Cobb hotspot

The Cobb Hotspot is a marine volcanic hotspot located at (46˚ 00' 0.00" N, -130˚ 00' 0.00" W), which is 460km (290mi) west of Oregon and Washington, North America, in the Pacific Ocean. Over geologic time, the Earth's surface has migrated with respect to the hotspot through plate tectonics, creating the Cobb-Eicklberg seamount chain. The hotspot is currently collocated with the Juan de Fuca Ridge.

The Cobb Hotspot has created an underwater mountain range that extends 1800km to the northwest and ends at the Aleutian Trench. The oldest mount in the chain is the Marchland Seamount, at 30 to 43 Ma (million years old). The old, northwestern end of the chain collides with a subduction zone; therefore, the true age of the hotspot is difficult to determine as the oceanic crust is being consumed. Axial Seamount is the hotspot's most recent eruptive center, which last erupted in 2015, 2011 and 1998. The central ridge of the hotspot is thicker than the surrounding crust by a few kilometers and may be accumulated buildup from the magma released at the hotspot, which is essentially a submarine volcano with a root twenty to forty kilometers in diameter, reaching a depth of 11 kilometres (6.8 mi) beneath the volcano. The magma flows at a rate of 0.3 to 0.8 m³/s. The caldera is 1,450 metres (4,760 ft) below sea level.

Hotspots are formed when plumes of magma from the lower mantle upwells to the crust of Earth and breaks through the surface crust, whether that be oceanic crust or continental. This movement of magma breaks through the upper mantle, or the lithosphere, and creates a volcanic spot. This does not mean that all volcanoes are hotspots, some are created through interactions at plate boundaries. Tectonic plates move over hotspots creating a chain of volcanically-formed mountains over time. This is supported by the theory of plate tectonics. The peaks and mountains left behind are no longer active volcanoes. Hotspots do not necessarily occur on a plate boundary, though the Cobb Hotspot does.

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