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Antarctica Geology
With crystalline air and ancient ice, Antarctica is Earth’s harshest land.

Antarctica Expedition 2003 - Polar Pioneer at AnchorMost visitors to Antarctica glimpse only fragments of the actual continent. Antarctica is 98% covered with ice and it is sometimes difficult to remember that there is rock lying below the tons of ancient frozen water.

However, scientists have managed to study the continent and have drawn some interesting observations and conclusions about this land covered with ice.

Antarctica is the world’s fifth largest continent, with an area of 5.9 million square miles. It is almost twice the size of Australia or Europe and three-quarters the size of South America. The continent is roughly shaped like a comma with its tail pointing towards South America. The comma tail and its root are generally referred to as West Antarctica and the main body of the comma is usually called East Antarctica. Geologists have determined that the underlying rocks and sediment of East Antarctica are a stable platform of sedimentary rocks, heavily metamorphosed and over-laid with younger sediments. The western side of the continent is a complex of folded and metamorphosed sediments, mostly of volcanic origin. Visitors can most clearly see this structure in the mountains of the Antarctic Peninsula. Interestingly, East and West Antarctica evolved in different ways and only came together relatively recently in geological terms. The mountains of the Trans-Antarctic Range separate the two sides of the continent.Map of Antarctica: Click for larger imager

The rocks of East Antarctica are among the oldest found on the planet. Many of the rocks found here are at least 3 billion years old. The oldest rock discovered on Earth came from Enderby Land in 1986 and is estimated to be 3.86 billion years old. In contrast, the rocks on Western Antarctica are relatively new: 700 million years old on average.

The continent fits within the polar circle, which is a circular line drawn 23 degrees 27’ from the South Geological Pole. (A distance of 1618 miles). The polar circle cuts through the Antarctic Peninsula, leaving the northern end of the peninsula and the South Shetland Islands north of the polar circle.

Antarctica contains some very large mountains. Interestingly, much of the mass of these mountains is actually buried beneath the massive ice accumulations. The highest mountain on the continent is Vinson Massif with a peak of 16,859 feet. This mountain is part of a cluster of mountains in the Eternity Range on the Western side of Antarctica.

Active volcanoes are found in three locations on Antarctica: the western Ross Sea, Western Antarctica and along the Antarctic Peninsula. These are truly active volcanoes and the probability that a major eruption could occur at any time in Antarctica is high. In the Ross Sea region, much of the activity occurs along the front of the Trans-Antarctic Range, although a number of small volcanic vents have been detected beneath the sea itself. High in the Transantarctic Mountains of northern Victoria Land are the Pleidas, a set of very young volcanic domes which first erupted about 1000 years ago. Mt. Melbourne is near Terra Nova Bay and has steaming ground at its summit and an ash layer that indicates that it erupted less than 200 years ago.

In Marie Byrd Land on West Antarctica, Mt. Berlin is considered an active volcano. Aerial studies seem to indicate depressions in the nearby ice, which might indicate an ongoing eruption beneath the ice of the West Antarctic Ice Sheet from this volcano. In the Peninsula region, Deception Island is a volcanic island complete with black rocks andMt. Erebus on Ross Island: Photo Courtesy - Philip Kyle sand on the beaches.

Antarctica’s most famous volcanic peak is Mt. Erebus on Ross Island. Erebus is one of the largest volcanoes in the world, ranking in the top 20 in total size and reaching 12,451 feet in height. Small eruptions are common even today, occurring 6 to 10 times each day since the mid-1980s.
Mt. Terror is an extinct volcano nearby to Mt. Erebus, rising to 10,957
feet.

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2003 South Pole USGS Marker

2003 South Pole USGS MarkerSince Eco-Photo Explorers visited Antarctica in 2003, we decided to show you what the 2003 South pole marker looks like.

Location: Antarctica
Coordinates: 90 Degrees South
Elevation: 9,300 ft

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The 2003 South Pole marker has been designed to show both the existing geodesic dome station as well as the new elevated station. The existing dome side of the mark has perfectly captured a mid-winter scene complete with moon and aurora. This part of the mark is recessed and gives a darkened (night) appearance. The (new) elevated station is shown with a brilliant sun and South Pole characteristic "sun dogs" surrounding it.

The geographic pole marker is a convenient tool to determine this flow speed; by measuring the distance between successive pole markers, one can determine the total distance that the ice has flowed in one year.  The Geographic South Pole is 9300 feet (2835m) above sea level. Because the actual South Pole is covered by roughly 9000 feet (2700m) of moving glacial ice the surface mark actually moves approximately 30 feet (10m) annually. Each January 1st the position of 90 degrees south is re-determined and a new unique survey marker is erected.

If you measure the distance between the last four successive pole markers, you would find that the distance was the same between each successive pair meaning that the speed of the two-mile-thick glacier has remained at a constant 9-10 m/year for at least the last three years (grid West). What's pretty interesting, is that by standing inline with these markers and looking out to the horizon, you will see that at some point in the near future the geographic South Pole will pass between the silver geodesic dome and the orange Skylab building.

How is the Pole Located?

Cathleen McDermott and Dale Benson of the USGS (United States Geological Service) explain how the they moved the South pole marker during their stay. Since they know the geographical marker on the pole moves approximately 30 feet (10m) annually with the flowing ice. They used two methods to find the new spot:

Information Courtesy:
University of Chicago Department of
Astronomy and Astrophysics

One is called the Shadow Tip Method - If you stand where the pole is and look, you can see the straight line of poles stretching off toward the distance. The Shadow Tip method involves putting a tripod on top of the old marker and sticking an eight foot rod vertically on the tripod.

Of course all directions at the South Pole are technically "north". For that reason we have to define another type of north, called "grid north," which points along the longitude line called the Prime Meridian. If you were to follow this line of longitude north eventually you would reach Greenwich, England. Other directions at the South Pole are then defined with respect to grid north and are expressed as angles of azimuth. Zero degrees azimuth is in the direction of grid north. Other azimuths angles are then described as west (turning to the left) or east turning to the right) of grid north. For example, if you faced exactly grid north and then put your left hand straight out to your side it would be pointing to ninety degrees west azimuth.

When the sun gets to azimuth 40 degrees west of grid north, it is lined up with the other markers, and the tip of the shadow of the eight foot pole marks where the new pole should go. (The first of these pole markers was places with the sun at that azimuth.) And an eight foot rod is used on top of a six foot tripod, because together they cast a shadow that is the right length for the rate that the ice is moving each year. At this time of the year the Sun is near its maximum elevation of 23.5 degrees. This method is approximate, but is an easy way to find where the pole should be based upon what we know about the direction and rate of the flow of the ice.

The other method used the Global Positioning system (GPS) - A satellite network was used to determine the exact spot where 90 degrees south latitude is on planet Earth. The GPS reading is a few inches off from the shadow-tip reading, so that there is an official South Pole at the shadow tip and a little pipe at the GPS spot.

Setting the Southpole using GPS - Click here for a larger image...Data is recorded from the GPS antenna on the tripod in order to locate the site for the geographic South Pole for January 1, 2004. This data is used in conjunction with base station data that is acquired from the GPS reference station on the Skylab building. The location of the pole on January 1, 2003 is seen about ten meters away in the background.

Photo Courtesy: J. Dana Hrubes
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Once the location is found, its time to set the marker - The South Pole marker is about twelve feet long, but about two-thirds gets pounded into the ground (ice).

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Southern Lights at the South Pole

By National Science Foundation
posted: 11:09 am ET 22 May 2002

Aurora Australis - click here to view larger image...Rarely seen images of the Aurora Australis, the atmospheric phenomenon known familiarly as the Southern Lights, are available from the National Science Foundation (NSF). Like its more familiar counterpart, the Aurora Borealis, or Northern Lights, the phenomenon is caused by the solar wind passing through the upper atmosphere. But the Southern Lights is much less frequently observed because so few people live in Antarctica during the austral winter.

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Jonathan Berry, who is wintering at NSF's Amundsen-Scott South Pole Station, took the photo shown above against the backdrop of the months-long polar night. NSF operates the only scientific station at the South Pole and conducts astrophysical research there. NSF also is currently rebuilding and modernizing the station in a logistically difficult, multiyear operation.

The Cause of Auroras - Auroras are caused by high energy particles from the solar wind that are trapped in the Earth's magnetic field. As these high energy particles move back and forth along the magnetic field lines, they will eventually drift down into the atmosphere near the north and south magnetic poles where the magnetic field lines disappear into the Earth.

The delicate colors in the night sky are caused by electrons colliding with other molecules in the atmosphere and transferring its energy to the atom it hits, thus exciting these molecules. When these molecules start to decay, the atom returns to its original state and releases the electron and also some of the energy it gained from the electron in the form of light. This emitted light is what we see as the aurora. The color of the light is determined by what atom released it.  Every type of atom releases a specific color of light, and no two types of atoms release the same color of light.

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Last Modified: December 21, 2009

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