Abstract Erebus volcano, Antarctica, is the southernmost active volcano on the globe. Despite its remoteness and harsh conditions, Erebus volcano provides an unprecedented and unique opportunity to study the petrogenesis and evolution, as well as the passive and explosive degassing, of an alkaline magmatic system with a persistently open and magma-filled conduit. In this chapter, we review nearly five decades of scientific research related to Erebus volcano, including geological, geophysical, geochemical and microbiological observations and interpretations. Mount Erebus is truly one of the world's most significant natural volcano laboratories where the lofty scientific goal of studying a volcanic system from mantle to microbe is being realized.

Abstract Crustal S -wave anisotropy has been suggested as a possible tool for monitoring stress and/or fluid changes associated with the earthquake cycle. We analyzed 363 microearthquakes occurring between 1981 and 1995 beneath Southern California Seismic Network station BWC, located approximately 25 km south of the Landers, California earthquake hypocenter( M 1 = 7.3; June 28, 1992) and 5 km west of the Joshua Tree earthquake ( M w = 6.1; April 23, 1992). S -wave seismograms exhibit a strong initial polarization alignment of approximately N4.5°E (in the seismometer coordinate system), followed by a 30-degree eastward rotation beginning around the time of the Landers earthquake. However, P -wave particle motions, similar earthquake analysis, and further investigation of the station service record indicate that this apparent rotation is an instrumental artifact due to a reorientation of the horizontal seismometers during post-Landers station maintenance. After using P -waves to calibrate horizontal seismometer azimuths both before and after the reorientation, the data are consistent with a stable fast horizontal anisotropic axis of 16.5 ± 14° E of N throughout the study period. Clear examples of S -wave splitting are observed, corresponding to a minimum inferred shallow (≲10 km) S -wave anisotropy of approximately 2%. S -wave splitting time difference estimates from similar earthquakes suggest a subsample (approximately 10%) decrease in anisotropy during the last month of the Joshua Tree aftershock-Landers foreshock interval. This trend was subsequently unaffected by the Landers mainshock. However, more detailed hypocenter estimates will be required to adequately separate effects due to hypocenter differences from the apparent temporal change in anisotropy.