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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]
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]
Mafic magma is less viscous; it produces lava flows and is less prone to explosive eruptions than silicic magma. [18] The Mount Bachelor volcanic chain, southeast of South Sister, consists of Mount Bachelor, [19] which is the largest [5] and northernmost volcano of the group, [19] and a series of cinder cones, lava flows, and three shield ...
Shield volcanoes fed Mazama's expansion with basaltic andesite lava flows that covered large expanses on the slopes of the mountain. Forming lava fountains similar to those observed in Hawaiian eruptions, the shield volcanoes erupted incandescent lava bombs and were deposited on the southern, western, and eastern flanks of the complex.
Markagunt Plateau. / 37.58; -112.67. 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.
Topographic map of the MEVC with Mount Edziza Provincial Park in green. The eruption rate of the MEVC has varied throughout its long volcanic history. When the volcanic complex started erupting at least 7.4 million years ago, it increased the rate of magmatism in the Northern Cordilleran Volcanic Province from 100,000 to 300,000 cubic metres (3,500,000 to 10,600,000 cubic feet) per year.
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 ...
A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it upwards. [ 1] If the magma finds a path to the surface, then the result will be a volcanic eruption ...