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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]
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 ...
Pahoehoe lava is smooth and ropy while Aa lava is blocky and hard. Lava flows normally follow the topography, sinking into depressions and valleys and flowing down the volcano. Lava flows will bury roads, farmlands and other forms of personal property. [1] This lava could destroy homes, cars, and lives standing in the way. [2]
Hawaii's Big Island continues to be plagued by volcanic eruptions, which have destroyed several homes and forced roughly 2,000 people to evacuate.
In volcanology, a pressure ridge or a tumulus (plural: tumuli), and rarely referred to as a schollendome, is sometimes created in an active lava flow. [1] Formation occurs when the outer edges and surfaces of the lava flow begin to harden. [1] If the advancing lava underneath becomes restricted it may push up on the hardened crust, tilting it ...
Around Aberdeen, lava flows from diverse vents form a large field with aa and pahoehoe forms [11] and neatly preserved surface features. [9] Lava flows reach lengths of 9 kilometres (5.6 mi) [3] and have thicknesses of 0.01–30 metres (0.39 in – 98 ft 5.10 in) and sometimes lava flows from separate cones overlap, such as in Papoose Canyon. [8]
A further control on the morphology and characteristics of a deposit is the water to magma ratio. It is considered that the products of phreatomagmatic eruptions are fine grained and poorly sorted where the magma/water ratio is high, but when there is a lower magma/water ratio the deposits may be coarser and better sorted. [4]
The pressure and instantaneous cooling of being underwater stops, replaced instead by contact with air. Lava and seawater make intermittent contact, resulting in a lot of steam. [1] The change in environment also engenders a change in lava type, and the lava from this stage is mostly fragmented into volcanic ash.