11/22/2023 0 Comments Mount erebus volcanoOn 23 December 1978, New Zealand volcanologist W. Scientists tried to descend into the inner crater in order to collect fresh samples. In 1978, the lava lake activity consisted of 1) lava upwelling in nearly circular areas, 2) small bubble-like degassing eruptions, and 3) downwelling of the consolidated crust along planar troughs or 'subduction zones.' Doming of the lava lake surface was occasionally observed, including one large bubble, that grew to ~80 m height before bursting. In 1978, the lake was 130 m wide and oval-shaped, with 2 zones of active upwelling of lava. Occasionally, such bombs were landing outside the crater. Strombolian eruptions were occurring from time to time, 2-10 per day typically, sometimes throwing bombs up to a few hundred meters above the outer rim. Throughout the 1970's, activity remained relatively constant, with a slight tendency of gradual increase in level. Erebus Volcano Observatory, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA (URL: ) Hawai'i Institute of Geophysics and Planetology (HIGP) MODIS Thermal Alerts, School of Ocean and Earth Science and Technology (SOEST), Univ of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: ).1972-80 activityIn 1976, it was noted that the lava lake had slowly increased since its discovery 4 years ago in 1972 and was about 100 m wide. Continuous lava-lake activity with minor explosions, punctuated by occasional larger Strombolian explosions that eject bombs onto the crater rim, has been documented since 1972, but has probably been occurring for much of the volcano's recent history. The glacier-covered volcano was erupting when first sighted by Captain James Ross in 1841. An elliptical 500 x 600 m wide, 110-m-deep crater truncates the summit and contains an active lava lake within a 250-m-wide, 100-m-deep inner crater other lava lakes are sometimes present. A summit plateau at about 3,200 m elevation marks the rim of the youngest caldera, which formed during the late-Pleistocene and within which the modern cone was constructed. The summit of the dominantly phonolitic volcano has been modified by one or two generations of caldera formation. It is the largest of three major volcanoes forming the crudely triangular Ross Island. Mount Erebus, the world's southernmost historically active volcano, overlooks the McMurdo research station on Ross Island. Johnson, J.B., Aster, R.C., Ruiz, M.C., Malone, S.D., McChesney, P.J., Lee, J.M., and Kyle, P.R., 2003, Interpretation and utility of infrasonic records from erupting volcanoes: Journal of Volcanology and Geothermal Research, v. Johnson, J.B., Aster, R.C., and Kyle, P.R., 2004, Volcanic eruptions observed with infrasound: Geophysics Research Letters, v. Johnson, J.B., and Aster, R.C., 2005, Relative partitioning of acoustic and seismic energy during Strombolian eruptions: Journal of Volcanology and Geothermal Research, v. Le Pichon, 2003 (December), Infrasound from Erebus Volcano at 155US in Antarctica, Inframatics-The Newsletter of Subaudible Sound, no. Large and very large eruptions recorded at Erebus, January-November 2006. The largest event had an index of 116.6 on 26 February. Although the total number of eruptions remained high during most months of 2006, large or very large events were rarely recorded after 1 June (table 1). This eruption index scale is divided into small (0-19), medium (20-39), large (40-59), and very large (>=60) events. Erebus eruption sizes are based on the infrasonic overpressure at Station E1S.IS1, measured in pascals (Pa) (see references articles on infrasound measurements). The MEVO activity log gives information on each eruption measured and shows daily activity that usually includes several eruptions. Because of extreme weather, the seismic network is subject to power loss during the darkness of winter. In recent years the use of a video camera, infrasound, and broadband seismic records have allowed better recognition of eruptions. The older records are based on interpretation of short-period seismographs, and many of the events could have been icequakes (seismic events related to the stick and slip nature of glacial ice movement) and not eruptions. Courtesy of MEVO web site ("Current Erebus Activity Plot"). Quantitative assessment of eruption sizes using infrasonic recordings started in 2006. Note that significant incompleteness may exist due to variable reporting criteria and/or instrumentation outages. Collective vent and lava lake eruptions per month from January 1992 to September 2006 at Erebus (plotted on a vertical log scale).
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