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Map of hazards from the Three Sisters showing risk of lava flows and lahars in the immediate area Neither North nor Middle Sister is likely to resume volcanic activity. [ 60 ] An eruption from South Sister would pose a threat to nearby life, as the proximal danger zone extends 1.2 to 6.2 mi (2 to 10 km) from the volcano's summits. [ 69 ]
Magma chambers above a subducting plate. Magma rises through cracks from beneath and across the crust because it is less dense than the surrounding rock. When the magma cannot find a path upwards it pools into a magma chamber. These chambers are commonly built up over time, [4] [5] by successive horizontal [6] or vertical [7] magma injections
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]
It is likely that the lava spreads by a process of inflation in which the lava moves beneath a solid insulating crust, which keeps it hot and mobile. [36] Studies of the Ginkgo flow of the Columbia River Plateau, which is 30 to 70 meters (98 to 230 ft) thick, show that the temperature of the lava dropped by just 20 °C (68 °F) over a distance ...
Magma mixing is a common process in volcanic magma chambers, which are open-system chambers where magmas enter the chamber, [10] undergo some form of assimilation, fractional crystallisation and partial melt extraction (via eruption of lava), and are replenished. Magma mixing also tends to occur at deeper levels in the crust and is considered ...
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 ...
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 ...
Pahoehoe lava is a relatively smooth lava flow that can be billowy or ropey. They can move as one sheet, by the advancement of "toes", or as a snaking lava column. [10] A'a lava flows are denser and more viscous than pahoehoe, and tend to move slower. Flows can measure 2 to 20 m (7 to 66 ft) thick.