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Earth’s mysterious D” layer
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- Context (Phys): Deep within Earth, there lies a mysterious layer called the D” layer.
Credits: Spring8
- Located roughly 3,000 kilometres down, this zone sits just above the boundary between the planet’s molten outer core and its solid mantle.
- Theory relying on the Giant Impact hypothesis believes the D” layer may be a unique composition leftover from this colossal impact, potentially holding clues to Earth’s formation.
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- The D” layer is not perfectly sphere and is surprisingly patchy. Its thickness varies greatly from place to place, with some regions even lacking a D” layer altogether.
- The D” layer may also be where deep mantle plumes originate and where subducting slabs terminate.
- The new research highlights the presence of a substantial amount of water within this global magma ocean. The exact origin of this water remains a topic of debate.
- Some suggest that water would have concentrated towards the bottom of the magma ocean as it cooled, forming hydrous oceans. This hydrous magma ocean favoured the formation of an iron-rich phase called iron-magnesium peroxide.
- The presence of this iron-rich peroxide phase would alter the mineral composition of the D” layer, deviating from our current understanding.
- According to the new model, minerals in D” would be dominated by a new assemblage: the iron-poor silicate, iron-rich (Fe, Mg) peroxide, and iron-poor (Fe, Mg) oxide.
- This iron-dominant peroxide also possesses low seismic velocities and high electrical conductivity, making it a potential candidate to explain the D” layer’s unique geophysical features.
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