Geology - Continental Drift - Crustal Displacement


Quakes reveal 'core within a core' October 2002 - BBC

Earth's early battering revealed July 2002 - BBC
The first convincing evidence that the Earth was bombarded by a devastating and prolonged storm of meteoroids and asteroids four billion years ago has been found in the Earth's oldest rocks.


Ancient rock points to life's origin July 2002 - BBC

The continents were moving across the face of the Earth much sooner than had been thought, according to new evidence from China. The new data come from a huge chunk of the rock that lay beneath the sea floor 2.5 billion years ago. Tim Kusky, of St Louis University, US, says it is the first large intact piece of oceanic mantle ever found from our planet's earliest period, the Archean.

Located not far from the Great Wall of China, the ancient mantle rocks are preserved in a highly faulted belt 100 kilometres (62 miles) long.


Ancient oil points to 'cradle of life'

Oil droplets (white) from the Earth's earliest days

October 5, 2000 - BBC

Australian scientists have discovered the world's oldest oil in rocks that date back 3.2 billion years.

The find suggests that oil-forming micro-organisms were widespread very early in the Earth's history.

The researchers suggest that oil-forming bacteria may have been among the earliest inhabitants of our planet and that the sulphur-springs that formed the rocks studied by the researchers may have been the "cradle of life on Earth".

The scientists are now looking for molecular fossils that might be present in the oil.

Dr Birger Rasmussen of the University of Western Australia and Dr Roger Buick of the University of Sydney have published details of their work in the journal Geology.

The tiny droplets of oil they found were extracted from rocks formed in an ancient sulphur spring that left behind huge deposits at a site in Australia.

The minute droplets of oil are at least 250 million years older than similar droplets found by the same team in 1998. Before these discoveries, the oldest known oil had been dated as 1.5 billion years old.

Fluid inclusions

The researchers found oil preserved within fluid inclusions, microscopic-sized droplets of fluid trapped within mineral grains, similar to gas bubbles trapped in ice cubes.

The inclusions measure less than a hundredth of a millimetre across and are detectable by their fluorescence when exposed to ultraviolet light.

The hydrocarbons in the ancient oil must be a decay product of the living creatures that were around on earth 3.2 billion years ago.

The oil leads scientists to speculate that oil generation early in Earth's history was widespread and that aquatic life at the dawn of evolution was more abundant than previously thought.

A detailed analysis of the droplets could yield valuable information about the early biosphere, especially if they turn out to contain molecular fossils of the primordial organisms from which the oil was made.

Sulphur springs, like the one that laid down the sulphur-rich rocks looked at in this study, may be "the cradle of life itself", according to the researchers.

This research is also important for oil companies as it suggests that exceptionally old rocks may contain oil reserves. To date, such rocks have not been a priority for oil prospectors.


World's Deepest Rocks Recovered

May 20, 2000 - BBC

The deepest rocks ever seen have been recovered by Australian and American researchers.

They were found at the Earth's surface on the island of Malaita, east of Papua New Guinea. But they originate from deep within the planet, between 400km and 670km down. This is about twice as deep as anything studied before.

These depths are an important region of the planet's interior, where sudden changes in the densities of rocks occur.

The discovery should reveal new information about the chemistry and large-scale movement of material passing through this transition zone between what is known as the upper and lower mantle.

At the moment, our picture of what the planet is like at these depths has been built up from studying the powerful waves of energy released by earthquakes. Tiny mineral inclusions found in diamonds and laboratory simulations have also helped construct geologists' models.

But Professor Ken Collerson, from Queensland University, who led the Malaita research, says the new rocks will greatly refine the detail.

"It's a terrific opportunity for people interested in the physical properties of rocks to establish that information for these depths," he told BBC News Online.

"It's a bit like the Hubble Space Telescope when it was out of focus. We now have a means of getting a much clearer image of the tomography of the lower mantle because we'll have physical properties to put in our equations."

Professor Collerson, and colleagues, report their work in the journal Science. They describe the Malaita specimens as being mostly made of the mineral garnet. In particular, they contain majorite, a silica-rich form of the mineral that only forms under extreme pressures.

"As garnet experiences higher pressure, more silica can be forced into the crystal structure and it starts to substitute in different crystallographic positions," Professor Collerson says.

"What you end up with is a garnet composition that has a lot of silica and a fairly low amount of aluminium and chromium."

Micro-diamonds

The team used this information to work out the sorts of pressures the rock must have experienced. They calculated pressures of up to 22 or 23 gigapascals.

"This is a huge pressure. It's equivalent to about 250,000 times atmospheric pressure at the surface of the Earth."

In addition to majorite, some of the deep mantle samples also contain micro-diamond.

The rocks would have exploded up through the Earth via deep volcanic pipes. Although this is thought to have happened on Malaita 34 million years ago, the journey itself could have taken just a few days.

"These pipes are similar to the kimberlite pipes of South Africa and elsewhere which commonly carry diamonds originating from depths of more than 150kms to the surface," Professor Collerson said.

Further detailed study of the crystal structure of the unique minerals is to be carried out with a number of international collaborators and with members of the university's Centre for Microscopy and Microanalysis over the next year.


THEORY OF CONTINENTAL DRIFT

According to the theory of continental drift, the world was made up of a single continent through most of geologic time. That continent eventually separated and drifted apart, forming into the seven continents we have today. The first comprehensive theory of continental drift was suggested by the German meteorologist Alfred Wegener in 1912. The hypothesis asserts that the continents consist of lighter rocks that rest on heavier crustal material - similar to the manner in which icebergs float on water. Wegener contended that the relative positions of the continents are not rigidly fixed but are slowly moving - at a rate of about one yard per century.

According to the generally accepted plate-tectonics theory, scientists believe that Earth's surface is broken into a number of shifting slabs or plates, which average about 50 miles in thickness. These plates move relative to one another above a hotter, deeper, more mobile zone at average rates as great as a few inches per year. Most of the world's active volcanoes are located along or near the boundaries between shifting plates and are called plate-boundary volcanoes. However, some active volcanoes are not associated with plate boundaries, and many of these so-called intra-plate volcanoes form roughly linear chains in the interior of some oceanic plates.

The Hawaiian Islands provide perhaps the best example of an intra-plate volcanic chain, developed by the northwest-moving Pacific plate passing over an inferred - hot spot - that initiates the magma-generation and volcano-formation process. The peripheral areas of the Pacific Ocean Basin, containing the boundaries of several plates, are dotted by many active volcanoes that form the so-called Ring of Fire. The Ring provides excellent examples of plate-boundary volcanoes, including Mt. St. Helens.

It was not until the 1960's that geologists gained the technology to fully understand the processes that could move the Earth's plates. They concluded that the Earth's surface was composed of not one large sheet but was composed of more than twelve major pieces of crust. Geologists call these pieces plates.

These plates float across the surface of the Earth like an iceberg floats on the ocean. The driving force behind these plate movements are the convection currents in the mantle. The convection currents turn very slowly dragging the plates along with these movements. The convection currents move the plates very slowly. These plates move at only 1 to 4 inches per year!


DATING THE EARTH

The chief method for dating the earth is the URA method - meaning uranium turns into lead over a period of time. You measure the amount of uranium in the earth's crust and you measure the amount of lead. That tells you how old the earth's crust is. The figure you arrive at when you use that technique is 4,500 million years. Some theorize that the changes are slow. Others feel that the earth could go through changes rapidly due to cyclic shifts of the planet itself.


NEWS ARTICLES


New Crater Found Down Under

April 22, 2000 - Science Daily - Sydney

A new crater, the world�s fourth-largest at 75 miles (120 kilometers) across, has been found in western Australia. Scientists believe the impact crater was caused by a 3-mile (5-kilometer) wide asteroid slamming into the area, causing a wave of extinction 200 million to 360 million years ago. Upon impact, massive earthquakes pulsated out hundreds of miles (kilometers) from the site.

Local animal life was vaporized by intense heat or pulverized by massive sonic waves. The crash also fostered regional volcanic activity and almost certainly sparked tsunamis, or tidal waves, in the nearby ocean.

Worst of all, the violent crash must have shot huge amounts of dust into the sky that blocked out the sun for months, killing plant and animal life dependent upon stable atmospheric conditions.

"Lack of sunlight, temporary changes in climate and associated acidification of rain would have resulted in an environment similar to a prolonged nuclear or volcanic 'winter,' " said Western Australia government geoscientist Robert Lasky.

He and a colleague confirmed the crater's existence last year while researching the isolated region's mineral exploration potential.

The new crater has been named Woodleigh in honor of the sheep station north of Perth, where it was found.

The crater now enters the record books as smaller in size only to Vredefort crater in South Africa (at 1,865 miles, or 300 kilometers across), the Sudbury crater in Canada (at 155 miles, or 250 kilometers) and the Chicxulub crater in the Gulf of Mexico (at 110 miles, or 180 kilometers).

It displaces the Manicougan crater in Quebec and Popigai crater in Russia (both roughly 60 miles, or 100 kilometers across), which now become Earth�s fifth-largest known craters.

Once in a lifetime find

Lasky, who works for the Geological Survey of Western Australia, became interested in the crater�s potential existence after looking through drilling reports of a company prospecting for coal in the region in 1981.

The report noted unusual deformations of quartz, but the company shrugged off the data.

Intrigued, Iasky and geoscientist Arthur Mory looked further, taking their own drilling samples in April 1999 and concluding the deformations were from a massive impact.

Their peer-reviewed findings are soon to be published in the scientific journal Earth and Planetary Science Letters.

"This is the kind of find that comes once in a lifetime," Iasky said.

The huge crater lies mostly on private land, and is virtually imperceptible to the untrained eye amid the region's rolling hills and barren rock land. Geologic evidence of the crater can only be gained by analyzing rock samples lying 195 to 650 feet (60 to 200 meters) below ground for signs of metamorphism.

What's more, there's no direct evidence of the asteroid, which itself was pulverized as the crash�s first victim. "This is the kind of find that comes once in a lifetime." Robert Lasky, geoscientist

The find poses new avenues for future research. The most immediate is to pin down more precisely when the impact occurred � since it would significantly add to our knowledge of prehistoric evolution.

Three extinction waves occurred during the likely date range.

New avenues for research

An extinction episode took place in the late Devonian Period (roughly 364 million years ago), a time when reptiles were migrating from the oceans to the continents.

Another extinction wave occurred at the end of the Permian Period (247 million years ago) and a third at the end of the Triassic Period (214 million years ago).

Perhaps the best known wave of extinction occurred 65 million years ago, when the impact that created the Chicxulub crater likely caused the extinction of the dinosaurs. The Woodleigh crater was created by an impact likely very close in its force to the Chicxulub, Iasky said.

Follow-up research at the Woodleigh crater could include searching for fossilized bacteria in and around the structure as a means of gauging how long it took before Earthly life began regenerating.

It's also possible the asteroid itself carried hardy organisms that survived the crash and took root on Earth. Pursuing these avenues of research are highly relevant to exploring crater-scarred Mars � since they could help scientists devise more sophisticated tests for future missions there.

The center of the Woodleigh crater is located roughly 100 miles (160 kilometers) southeast of the Western Australian pastoral town of Carnarvon, roughly halfway between Carnarvon and Geraldton in the Shark Bay region north of Perth.

Australia has long presented a rich field for researchers due to the continent�s geologic stability.

Because the country hasn't known many episodes of volcanic activity and metamorphic change, it offers an incredibly well preserved window into Earth's deep geologic past.


Ancient iron-rich rocks point to early occurrence of land-based life

October 26, 1999 - Denver

Iron-rich rock formations dating to 2.3 billion years ago suggest that the Earth's land masses were covered with living things at least a billion years earlier than previously thought, according to a Penn State geologist.

"Until now, the earliest accepted date for land-based life was 1.2 billion years ago, but now we can push that back at least another billion years," says Dr. Hiroshi Ohmoto, professor of geosciences and director of the Penn State Astrobiology Research Center. "Of course, terrestrial life back then was more in the nature of bacterial mats than oak trees and mammals."

Ohmoto, in collaboration with Nick Beukes of Rand Afrikaans University, Johannesburg, South Africa, investigated laterites, iron-rich deposits that form when organic acids -- those acids created when living things decay -- leach iron from upper layers of rock and then deposit them as oxides in layers below. The normal make-up of a laterite is three bands -- an iron-deficient layer covered by an iron-rich layer that is covered by an iron-deficient layer. Modern laterites form in the tropics where large amounts of organic material rapidly decay.

"In order for laterites to form, there must be organic material and atmospheric oxygen," Ohmoto told attendees at the annual meeting of the Geological Society of America today (Oct.26) in Denver. "Since we have now traced these laterites to 2.3 billion years ago, there must have been atmospheric oxygen and terrestrial life at that time." Ohmoto originally looked at formations in Waterval Onder, South Africa, an area near Pretoria. However, in this area, the iron-rich layer and upper iron-poor layer have eroded away. To get the big picture, the researchers looked at core samples drilled by miners who typically drill through these layers looking for gold and uranium ores buried much farther down.

"We looked at two cores in South Africa and one in Botswana that showed the complete series of rocks," says Ohmoto. "It appears that this laterite formation covers a rather large area."

There are several places further west where the formation is actually exposed, but these locations had previously been dated as much younger rock. The researchers have now identified these laterite formations as part of the same, much older formation, because it sits directly on the Hekpoort basalt, an extensive basalt formation that was extruded 2.3 to 2.4 billion years ago.

"Because we can trace the basalt all the way across, even to a depth of 2,600 feet, we know that the laterite deposits directly above are only slightly younger than the basalts," says Ohmoto.

Geologists currently are involved in a debate as to when significant amounts of oxygen appeared in the Earth's atmosphere. These laterites suggest that oxygen was plentiful 2.3 billion years ago, both for the generation of land-based biota and to convert iron to iron oxides.


Core, what a scorcher

September 30, 1999 - Journal of Nature

British scientists have worked out the temperature at the centre of the Earth - 5,500 degrees C - hotter than many previous estimates.

The new temperature is about as hot as the Sun's surface and the team from University College London believe their figure is the most accurate yet achieved.

"Its crucial to know the temperature of the Earth's core," explained Professor David Price. "There's tremendous heat energy stored down there and the heat flowing out of the core causes earthquakes, volcanoes and the drift of continents.

"It also causes the turbulent swirling motion of liquid iron in the core that creates the Earth's magnetic field. But if you don't know the core temperature you just can't understand how this all works," he said.

Iron smelting

The team used a Cray T3E supercomputer to make a remarkable calculation of the melting point of iron, the predominant element in the Earth's core.

The Earth's inner core is solid, whereas the outer core is liquid, so the melting point of iron is a good indication of the temperature.

"If we know the melting temperature of iron at the pressure of the boundary between the solid and the liquid core, then we know the temperature of the Earth at that boundary," team leader Dr Dario Alfe told BBC News Online.

The new "ab initio" calculation was explained by another team member Professor Mike Gillan: "By using the basic laws of physics you can model any material as a collection of atoms and calculate the melting temperature - and anything else you want - completely from scratch."

The key to the calculation was predicting the melting point at the crushing pressures which exist at our planet's centre, 6,370 kilometres down.

The big squeeze

Previous estimates of the temperature have been made by trying to simulate these ultra-extreme conditions in the laboratory, but the results have varied by over 2,000�C. The UCL team claim an uncertainty in their figure of plus-or-minus 600�C.

The team calculated the melting temperature of pure iron at the core to be 6,400�C but the 10% impurities of nickel, sulphur and other elements reduce the figure to 5,500�C.

"The idea that we are sitting on top of a seething mass of molten iron as hot as the Sun may be pretty scary," remarked Professor Mike Gillan. "But scientifically the core temperature is important because it is a crucial in understanding how the Earth changes over time."


Georgia cave yields unexpected treasures

Nando News - June 14, 1999 - Climax, Ga.

Climax Cave's dark, jagged mouth sits at the bottom of a 65-foot depression hewn, over eons, from limestone by rainwater. It's a sizable feat just to reach it. Visitors clamber down steep banks littered with uprooted trees and leaves. One false step could mean a dangerous tumble.

Biologists are willing to make the journey to Climax Cave and about 200 other caves in Georgia. They hope to identify species, assess the condition of the caves and develop a plan for protecting the delicate and sensitive ecosystems.

During a six-hour visit to Climax Cave, near the small town of Climax in the state's southwest, the biologists discovered the rare Georgia blind salamander, known to live at only two locations.

They also found the Dougherty Plain crayfish and the Southeastern myotis bat, both rare and in need of preservation. Thousands of years of evolution in a dark environment have left the crayfish and salamander completely devoid of skin pigment.

"We really don't know what lives in caves," said John Jensen, a biologist for the Georgia Department of Natural Resources. "We've kind of put the cave ecosystems on the back burner, but it's important to know what occurs in caves so we can conserve and manage them."

Species documented so far in north Georgia caves include the Tennessee cave salamander, the gray bat and a host of beetles, crayfish and spiders.

Periodically, Jensen and fellow biologist Jim Ozier crawl into coveralls and don helmets to descend into the darkness of a new cave. They have checked about 30 since the study started last July.

"Most of the things we're taking a look at are tiny things - beetles, spiders, millipedes," Ozier said. "Some occur nowhere else but in caves and sometime just in one or two caves."

Among other caves on the biologists' list is Ellison's Cave in northwest Georgia. It's a 600-foot pit thought to be the deepest in the eastern United States.

"Every cave is different," Jensen said. "Some have vertical pits that you have to rappel into. They're big black holes and that can be spooky.

"Some have big doors," he said. "Some have narrow cracks that you have to crawl through. That's kind of spooky, but once you get in there, the stuff that's there is so interesting and beautiful that it kind of takes the fear away."

Information collected during the survey will be used to preserve caves on public land and to advise people who own caves on private land - like Climax Cave owned by cattle rancher G.W. Long.


San Francisco - AP - August 1, 1997

A NASA physicist said on Friday he had found what may be the fossilized remains of extraterrestrial microorganisms in a meteorite, providing more evidence that life may have existed beyond Earth.

Astrophysicist Richard Hoover said that while investigating samples of the Murchison meteorite that fell on Australia in 1969, he had found complex structures that appeared to be biological.

"It is potentially the case that it's signs of life from somewhere other than the planet Earth. That is a real possibility that must be considered," Hoover told Reuters in a telephone interview from San Diego.

Hoover, an astrophysicist at the National Aeronautics and Space Administration's George C. Marshall Space Flight Center in Huntsville, Alabama, cautioned that more study was needed and he could not say for sure where the microscopic structures came from.

Hoover's work appears to support the findings of U.S. scientists who announced last year that they had found possible fossilized microbes in a meteorite from Mars.

In a scientific paper presented at a conference in San Diego this week, Hoover said he had concluded that the Murchison meteorite contained "a population of indigenous microfossils," shaped like mushrooms, stalks or filaments.

The mushroom-shaped bodies "are considered to represent the carbonized remains of biological forms," he wrote.

Hoover obtained images of the forms using an environmental scanning electron microscope and analyzed them with x-ray energy dispersive spectroscopy.

The bodies resembled some types of bacteria, but experts had been unable to identify them as known earthly microbial groups, Hoover said. He said the bodies resembled other unidentifiable forms found in another meteorite by earlier researchers.

"It is concluded that this population of complex structures may represent remains of extraterrestrial microorganisms which lived within or contaminated the parent body of the Murchison meteorite at various times during the past 4.4 billion years," Hoover wrote.

The parent body of the Murchison meteorite is unknown, but Hoover said there was strong evidence that it did not come from Earth, the moon or Mars and may have come from a comet or asteroid. He said the structures he had observed appeared to have arrived on Earth with the meteorite and not be something that found its way there after it landed.

It was also possible that asteroid impacts on Earth billions of years ago could have catapulted materials from Earth into space and that any microfossils in the meteorite could have originated on Earth. But the same thing could have happened on Mars or another body, he said.

"We are doing additional work to determine what (the structures) are ... and to determine if we can obtain carbon isotope measurements to give an idea of whether they are terrestrial or extraterrestrial in nature." He said that earlier this year a scientific team in Russia reported finding similar structures within the Murchison meteorite. Hoover said scientists must continue studying meteorites.

"The meteorites are messages from space. They are bringing us information that we must study and learn, telling us where to go to seek conclusive proof for the existence of extraterrestrial life," he said.




GEOLOGY

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