A wayward plume?

Article Abstract:

A region of low seismic velocity has been found at a depth of 200-500 km beneath the Brazilian shield. This region is considered to have originated 135 million years ago by thermal diffusion. Low seismic velocity shown at elevated temperatures in rocks indicate that the flow within the mantle is harmful for local hot regions. A 3,000 km of motion between the lower mantle and plate has occurred over a 600 km depth range.

Research, Brazil, Natural history, Plumes (Fluid dynamics)

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Creep, compaction and the weak rheology of major faults

Article Abstract:

The porosity of materials in fault zones may provide a mechanism that would explain their weakness relative to surrounding rock and relative to laboratory standards. Variation in porosity over time would cause fluid pressure to vary as well, with friction reduced when that pressure rises above hydrostatic levels in the surrounding rock. A one-dimensional model relating creep to compaction is presented.

Models, Faults (Geology), Seismological research

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Oxygenating the atmosphere

Article Abstract:

Issues are presented concerning the transition to an atmosphere rich in oxygen in the Archaean-Proterozoic boundary through the stratification of the mantle rock. The oxidization of the mantle is discussed.

Environmental aspects, Oxygen, Earth, Atmosphere

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