Well-preserved layer of material ejected from Chesapeake Bay meteor-strike discovered

Aug 23, 2004

People in Georgia's Dodge and Bleckley counties have for years picked up small pieces of natural glass called "Georgiaites," which were produced by an unknown asteroid or comet impact millions of years ago. Just where these small, translucent green objects came from, however, was unclear.

Now researchers at the University of Georgia, studying a kaolin mine in Warren County, have found a layer of tiny grains, which indicate that the grains and the Georgiaites were products of a recently discovered impact that left a huge crater beneath the waters of the Chesapeake Bay. "We knew we had these tektites here, but we'd never found them in place," said Michael Roden, a geologist and part of the research team. "We believe this layer is further evidence that the Chesapeake Bay impact was an enormous event with widespread consequences."

The research was published in the August issue of the journal Geology.

The work was spearheaded by UGA graduate student Scott Harris (now with Brown University) in collaboration with Roden, Paul Schroeder and Steven Holland of UGA, Ed Albin of Fernbank and Mack Duncan of J.M. Huber Corporation.

Tektites are brown to green glassy objects, generally small and rounded, and thought to be of extraterrestrial origin. The only other state in the United States where tektites have been found in abundance is Texas. Some 1,700 have been found in Georgia to date, and potassium-argon geochronology has dated them to around 35 million years of age.

The Chesapeake Bay impact crater was only discovered about a decade ago, but before the current discovery, there was no known deposition layer from it extant, and it was unclear whether Georgiaites were the result of the cataclysmic collision of the Chesapeake Bay bolide with the Earth. ("Bolide" is a generic term for an impacting body.)

The now-unused kaolin mine in Warren County where the discovery was made was near the sea's edge in ancient times. This former shore, now across the central part of Georgia, is more or less coincident with the Fall Line, and marks the place where ancient seas lapped the land. The impact in the Chesapeake Bay clearly caused a huge amount of material, both from the Earth and the asteroid, to become airborne, and the layer -- discovered at a depth of 25 feet in the kaolin mine -- was probably laid down by the event.

It was an active time: In the period between 34 million and 37 million years ago, at least five comets and/or asteroids collided with the Earth. Since some of the events may have caused climate alterations and caused at least regional disruptions of ecosystems, knowing more about the ejecta from the impacts is important.

The layer reported in Geology is perhaps the most easily accessible, undisturbed layer of materials that probably came from the Chesapeake Bay impact and can therefore add knowledge about that event. The search for the layer, led by Harris, led to the discovery of so-called shocked quartz -- grains whose physical "thumbprint" mark them as having originated from the extremely high pressures characteristic of an impact event.

Just how big the explosion was when this celestial visitor hit the Earth is unclear, but Roden said it was many times bigger than such events as the explosions of Mt. St. Helen's or even Krakatoa.

Source: University of Georgia

Explore further: Planetary Society hopes tiny satellite sets sail above Earth

add to favorites email to friend print save as pdf

Related Stories

Physicists discuss quantum pigeonhole principle

11 hours ago

The pigeonhole principle: "If you put three pigeons in two pigeonholes at least two of the pigeons end up in the same hole." So where's the argument? Physicists say there is an important argument. While the ...

Giant crater in Russia's far north sparks mystery

13 hours ago

A vast crater discovered in a remote region of Siberia known to locals as "the end of the world" is causing a sensation in Russia, with a group of scientists being sent to investigate.

NASA Mars spacecraft prepare for close comet flyby

14 hours ago

NASA is taking steps to protect its Mars orbiters, while preserving opportunities to gather valuable scientific data, as Comet C/2013 A1 Siding Spring heads toward a close flyby of Mars on Oct. 19.

Recommended for you

Fermi satellite detects gamma-rays from exploding novae

5 hours ago

The Universe is home to a variety of exotic objects and beautiful phenomena, some of which can generate almost inconceivable amounts of energy. ASU Regents' Professor Sumner Starrfield is part of a team that ...

Exploring Mars in low Earth orbit

11 hours ago

In their quest to understand life's potential beyond Earth, astrobiologists study how organisms might survive in numerous environments, from the surface of Mars to the ice-covered oceans of Jupiter's moon, ...

Image: Hubble serves a slice of stars

12 hours ago

The thin, glowing streak slicing across this image cuts a lonely figure, with only a few foreground stars and galaxies in the distant background for company.

User comments : 0