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A lahar travels down a river valley in Guatemala near the Santa Maria volcano, 1989. A lahar (/ ˈ l ɑː h ɑːr /, from Javanese: ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. [1]
A'a lava moves in a peculiar way—the front of the flow steepens due to pressure from behind until it breaks off, after which the general mass behind it moves forward. Pahoehoe lava can sometimes become A'a lava due to increasing viscosity or increasing rate of shear, but A'a lava never turns into pahoehoe flow. [11]
A lahar is a debris flow related in some way to volcanic activity, either directly as a result of an eruption, or indirectly by the collapse of loose material on the flanks of a volcano. A variety of phenomena may trigger a lahar, including melting of glacial ice, sector collapse , intense rainfall on loose pyroclastic material, or the outburst ...
The cold lava flow, known in Indonesia as a lahar, came from Mount Marapi, one of Sumatra's most active volcanoes. In December, more than 20 people were killed after Marapi erupted. A series of ...
Two explosions occurred within an hour of each other, causing a lahar lava flow. [10] Next to lava, toxic gas was released which could be seen, smelled or tasted. [4] As the eruption took place during the night, people inhaled the poisonous gases during their sleep and died.
Large horseshoe-shaped craters formed by landslides at volcanoes will likely direct subsequent lava flows, pyroclastic flows or lahars toward its breached opening if the primary eruptive vent is located within these deep craters. [2]
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 ...
The shape of effusive lava flows is governed by the type of lava (i.e. composition), rate and duration of eruption, and topography of the surrounding landscape. [ 3 ] For an effusive eruption to occur, magma must be permeable enough to allow the expulsion of gas bubbles contained within it.