Cratonically Yours: Thinner Lithosphere and Crust in Western Antarctica Than in Eastern Antarctica

        The frozen landmass of Antarctica has been studied using satellite imagery to understand some of the  earth's tectonics, revealing  several hidden structures of the least-understood continent in research published 11/5/18.

      Due to its remote location and abundance of ice, charting the geological characteristics of Antarctica is complicated, but the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite can see what other satellites can't. GOCE precisely measured the pull of earth's gravity to map out hidden terrain.

     GOCE crashed out of orbit after running out of fuel in late 2013, but researchers are still poring over the data it collected. The researchers say it offers new insights into how Antarctica was formed, and how plate tectonics can function. See the colorful, newly-created video of continental movement.

      "In East Antarctica we see an exciting mosaic of geological features that reveal fundamental similarities and differences between the crust beneath Antarctica and other continents it was joined to until 160 million years ago," says one of the team, Dr. Fausto Ferraccioli from the British Antarctic Survey. The shape index, tectonic regularization, and crystal thickness were combined to create the above video.

      Antarctica was once part of the supercontinent Gondwana, which began to disintegrate about 130 million years ago, although the bond between Antarctica and Australia held together as recently as 55 million years ago.

      By combining GOCE readings with seismological data, the researchers were able to create 3D maps of Earth's lithosphere, made up of the crust and the molten mantle beneath. That lithosphere includes mountain ranges, ocean backs, and rocky zones or cratons, the leftovers of ancient continents embedded in continents as we know them today.

      
     "The satellite gravity data can be combined with seismological data to produce more consistent images of the crust and upper mantle in 3D, which is crucial to understand how plate tectonics and deep mantle dynamics interact," says researcher, Dr. Jörg Ebbing from Kiel University in Germany.

     The GOCE satellite circled our planet for over four years, from March 2009 to November 2013. During that time it got unusually close to Earth – an altitude of just 225 km (140 miles) – to maximize the accuracy of its measurements.


     The International Space Station, by comparison, is about two times farther away from earth's surface.

      Among the findings from the new study was the discovery of a thinner crust and lithosphere under West Antarctica compared to East Antarctica.  The latter has a mosaic of older cratons interspersed with thinner regions of rock, similar to India and Australia, to which it was once joined.

      And the data is useful for more than just tracing the remnants of ancient continents across the past 200 million years: It can be used to help figure out how ice sheets above the underlying terrain might react to warmer temperatures.

     With so many variables to consider, predicting how ice melt might progress across Antarctica is a real challenge, so any help scientists can get will be welcome. GOCE is still proving its use long after its mission ended.

Antarctically yours,
Steph

Brussels Sprouts and Heirloom Tomato Omelette

Seven Unusual Landforms from the Giant Blue Eye of the Sahara to the Carnallite Salt Mines of Russia

      Seven unusual landforms are the focus of this somewhat trippy and anthropomorphic article about the "giant muscular space wizard that keeps our planet spinning and loses its balance, sending those mountains and rivers and oceans crashing together in unexpected ways." Here is the Giant Blue Eye of the Sahara in Mauritania, western Africa.

       Check out the article linked above to discover more about these odd landforms. Here are the dry, dry, dry carnallite salt mines in Russia, representing Asia:

       Number three on the Landforms List is The "Iceman's Pompadour," Antarctica:

  
      The Marble Caves of Chile are South America's contributions to the weird landform list:

      Number five on the list is Izvorul Bigar, the "Weeping Waterfall" of Romania, Europe. It is only 26 feet tall and the source of the dripping water is unknown.

      Number six, representing Australia/New Zealand is Split Apple Rock or "Toko Ngawha:"

      And last on the list is the second European location at "The Giant's Causeway" in Ireland:

      Nothing from North America made their list. How about Bryce Canyon hoodoos in Utah?

Or the Vermillion Cliffs of Arizona?

      We've discussed at least one of these landforms here at Partial Ellipsis of the Sun. Which one(s)?

What would make your list?
Steph

Finishing Blows: Not Muhammad Ali's but Antarctica's Larsen B Ice Shelf

     "The biggest ice shelf collapse on record was set in motion years earlier than previously thought, new research reveals."

     "Analyzing declassified images from spy satellites, researchers discovered that the downhill flow of ice on Antarctica’s Larsen B ice shelf was already accelerating as early as the 1960s and ’70s. By the late 1980s, the average ice velocity at the front of the shelf was around 20 percent faster than in the preceding decades, the researchers report in a paper to be published in Geophysical Research Letters."

     "Rising temperatures since the 1950s probably quickened the ice flow, which in turn put more strain on the ice and further weakened the shelf, says study coauthor Hongxing Liu, a geographer at the University of Cincinnati. Previous work had suggested that the ice shelf’s downward slide began only a few years before a Rhode Island-sized region of ice disintegrated into thousands of icebergs in 2002."

     "The new data will help scientists more confidently predict how Antarctic ice will fare in the coming decades, says Penn State glaciologist Richard Alley, who was not involved in the work. The early response of Larsen B to warming “is consistent with this ice shelf system being sensitive, and gives a target for future modeling studies to learn how sensitive, and for what reasons,” he says."

     "Ice shelves such as Larsen B line Antarctica’s coast and slow the flow of the continent’s glaciers and ice sheets into the sea. Rising temperatures are shrinking Antarctica’s ice, with several ice shelves on track to disappear completely within 100 years.Tracking the long-term decline of ice shelves is tricky, though. Scientific satellite images are sparse prior to the 1990s and next to nonexistent before the 1980s."

     Liu and others turned to another group that peered at Antarctica, a U.S. intelligence agency called the National Reconnaissance Office. In 1963, the agency photographed the continent as part of an intelligence-gathering mission. While these images were declassified in 1995, the photos were too distorted by effects such as the camera used and Earth’s curvature to use for ice flow measurements.  

     "Making the photographs usable required identifying stationary landmarks for reference, a difficult task on a continent covered with shifting white ice. Comparing the spy photos with later scientific images, Liu and colleagues identified 44 potential landmarks. Then, using the locations as anchor points, the researchers unwarped the images. Along with additional satellite images taken in 1979 and the 1980s, the modified images allowed the researchers to track Larsen B’s ice flow over time."

   
     "The ice on Larsen B’s front flowed at around 400 meters per year on average between 1963 and 1986, calculations using images from those years indicate. From 1986 to 1988, the average was 490 meters per year. That speed boost suggests that the ice flow accelerated between the 1963 to 1986 satellite images. Several glaciers that feed into Larsen B underwent similar accelerations, the researchers found."

     Larsen B’s early acceleration hints that the ice shelf was already weakening well before the 1990s, says Ted Scambos, a polar scientist at the National Snow and Ice Data Center in Boulder, Colorado, USA, who was not involved in the study. 

     Previous studies suggested that balmy surface temperatures caused Larsen B’s demise by forming meltwater pools 

on top of the ice shelf that forced open cracks in the ice. The new satellite data suggest that this fracturing was a finishing blow*

 following long-term weakening by forces such as relatively warm seawater eroding the ice shelf’s underside, Scambos said.

      I wonder what else is to be revealed in older aerial photographs and Landsat images of Antarctica and other areas. . .

Unwarpedly, ;-)
Steph

*My dad was such a Muhammad Ali fan and I wanted to pay homage to the man; Dad and Mom were in Atlanta in 1996 for the Olympics. It was a very special opening ceremony. . .