April GEOLOGY and GSA TODAY media highlights

Boulder, CO, USA - Topics include: new evidence supporting the existence of mantle plumes; evidence from northwest Scotland of the largest meteorite ever to hit the British Isles; insights into California's still-active Long Valley caldera volcano; discovery of a microtektite field (microscopic impact glass particles) from Victoria Land Transantarctic Mountains; and long-term effects of the Chesapeake Bay impact structure on coastal Virginia. The GSA TODAY science article presents surprising evidence regarding depth and strength of Earth's tectonic plates.

Seismic imaging of subduction zone metamorphism

Stéphane Rondenay et al., Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue 54-512, Cambridge, Massachusetts 02139, USA. Pages 195-198.

Rondenay et al. seek to determine the depths at which fluids are released in subduction zones. This is an important objective because fluid release in such areas may trigger arc volcanism and intraslab earthquakes. By analyzing seismic images of the Alaska and Cascadia subduction zones in conjunction with thermal models and petrological constraints, they found that (1) seismic images provide a direct estimate of the depth range over which fluids are released in the system; (2) this depth range corresponds to that where the subducted crust transforms into eclogite, a high-pressure/temperature mineral assemblage; and (3) the location of this reaction is dependent on the thermal structure of the subducted plate.

Did magma ascent rate control the explosive-effusive transition at the Inyo Volcanic Chain, California?

Jonathan M. Castro, Smithsonian Institution, Mineral Sciences, National Museum of Natural History, 10th and Constitution Ave. NW, Washington, DC 20013, USA, and James E. Gardner, University of Texas at Austin, Department of Geological Sciences, 1 University Station C1100, Austin, Texas 78712-0254, USA. Pages 275-278.

Castro and Gardner’s paper describes natural and experimental evidence for the rage of magma rise beneath the Inyo Volcanic Chain, California. The authors found that magma may rise very slowly, yet despite these conditions, the magma may still explode violently.

Excess temperatures at ocean islands: Implications for mantle layering and convection

Keith Putirka, California State University–Fresno, Department of Earth and Environmental Sciences, 2576 E. San Ramon Avenue, MS/ST24, Fresno, California 93710-8039, USA. Pages 279-282.