Volcanoes are vents or cracks in the earth.s surface where molten rock, pyroclastic debris, steam, and other materials are ejected. Volcanoes have played an important part in the development of earth and affecting the geography by providing water, atmospheric gas, and other essential materials/nutrients to the environment. Volcanoes are also associated with the borders of tectonic plates. Only until recent history, have the intricate workings of volcanoes been understood.
- Layers of the Earth
The arrangement of he layers of the earth is an integral part to understanding how volcanoes work. The top layer is the thin crust that everything all life lives on, next is the mantle, and at deepest level is the core. The mantle and the crust are what allow for the formation of volcanoes. The mantle is the largest layer of earth, and although it is very hot, the mantle is mostly solid due to the high pressure preventing most of the material from melting. However, on the upper part of the mantle, there are areas that melt, which is the main cause of the movement of tectonic plates, an intricate part of the cause of volcanoes. This liquid part of the mantle, called magma, has the ability to allow volcanoes to form in a variety ways.
- Rising Magma
In general, volcanoes are created when magma, or molten rock, rises through the earth.s crust to the surface. The magma is usually originates from under the earth.s crust, located in the mantle layer of the earth. The magma rises, melting and pushing itself up through the earth.s surface. The main factor that causes the magma to rise is the properties of tectonic plates which create weak areas in the earth.s crust where magma can flow through.
- Tectonic Plates and Magma
The main reason magma is able to rise to the surface to create volcanoes is due to tectonic plates. Volcanoes are most common at areas where tectonic plates meet. At those areas, the tectonic plates are moving slowly, diverging or converging, allowing volcanoes to form in different ways.
When tectonic plates are diverging, this leaves an opening in the earth.s crust which allows the liquid magma to flow up creating volcanoes. This normally happens in the ocean, like the Mid-Atlantic Ridge, which creates underwater volcanoes and islands.
When tectonic plates are converging, normally one plate goes under the other. This creates a lot of friction and when the lower plate goes low enough, it begins to melt, creating magma. This magma flows upward through the upper plate melting the crust and creating a magma chamber. If the magma is restricted from flowing onto the surface, the pressure builds up in the chamber and eventually the magma is ejected through the crust as a volcanic eruption.
- Other Causes of Volcanoes
Another less common cause of volcanoes is when unusually hot magma forms in the lower regions of the mantle and rises up to the crust. This magma can potentially form a magma chamber in the middle of a tectonic plate and crust, creating what is known as a hot spot. Then volcanoes can form similar to how they form in convergent plate areas. This type of magma chamber also creates another effect, as the plate above it moves. When the plate moves, the magma chamber remains stationary, creating a string of volcanoes, like the Hawaiian Islands.
- Volcanoes on the Surface
Once a volcano erupts, it can release pyroclastic rock, gas and other material into the air. Magma/lava also flows onto the surface. This is very important to the geography of the volcano and effects the surrounding environment. When the lava flows out onto the surface, it starts to cool, normally creating a conic shaped volcano. The ejected pyroclastic material can settle around the volcano, affecting the geography. Volcanoes also affect the environment in different ways, adding to its geography and other elements.