Meteor hits Canyonlands

The Canyonlands National Park web site carries two possible explanations for Upheaval Dome, a rugged set of ring walls a few miles west of Island in the Sky Visitor Center. The rock strata are highly deformed, says the site. The feature looks like a dome with its top sheared off.

The inner ring wall is about one mile in diameter, while the outer ring is about 1.8 miles across, according to Salt Lake City resident Kurt A. Fisher, who took a remarkable panoramic photo of the structure.

What caused the feature? “Geologists do not know for sure, but there are two main theories which are hotly debated,” says the official web site. They are the “salt dome theory” in which salt left behind by an ancient sea was pushed upward by the weight of rock overburden, forming a salt bubble that reached the surface and was subjected to erosion; and the “impact crater theory” that it is the crater left by a meteor strike.

“Some geologists estimate that roughly 60 million years ago [that date is disputed], a meteorite with a diameter of approximately one-third of a mile hit at what is now the Upheaval Dome. The impact created a large explosion, sending dust and debris high into the atmosphere. The impact initially created an unstable crater that partially collapsed. As the area around Upheaval Dome reached an equilibrium, the rocks underground heaved upward to fill the void left by the impact. Erosion since the impact has washed away any meteorite debris, and now provides a glimpse into the interior of the impact crater, exposing rock layers once buried thousands of feet underground,” adds the site.

Geological research of recent years pointed to the meteor strike as the more likely scenario. But proof was needed that no other force could have formed the rings. With the publication of a March 2008 study, the evidence seems irrefutable. Canyonlands was slammed by a huge meteor.

The report in Geology Magazine, published by the Geological Society of America, is titled, “Upheaval Dome, Utah, USA: Impact Origin Confirmed.” It was written by Thomas Kenkmann of the Museum fur Naturkunde-Mineralogie, Berlin, Germany and Elmar Buchner of the Institut fur Planetologie, Universitat Stuttgart.

In the six-year study, they obtained shocked quartz crystals from Upheaval Dome. When examined by an electron microscope, this evidence proved the quartz was subjected to an incredible explosive force, a shock wave far too great for any strictly earthly event like a volcano.

“It’s kind of a classic scientific discovery story,” Fisher said.

A paralegal and an amateur astronomer, he shot a series of digital photos of the double-walled crater last fall; another astro-buff, Howard Jackman of West Jordan, assembled them into a panorama. In late November 2008 the view was showcased on the Internet’s Lunar Photo of the Day Site.

The panorama [click here] shows the ancient bottom of the crater formed when a meteor hit an estimated 170 million years ago. Between about half a mile to a mile of the landscape above today’s ground level eroded away long ago, according to the caption. Originally, the crater would have been a bowl five miles across.

“If you do lunar observing you look at a lot of lunar impact” craters, Fisher said. Over the past several years he has examined fascinating formations on the moon and has contributed to “Selenology Today” and to the Lunar Picture of the Day. Because Upheaval Dome shows the exposed roots of a meteor-strike crater like those on the moon, the panorama was a natural for posting.

The debate isn’t quite over. “To fully close the book,” he said, “there’s one more step. There’s got to be independent confirmation.” When another geologist hikes to the outer ring, collects shocked quartz crystals and analyzes them, there will be no question.

Meanwhile, Canyonlands would be wise to rewrite its web information.

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