February Geology and GSA Today media ...( Boulder CO USA - Topics include: tre...)

Boulder, CO, USA - Topics include: tree ring-based reconstruction of an extinct polar forest's seasonal environment; geological vs. seismological views of paleo-earthquakes; impact of Lake St. Martin bolide on groundwater quality; analysis of earthquakes at the Cascadia plate boundary; radar images of volcanic and impact deposits on lunar Aristarchus Plateau; dynamics of methane escape into the atmosphere; use of charred plants in modeling pyroclastic density currents; and the possibility we've left the Holocene and are in the Anthropocene.

Annual patterns within tree rings of the Arctic middle Eocene (ca. 45 Ma): Isotopic signatures of precipitation, relative humidity, and deciduousness
Hope Jahren, Earth and Planetary Sciences, 301 Olin Hall, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, USA; and Leonel Sternberg, University of Miami, Department of Biology, Coral Gables, Florida 33124, USA. Pages 99-102.

Jahren and Sternberg's study explains that the spectacular preservation of Eocene (approximately 45-million-year-old) tree rings allowed the reconstruction of the seasonal environment of an extinct polar forest. Deciduous conifer trees experienced high levels of humidity and a fluctuating water source during the short, intense (no darkness) Arctic winter.

Stretching of fluid inclusions in calcite as an indicator of frictional heating on faults
Kohtaro Ujiie et al., Institute for Research on Earth Evolution, Japan Agency for Marin-Earth Science and Technology (JAMSTEC), 3173-25 Showa-machi, Kanazawa-ku, Yokohama 236-0001, Japan. Pages 111-114.

The geological recognition of seismic slip on exhumed faults is one of those holy grails in the earth sciences. Overall, the structural geological community is conservative, with most only accepting frictional melts (pseudotachylytes as evidence of high-velocity slip). Ujiie et al. provide another line of evidence tha
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