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

Slab Melting: Quite Continental!

       Plate tectonics theory has generally espoused that all continental crust, rich in silica, has been recycled. 

     Virginia Technical University geologists have published research today indicating some of that continental crust may actually be new or "juvenile" crust.

       Some of the type areas for this discovery are in Costa Rica and Panama:

The March 31, 2015, research includes this description of continental and oceanic crust:

     "The researchers used geochemical and geophysical data to reconstruct the evolution what is now Costa Rica and Panama, which was generated when two oceanic plates collided and melted iron- and magnesium-rich oceanic crust over the past 70 million years."

      "Melting of the oceanic crust originally produced what today are the Galapagos islands, reproducing Achaean-like conditions to provide the "missing ingredient" in the generation of continental crust."

     "The researchers discovered the geochemical signature of erupted lavas reached continental crust-like composition about 10 million years ago. They tested the material and observed seismic waves traveling through the crust at velocities closer to the ones observed in continental crust worldwide."

        The study continues "It raises questions about the global impact newly generated continental crust has had over the ages, and the role it has played in the evolution of not just continents, but life itself. 

        For example, the formation of the Central American land bridge resulted in the closure of the seaway, which changed how the ocean circulated, separated marine species, and had a powerful impact on the climate on the planet."

        Older names for continental and oceanic crust are SIAL and SIMA, respectively. Sial is a short for silica aluminum (or aluminum silicate) and sima is short for silica magnesium (or magnesium silicate). The sial is less dense than the sima. And now, researchers have shown that some of that sial is juvenile. 

SIAL LATER!

Steph