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Mafic lava, before cooling, has a low viscosity, in comparison with felsic lava, due to the lower silica content in mafic magma. Water and other volatiles can more easily and gradually escape from mafic lava. As a result, eruptions of volcanoes made of mafic lavas are less explosively violent than felsic-lava eruptions. [10]
Magmatic water. Magmatic water, also known as juvenile water, is an aqueous phase in equilibrium with minerals that have been dissolved by magma deep within the Earth's crust and is released to the atmosphere during a volcanic eruption. It plays a key role in assessing the crystallization of igneous rocks, particularly silicates, as well as the ...
Markagunt Plateau. Markagunt Plateau is a volcanic field in southern Utah, United States. Formed in a region of older volcanics, it consists of several cinder cones and associated lava flows. Some of the lava flows feature lava tubes such as Mammoth Cave, while others have formed lava dams and lakes like Navajo Lake.
Magma that is extruded as lava is extremely dry, but magma at depth and under great pressure can contain a dissolved water content in excess of 10%. Water is somewhat less soluble in low-silica magma than high-silica magma, so that at 1,100 °C and 0.5 GPa , a basaltic magma can dissolve 8% H 2 O while a granite pegmatite magma can dissolve 11% ...
The initial magma was basaltic, though this was replaced several hundred years later by more evolved, basaltic andesite magma. [20] Eruptions at Sand Mountain Field were fed by two or three magma chambers, [21] including a number of mafic magma sources over a brief span of distance and time. [22]
A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. [1] Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit ...
Types of volcanic eruptions. Some of the eruptive structures formed during volcanic activity (counterclockwise): a Plinian eruption column, Hawaiian pahoehoe flows, and a lava arc from a Strombolian eruption. Several types of volcanic eruptions —during which material is expelled from a volcanic vent or fissure —have been distinguished by ...
The presence of water can greatly alter the characteristics of a volcanic eruption and the explosions of underwater volcanoes in comparison to those on land. For instance, water causes magma to cool and solidify much more quickly than in a terrestrial eruption, often turning it into volcanic glass. The shapes and textures of lava formed by ...