Are These Tektites Out of This World? Geology Professor has Proof Local Asteroid Field is Largest in Western North America.

rolfe.jpegPaul Le Brett remembers first thinking they were good for use in his sling shot.

They just didn't look like they belonged," he said, about the first tektites he picked up in his wanderings through the Dry Creek Valley area of Healdsburg as a young boy.

"They looked weird, but they were cool," he says. Now, nearly 50 years later, Le Brett, an SSU criminal justice major, has amassed a 1500 piece collection of the rocks that are being used to prove that the area may be the site of the largest tektite field in western North America.

Tektites have been the focus of SSU Emeritus Geology Professor Rolfe Erickson's work for many years. He announced this month at a symposium of the American Geophysical Union that new tests prove the Healdsburg-area rocks are 2.8 million years old. And, they are definitely tektites.


They have now been officially named "healdsburg-ites" and Erickson and his co authors (Stephen Norwick and Caitlin Byrd, Sonoma State University; Alan Deino, Berkeley Geochronology Center) say they are indicative of an asteroid impact whose size and location have yet to be determined.


Tests of four samples of the Healdsburg glass were made at the Berkeley Geochronology Center which included crushing them and then irradiating them to determine their age of 2.8 million years. Chemical analysis of four different tektites also confirmed their origins.


fieldpicture.jpg What are tektites

Tektites were made in the distant past when asteroids hit the earth at enormous speeds and the impact pushed vaporized gas into the atmosphere. 




Shaped by frictional forces on the way back down to earth, the gas froze in the cold of space and rained in various shapes and sizes back onto the planet in areas spanning 1,000 miles.


Some have called them "teardrops from the moon." Ancient cultures have seen them as a source of magic and sorcery. 



Geologists call the tektites littered over a large area a "strewnfield." Until this discovery, there were only four known strewnfields on the planet in the Czech republic, the southeastern United States, Indochina and the Gold Coast in Africa. 




Discovery of the healdsburg-ite tektites establishes a fifth strewnfield, named after the nearest city. Tektites from these areas each have their own distinctive look and feel.


paullebrett.pngLooking for tektites


In this region, tektites are most easily found among the "pebble population" in vineyards or road cuts where the soil has been deeply churned up. 



"People are somehow attracted to these strange little pebbles," Erickson says. 

They seem to be the kind of things people want to pick up off the ground and throw into a mason jar or bucket until they have a "collection."


Rockhounds should be on the lookout for pebbles that are:

1. extremely black
2. have a dimpled surface or look like dark, dusty, pitted glass.
3. generally range in size from a walnut to a peach pit or an olive


See more detail in the poster's summary posted on the meeting website at http://fallmeeting.agu.org/2012/eposters/eposter/p11b-1811/.


The search is still on. If you have been collecting tektites, contact Professor Rolfe Erickson at (707) 664-1420.


- Jean Wasp

CAPTIONS,

Top, Emeritus Geology Professor Rolfe Erickson with a range of tektites from all over the world.


Middle, Four tektites taken fresh from a vineyard, Dry Creek Valley, near Healdsburg.


Bottom, Paul Le Brett, an avid Healdsburg tektite collector, has more than 1500 in his collection. While posing for this picture he found a tektite on the ground in this vineyard in the Dry Creek Valley.

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