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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
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    Mysteries of the Earth: Researchers predict how fast ancient magma ocean   
   solidified    
      
     Date:   
         February 27, 2023   
     Source:   
         Florida State University   
     Summary:   
         Previous research estimated that it took hundreds of million years   
         for the ancient Earth's magma ocean to solidify, but new research   
         narrows these large uncertainties down to less than just a couple   
         of million years.   
      
      
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   FULL STORY   
   ==========================================================================   
   Early in the formation of Earth, an ocean of magma covered the planet's   
   surface and stretched thousands of miles deep into its core. The rate at   
   which that "magma ocean" cooled affected the formation of the distinct   
   layering within the Earth and the chemical makeup of those layers.   
      
      
   ==========================================================================   
   Previous research estimated that it took hundreds of million years   
   for that magma ocean to solidify, but new research from Florida State   
   University published in Nature Communications narrows these large   
   uncertainties down to less than just a couple of million years.   
      
   "This magma ocean has been an important part of Earth's history, and this   
   study helps us answer some fundamental questions about the planet," said   
   Mainak Mookherjee, an associate professor of geology in the Department   
   of Earth, Ocean and Atmospheric Science.   
      
   When magma cools, it forms crystals. Where those crystals end up   
   depends on how viscous the magma is and the relative density of the   
   crystals. Crystals that are denser are likely to sink and thus change the   
   composition of the remaining magma. The rate at which magma solidifies   
   depends on how viscous it is. Less viscous magma will lead to faster   
   cooling, whereas a magma ocean with thicker consistency will take a   
   longer time to cool.   
      
   Like this research, previous studies have used fundamental principles of   
   physics and chemistry to simulate the high pressures and temperatures in   
   the Earth's deep interior. Scientists also use experiments to simulate   
   these extreme conditions. But these experiments are limited to lower   
   pressures, which exist at shallower depths within the Earth. They don't   
   fully capture the scenario that existed in the planet's early history,   
   where the magma ocean extended to depths where pressure is likely to be   
   three times higher than what experiments can reproduce.   
      
   To overcome those limitations, Mookherjee and collaborators ran their   
   simulation for up to six months in the high-performance computing   
   facility at FSU as well as at a National Science Foundation computing   
   facility. This eliminated much of the statistical uncertainties in   
   previous work.   
      
   "Earth is a big planet, so at depth, pressure is likely to be very high,"   
   said Suraj Bajgain, a former post-doctoral researcher at FSU who is now   
   a visiting assistant professor at Lake Superior State University. "Even   
   if we know the viscosity of magma at the surface, that doesn't tell   
   us the viscosity hundreds of kilometers below it. Finding that is very   
   challenging."  The research also helps explain the chemical diversity   
   found within the Earth's lower mantle. Samples of lava -- the name for   
   magma after it breaks through the surface of the Earth -- from ridges   
   at the bottom of the ocean floor and volcanic islands like Hawaii and   
   Iceland crystallize into basaltic rock with similar appearances but   
   distinct chemical compositions, a situation that has long perplexed   
   Earth scientists.   
      
   "Why do they have distinct chemistry or chemical signals?" Mookherjee   
   said.   
      
   "Since the magma originates from underneath the Earth's surface, that   
   means the source of the magma there has chemical diversity. How did that   
   chemical diversity begin in the first place, and how has it survived   
   over geological time?"  The starting point of chemical diversity in the   
   mantle can be successfully explained by a magma ocean in the Earth's   
   early history with low viscosity.   
      
   Less viscous magma led to the rapid separation of the crystals suspended   
   within it, a process often referred to as fractional crystallization. That   
   created a mix of different chemistry within the magma, rather than a   
   uniform composition.   
      
   Doctoral student Aaron Wolfgang Ashley from FSU as well as Dipta Ghosh and   
   Bijaya Karki from the Department of Geology and Geophysics at Louisiana   
   State University were co-authors of this paper.   
      
   This work was funded by the National Science Foundation.   
      
       * RELATED_TOPICS   
             o Earth_&_Climate   
                   # Earth_Science # Volcanoes # Geology # Geochemistry   
             o Fossils_&_Ruins   
                   # Early_Climate # Origin_of_Life # Fossils # Anthropology   
       * RELATED_TERMS   
             o Geology_of_the_Capitol_Reef_area o Ichthyosaur   
             o Geologic_temperature_record o Homo_(genus) o   
             Structure_of_the_Earth o Timeline_of_evolution o Dinosaur   
             o Extinction   
      
   ==========================================================================   
   Story Source: Materials provided by Florida_State_University. Original   
   written by Bill Wellock. Note: Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Suraj K. Bajgain, Aaron Wolfgang Ashley, Mainak Mookherjee, Dipta B.   
      
         Ghosh, Bijaya B. Karki. Insights into magma ocean dynamics from   
         the transport properties of basaltic melt. Nature Communications,   
         2022; 13 (1) DOI: 10.1038/s41467-022-35171-y   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/02/230227161352.htm   
      
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