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    A bill has been introduced in the Kansas legislature this week that would prohibit the promotion of sustainability. Here is a link to the one-page bill: http://www.kslegislature.org/li/b2013_14/measures/documents/hb2366_00_0000.pdf. See report on Bloomberg News.
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    Scientists have determined the temperature near the Earth’s center to be 6000 degrees Celsius, 1000 degrees hotter than in a previous experiment run 20 years ago. These measurements confirm geophysical models that the temperature difference between the solid core and the mantle above, must be at least 1500 degrees to explain why the Earth has a magnetic field. For more information about this study, see the press release from the European Synchrotron Radiation Facility.
  • Ocean Volcanic Rocks Contain Samples of Recycled Crust
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    Ocean Volcanic Rocks Contain Samples of Recycled Crust

    Scientists have long believed that lava erupted from certain oceanic volcanoes contains materials from the early Earth’s crust. But decisive evidence for this phenomenon has proven elusive. New research from a team including Carnegie’s Erik Hauri demonstrates that oceanic volcanic rocks contain samples of recycled crust dating back to the Archean era 2.5 billion years ago. Their work is published in Nature. Oceanic crust sinks into the Earth’s mantle at so-called subduction zones, where two plates come together. Much of what happens to the crust during this journey is unknown. Model-dependent studies for how long subducted material can exist in the mantle are uncertain and evidence of very old crust returning to Earth’s surface via upwellings of magma has not been found until now. For more information about these results, see the press release from the Carnegie Institution.
This diagram of Bowen's Reaction Series shows how the common silicate minerals crystalize at different temperatures.
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Bowen's Reaction Series

As magma cools slowly, elements within it become chemically bonded forming crystals of minerals. However, not all minerals form at the same time during the cooling process. Some minerals crystallize when magma is at a higher temperature, while others only crystallize when magma is at a lower temperature. Bowen's Reaction Series describes when the eight most common silicate minerals form during the cooling process.

In the Bowen's Reaction Series diagram to the left, minerals that form at high temperatures are listed at the top and minerals that form at lower temperatures are listed at the bottom.

Rocks that form from magma or lava cooled from high temperatures tend to contain a lot of iron and magnesium but little silica. These rocks are called mafic and tend to be dominated by dark colored minerals such as amphibole and pyroxene.

When magma cools slowly, minerals that form at cooler temperatures dominate the resulting rock. These rocks are called felsic and tend to be light colored with minerals such as feldspar and quartz.


Last modified June 17, 2003 by Lisa Gardiner.

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TES XXVI, 3 fall 2010 The Fall 2010 issue of The Earth Scientist, focuses on rocks and minerals, including articles on minerals and mining, the use of minerals in society, and rare earth minerals, and includes 3 posters!

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