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According to the plate theory, the principal cause of volcanism is extension of the lithosphere. Extension of the lithosphere is a function of the lithospheric stress field. The global distribution of volcanic activity at a given time reflects the contemporaneous lithospheric stress field, and changes in the spatial and temporal distribution of ...
On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example, a mid-ocean ridge , such as the Mid-Atlantic Ridge , has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has ...
Tephra is a generalized word for the various bits of debris launched out of a volcano during an eruption, regardless of their size. [4] Pyroclastic materials are generally categorized according to size: dust measures at <1/8 mm, ash is 1/8–2 mm, cinders are 2–64 mm, and bombs and blocks are both >64 mm. [5] Different hazards are associated with the different kinds of pyroclastic materials.
The classical world of Greece and the early Roman Empire explained volcanoes as sites of various gods. Greeks considered that Hephaestus, the god of fire, sat below the volcano Etna, forging the weapons of Zeus. The Greek word used to describe volcanoes was etna, or hiera, after Heracles, the son of Zeus.
Volcanoes known to have Surtseyan activity include: Surtsey, Iceland. The volcano built itself up from depth and emerged above the Atlantic Ocean off the coast of Iceland in 1963. Initial hydrovolcanics were highly explosive, but as the volcano grew, rising lava interacted less with water and more with air, until finally Surtseyan activity ...
Although the largest volcanoes like Mount St. Helens get the most attention, the Cascade Volcanic Arc includes a band of thousands of very small, short-lived volcanoes that have built a platform of lava and volcanic debris. Rising above this volcanic platform are a few strikingly large volcanoes that dominate the landscape. [1]
Hotspot volcanoes are considered to have a fundamentally different origin from island arc volcanoes. The latter form over subduction zones, at converging plate boundaries. When one oceanic plate meets another, the denser plate is forced downward into a deep ocean trench.
A volcano tectonic earthquake or volcano earthquake is caused by the movement of magma beneath the surface of the Earth. [1] The movement results in pressure changes where the rock around the magma has a change in stress. At some point, this stress can cause the rock to break or move. This seismic activity is used by scientists to monitor ...