WHAT'S UNDER THE ANTARCTIC?
Scientists create stunning map of what's under the Antarctic - and reveal mysterious volcanic ‘hot zones’ are recently active
- Recordings of earthquake vibrations used to create maps of below valley
- Giant blob of super heated rock beneath Mount Sidley seen on the map
- Hot rock beneath Bentley Subglacial Trench, which recently became active
- Line of volcanoes means there might be hidden mantle plumes
- Reported heat flow in an area was 4 times higher than the global average
By Stacy Liberatore For Dailymail.com
Published: 13:31 EST, 10 December 2015
There is a mysterious line of volcanoes that have formed in certain areas of Antarctica - and could hold the key to the area's future.
For years researchers have been trying to look below the ice sheets to find out why but, due to extreme cold, their technology has not been able to gather any answers.
Now with the assistance of ruggedized seismometers, geologists have been able to get the first look at the mantle below the ice, revealing areas of 'hot rock'.
Our understanding of what’s going on is really hampered because we can’t see the geology,’ said Andrew Lloyd, a graduate student in earth and planetary sciences in Arts & Sciences at Washington University in St. Louis.
‘We have to turn to geophysical methods, such as seismology, to learn more.’
During the austral summer of 2009 to 2010, Lloyd was part of an expedition that used seismometers across the West Antarctic Rift System and Marie Byrd Land.
When he returned to collect the data, he traveled more than 1,000 miles and live in a Scott.
The recordings from the instrument were of earthquakes from January 2010 to January 2012, which were used to create maps of seismic velocities below the first valley.
This was the first time researchers had technology that was tough enough to withstand Antarctica’s harsh weather and the first time humans eyes have seen below this region.
A giant blob of super heated rock about 60 miles beneath Mount Sidley was seen on the map.
This is the last chain of volcanic mountains in Marie Byrd Land at one end of the transect.
WHAT IS A SEISMOMETER?
A seismograph is a device for measuring the movement of the earth, and consists of a ground motion detection sensor, called a seismometer, coupled with a recording system.
A simple seismometer that is sensitive to up-down motions of the earth can be understood by visualizing a weight hanging on a spring.
The spring and weight are suspended from a frame that moves along with the Earthʼs surface.
As the earth moves, the relative motion between the weight and the earth provides a measure of the vertical ground motion.
If a recording system is installed, such as a rotating drum attached to the frame, and a pen attached to the mass, this relative motion between the weight and earth can be recorded to produce a history of ground motion, called a seismogram.
Seismographs operate on the principle of inertia -- stationary objects, such as the weight in the above picture, remain stationary unless a force is applied to them.
The weight thus tends to remain stationary while the frame and drum are moving. Seismometers used in earthquake studies are designed to be highly sensitive to ground movements, so that movements as small as 1/10,000,000 centimeters (distances almost as small as atomic spacing) can be detected at very quiet sites.
What surprised researchers the most was the hot rock beneath Bentley Subglacial Trench, a deep basin at the other end of the transect.This means the rift system just recently became active.
Mount Sidley, the highest volcano in Antarctica, sits directly above a hot region in the mantle, Lloyd said.
Mount Sidley is the southernmost mountain in a volcanic mountain range in Marie Byrd Land, a mountainous region dotted with volcanoes near the coast of West Antarctica.
‘A line of volcanoes hints there might be a hidden mantle plume, like a blowtorch, beneath the plate,’said Doug Wiens, PhD, professor of earth and planetary sciences and a co-author on the paper.
Lloyd on his Skidoo towing a Conestoga (the cook shack for the traverse team) in front of Mount Sidley, a volcano that blew out its side much as Mount St. Helens did (pictured). A giant blob of super heated rock about 60 miles beneath Mount Sidley was seen on the map
‘The volcanoes would pop up in a row as the plate moved over it.’
‘But it's a bit unclear if this is happening here,’ he said.
‘We think we know which direction the plate is moving, but the volcanic chain is going in a different direction and two additional nearby volcanic chains are oriented in yet other directions.’
‘If this was just a plate moving over a couple of mantle plumes, you'd expect them to line up, as they do in the Hawaiian Islands.’
It was apparent that there was higher heat flow into the bottom of the ice sheet in this area, regardless of the hot zone’s ill-defined shape, according to the researchers
A team maintains a seismic station on Thwaites Glacier, an area of heavy snowfall. The seismometer is in the orange dome in the lowest part of the three-step snow pit (pictured). What surprised researchers the most was the hot rock beneath Bentley Subglacial Trench, a deep basin at the other end of the transect
‘If you removed the ice, West Antarctica would rebound, and most of it would be near sea level.'
'But the narrower and deeper basins might remain below it,’ Lloyd said.
‘The Bentley Subglacial Trench, which is the lowest point on Earth not covered by an ocean, would still be a kilometer and a half below sea level if the ice were removed.’
The West Antarctic Rift is less known, because it’s so hidden and leaves a lot of room for research and discovery.
‘We didn't know what we'd find beneath the basin,’ Wiens said.
‘For all we knew it would be old and cold.’
‘We didn't detect any earthquakes, so we don't think the rift is currently active, but the heat suggests rifting stopped quite recently.’
There was higher heat flow into the bottom of the ice sheet in this area, regardless of the hot zone’s ill-defined shape. The rift valley was created in the late Cretaceous period, a time of diffuse extension, and more focused extension created deep basins like the Bentley Subglacial Basin and the Terror Rift in the Ross Sea
The rift valley was created in the late Cretaceous period, a time of diffuse extension, and more focused extension created deep basins like the Bentley Subglacial Basin and the Terror Rift in the Ross Sea.
‘This period of more focused extension likely occurred in the Neogene,’ Lloyd said.
‘If it's still hot there, it might also be hot under other basins in the rift system.’
This system is known to have the most influence on ice streams in West Antarctica.
The researchers believe that seismic surveys, similar to this one, will improve the models of the ice sheets, as the modelers require an estimate of the heat flow and need to know what the geological conditions at the bottom of the ice are in order to estimate drag.
The heat flow in Antarctica has only been measure in less than a dozen places, compared to the entire Earth’s crust that has been measure in 34,000 different locations.
The heat flow in Antarctica has only been measure in less than a dozen places, compared to the entire Earth’s crust that has been measure in 34,000 places.
In July, scientists reported the heat flow at one of these spots was four times higher than the global average, which raised the question to why the reading was so high.
In July, scientists reported the heat flow at one of these spots was four times higher than the global average, which raised the question to why the reading was so high.
Researchers think this recent extension in the Bentley Subglacial Trench might explain these findings.
The second issue was understanding the structure under the Thwaite and Pine Island Pine Island glaciers, which are closer to the shoreline than the Bentley Subglacial Trench.
The two glaciers have been described as the ‘weak underbelly’ of the ice sheet because surges in the ice flow there could possibly cause the rapid disintegration of the entire West Antarctica ice sheet.
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