An active volcano, such as in the Hawaiian islands, is a weak spot in the Earth's crust.
A mid-ocean ridge is where magma pushes up on oceanic lithosphere, creating new oceanic crust as the magma solidifies. The heat from the magma causes the lithosphere to rise and spread apart, resulting in seafloor spreading. This process is fundamental in plate tectonics theory.
The inner core of the earth has a temperature of about 5700 degrees C. About the same as the surface of the Sun. Above this is the outer core, which has a similar temperature, but as it is under less pressure, it is molten.This molten material undergoes convection and this is the primary driving force for the movement of the magma just below the crust. There appear to be some stationary 'hot spots' of which Hawaii and Iceland are conspicuous examples. Even though the plates there are moving, the hot spot seems stationary.So magma is just a hot liquid form of rock. Not necessarily very viscous.
Magma is a product of earth processes. To say it has a purpose may be a subjective statement.**The first question this raises is: what exactly is this "material from the inside"? On our planet, it's magma, fluid molten rock. This material is partially liquid, partially solid and partially gaseous.magma production around plate boundaries. This interplatevolcanic activity is caused by unusually hot mantle material forming in the lower mantle and pushing up into the upper mantle. The mantle material, which forms a plume shape that is from 500 to 1000 km wide, wells up to create a hot spot under a particular point on the earth. Because of the unusual heat of this mantle material, it melts, forming magma just under the earth's crust. The hot spot itself is stationary; but as a continental plate moves over the spot, the magma will create a string of volcanoes, which die out once they move past the hot spot. The Hawaii volcanoes were created by such a hot spot, which appears to be at least 70 million years old.So what happens to the magma formed by these processes? We saw that the magma produced at ocean ridges just hardens to form new crust material, and so doesn't produce spewing land volcanoes. There are a few continental ridge areas, where the magma does spew out onto land; but most land volcanoes are produced by subduction zone volcanism and hot spot volcanism.When the solid rock changes form to a more liquid rock material, it becomes less dense than the surrounding solid rock. Because of this difference in density, the magma pushes upward with great force (for the same reason the helium in a balloon pushes up through the denser surrounding air and oil pushes upward through denser surrounding water). As it pushes up, its intense heat melts some more rock, adding to the magma mixture.The magma keeps moving through the crust unless its upward pressure is exceeded by the downward pressure of the surrounding solid rock. At this point, the magma collects in magma chambers below the surface of the earth. If the magma pressure rises to a high enough level,or a crack opens up in the crust, the molten rock will spew out at the earths surface.
Volcanic mountains are formed when magma rises towards the Earth's surface through a weak spot in the Earth's crust, causing a volcanic eruption. Over time, repeated eruptions build up layers of solidified lava and volcanic ash, creating a mountain. The shape and size of the mountain depend on the type of eruption and the characteristics of the magma.
There is a 'Hot-spot' in the mantle underneath the crust near the Hawaiian islands, it causes the magma to bubble up through fissures in the sea floor and eventually create new islands. this is how they were formed. for more info look at mantle convection.
In the crust the weak spot we have is the Magma Chamber. But, deep down to the mantle such weak zone is the Asthenosphere.
A hot spot is an area where magma from deep within the mantle rises through the crust in the middle of a tectonic plate, creating volcanic activity and forming a chain of volcanic islands or seamounts. The Hawaiian Islands are a well-known example of hot spot activity.
A caldera is a large volcanic crater typically formed by the collapse of land following a volcanic eruption. It is not necessarily a weak spot in the crust where magma comes through, but rather a feature that results from the massive release of pressure during an eruption. Magma may still come through the caldera, but it is not the primary defining characteristic of this geological feature.
Hot spot.
magma comes from the outer core and when an earthquake or something happends, a crack froms and the pressure of lava shoots up like a geyser.
hot spot
Magma from deep within the mantle melts through the crust which is what causes hot spot volcanoes to form
Volcano
A Volcano.
A volcano is technically a weak spot in Earth's crust where molten material like magma reaches the surface. Magma is made near the surface by convergent (colliding) or divergent (spreading) boundaries. Most volcanoes form near convergent boundaries where the oceanic plate submerges because of the density of the plate.Also, a hot spot may form a volcano. A hot spot is where magma from the mantle reaches the surface. As the crust moves from convection currents in the mantle, the hot spot is near the crust. Whenever the hot spot passes under a weak spot in the crust, the pressure in the magma is strong enough to push through. As the crust continues moving, the hot spot makes different volcanoes in a row, called an island arc. An example of this is Hawaii.
It depends on where the hot spot is located. Felsic magma would be produced if it was under a continent (such as in Yellowstone) whereas Mafic magma would be produced if it was under oceanic crust (such as in Hawaii)
Mt. St. Helens was formed when the North American Plate passed over a hot spot on the Earth's crust. A hot spot is a weak spot in the Earth's crust that magma can escape through. This hot spot is now the vent of Mt. St. Helens.