Low Gravity Levels along Antarctic Coast South of New Zealand Explained
18.05.2010 - Water & Oceans, Land & Geology, Antarctic
In a recent study released in Nature Geoscience, scientists have found a new explanation for the very low gravity levels along the Antarctic coast to the south of New Zealand.
Geophysicist Michael Gurnis and his colleagues from Caltech explained that the anomaly, which also occurs in parts of south of Asia, the northeastern Pacific and in the western Atlantic, is due to giant country-sized slabs of rock they refer to as “slab graveyards” buried deep near the planet's core. The rock, buried long ago, released water that reduced the density of overlying rock. Less dense rock in these areas leads to less gravitational pull.
Scientists had previously believed that these spots of lower gravity were due to hot spots along the core-mantle boundary, which created buoyant plumes of rock that rose within Earth's mantle. However the new research shows changes in the composition of rock and not its temperature lowered the density of the rock.
The relative buoyancy of the top layer is due to the fact that it is rich in water, which could have been injected into the mantle during slow-motion collisions between lighter and heavier tectonic plates: dense slabs slipped down through the mantle, releasing water from those rocks and the seafloor sediments.
