Crusty Old Discovery Reveals Early Earth's History (3.8 billion years old outer crust)

LiveScience.com on yahoo ^ | 3/24/07 | Robert Roy Britt

[NormsRevenge]

Only in science could the discovery of something old and crusty be exciting.

And researchers are very excited about finding chunks of Earth's outer crust that are 3.8 billion years old. Most stuff that old has been folded back into the planet and lost forever or spat back out after being melted into unrecognizable magma.

The discovery, detailed in today's issue of the journal Science, provides solid evidence that Earth had crustal plates way back then that were banging into each other much as they do today in a process that drives earthquakes and reshapes continents. That activity, and the chemical changes to land, sea and air that accompany it, are thought to have been crucial to the instigation of life on Earth, an event that remains utterly mysterious in terms of timing and method.

New thinking

Earth is 4.5 billion years old. For a long time, geologists thought all this activity, called plate tectonics, did not start until about 2.5 billion years ago. They speculated that for a long time after its formation, the planet might have been a fiery hell or a total waterworld. More recently, however, geochemical analysis of rocks had suggested there were continents and plate tectonics 4.3 billion years ago—very soon after the planet's birth.

The new study is the first to provide physical evidence of tectonics among Earth's oldest known rock structures, said study team member Hubert Staudigel of Scripps Institution of Oceanography at UC San Diego.

“The fact that this rock structure is so well preserved is particularly lucky,” Staudigel said. “The materials were formed as seafloor along a spreading center and accreted to a continental plate and just stuck there, surviving almost unscathed for as long as 3.8 billion years.”

The crusty old stuff was found in a rare outcrop of rock near the southwestern coast of Greenland.

How it happened

The Isua deposits, as they are called, have been studied since the 1960s. They also contain fossilized evidence of the earliest bacterial life on Earth, also from about 3.8 billion years ago.

The rocks have two components. Some was lava that was once below the seafloor and rose to the surface as crustal plates spread apart long ago. Embedded in that lava rock are sheets of basalt rock that got mixed in after the lava formed, the new study reveals. Even though the rocks have physically changed over time, the scientists were able to discern their original characteristics from fine-grained crystals that were cooled by contact with surrounding colder rocks.

“Our work shows that some form of seafloor spreading and oceanic crust formation occurs as far back in history as geological records go,” said Staudigel 's colleague Maarten de Wit of University of Cape Town, South Africa.

[NormsRevenge]

I almost didn't post this.. for fear of all the 'Crusty' shots to come. ;-)

[NormsRevenge]

The Earth’s radius is about 4,000 miles (6,400 kilometers). The main layers of its interior are in descending order: crust, mantle and core.

The crust thickness averages about 18 miles (30 kilometers) under the continents, but is only about 3 miles (5 kilometers) under the oceans. It is light and brittle and can break. In fact it's fractured into more than a dozen major plates and several minor ones. It is where most earthquakes originate.

The mantle is more flexible – it flows instead of fractures. It extends down to about 1,800 miles (2,900 kilometers) below the surface.

The core consists of a solid inner core and a fluid outer core. The fluid contains iron, which, as it moves, generates the Earth’s magnetic field. The crust and upper mantle form the lithosphere, which is broken up into several plates that float on top of the hot molten mantle below.

SOURCE: LiveScience reporting

[Jeff Chandler]

Please no Helen Thomas photos.

[stephenjohnbanker]

I know this, I was there.

[stephenjohnbanker]

What crusty? Hillary wasn't there.

[doc1019]

She was to busy being named for the famous climber of Mount Everest.

[AGreatPer]

Yea, I thought it was a story about "Old Crusty" the pants suit Hitlery wears all the time.

Sorry Norm, I had to post that. LOL, you saw it coming.

[stephenjohnbanker]

: ) Thompson/Hunter or Hunter/Thompson 08!

[hosepipe]

Anybody that says they know what happened a Billion years ago is on some strong drugs..
or lying..

[gondramB]

>>Only in science could the discovery of something old and crusty be exciting.<<


Ha... They should see my mother on an antiquing expedition - and she doesn't have a scientific bone in her body.

[Fireone]

"Crusty Old Discovery"
Headlines from the White House laundry?

[gondramB]

>>Anybody that says they know what happened a Billion years ago is on some strong drugs..
or lying..<<

Its a lot like a murder investigation without an eye witness - with enough evidence you can still get a conviction. Except instead of looking for reasonable certainty they use the term "scientific certainty." Its subject to revision as more data is found and scientists all around the world double check each other.

[LiteKeeper]

YEC INTREP

[Ernest_at_the_Beach]

Nice diagram....

BBC article:

Sea floor records ancient Earth

[TexasTransplant]

4.5 or 2.5 Billion years... as a Science Fiction Novel reader I would wonder how many times Dinosaurs - Mammals or whatever spent Millions of years evolving before SUV's eventually wiped them out.

TT

[Ernest_at_the_Beach]

My thread has maps.....

[Ernest_at_the_Beach]

Fred Flintstone had SUV's?

[Shadowstrike]

Great article. Thanks for the ping.

[Ernest_at_the_Beach]

I pinged you because of the neat diagram and the tie in to earthquakes....the earth has had earthquakes as a consequence of the crustal movement which has been going on since the earliest days....

[NormsRevenge]

Thanks! I missed this one. Good pics.