Possible Second Crater Linked to Dinosaur Extinction

It is believed that about 65 million years ago, an asteroid entered Earth's atmosphere and slammed down into the Yucatan Peninsula, and in doing so, brought an end to the reign of the largest animals which ever roamed the Earth: the dinosaurs. The crater is called Chicxulub. Now, researchers are looking at another location off the coast of Maine, near Small Point, where there is evidence of another impact. It could well be that the dinosaur killing asteroid was not alone when it slammed into the Earth.

USGS Image Small Point, Maine

The two people looking at this event are Dominic Manzer, an engineer from NASA, and Dallas Abbott from the Earth Observatory at Columbia University. Both admit that their finding are in the preliminary stages, and they as yet have not found strong evidence to support their theory. Abbott and Manzer presented their initial findings on what they are calling the Small Point crater late last week at a regional meeting of the Geological Society of America in Halifax, Nova Scotia.

The two scientists were studying the magnetism of the crust around the Gulf of Maine when they noticed an anomaly. They detected a very large, and as yet, unexplainable, difference in the magnetism of the crust from the Gulf area from that of the surrounding areas. Additionally, there is an arrangement of ridges on land that channels rivers and streams in Maine and Massachusetts along arcs that might be ridges of the western part of an eroded crater.

Other scientists are less optimistic that this is indeed an impact crater. David Kring of the Lunar and Planetary Laboratory at the University of Arizona. Insists that there is no evidence of an impact. King believes that if there were a second impact, there would be a second blanket of debris at the K-T Boundary, which there is no evidence of. The K-T boundary marks an interval of abrupt change in Earth's history 65 million years ago at the end of the Cretaceous (K) Period and beginning of the Tertiary (T) Period. Geologically, it is marked by large levels of Iridium, a very rare chemical on Earth, found mostly at the core. There are however, large amounts of Iridium in comets and some asteroids. It was the presence of Iridium which first led scientists to think that there had been a major impact at the K-T boundary.

If Abbott and Manzer are correct, this crater is even larger than the Chicxulub crater. To prove this impact is related to that of Chicxulub, the two will need to get age data to confirm it, and that won't be an easy task. Glaciers from the past Ice Ages would have scoured away all of the rock evidence from an impact long ago. Slim though any evidence might be, Abbott is not giving up any time soon. Rather, she intends to look further south in the Marth's Vineyard area off Cape Cod. There, she is hoping to find impact related rocks of the right age that might have been deposited after the glaciers retreated.

Menzer believes the possible scenario of the event 65 million years ago was that the asteroid or comet broke up before hitting Earth and pieces of the larger body slammed down in a rapid fire line of craters. Such a line of craters has been spotted on other Solar System bodies. The missing pieces though, and what the two scientists will search for this summer, are impact related rocks to prove it was an impact event. The rocks can then be age dated to pinpoint just when the impact took place.

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