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A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity ) lava , which travels farther and forms thinner flows than the more viscous lava erupted from a stratovolcano .
Debris avalanche deposit of Tata Sabaya in Bolivia Cross-section diagram showing (a) pre-collapse volcano, (b) after collapse, (c) new edifice built on top of collapsed old edifice. At volcanoes, the term landslide is commonly used for slope movements with shear and displacement in a relatively narrow zone. [7]
The formation of this harbour has occurred due to active erosional processes on an extinct shield volcano, whereby the sea has flooded the caldera, creating an inlet 16 km in length, with an average width of 2 km and a depth of −13 m relative to mean sea level at the 9 km point down the transect of the central axis. [5]
This list of shield volcanoes includes active, dormant and extinct shield volcanoes. Shield volcanoes are one of the three types [ specify ] of volcanoes. They have a short cone shape, and have basaltic lava which means the lava has low viscosity (viscosity is a measure of the ability for a liquid to flow)
There were three main shield volcanoes built on the seamount base (from north to south): the Northern Edifice, the Central Edifice and the Jandia Edifice. [74] [26] The central shield volcano is the oldest, built mostly from 22 to 18 Ma but with a later phase from 17.5 to 13 Ma. The southern shield volcano formed from 21 to 14 Ma.
The most important types of volcanic mountain are composite cones or stratovolcanoes and shield volcanoes. [10] [11] A shield volcano has a gently sloping cone because of the low viscosity of the emitted material, primarily basalt. Mauna Loa is the classic example, with a slope of 4°-6°.
[1] [3] On shield volcanoes forming from level seafloor without neighboring vents, flank rifting occurs more evenly distributed around the vent. [1] However, where the flanks of a volcano may be supported on one side by the presence of a pre-existing feature, or burdened with various planes of weakness, rift zone formation promulgates according ...
Recent argon–argon dating suggests that eruptive activity at the Boring Lava Field began between 2.6 and 2.4 million years ago, yielding far-reaching basalt lava flows, the Highland Butte shield volcano, a number of monogenetic vents, and one andesitic lava flow. These took place near the southern Portland Basin, and were followed by about ...