* Astronomy

Members Login
Post Info
TOPIC: The Earth


L

Posts: 131433
Date:
Space Weather
Permalink  
 


First Global Connection Between Earth And Space Weather Found
Weather on Earth has a surprising connection to space weather occurring high in the electrically-charged upper atmosphere, known as the ionosphere, according to new results from NASA satellites.

"This discovery will help improve forecasts of turbulence in the ionosphere, which can disrupt radio transmissions and the reception of signals from the Global Positioning System" - Thomas Immel of the University of California, Berkeley, lead author of a paper on the research published August 11 in Geophysical Research Letters.

Researchers discovered that tides of air generated by intense thunderstorm activity over South America, Africa and Southeast Asia were altering the structure of the ionosphere.

Read more

__________________


L

Posts: 131433
Date:
RE: The Earth
Permalink  
 


Planet Earth may have 'tilted' to keep its balance, say scientists

Imagine a shift in the Earth so profound that it could force our entire planet to spin on its side after a few million years, tilting it so far that Alaska would sit at the equator. Princeton scientists have now provided the first compelling evidence that this kind of major shift may have happened in our world's distant past.
By analysing the magnetic composition of ancient sediments found in the remote Norwegian archipelago of Svalbard, Princeton University's Adam Maloof has lent credence to a 140-year-old theory regarding the way the Earth might restore its own balance if an unequal distribution of weight ever developed in its interior or on its surface.
The theory, known as true polar wander, postulates that if an object of sufficient weight -- such as a supersized volcano -- ever formed far from the equator, the force of the planet's rotation would gradually pull the heavy object away from the axis the Earth spins around. If the volcanoes, land and other masses that exist within the spinning Earth ever became sufficiently imbalanced, the planet would tilt and rotate itself until this extra weight was relocated to a point along the equator.

"The sediments we have recovered from Norway offer the first good evidence that a true polar wander event happened about 800 million years ago. If we can find good corroborating evidence from other parts of the world as well, we will have a very good idea that our planet is capable of this sort of dramatic change" - Adam Maloof, an assistant professor of geosciences.

Maloof's team, which includes researchers from Harvard University, the California Institute of Technology and the Massachusetts Institute of Technology as well as Princeton, will publish their findings in the Geological Society of America Bulletin on Friday, Aug. 25.
True polar wander is different from the more familiar idea of "continental drift," which is the inchwise movement of individual continents relative to one another across the Earth's surface. Polar wander can tip the entire planet on its side at a rate of perhaps several meters per year, about 10 to 100 times as fast as the continents drift due to plate tectonics. Though the poles themselves would still point in the same direction with respect to the solar system, the process could conceivably shift entire continents from the tropics to the Arctic, or vice versa, within a relatively brief geological time span.
While the idea that the continents are slowly moving in relation to one another is a well-known concept, the less familiar theory of true polar wander has been around since the mid-19th century, several decades before continental drift was ever proposed. But when the continents were proven to be moving under the influence of plate tectonics in the 1960s, it explained so many dynamic processes in the Earth's surface so well that true polar wander became an obscure subject.

"Planetary scientists still talk about polar wander for other worlds, such as Mars, where a massive buildup of volcanic rock called Tharsis sits at the Martian equator. But because Earth's surface is constantly changing as the continents move and ocean crustal plates slide over and under one another, it's more difficult to find evidence of our planet twisting hundreds of millions of years ago, as Mars likely did while it was still geologically active." - Adam Maloof.

However, the sediments that the team studied in Svalbard from 1999 to 2005 may have provided just such long-sought evidence. It is well known that when rock particles are sinking to the ocean floor to form layers of new sediment, tiny magnetic grains within the particles align themselves with the magnetic lines of the Earth. Once this rock hardens, it becomes a reliable record of the direction the Earth's magnetic field was pointing at the time of the rock's formation. So, if a rock has been spun around by a dramatic geological event, its magnetic field will have an apparently anomalous orientation that geophysicists like those on Maloof's team seek to explain.

"We found just such anomalies in the Svalbard sediments. We made every effort to find another reason for the anomalies, such as a rapid rotation of the individual crustal plate the islands rest upon, but none of the alternatives makes as much sense as a true polar wander event when taken in the context of geochemical and sea level data from the same rocks" - Adam Maloof.

The findings, he said, could possibly explain odd changes in ocean chemistry that occurred about 800 million years ago. Other similar changes in the ocean have cropped up in ancient times, but at these other times scientists know that an ice age was to blame.

"Scientists have found no evidence for an ice age occurring 800 million years ago, and the change in the ocean at this juncture remains one of the great mysteries in the ancient history of our planet. But if all the continents were suddenly flipped around and their rivers began carrying water and nutrients into the tropics instead of the Arctic, for example, it could produce the mysterious geochemical changes science has been trying to explain" - Adam Maloof.

Because the team obtained all its data from the islands of Svalbard, Maloof said their next priority would be to seek corroborating evidence within sediments of similar age from elsewhere on the planet. This is difficult, because most 800-million-year-old rocks have long since disappeared. Because the Earth's crustal plates slide under one another over time, they take most of geological history back into the planet's deep interior. However, a site his team has located in Australia looks promising.

"We cannot be certain of these findings until we find similar patterns in rock chemistry and magnetics on other continents. Rocks of the same age are preserved in the Australian interior, so we'll be visiting the site over the next two years to look for additional evidence. If we find some, we'll be far more confident about this theory's validity" - Adam Maloof.

Maloof said that true polar wander was most likely to occur when the Earth's landmasses were fused together to form a single supercontinent, something that has happened at least twice in the distant past. But he said we should not worry about the planet going through a major shift again any time soon.

"If a true polar wander event has occurred in our planet's history, it's likely been when the continents formed a single mass on one side of the Earth. We don't expect there to be another event in the foreseeable future, though. The Earth's surface is pretty well balanced today."

Maloof's research was sponsored in part by the National Science Foundation.

Source

__________________


L

Posts: 131433
Date:
6Q0B44E
Permalink  
 


Something has been spotted orbiting around our planet.

6Q0B44E

Date       UT      R.A. (J2000) Decl.  Elong.  V        Motion      Distance
2006 08 30 1200 23 40 00.3 -17 09 34 162.1 19.8 13.29 127.6 710538
2006 08 31 1200 23 57 35.0 -20 16 27 157.5 20.0 12.70 126.0 726248
2006 09 01 1100 00 14 19.9 -23 01 02 153.3 20.2 12.14 124.3 741697


Source

-- Edited by Blobrana at 13:41, 2006-08-30

__________________


L

Posts: 131433
Date:
RE: The Earth
Permalink  
 


Planet Earth may have 'tilted' to keep its balance, say scientists

Imagine a shift in the Earth so profound that it could force our entire planet to spin on its side after a few million years, tilting it so far that Alaska would sit at the equator. Princeton scientists have now provided the first compelling evidence that this kind of major shift may have happened in our world's distant past.

By analysing the magnetic composition of ancient sediments found in the remote Norwegian archipelago of Svalbard, Princeton University's Adam Maloof has lent credence to a 140-year-old theory regarding the way the Earth might restore its own balance if an unequal distribution of weight ever developed in its interior or on its surface.
The theory, known as true polar wander, postulates that if an object of sufficient weight --such as a supersized volcano -- ever formed far from the equator, the force of the planet's rotation would gradually pull the heavy object away from the axis the Earth spins around. If the volcanoes, land and other masses that exist within the spinning Earth ever became sufficiently imbalanced, the planet would tilt and rotate itself until this extra weight was relocated to a point along the equator.

"The sediments we have recovered from Norway offer the first good evidence that a true polar wander event happened about 800 million years ago. If we can find good corroborating evidence from other parts of the world as well, we will have a very good idea that our planet is capable of this sort of dramatic change" - Adam Maloof, an assistant professor of geosciences.

Maloof's team, which includes researchers from Harvard University, the California Institute of Technology and the Massachusetts Institute of Technology as well as Princeton, will publish their findings in the Geological Society of America Bulletin on Friday, Aug. 25.
True polar wander is different from the more familiar idea of "continental drift," which is the inchwise movement of individual continents relative to one another across the Earth's surface. Polar wander can tip the entire planet on its side at a rate of perhaps several meters per year, about 10 to 100 times as fast as the continents drift due to plate tectonics. Though the poles themselves would still point in the same direction with respect to the solar system, the process could conceivably shift entire continents from the tropics to the Arctic, or vice versa, within a relatively brief geological time span.
While the idea that the continents are slowly moving in relation to one another is a well-known concept, the less familiar theory of true polar wander has been around since the mid-19th century, several decades before continental drift was ever proposed. But when the continents were proven to be moving under the influence of plate tectonics in the 1960s, it explained so many dynamic processes in the Earth's surface so well that true polar wander became an obscure subject.

"Planetary scientists still talk about polar wander for other worlds, such as Mars, where a massive buildup of volcanic rock called Tharsis sits at the Martian equator. But because Earth's surface is constantly changing as the continents move and ocean crustal plates slide over and under one another, it's more difficult to find evidence of our planet twisting hundreds of millions of years ago, as Mars likely did while it was still geologically active" - Adam Maloof.

However, the sediments that the team studied in Svalbard from 1999 to 2005 may have provided just such long-sought evidence. It is well known that when rock particles are sinking to the ocean floor to form layers of new sediment, tiny magnetic grains within the particles align themselves with the magnetic lines of the Earth. Once this rock hardens, it becomes a reliable record of the direction the Earth's magnetic field was pointing at the time of the rock's formation. So, if a rock has been spun around by a dramatic geological event, its magnetic field will have an apparently anomalous orientation that geophysicists like those on Maloof's team seek to explain.

"We found just such anomalies in the Svalbard sediments. We made every effort to find another reason for the anomalies, such as a rapid rotation of the individual crustal plate the islands rest upon, but none of the alternatives makes as much sense as a true polar wander event when taken in the context of geochemical and sea level data from the same rocks" - Adam Maloof.

The findings, he said, could possibly explain odd changes in ocean chemistry that occurred about 800 million years ago. Other similar changes in the ocean have cropped up in ancient times, but at these other times scientists know that an ice age was to blame.

"Scientists have found no evidence for an ice age occurring 800 million years ago, and the change in the ocean at this juncture remains one of the great mysteries in the ancient history of our planet. But if all the continents were suddenly flipped around and their rivers began carrying water and nutrients into the tropics instead of the Arctic, for example, it could produce the mysterious geochemical changes science has been trying to explain" - Adam Maloof.

Because the team obtained all its data from the islands of Svalbard, Maloof said their next priority would be to seek corroborating evidence within sediments of similar age from elsewhere on the planet. This is difficult, Maloof said, because most 800-million-year-old rocks have long since disappeared. Because the Earth's crustal plates slide under one another over time, they take most of geological history back into the planet's deep interior. However, Maloof said, a site his team has located in Australia looks promising.

"We cannot be certain of these findings until we find similar patterns in rock chemistry and magnetics on other continents. Rocks of the same age are preserved in the Australian interior, so we'll be visiting the site over the next two years to look for additional evidence. If we find some, we'll be far more confident about this theory's validity" - Adam Maloof.

Maloof said that true polar wander was most likely to occur when the Earth's landmasses were fused together to form a single supercontinent, something that has happened at least twice in the distant past. But he said we should not worry about the planet going through a major shift again any time soon.

"If a true polar wander event has occurred in our planet's history, it's likely been when the continents formed a single mass on one side of the Earth. We don't expect there to be another event in the foreseeable future, though. The Earth's surface is pretty well balanced today."

Source

__________________


L

Posts: 131433
Date:
Permalink  
 

Earth's Wobble
New technologies are enabling scientists to determine precisely the extent and causes of Earth's short-term wobbling. Like a spinning top, Earth wobbles as it rotates on its axis. In fact, it displays many different wobbling motions, ranging in period from a few minutes to billions of years. Some of these are well studied, like the Chandler wobble of 433 days and the annual wobble, which together can tilt Earth's axis up to 10 meters from its nominal centre.

Earth's irregular, shorter term wobbles, lasting a week or so, have been more difficult to study, partly because these motions are usually masked by those of more prominent wobbles. Now, scientists in Belgium and France have taken advantage of a quirk in the pattern of large-scale motions and the advent of the Global Positioning System (GPS) to pin down short-term wobbles that occurred from November 2005 through February 2006.
During this period, the Chandler wobble and the annual wobble essentially cancelled each other out, an event that occurs every 6.4 years, allowing the researchers to focus on the short-period wobbles. Over these three and a half months, the pole position traced small loops, ranging in size from that of a sheet of A4 paper down to that of a cell phone, and it remained within a one meter square during these four months.

wobble1
Wobbles in Earth's rotation at the North Pole from Nov. 1, 2005 to Feb. 14, 2006. Each marker represents the position of the pole on one day, with five loops identified in an unprecedented display of precision.
Image credit: AGU


Sébastien Lambert of the Royal Observatory of Belgium and colleagues there and at the Paris Observatory took advantage of the opportunity to track short-term wobbles, using newly available GPS data that establish the location of the poles precisely. They then sought to determine why these motions occurred when they did.
In a paper scheduled to be published 1 July in Geophysical Research Letters, they conclude that weather patterns in the northern hemisphere played a significant role. Both the location of high- or low-pressure centres--for example, over Asia or northern Europe--and the relationship of these weather systems to each other played a measurable role in creating, or "exciting," small, short-term wobbles, they report.

The ocean also affects short-term wobbles, according to Lambert and his colleagues. They were able to correlate oceanic and atmospheric pressure variations with the small observed wobbles during the study period. Although these forces had been credited by previous researchers with maintaining the large Chandler wobble, this was the first time that scientists have been able to demonstrate that day-to-day changes in atmospheric pressure produce a measurable effect on Earth's rotation.

Source

__________________


L

Posts: 131433
Date:
Permalink  
 

For a decade now, ESA satellites have been continuously surveying fires burning across the Earth’s surface. Worldwide fire maps based on this data are now available to users online in near real time through ESA's ATSR World Fire Atlas.

Read more



http://dup.esrin.esa.int/ionia/wfa/index.asp

-- Edited by Blobrana at 17:02, 2006-05-24

__________________
«First  <  110 11 12 | Page of 12  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard