View Full Version : 6.7 (originally posted as a 7.0)earth quake north of Australia+
06-23-2009, 01:04 PM
"Big Quake Must have been just off the coast underwater.
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Worldwide earthquakes with M4.5+ located by USGS and Contributing Agencies.
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Three Tectonic Plates Collide Down Under
Australia, which sits at the leading edge of the giant Indo-Australian Plate, moves in a northeasterly [right] direction. In so doing it collides with the western edge of the Philippine Plate. This collision pushes up the ocean floor above sea level, creating island chains, island arcs, and a twisted, tumultuous sea floor .
The Pacific Plate, moving northwest, subducts under the eastern edge of the Philippine Plate. This area of subduction is a hotbed of volcanic and earthquake activity and part of the infamous "Ring of Fire." You can see a mid-ocean ridge to the south of Australia, the site of sea-floor spreading. New Zealand, to the southeast, exists along this complex tectonic boundary.
World Ocean Floors
Underwater map of the ocean floors
This amazing piece of work accurately illustrates the Tectonic Earth. Mid-ocean ridges,
the sight of sea-floor spreading, girdle the planet like seams on a baseball. Behold the
giant Pacific Plate, continental shelves, and undersea mountain chains.
06-23-2009, 05:38 PM
Sea-Floor Spreading and Subduction Zones
The Andes Mountain Range spans the entire length of South America, along the western coast. This close-up shows that coast, which represents the western terrestrial edge of the South American Plate. The leading edge of the Nazca Plate is subducting below the South American Plate at a plate boundary known as a subduction zone. During this subduction some Nazca crust is scraped off along base of the Andes, adding height to the entire range.
The East Pacific Rise [the ridge to the left] is part of the global network of mid-ocean ridges that girdle the planet. As the sea-floor spreads on either side of this ridge, the Nazca Plate moves easterly while the Pacific Plate moves westerly. The Galapagos Islands, off the northwestern coast of South America, are the result of a "Hot Spot" that exists over a mid-ocean ridge.
06-23-2009, 05:45 PM
Bear with me for a while as I pontificate a bit on plate tectonics.Our earth is a big ball of rocks and Hot mud with a plastic semi molten core that's about twenty five thousand miles around at the equator.It takes about twenty four hours for one revolution so we are going around at about one thousand mph at the equator !The distance from Earth's surface to its center is about 3,975 miles and the continents and ocean floors rest on those vast columns to the core .
The surface of the earth is under tremendous stress as it spins due to centrifugal force and the outer earth surfaces mass lag .The core of the earth also rotates but at a different velocity than the surface,that makes sense,yes?
Because of the rotational velocity differentials and tidal forces within the earth the interface between the core and the upper levels have broken into plates and the continents rest of great subterranean masses of fractured rock and a sort of hot plastic mud.
The plates move in more or less in the direction of the earths rotation and when one plate catches up with another the leading edges subduct or slide under the other,slower plate.This movement is very slow and takes several thousand of years to happen but it does all over the earth.The subducted earth mass melts as it slides into the molten layer and produces an excess of magma,a sort of very hot semi liquid plastic mud .
As the volume of magma increases it forces itself up through the space between the plates and gathers in vast chambers called Chaldea's .The volcanic heat and pressure melts the subsurface rock and form vent pipes that rise to the surface and vent to the atmosphere as volcano's .Volcanic ridges are a series of volcanic vents from past eruptions that anchor the plate edges against tipping upward due to plates forcing the edges upwards as they subduct .The grinding of one plate against another as they move past but don't subduct and this friction plate against plate builds up tremendous stress that over time snap back into alignment to reduce the stress.This is called an earthquake.
Earths rotational speed .
The circumference of the Earth at the equator is 25,000 miles. The Earth rotates in about 24 hours. Therefore, if you were to hang above the surface of the Earth at the equator without moving, you would see 25,000 miles pass by in 24 hours, at a speed of 25000/24 or just over 1000 miles per hour. Multiply by cosine of your latitude to see how fast the Earth is rotating where you are. Earth is also moving around the Sun at about 67,000 miles per hour.
Earths Depth to the core .
The distance from Earth's surface to its center is about 3,975 miles (6,395 kilometers). Scientists have divided the interior of Earth into various layers, based on their composition.
The crust, or outer portion, varies in depth from 5 to 25 miles (8 to 40 kilometers).
Below the crust is the mantle, which extends to a depth of about 1,800 miles (2,900 kilometers).
Below that is the core,
composed of a liquid outer core about 1,380 miles (2,200 kilometers) in depth,
and a solid inner core about 780 miles (1,300 kilometers) deep.
What causes the Earths core To Be molten .
"The vast majority of the heat in Earth's interior—up to 90 percent—is fueled by the decaying of radioactive isotopes like Potassium 40, Uranium 238, 235, and Thorium 232 contained within the mantle. These isotopes radiate heat as they shed excess energy and move toward stability. The amount of heat caused by this radiation is almost the same as the total heat measured emanating from the Earth"
But we now have another way for everybody to die to add to mega-tsunamis, super-volcanos, asteroid collisions, close proximity novas, black holes, magnetic pole flipping, global warming, global cooling, pandemic bird flu-ebola, penicillin-resistant bacteria, atomic terrorist attacks ... hey, I'm keepin' track of all these things.
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