Our Earth is constantly changing; materials are being subducted where plates pass each other, and molten materials are expelled at volcanic sites and plate junctures. As materials are dragged towards the center of the Earth, extreme temperature and pressure cause abrupt changes in their properties. To fully understand the earth we live on requires a detailed knowledge of the properties materials at extremely high temperatures, possibly as high as 7000 C and extremely high pressures, somewhere near 100,000 atmospheres.

Extreme conditions such as these can be duplicated in a very small laboratory called a "diamond-anvil cell," or DAC for short. The DAC consists of two perfect gem-quality diamonds cut with large taper angles, which together squeeze a specimen that is place on the inside of a toroidal metal gasket. In addition to their strength, diamonds are transparent to laser light and X-rays; the laser light heats the specimens while high-energy X-ray beams simultaneously measure their crystalline properties.

Visitors to the CHESS high-pressure facility measure the unusual phases of matter that exist at extreme temperatures and pressures. Examples of recent work includes solving the unusual phases of FeS by Y. Fei (Carnegie Institute of Washington), a material that determines the internal structure of Mars. Professor W. Bassett (Geology, Cornell) invented a hydrothermal DAC that allows microscopic observations of changes in samples immersed in water at temperatures up to 1000°C and pressures up to 25 kbar. His X-ray studies of montorillonite clays suggest a new mechanism by which water is carried into the Earths’ crust. He observed a new stable phase (at high pressure up to 380°C) in which three layers of water can be trapped between sheet-like planes of clay. This suggests that clays could carry large amounts of surface water to great depths within the Earth, where, at higher pressures and temperatures, the water is forced out. This release may play an important role in transporting water to great depths in the subduction of ocean floor sediments, and could contribute to earthquakes and volcanic materials along the boundaries of tectonic plates.