Posted on 06/01/2004 4:21:15 PM PDT by Rebelbase
CAPE CHARLES, Va. - Geologists drilling half a mile below Virginia's Eastern Shore say they have uncovered more signs of a space rock's impact 35 million years ago.
For more than two weeks, scientists drilled around the clock alongside a parking lot across the harbor from Cape Charles. They stopped at 2,700 feet.
From the depths came jumbled, mixed bits of crystalline and melted rock that can be dated, as well as marine deposits, brine and other evidence of an ancient comet or asteroid that slammed into once-shallow waters near the Delmarva Peninsula.
Cape Charles is considered Ground Zero for the resulting 56-mile-wide depression below what's now the Chesapeake Bay. The drilling project marks the first time the geologists explored the inner portion of the inverted-sombrero-shaped crater.
"We expected to see some pretty strange rocks because of the extreme pressure and temperatures that occurred" approximately 35 million years ago, said geologist Greg Gohn, who led the $180,000 project for the U.S. Geological Survey (news - web sites).
Over the past decade, USGS (news - web sites) and Virginia scientists have investigated indications that a 2-mile-wide brilliant ball traveling tens of thousands of miles per hour crashed off the Virginia coast, burrowing thousands of feet and depressing and fracturing the bedrock.
Billions of tons of ocean water vaporized. Millions of tons of debris spewed 30 miles high before collapsing back into the excavation. A train of giant waves inundated the land. The waves then dragged debris as they washed back into the crater, preserving it beneath a blanket of rock and sediment.
It probably took just a few minutes to create the largest crater in the United States and sixth-largest known on the planet, according to computer simulations.
The catastrophe squeezed freshwater from many of the aquifers of southeastern Virginia and filled others with briny water. Its legacy is well-known to residents who try to drill for drinkable groundwater and encounter the saltwater "wedge," pockets of brine nestled in an arc from the lower Eastern Shore to the Hampton Roads-Newport News area.
Geological research off the coast of New Jersey and in Virginia, begun in 1983, led to the crater's discovery a decade later. Drilling and further study of seismic data narrowed the location in the Chesapeake Bay.
"We're getting evidence about how hot this thing (was) and what was the energy," said USGS hydrologist David Powars, one of those credited with the crater's discovery.
More clues to the space rock's identity will come from cores taken in the drill's final 280 feet.
A $1.2 million proposal to dig 7,000 feet not far from Cape Charles is before the International Continental Scientific Drilling Program, which would then assist the USGS with funding.
all the tags work."
I went to my Yahoo email and tried to figure it out and couldn't. I'm to tired presently to work on it anymore. Maybe I'll contact you later for futher instructions, thanks.
bookmark bump
Odessa American - 6/2/04
Scientists probe Odessa meteor crater
University of Arizona researchers hope to learn more about when the impact occurred.
A team of University of Arizona scientists took samples of millennia-old dust in the Odessa meteor crater Tuesday hoping to learn more about the region’s geological history. Vance Holliday, a professor of anthropology and geoscience, said the team missed its goal of taking core samples as deep as 80 feet.
“We only got to 53 feet. It would’ve been nice to get to 70, but we’ll manage,” he said.
Despite not reaching 80 feet, Holliday said he thinks the samples collected can still help pinpoint the crater’s age.
“We’ll still be able to get a reasonable approximation of the age. We got pretty close I think,” he said. “This is a terrific core. It’s by far better than anything we’ve seen before.”
Tuesday was the third time Holliday led a team to take samples from the crater since 2001. Last year, the digging stopped at 20 feet when the corer couldn’t punch through a caliche layer.
Holliday and his team were trying to take core samples of the soil that would indicate when the meteor crashed into the soil.
“We know it’s on the order of tens of thousands of years,” he said Tuesday morning. “Basically what we’re trying to do is to get as deep as we can and date the sediment that’s filled in the crater.”
Holliday said knowing the crater’s age would help paint a picture of the changes in the Odessa landscape over eons. He said it could also give insight into the history of meteoric impacts on the earth’s surface. “The more data points we can get, the better understanding we can get of the frequency of impacts,” he said.
Research assistant James Mayer said knowing how old the crater is would give him a point of reference for his research into environmental change in the high plains region.
“A key to the whole thing is figuring out how old this damn thing is,” Mayer said.
Mayer said the team would use carbon dating and a process called luminescence dating to determine the crater’s age.
Holliday said the samples might even provide a more detailed picture of the landscape than he expected. He said he suspects the crater had served as a shallow, temporary lake at some point in its history, which is indicated by the different soil types in the samples. But Tuesday’s sample indicated the crater was filled with water at a different time than the sample taken last year.
“This core is different than last year’s, and I think it’s telling us more about the history that we didn’t know before,” he said. “There’s a good story here.”
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I never knew or heard of this and we were living 25 miles north of Cape Charles and worked 5 miles North of Cape Charles at the time.
bttt for later
I never knew or heard of this and we were living 25 miles north of Cape Charles and worked 5 miles North of Cape Charles at the time. Am emailing it to family.
and brackish
bttt
Limestone (calcium carbonate) is formed by deposits of shells and other dead sea creatures.
"...I wonder if this eventhad anything to do with the Carolina Bays...."
Nope. The Carolina Bays are of Pleistocene age...they postdate this crater by some 34 1/2 million years or so...
Maybe it was "global warming"? Al Gore would know all about it.
Seismic Study of Ancient Cataclysm Begins"The seismic recordings will give us a look at the subsurface rock and sediment layers, faults, and other structures produced 35 million years ago by the Chesapeake Bay impact," said USGS scientist Greg Gohn. "This ancient event probably fractured bedrock to a depth of at least 5 miles. These surveys will tell us more about the impact processes and products and their effects on ground-water resources available today in the southern Delmarva Peninsula."
United States Geological Survey
Monday, October 4, 2004
The project will involve 30 small explosions buried at depths of about 60 feet, and about 800 seismic-shotgun blasts at depths of about one foot. As energy waves from the blasts travel through the ground they will be recorded by portable seismometers placed throughout the area. Because the ground motion being recorded is less than that caused by normal daylight activities, such as vehicular traffic or vibrations from pumps, most of the blasting and recording will be done at night, usually between 10 p.m. and 3 a.m. over a 2 or 3 day period...
Scientist Rufus Catchings, who is with the USGS Western Region Earthquake Hazards Team in Menlo Park, Calif., is leading the seismic survey. He expects the high-resolution seismic imaging effort to locate crater features to depths of about one mile, and the lower-resolution survey to image structures to depths of more than 3 miles across a broad area.
"...I didn't either. My friend and I were talking about the fossils we find in his creek gravel in the hills of central KY. They're old, old looking sea shells, and other marine fossils that look like they've been embedded for forever and a day. We were hypothesizing that they were maybe brought there by tsunami or something, but this would make sense.
Does anyone know if they have an estimate for how far inland the waves came?..."
I grew up there (in Clark County), and was a fossil hunter from a very young age; I probably have the same fossils; mostly brachiopods, a few cephalopods, some sea cucumbers, etc. They are of upper Ordovician age (meaning that they are at leat 443 million years old). These fossils have absolutely nothing to do with the Chesapeake crater.
The sea fossils you are finding were deposited when that strata was a marine environment.
Well, Duh. I never would have guessed.
"We were hypothesizing that they were maybe brought there by tsunami or something, but this would make sense. "
Sorry, didn't catch the last 4 words.
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