Literature Review: Inside the Earth

by Carl Strang

Sea cliffs, Adak Island. Formations like this have inspired scientists to discover the dynamics of the Earth that produced them.

Sea cliffs, Adak Island. Formations like this have inspired scientists to discover the dynamics of the Earth that produced them.

Naif, S., K. Key, S. Constable, R. L. Evans. 2013. Melt-rich channel observed at the lithosphere–asthenosphere boundary. Nature  495 (7441): 356 DOI: 10.1038/nature11939  As described in a ScienceDaily article. They found a previously unknown layer of magma in the upper mantle which apparently is the lubricant for tectonic motion of crustal plates.

Livermore, P.W., R. Hollerbach and A. Jackson. 2013. Electromagnetically driven westward drift and inner-core superrotation in Earth’s core. PNAS, DOI: 10.1073/pnas.1307825110  From a ScienceDaily article. The solid iron inner core of the Earth, about the size of our moon, rotates to the east but at a faster speed than the planet as a whole. The outer core, also of iron but liquid, rotates slowly to the west. These dynamics result in the planet’s geomagnetic field, which itself rotates very slowly to the west. At the same time, the field produces the observed motions of the two parts of the core.

Kerr, Richard A. 2013. The deep Earth machine is coming together. Science 340:22-24. In this news review article, Kerr reports on progress geologists are making in understanding and mapping out details of the planet’s mantle. It is increasingly understood to be a complex mix of descending crustal slabs from plate boundaries, various masses of somewhat mysterious deep matter, and rising plumes from the deep mantle. This mapping is difficult and produces some contention over results, but consensus is growing. Plumes are recently accepted by many as existing, and accounting for a variety of phenomena including the Hawaiian Islands, the extraordinary eruption history of the Yellowstone area, Iceland’s volcanism, and the large volcanic traps eruptions involved in some of the massive species extinction events (most notably the end-Permian one). At present there are two very large “piles” of deep matter, one centering in the equatorial Pacific Ocean region, and one extending down the west coast of Africa and into the ocean to its south, with which are associated most of the active hot spots (mainly around their edges) and, in the African one, concentrations of diamond-bearing Kimberlites. The descending “curtains” of plate edges from subduction zones may be driving the movements and concentrations of different materials in various depths of the mantle. Heat from the core interacts with these materials in ways that remain to be determined.

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