The Advanced Photon Source (APS) is a third-generation synchrotron storage ring that became operational in 1996. A national user facility at the APS is being constructed for research in Earth, soil, and environmental sciences by the GeoSoilEnviroCARS (GSECARS) group of the Consortium for Advanced Radiation Sources (CARS). The GSECARS sector consists of an undulator and a bending magnet beamline, both of which have been designed to allow for a wide range of possible experiments on geological materials. An experimental station on the undulator beamline will be dedicated to high-pressure experiments using a multi-anvil press and diamond anvil cells. Energy-dispersive and monochromatic diffraction experiments will be performed in this and other stations using solid state and two-dimensional detectors. A high-pressure support laboratory is being developed concurrently. The first high-pressure experiments at the GSECARS sector were successfully conducted in December, 1996.