From Simple English Wikipedia, the free encyclopedia
In
geology
, a
hotspot
or
hot spot
is a portion of the Earth's surface which is
volcanic
. This may be caused by a rising
mantle plume
or some other cause.
[2]
Hotspots may be far from
tectonic plate boundaries
.
A
volcanic
hotspot is where
magma
pushes up from deep in the Earth's crust or
mantle
, and creates a volcano. The Earth's plates may move along, creating a new volcano above the hotspot while moving the older volcanoes away. This creates a chain of volcanoes, such as in
Hawaii
.
Standard account of volcanic activity
[
change
|
change source
]
Most volcanoes are explained by the collision or splitting apart of continental plates. This explains the long mountain ranges which have many volcanoes, such as the western edge of the
Americas
. It also explains the huge rift valleys such as the
East African Rift
Valley. Most Earth scientists accept that the cause of these great features is
plate tectonics
.
The problem arises with volcanoes which are not at the edges of plates. In the United States, the
Yellowstone
Caldera
is obviously active. It has
geysers
caused by constant
geothermal energy
activity, and the floor of the
crater
moves up and down as much as 50 meters in a few years. The
Pacific Ocean
has six or seven chains of islands formed by volcanic activity. Most of these cannot be explained simply as being on the edge of two or three plates.
J. Tuzo Wilson suggested in 1963 that volcanic chains like the
Hawaiian Islands
result from the slow movement of a
tectonic plate
across a fixed hot spot deep beneath the surface of the planet.
[3]
Hotspots are thought to be caused by a narrow stream of
hot
mantle
convecting
up from the Earth's
core
?mantle boundary called a mantle plume.
[4]
Other geologists think it is not high temperature that causes the
volcanism
. They think
lithospheric
extension (stretching of the
Earth's crust
) allows melted mantle to rise from shallow depths.
[2]
[5]
[6]
[7]
Geologists have identified some 40?50 such hotspots around the globe. Those under
Hawaii
,
Reunion
, and
Yellowstone
are the most active at present.