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How Earthquakes in Chile Have Permanently Deformed Earth
YahooNewsOnline from ^ | April 28, 2013 | Charles Q. Choi

Posted on 04/28/2013 11:43:29 PM PDT by LucyT

Earthquakes can permanently crack the Earth, an investigation of quakes that have rocked Chile over the past million years suggests.

Although earthquakes can wreak havoc on the planet's surface, more than a century of research has suggested the Earth actually mostly rebounds after quakes, with blocks of the world's crust elastically springing back, over the course of months to decades, to the way they initially were. Such rebounding was first seen after investigations of the devastating 1906 San Francisco temblor that helped lead to the destruction of more than 80 percent of the city. The rebound is well-documented nowadays by satellite-based GPS systems that monitor Earth's movements.

However, structural geologist Richard Allmendinger of Cornell University and his colleagues now find major earthquakes of magnitude 7 or greater apparently caused the crust in northern Chile to crack permanently.

(Excerpt) Read more at ...

TOPICS: Science
KEYWORDS: earthquakes; planetearth; science; society
In northern Chile, "the driest place on Earth, we have a virtually unique record of great earthquakes going back a million years," Allmendinger said. Whereas most analyses of ancient earthquakes only probe cycles of two to four quakes, "our record of upper plate cracking spans thousands of earthquake cycles," he noted.

"It is only in a place like the Atacama Desert that these cracks can be observed — in all other places, surface processes erase them within days or weeks of their formation, but in the Atacama, they are preserved for millions of years,"

1 posted on 04/28/2013 11:43:29 PM PDT by LucyT
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To: LucyT

Where I live near the the mouth of the Columbia River, the effects of subduction earthquakes can still be seen.

Along the road to Mt.Saint Helens, alongside roadcuts within the blast zone is evidence of past earthquakes millions of years old.

The Cascade Mountains and coast mountains here were formed from upthrusts caused by subduction quakes.

The volcanoes form upon the Cascades due to a huge, interconnected underground well of molten lava far beneath the surface resulting from when a plate is forced under the continental crust. When looking at the interior of the U.S., it is possible to see dead eroded volcanoes as evidence of continental formation.

2 posted on 04/29/2013 12:35:56 AM PDT by SatinDoll (NATURAL BORN CITZEN: BORN IN THE USA OF CITIZEN PARENTS.)
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To: SatinDoll

You live in beautiful country.

3 posted on 04/29/2013 12:48:56 AM PDT by laplata (Liberals don't get it. Their minds have been stolen.)
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To: LucyT
Chile today. Hot tamale!
4 posted on 04/29/2013 3:41:16 AM PDT by BigCinBigD (...Was that okay?)
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To: LucyT

Crack in the World

5 posted on 04/29/2013 5:36:13 AM PDT by eCSMaster ("God bless Planned Parenthood"- B.H.Obama, 2013)
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To: SatinDoll
There's an ancient volcano right in the heart of the San Fran Bay Area and most people here don't know about it. "Round Top" in the Sibley Volcanic Regional Preserve, one of the area's highest peaks, is made up of lava and volcanic debris left over from a 10-million-year-old volcano. During the past 10 million years, massive tectonic forces on the Hayward and Moraga earthquake faults uplifted the Berkeley hills, folding bedrock formations and tilting the Round Top volcano complex on its side. Softer sedimentary rock from the Orinda Formation eroded away, exposing the Round Top volcano. In addition, quarrying in the north half of the preserve has revealed cross sections of the bedrock geology, providing an unsurpassed outdoor laboratory for studying volcanism in the Central Coast Ranges.

OK everybody, you can now let loose the snarky remarks about hoping it blows.

6 posted on 04/29/2013 6:01:57 AM PDT by ProtectOurFreedom
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To: ProtectOurFreedom

This is so-o-o cool! I almost became a geologist 40-years ago. What a mistake I made by not doing so.

7 posted on 04/29/2013 6:07:39 AM PDT by SatinDoll (NATURAL BORN CITZEN: BORN IN THE USA OF CITIZEN PARENTS.)
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To: SatinDoll

-——upthrusts caused by subduction quakes.-——

Or alternatively, as the subduction movement occurs, the dynamic force is transmitted upward through the rock and is felt as a quake.

8 posted on 04/29/2013 6:08:18 AM PDT by bert ((K.E. N.P. N.C. +12 .....History is a process, not an event)
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To: bert

Uh, I don’t know about that scenario.

Here in the northwest along the coast the subduction earthquake is out at sea where the marine plate is forced under the edge of the continental plate.

The coastline has been known historically (drowned forests along the coast) to cause the coastal areas to subside as much as 16 feet.

9 posted on 04/29/2013 6:16:29 AM PDT by SatinDoll (NATURAL BORN CITZEN: BORN IN THE USA OF CITIZEN PARENTS.)
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To: SatinDoll; All
Sounds to me like this is a cheap, attention grabbing headline..

I'm no geologist, far from it..but the overwhelming majority of earthquakes of 7.0 or greater magnitude occur where the tectonic plates meet...IOW, where the earth is already cracked. Also, they're finding that most quakes NOT near a plate boundary are on fault lines that they didn't know existed before...and fault lines are just really smaller cracks.

10 posted on 04/29/2013 9:55:18 AM PDT by ken5050 (Not every Muslim is a terrorist, but just about every terrorist is a Muslim..)
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