A volcano is formed when magma, present in the Earth's interior, manages to rise up to the surface via a vent or a fissure. Hot ash and gases also escape from the interior of the Earth, along with magma. While the gases get thrown into the air, the magma and ash cool down forming distinctive volcanic landforms.
To understand in detail, the process of formation of volcanoes, one needs to understand what is inside the Earth.
To understand in detail, the process of formation of volcanoes, one needs to understand what is inside the Earth.
![Picture](/uploads/2/4/2/8/24280512/3759308.jpg)
• The Earth is essentially made up of five different layers as shown in the picture, the solid inner core, the liquid outer core, the liquid inner mantle, the upper mantle, and the crust. It is extremely hot in the core.
• The upper mantle comprises two distinct layers. The lower layer is the asthenosphere, which is semi-fluid in form, and the upper layer is that of the uppermost mantle, a.k.a rigid mantle, which is a solid layer of rock, just below the Earth's crust.
• The Earth's crust and the uppermost solid mantle together form the lithosphere.
• The Earth's lithosphere is like a huge jigsaw puzzle, with pieces of different shapes and sizes fitting into each other perfectly. These pieces are known as tectonic plates.
• The upper mantle comprises two distinct layers. The lower layer is the asthenosphere, which is semi-fluid in form, and the upper layer is that of the uppermost mantle, a.k.a rigid mantle, which is a solid layer of rock, just below the Earth's crust.
• The Earth's crust and the uppermost solid mantle together form the lithosphere.
• The Earth's lithosphere is like a huge jigsaw puzzle, with pieces of different shapes and sizes fitting into each other perfectly. These pieces are known as tectonic plates.
![Picture](/uploads/2/4/2/8/24280512/8156338.gif?765)
The magma in the asthenosphere is under tremendous pressure. Volcanoes are formed when the hot magma underneath the Earth's crust hits upon a weak spot in the crust's composition. This allows the magma to 'erupt', thus venting the heavy pressure that is built up underneath the crust. These weak spots are often found along the boundaries of tectonic plates.
As mentioned above, the tectonic plates may move in three ways. While, the convergent and the divergent boundaries might lead to the formation of volcanoes, the transform boundaries are not related to volcanic formation.
A: When one tectonic plate rises above the other
The plate with greater weight/momentum rises above, while the other plate is depressed/subdued. This subduction of the depressed plate into the asthenosphere, and the friction between the two plates causes an imbalance in pressure and temperature. This causes the asthenospheric magma and gases to erupt with enhanced force.
B:When both tectonic plates rise together
Volcanoes are not usually formed in this case. However, such a movement gives rise to the formation of mountain ranges.
C:When two plates diverge, or pull away from each other, the underlying magma emerges from the resultant crack or fault, forming a volcano.
The plate with greater weight/momentum rises above, while the other plate is depressed/subdued. This subduction of the depressed plate into the asthenosphere, and the friction between the two plates causes an imbalance in pressure and temperature. This causes the asthenospheric magma and gases to erupt with enhanced force.
Divergent boundaries are usually found in oceanic plates, and are primary sources of newly formed ocean floors. The emergent lava may go on to form islands.
Read more at Buzzle: http://www.buzzle.com/articles/how-are-volcanoes-formed.html
As mentioned above, the tectonic plates may move in three ways. While, the convergent and the divergent boundaries might lead to the formation of volcanoes, the transform boundaries are not related to volcanic formation.
A: When one tectonic plate rises above the other
The plate with greater weight/momentum rises above, while the other plate is depressed/subdued. This subduction of the depressed plate into the asthenosphere, and the friction between the two plates causes an imbalance in pressure and temperature. This causes the asthenospheric magma and gases to erupt with enhanced force.
B:When both tectonic plates rise together
Volcanoes are not usually formed in this case. However, such a movement gives rise to the formation of mountain ranges.
C:When two plates diverge, or pull away from each other, the underlying magma emerges from the resultant crack or fault, forming a volcano.
The plate with greater weight/momentum rises above, while the other plate is depressed/subdued. This subduction of the depressed plate into the asthenosphere, and the friction between the two plates causes an imbalance in pressure and temperature. This causes the asthenospheric magma and gases to erupt with enhanced force.
Divergent boundaries are usually found in oceanic plates, and are primary sources of newly formed ocean floors. The emergent lava may go on to form islands.
Read more at Buzzle: http://www.buzzle.com/articles/how-are-volcanoes-formed.html