![]() These provide stringent upper limits for solar gamma-ray line and hard X-ray and gamma-ray continuum emission, which in turn can constrain the storage and/or continuous acceleration of ions and electrons by the Sun. Excellent high resolution quiet Sun hard X-ray and gamma-ray spectra were obtained. Because the Sun was inactive during the flight, more » only one small flare was detected on UT. 30.5 hours of observation were obtained between -2130 UT and -1900 UT. HIREGS was flown on a 10-day (31 Dec 92-10 Jan 93) circumpolar balloon flight from McMurdo Station, Antarctica. The energy resolution is one to several keV FWHM over the instrument energy range of 20 keV to 16 MeV. A CsI front collimator defines a 24 degree FWHM field-of-view. HIREGS consists of an array of twelve 6.7 cm diameter x 6.1 cm long liquid nitrogen-cooled segmented germanium detectors enclosed in a bismuth germanate (BGO) active anticoincidence shield. Unlike H 2O-rich subduction arc volcanoes, CO 2-dominated Erebus geophysically shows continuous magmatic structure to shallow crustal depths of < 1 km, as the melt does not experience decompression-related volatile supersaturation and viscous stalling. This magmatic valve lies within an inferred, east-west structural more » trend forming part of an accommodation zone across the southern termination of the Terror Rift, providing a dilatant magma pathway. The lateral turn represents a structural fault-valve controlling episodic flow of magma and CO 2 vapour, which replenish and heat the high level phonolite differentiation zone. Here we show using magnetotelluric data that a steep, melt-related conduit of low electrical resistivity originating in the upper mantle undergoes pronounced lateral re-orientation in the deep crust before reaching shallower magmatic storage and the summit lava lake. Seismic studies provide limited images of the magmatic system. « lessĮrebus volcano, Antarctica, with its persistent phonolite lava lake, is a classic example of an evolved, CO 2-rich rift volcano. Final crystal growth occurred after intrusion into the convecting lava lake less than decades before eruption. On May 18, 1980, Mount Saint Helens experienced an explosive eruption, sending a column of ash, steam, and gases. The implied residence time of phonolite magmas in the shallow magma chamber system of Erebus is about 3,000 y. The global estimates fell within a range of about 0.3 0.15 billion metric tons of carbon dioxide per year, implying that human carbon dioxide emissions were more than 90 times greater than global volcanic carbon dioxide emissions. = Th)/BA, the glass-anorthoclase pairs produce isochrons averaging 2,380 y, which represents the average age of anorthoclase growth in the shallow magma system at Erebus. ![]()
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