California Volcano Observatory

Magma Dynamics Laboratory

Building 2, contact Tom Sisson

A scientist stands in front of a laboratory hood, wearing fire-resistant safety gear, and cooling a glowing cylindrical sample

Experimental samples are quenched rapidly to preserve features of the melt, rather than allowing sample material to cool slowly and crystallize. The high temperature of the samples as they leave the furnace requires the experimenter to wear fire-resistant safety gear and face protection. 

(Credit: Tom Sisson, USGS. Public domain.)

The Magma Dynamics Laboratory investigates how partially or fully molten rock forms in the Earth, ascends toward the surface, changes in chemical composition and properties, and erupts effusively as lavas, explosively as pyroclasts (volcanic ash, pyroclastic flows, etc.), or drives hydrothermal systems and creates mineral deposits. In direct experiments, natural or synthetic rocks are melted at the pressures, temperatures, and abundances of volatiles (H2O, CO2, S, Cl) appropriate for the conditions being recreated. In some cases this is at fixed (constant) pressure and temperature, and in other cases dynamically changing conditions are used to simulate movement toward the surface.

High pressures and high temperatures are produced with a variety of specialized equipment including end-loaded piston-cylinder presses, rapid-quench gas-pressurized vessels (Mo-rich alloy similar to “TZM”), H2O-pressurized cold-seal vessels (“Tuttle bombs”), and atmospheric-pressure gas-mixing furnaces.  The Magma Dynamics Laboratory also contains the various equipment and supplies necessary to prepare starting materials and capsules (microbalance, microwelder, furnaces, chemicals, etc.) and to mount, prepare, and examine quenched experimental run products by transmitted and reflected light microscopy. 

A laboratory technician is seated in front of a hydraulic press assembly in a metal frame, with a dashboard of dials nearby

Decompressing a pressurized experimental sample in a hydraulically-powered piston-cylinder press. This press allows controlled decompression of samples which have been held at high-pressure conditions approximating the Earth's interior.

(Credit: Tom Sisson, USGS. Public domain.)

Run products are typically then further examined and characterized for the chemical compositions and abundances of synthesized minerals and melt (glass) by scanning electron microscopy, electron-probe micro-analysis, and Fourier-transform infrared spectroscopy. These other labs are housed in and managed by the USGS California Volcano Observatory.

This is a research lab that chiefly conducts hypothesis-driven investigations that are released as peer-reviewed interpretive papers in the scientific literature. Modest service work is sometimes performed, such as homogenizing melt inclusions, synthesizing standards, and preparing starting materials for investigations in other laboratories.

Contacts

Thomas Winslow Sisson

Geologist
California Volcano Observatory
Phone: 650-329-5247