­rey Bay Aquar­i­um Re­search In­sti­tute
and World Science staff

Clues to what hap­pened to the di­no­saurs may lie in the wall of a Grand-Can­yon-like cliff un­der the Gulf of Mex­i­co, ge­ol­o­gists say.

Some 65 mil­li­on years ago, sci­en­tists be­lieve an as­ter­oid or com­et crashed in­to a shal­low sea near what is now Mex­i­co’s Yu­catán Pen­in­su­la. The re­sult­ing fire­storm and glob­al dust cloud killed off many land plants and large an­i­mals, in­clud­ing most of the di­no­saurs.

Base image: Google Earth


At this week’s meet­ing of the Amer­i­can Geo­phys­i­cal Un­ion in San Fran­cis­co, re­search­ers plan to pre­s­ent ev­i­dence that rem­nants from the im­pact are ex­posed along the Cam­pe­che Es­carp­ment—a gi­ant un­der­wa­ter cliff in the south­ern Gulf of Mex­i­co.

The im­pact cre­at­ed a huge crat­er about the size of New Jer­sey—un­for­tun­ate­ly al­most in­vis­i­ble to­day, bur­ied un­der de­bris and ma­rine sed­i­ments. 

Al­though some of the fall­out has been found in rocks around the world, lit­tle re­search has been done on the rocks near the im­pact site, in part be­cause they’re so deeply bur­ied, ge­ol­o­gists say.

But last March, re­search­ers led by Char­lie Paull of the Mon­te­rey Bay Aquar­i­um Re­search In­sti­tute in Flor­ida made the first de­tailed map of the Cam­pe­che Es­carp­ment. They used in­stru­ments known as mul­ti­-beam sonars on the re­search ves­sel Falkor, op­er­ated by the Palo Alto, Ca­lif.-based Schmidt Ocean In­sti­tute. The maps have been in­cor­po­rat­ed in Google Maps (maps.­google.­com) and Google Earth (earth­.­google.­com).

This close-up image of the Campeche Escarpment from the 2013 sonar survey shows a layer of resistent rock that researchers believe may contain rocks formed during an impact 65 million years ago. (Image: (c) 2013 MBARI)


Paull has long sus­pected that rocks as­so­ci­at­ed with the im­pact might be ex­posed along the es­carp­ment, a 600-km (370-mile) long cliff just north­west of the Yu­catán. 

Nearly 4 km (2.5 miles) tall, it’s one of Earth’s steep­est and tallest un­der­wa­ter fea­tures, com­pa­ra­ble to one wall of the Grand Can­yon—but deep un­der­wa­ter.

As with the can­yon, sed­i­men­ta­ry rock lay­ers ex­posed on the face of the es­carp­ment pro­vide a se­quen­tial rec­ord of events over mil­li­ons of years. Based on the maps, Paull be­lieves that rocks formed be­fore, dur­ing, and af­ter the im­pact are ex­posed along dif­fer­ent parts of the cliff.

Just as a ge­ol­o­gist can walk the Grand Can­yon, map­ping lay­ers of rock and col­lect­ing rock sam­ples, Paull hopes to one day per­form ge­o­log­ic “field­work” and col­lect sam­ples along the es­carp­ment. Only a cou­ple of dec­ades ago, the idea of per­forming large-scale ge­o­log­ical sur­veys miles un­der­wa­ter would have seemed a fan­ta­sy, he said. But such map­ping has be­come al­most rou­tine us­ing un­der­wa­ter robots.


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Clues to what happened to the dinosaurs may lie in the wall of a Grand-Canyon-Like cliff under the Gulf of Mexico, geologists say. Some 65 million years ago, scientists believe an asteroid or comet crashed into a shallow sea near what is now Mexico’s Yucatán Peninsula. The resulting firestorm and global dust cloud killed off many land plants and large animals, including most of the dinosaurs. At this week’s meeting of the American Geophysical Union in San Francisco, researchers plan to present evidence that remnants from the impact are exposed along the Campeche Escarpment—an immense underwater cliff in the southern Gulf of Mexico. The impact created a huge crater about the size of New Jersey—unfortunately almost invisible today, buried under debris and marine sediments. Although some of the fallout has been found in rocks around the world, little research has been done on the rocks near the impact site, in part because they are so deeply buried, geologists say. But last March, researchers led by Charlie Paull of the Monterey Bay Aquarium Research Institute made the first detailed map of the Campeche Escarpment. They used instruments known as multi-beam sonars on the research vessel Falkor, operated by the Schmidt Ocean Institute. The resulting maps have recently been incorporated in Google Maps (maps.google.com) and Google Earth (earth.google.com). Paull has long suspected that rocks associated with the impact might be exposed along the escarpment, a 600-km (370-mile) long cliff just northwest of the Yucatán. Nearly 4 km (2.5 miles) tall, it’s one of Earth’s steepest and tallest underwater features, comparable to one wall of the Grand Canyon—but deep underwater. As with the canyon, sedimentary rock layers exposed on the face of the escarpment provide a sequential record of the events that have occurred over millions of years. Based on the maps, Paull believes that rocks formed before, during, and after the impact are exposed along different parts of the cliff. Just as a geologist can walk the Grand Canyon, mapping layers of rock and collecting rock samples, Paull hopes to one day perform geologic “fieldwork” and collect samples along the escarpment. Only a couple of decades ago, the idea of performing large-scale geological surveys miles underwater would have seemed a fantasy, he said. But such mapping has become almost routine using underwater robots.