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These eruptions wear down the lava dome holding the magma down, and it disintegrates, leading to much more quiet and continuous eruptions. Thus an early sign of future Vulcanian activity is lava dome growth, and its collapse generates an outpouring of pyroclastic material down the volcano's slope. [24] Tavurvur in Papua New Guinea erupting
Large lahars hundreds of metres wide and tens of metres deep can flow several tens of metres per second (22 mph or more), much too fast for people to outrun. [9] On steep slopes, lahar speeds can exceed 200 kilometres per hour (120 mph). [9] A lahar can cause catastrophic destruction along a potential path of more than 300 kilometres (190 mi). [10]
These are initially molten blobs of lava, which rapidly cool into blocks often 2 to 3 m across. At Galeras, a Vulcanian eruption ejected bombs which struck several volcanologists who were in the crater, some of whom died or suffered severe injuries. The Gran Cratere, Vulcano. A sense of scale is provided by the tourist visible near the centre ...
The word lava comes from Italian and is probably derived from the Latin word labes, which means a fall or slide. [2] [3] An early use of the word in connection with extrusion of magma from below the surface is found in a short account of the 1737 eruption of Vesuvius, written by Francesco Serao, who described "a flow of fiery lava" as an analogy to the flow of water and mud down the flanks of ...
Low-silica magma is more fluid and usually erupts as lava in less explosive eruptions than dacite because gas and water vapor escape easily from it. Eruptions of basalt magma typically produce elongate lava flows, as well as build cinder cones (piles of small frothy lava fragments or 'cinders') around volcanic vents. [4]
Subglacial eruptions, those of ice-covered volcanoes, result in the interaction of magma with ice and snow, leading to meltwater formation, jökulhlaups, and lahars. Flooding associated with meltwater is a significant hazard in some volcanic areas, including Iceland, Alaska, and parts of the Andes.
In the broad sense [2] [4] of the term, volcaniclastics includes pyroclastic rocks such as the Bandelier Tuff; [5] cinder cones and other tephra deposits; the basal and capping breccia that characterize ʻaʻā lava flows; and lahars and debris flows of volcanic origin. [6] Volcaniclastics make up more of the volume of many volcanoes than do ...
Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition.