mugearite-benmoreite succession. The occurrence of rhyolite has also been reported. There appear to be two groups of volcanic rocks at Mount Waesche. Phenocrysts at Chang Peak include aenigmatite, alkali feldspar, ilmenite and quartz and at Mount Waesche olivine, plagioclase and titanaugite. Granulite and pyroxenite xenoliths have also been found. Despite their proximity, Mount Sidley and Mount Waesche have erupted distinctly different rocks. Unusually for volcanoes in Marie Byrd Land, the chemistry of volcanic rocks at Mount Waesche appears to have changed over time. The total volume of rocks is about . Eruption history The development of Mount Waesche began in the Pliocene, and Plio-Pleistocene tephra layers found in the Southern Pacific Ocean may originate at Mount Waesche. It appears that volcanism in the Executive Committee Range moved southwards over time, beginning at Mount Hampton and eventually arriving at Mount Waesche which is the young volcanic centre of the range. Chang Peak grew first, 1.6 million years ago or between 2.01.1 million years ago, while Mount Waesche formed within or about 1 million years ago; the youngest rocks at Waesche are less than 100,000 years old whereas there is no evidence of recent activity at Chang Peak. Argon-argon dating on rocks that today form moraines has yielded ages of about 200,000 years to over 500,000 years. One flank vent has been dated to be 170,000 years old and some rocks are too young to be dated by potassium-argon dating. A major pulse of lava flow emissions appears to have occurred 200,000-100,000 years ago and an older episode 500,000-300,000 years ago. The volcano was active during the Holocene and may be a source of tephra found in ice cores. A layer of volcanic ash was identified in the region through radar data and is about 8,000 years old; it probably originated at Mount Waesche. The volcano today is considered to be "probably active" or "possibly active". A magmatic system may exist south of Mount Waesche at depth below the ice. Present-day seismic activity has been recorded at Mount Waesche, but it might be either volcanic/tectonic or caused by ice movement. Future eruptions are unlikely to have any impact beyond the surroundings of the volcano. See also List of volcanoes in Antarctica Notes References Sources Bibliography Polygenetic shield volcanoes Volcanoes of Marie Byrd Land Inactive volcanoes Executive Committee Range