Different Types of Volcanoes - Structure and Mechanism

Volcanoes are classified on the basis of their nature of eruption that is how they erupt and on the basis of their formation that is their physical structure how they were developed over time. Below are five types of volcanoes that exists on earth and they are :-

1. Shield Volcanoes - These are the largest of all the volcanoes on the earth. The Hawaiian volcanoes are a perfect example of shield volcanoes. The unique thing about these volcanoes is that if you look at the picture, they resemble the shape of a warrior's shield. It's that wide in diameter. and the type of lava that gets out of this volcano is low in viscosity meaning it is not thick, it is more of a fluid quality and due to that these volcanoes are not steep. Since the lava is not thick therefore its eruption is like a fountain and is not explosive, however when water comes in contact it gets very explosive. The largest shield volcano is the Mauna Loa on the Big Island of Hawaii.

2. Composite Volcanoes - The meaning of the composite is made up of several parts or elements. hence these volcanoes are made up of multiple eruptions. So over time the lava cools down and forms thick layer of crust near the vent opening giving it a conical shape. The lava that comes out of this volcano has higher viscosity meaning it is thick. These volcanoes often result in explosive eruptions. Along with lava, large quantities of pyroclastic material and ashes find their way to the ground.

3. Caldera - These are the most explosive volcanoes. They are usually so explosive that when they erupt they tend to collapse on themselves rather than building any tall structure. when we say explosive we mean how hard it shoots upwards. because if the eruption is not explosive then the lava would flow in a nice river format. Explosive eruption means shooting harder upwards remember that. So caldera are explosive and because of that the vent opening collapses on itself, that creates a depression and this depression is called calderas. Their explosiveness indicates that the magma chamber supplying the lava is not only huge but is also in close vicinity. Because the gravity will not allow the lava to go very high therefore the distance between the magma chamber and the vent opening of the volcano has to be close.

4. Flood Basalt Provinces - If you look at the words flood, basalt and provinces they speak about river bed sort of physical appearance. Let me just break it down for you. by the word flood we mean a sudden rush of something in this case it has to be lava, then basalt is a dark-colored, fine-grained, igneous rock which is solidified state of lava and province is called an area. So collectively the term flood Basalt Provinces means out-pour of highly fluid lava that flows for long distances may be some thousands of sq. km forming a terrain, a landscape. The Deccan Traps from India, presently covering most of the Maharashtra plateau, are a much larger flood basalt province. That's why this region is made of vast sheets of massive granite rock, gneiss, quartzite etc.

5. Mid-Ocean Ridge Volcanoes - A mid-ocean ridge is an underwater mountain range, formed by plate tectonics. If you look at this diagram, these are the different layers of earth. Here you see there is an oceanic crust and a continental crust. The breaking of oceanic crust is referred to as a mid ocean ridge. Ridge means a crack that is formed due to elevation. Now this occurs due to divergent plate boundaries. If you see the lithosphere that is the region comprising of crust and upper mantle, they are in the form of plate which we call as tectonic plates. Whenever there is a movement between the plates they either move away from each other which is called as divergent boundary, or they move towards each other which is called as convergent boundary or they slide past each other. Now in oceans usually divergent mechanism takes place meaning the plates move away from each other. And when oceanic plates move away from each other, the central portion of the ridge experiences frequent volcanic eruptions. These are called as Mid-Ocean Ridge Volcanoes.