SUMMARY:Type: composite with caldera |
GEOLOGIC HISTORYGrozny Group is a complex volcano with a remnant (3-3.5 km diameter) caldera that contains several Holocene andesite/dacite domes. Previous activity has been characterized by explosive eruptions and formation of andesitic and dacitic domes. Ivan Grozny, located roughly 100 km SW of Kudriavy, is a large extrusive andesite dome that rises 590 m above the surrounding caldera floor. Talus covers the dome's lower slopes, the central flanks are dissected by narrow, shallow ravines, and the summit consists of 3 large blocks. At the top of the northern block, 2 large, overlapping funnel-shaped explosion vents combine to form a broad trench opening eastward. An additional poorly defined dome is located on the central dome's NE flank, and a group of large fumaroles that are active at frequent intervals occupy the boundary between the domes. Short, steep lava flows emerge from beneath agglomerate flows on the flanks of the central dome; those on the north reach the caldera wall. Flows extend several kilometers to the south, one reaching the coast 6 km away to form Drakon Cape, about 1.5 km wide and 30 to 50 m high. Historic Activity: Weak, periodic gas emissions were reported in 1964-65, but no historical eruptions were documented until 1968, when ash emission darkened snow along a road roughly 15 km NW of the volcano. That year, gas emissions became continuous, concentrated in the summit trench and on the central dome's NE flank. Other ash eruptions occurred in 1970 and on May 16, 1973, when ash was erupted to 600 m height. Recent Activity: The largest recorded eruption took place in 1989. Increasing fumarolic emissions accompanied by weak explosions began on May 3, 1989. Strong explosion on May 8 produced black ash colum that reached 1500 m above summit. Lahars were triggered by intense snowmelt. An eruption on June 19, 1989 sent ash and gas to about 2 km. An early August explosion formed new fumarolic vents on the dome's north flank. Data Sources
|
ADDITIONAL INFORMATION
|
|
Last Update: 2/21/00 |