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UK Impact Crater Debate Heats Up
BBC ^ | 3-30-2007 | Jonathan Fildes

Posted on 03/30/2007 2:44:14 PM PDT by blam

UK impact crater debate heats up

By Jonathan Fildes
Science and technology reporter, BBC News

Seismic surveys show a trough surrounded by concentric fractures

A deep scar under the North Sea thought to be the UK's only impact crater is no such thing, claims a leading geologist.

Professor John Underhill, from the University of Edinburgh, says the Silverpit structure, as it is known, has a far more mundane explanation.

Detailed surveys reveal nine similar vast chasms in the area, he says.

This suggests it was part of a more widespread process, probably the movement of salt rocks at depth, not a one-off meteorite impact, he believes.

"I feel like I'm spoiling a party," said Professor Underhill. "It's a less glamorous explanation, but that's what the scientific data is saying."

Professor Underhill first put forward his theory in 2004 and has spent the last three years collecting evidence to back it up.

However, the group that discovered the structure in 2002 stands by its original theory of a cataclysmic asteroid or comet impact about 60-65 million years ago.

"I can't understand why John keeps banging away at an alternative model," said team member Dr Simon Stewart, a geologist with BP.

"The crater interpretation of Silverpit still stands, in my opinion."

Regional view

The 3km-wide (1.8 miles) wide bowl was discovered in 2002 by Dr Stewart and his colleague Phil Allen, of geoscience firm PGL, about 130km (80 miles) east of the Yorkshire coast.

The structure, which comprises concentric, closely-spaced rings, is punched through a band of chalk. Today, it covered by shales and sandstones almost one kilometre deep.

It can only be seen on seismic data, collected by petroleum companies hunting for new oil and gas fields.

Two studies by Dr Stewart and Mr Allen, the latest of which mapped the structure in 3D, concluded that it was the result of a space impact. But Professor Underhill has never been convinced.

"I just felt that there was a bit more to the story than met the eye," he told BBC News.

To establish whether the feature was unique, he examined a 3,750-sq-km-area around the structure.

"I decided to throw a more regional view at it, and ended up finding a whole load of these features with very similar cross sections," he said.

Along with a colleague, Dr Zana Conway, he has identified at least nine major bowl-shaped depressions, known as synclines, and over 15 subsidiary structures including Silverpit itself. He says that more have also been identified elsewhere.

Salt push

He says that the swarm of structures is the result of movement of a thick layer of salt of Upper Permian (248-256 million years ago) age that lies below the whole area.

The salt is highly mobile and flows between areas of high and low pressure.

The alternative theory for the formation of Silverpit

In some regions, huge blisters of salt force the overlying rocks up into domes, known as anticlines; elsewhere the salt flows entirely away and the overlying layers buckle and subside.

This is what caused the crater-like Silverpit structure, argues Professor Underhill.

"The key observation is that every single syncline is exactly coincident with where the salt has thinned or withdrawn," he said.

"There is an absolute one-to-one correlation between these two levels."

In addition, Dr Conway has examined the coastlines of Denmark and the east of England for evidence of tsunami deposits of the right age.

If a space object did crash into the shallow North Sea, the argument goes, it would have caused great waves to dash the coastlines of surrounding countries. In addition, it would have left a layer with high levels of an element known as iridium in the rocks.

"There is a lack of any independent evidence for a meteorite impact for the time that they say in the place that they advocate," said Professor Underhill.

Missing links

Dr Stewart is un-moved. He points to a 300m-high central peak, or nipple, in the centre of the inner bowl, typical of impact craters.

In addition, he argues the seismic surveys show areas of undeformed rock underlying the crater.

The Silverpit structure has been mapped in 3D

He explained it was like finding a hole in the roof of your house at the same time as you were digging in the basement.

"With only this information, one might conclude your roof collapsed because of subsidence into the hole you made in the basement," he says.

"But if you then point out that the first floor is intact, undeformed, we would conclude the roof hole was unrelated to the basement hole and indeed was most likely to be caused by something dropping through it."

Professor Underhill is unconcerned by this argument. He says that different rocks are mechanically stronger than others and will react in different ways when the salt withdraws.

Conclusive proof

The debate has drawn in other researchers from the geological community.

Impact expert Dr Gareth Collins from Imperial College London has also examined the evidence and says the circular structure is geometrically similar to other craters, particularly those found on other planets.

Similarities exist with impact structures on Jovian ice moons

"On balance an impact origin is the simplest and most likely explanation," he says. "But to qualify that - it has absolutely not been proven to have an impact origin."

To unequivocally show Silverpit is a crater, he says, geologists would have to drill through its centre and look for evidence of minerals, such as shocked quartz, catastrophically altered by the crushing forces of the impact.

"The rocks and minerals affected by the impact would have been changed in a way which is absolutely diagnostic of high pressures that happen over a very short period of time," he said.

Other geologists with experience of the North Sea say that the large number of similar structures found by Professor Underhill strongly favours salt withdrawal.

"Given the abundance of these features and their distribution, it looks more like a salt withdrawal phenomenon than an impact, unfortunately," said Professor John Gluyas, of the University of Durham and co-founder of North Sea oil firm Fairfield Energy.

"On balance, I think John has it at the moment; but I think I'd like to see more evidence before I side with one camp."

Professor Underhill's and Dr Conway's work will be presented at the annual American Association of Petroleum Geologists meeting in Long Beach, California, in early April.

A REGIONAL VIEW OF SILVERPIT

Peeling away the complex geology around Silverpit reveals a series of basins thought to have been created by salt withdrawal (Seismic data courtesy of PGS, WesternGeco, British Gas and Shell)


TOPICS: News/Current Events
KEYWORDS: catastrophism; crater; cretaceous; debate; impact; paleontology; uk
There's more on the links at the site.
1 posted on 03/30/2007 2:44:15 PM PDT by blam
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To: blam
interesting. there's evidence both ways, but the salt hypothesis seems more likely. I'm no expert, but I'm considering getting a geology degree (and do have some real knowledge) and for what it's worth, a basin related to salt flow is exactly what popped into mind after reading 7 words into the article, to North Sea.
2 posted on 03/30/2007 3:17:06 PM PDT by verum ago (The Iranian Space Agency: set phasers to jihad!)
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To: verum ago

Would not some cores of the crater add more information? The presence of minerals known to be created in cosmic impacts would seem to confirm the impact theory, but the lack of minerals couldn't discount it, either, current erosion and all that.


3 posted on 03/30/2007 3:25:56 PM PDT by Calvin Locke
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To: verum ago
yes- cores of the crater would make or break the impact hypothesis very easily- since the site is under water and has in fact had further sediments deposited onto it, the original mineralogy of the sea-bottom crater should be intact. Even if it was destroyed, then there should still be distinctive 'shocked' mineral crystals in the bedrock underlaying the crater.(this is one of the nicer features of large impacts- they leave behind evidence in the nearby bedrock that wasn't macroscopically deformed, meaning that even if the entire crater structure (surface and subsurface) was erased there could still be evidence of the impact. of course, without the crater structures no one would look for these signs)
the problems here are that the geometry of the basin suggest an impact (as does the 'nipple' structure), but such extensive and symmetric concentric rings haven't been observed except on icy bodies elsewhere in the solar system- where the topmost layer is the most rigid and the ones beneath are more plastic or even fluid- it should be the opposite on earth. Of course no salt recession basin has ever been seen with so perfect geometry, but if it's true that the area is littered with similar features and that they correspond with thinning in the salt layer the salt theory would be a lot stronger. The fact is that the multitude of rings actually is a bit problematic for both hypotheses- it could theoretically be possible for both, but has never been observed under the circumstances for either.
4 posted on 03/30/2007 4:07:56 PM PDT by verum ago (The Iranian Space Agency: set phasers to jihad!)
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To: blam
"I can't understand why John keeps banging away at an alternative model," said team member Dr Simon Stewart, a geologist with BP.

Maybe they'll demand that his credentials be revoked and that his funding be rescinded?

-PJ

5 posted on 03/30/2007 4:12:03 PM PDT by Political Junkie Too (It's still not safe to vote Democrat.)
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To: verum ago; blam

And what about a strike into the ice-pack during the last major freeze when the sea would have been frozen to the bottom?


6 posted on 03/30/2007 7:01:17 PM PDT by brityank (The more I learn about the Constitution, the more I realise this Government is UNconstitutional !!)
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To: Political Junkie Too
It can only be seen on seismic data, collected by petroleum companies hunting for new oil and gas fields.

It was found by those evil oil companies. Nothing good can come from this.

7 posted on 03/30/2007 7:04:10 PM PDT by Erik Latranyi (The Democratic Party will not exist in a few years....we are watching history unfold before us.)
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To: brityank

well then I guess the evidence would be limited to a Tommy Lee Jones movie produced by Al Gore.


8 posted on 03/30/2007 7:04:43 PM PDT by verum ago (The Iranian Space Agency: set phasers to jihad!)
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To: brityank
"And what about a strike into the ice-pack during the last major freeze when the sea would have been frozen to the bottom?"

"However, the group that discovered the structure in 2002 stands by its original theory of a cataclysmic asteroid or comet impact about 60-65 million years ago. "

I don't know what the climate was like in that period. I think the dino's were just clobbered by the Chixlub impact down in Mexico.

9 posted on 03/30/2007 8:28:15 PM PDT by blam
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To: blam
Ice Ages have occurred at regular intervals, of approximately 100,000 years each. "However, the group that discovered the structure in 2002 stands by its original theory of a cataclysmic asteroid or comet impact about 60-65 million years ago. "

Their note does place it into one of the major ice sheet coverings, I think.

10 posted on 03/30/2007 9:31:01 PM PDT by brityank (The more I learn about the Constitution, the more I realise this Government is UNconstitutional !!)
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To: brityank

I've read that cosmic impacts on land causes it to get colder while an impact in water causes things to warm up. I think impacting into ice would be similar to results of a water impact, warming.


11 posted on 03/31/2007 6:36:47 AM PDT by blam
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To: brityank

BTW, some pretty respectable scientists think a comet or comet fragment impacts caused the last Ice Age to end and we're still enjoying the benefits from that.


12 posted on 03/31/2007 6:39:05 AM PDT by blam
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http://www.freerepublic.com/focus/bloggers/1607979/replies?c=36


13 posted on 12/22/2012 12:15:18 PM PST by SunkenCiv (Romney would have been worse, if you're a dumb ass.)
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14 posted on 12/22/2012 12:29:49 PM PST by SunkenCiv (Romney would have been worse, if you're a dumb ass.)
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To: 75thOVI; agrace; aimhigh; Alice in Wonderland; AndrewC; aragorn; aristotleman; Avoiding_Sulla; ...
Note: this topic was posted on March 30, 2007.
Thanks blam.


15 posted on 12/22/2012 12:31:15 PM PST by SunkenCiv (Romney would have been worse, if you're a dumb ass.)
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To: 75thOVI; agrace; aimhigh; Alice in Wonderland; AndrewC; aragorn; aristotleman; Avoiding_Sulla; ...
Note: this topic was posted on March 30, 2007.
Thanks blam.


16 posted on 12/22/2012 12:31:58 PM PST by SunkenCiv (Romney would have been worse, if you're a dumb ass.)
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Maine Crater Related to Dino-Killer Asteroid?
Discovery News | April 3, 2003 | Larry O’Hanlon
Posted on April 6, 2003 12:39:18 AM EST by SteveH
http://www.freerepublic.com/focus/news/886240/posts


17 posted on 12/22/2012 12:42:42 PM PST by SunkenCiv (Romney would have been worse, if you're a dumb ass.)
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To: brityank; SunkenCiv; blam; All

This chart is an indication of temperature changes over the last one million years. The article is about an event 60-65 million years ago. This chart has nothing to do with that time period. Also, any evidence of tsunami wash would have long ago been destroyed by many, many ice sheets.


18 posted on 12/22/2012 10:02:25 PM PST by gleeaikin
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To: Erik Latranyi; Political Junkie Too; verum ago; SunkenCiv; blam; All

Those evil oil companies supplied the data that enabled the Alvarez team to discover the Yucatan meteor crater of 65 million years ago (mya). Apparently oil deposits and the extreme pressure caused by these strikes can go hand in hand. There is an apparent crater off the Brazilian coast which seems to be an oil source. Given the oil in the North Sea, this goes along with that idea. Also, multiple craters around the same time period are not unheard of. The Chesapeake (Bay) Meteor strike of 34 mya, also had companions of roughly the same age, including a 10 mile wide crater off Toms River, NJ, and a 60 mile wide crater (Popogai (sp?) in Siberia. Another comment here mentions a possible crater off Maine of the right age (65 mya).

The Chesapeake Meteor was verified by deep coring which showed breccia and shocked quartz. They also hope to find oil around there.


19 posted on 12/22/2012 10:16:06 PM PST by gleeaikin
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To: SunkenCiv; Swordmaker; blam; ForGod'sSake

Thunderbolts of the Gods

http://www.youtube.com/watch?v=5i8m7XoaP8o

Tribute to Velikovsky.

THUNDERBOLTS OF THE GODS (OFFICIAL VERSION) NOW POSTED ON YOUTUBE

For a limited time, the full-length film Thunderbolts of the Gods, our most popular DVD, will be available on the ThunderboltsProject channel of YouTube:

http://www.youtube.com/watch?v=5AUA7XS0TvA

A VERY MERRY CHRISTMAS AND A PROSPEROUS, HAPPY NEW YEAR!


20 posted on 12/23/2012 9:54:53 PM PST by Fred Nerks (FAIR DINKUM!)
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To: Fred Nerks

Thanks FN!


21 posted on 12/24/2012 4:07:08 PM PST by SunkenCiv (Romney would have been worse, if you're a dumb ass.)
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To: Fred Nerks

Thanks Fred. I trust you and yours had a very merry Christmas. I had seen most of the ‘’movie’’ from the various clips already on Youtube. Still in all, well done. I suppose I shouldn’t be surprised there are so few viewings; it’s relatively new, but there should be millions wanting to have a look at a plausible alternative to conventional wisdom. Questioning authority and the company line used to be an American pastime but I’m afraid that ingredient has been removed from the pudding.


22 posted on 12/29/2012 8:42:05 AM PST by ForGod'sSake (2C7:14 If my people..shall humble themselves and pray..I will hear from heaven..and heal their land.)
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To: blam

It was not only the impact that formed the Caribbean Sea, but it was the one that formed the Scotia Sea (simultaneouly), too, that was the cataclysmic impact you describe. Slide presentation here has details: http://www.threeimpacts-twoevents.com/wp-content/uploads/2013/01/SIMULTANEOUS-IMPACTS-3JAN2013-WEBSITE.pdf


23 posted on 01/15/2013 12:51:07 PM PST by mj81
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To: mj81; Pharmboy; gleeaikin
You may like this interesting post by FReeper Pharmboy:

Ancient Crash, Epic Wave

24 posted on 01/15/2013 2:26:52 PM PST by blam
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