Intrusive and Extrusive Forces

It is a known fact that magma or lava is stored deep inside the surface of Earth. This magma is stored inside the surface of Earth in the form of reservoirs. These reservoir chambers are called magma chambers. It has a designated pathway called conduits. All the conduits and the chambers resemble the piping system of the volcano. This is a network that is spread over a large area. The magma cools down and solidifies. The solidification of the magma is done in two days. Either it solidifies above the surface or below the surface. The space in which it solidifies decides the fate of the structures. They are divided into intrusive landforms and extrusive landforms. These landforms are later formed into more advanced structures. The extrusive landforms are formed when the magma solidifies outside the surface. This is formed by the magma that is thrown out during volcanic activity. On the other hand, intrusive landforms are formed when the magma solidifies inside the crust of the Earth. 

What is Volcanism? 

The process of volcanism takes place when the tectonic plates of the Earth shift in a way that they can override each other. In simple words, it means that one plate can come over the other.  

Volcanism also occurs in one other condition. In this condition, the plates move apart from each other in such a way that a ridge is created between them—the magma lying underneath the ridges wells upwards. The magma fills up the gap in between, and it gives rise to a new ocean floor. It is seen that all these activities particularly take place under the ocean floor. 

What is the process of Volcanism?

The magma present deep down on the Earth’s surface rises to give rise to an eruption. The behaviour of the magma that reaches the surface can be characterised by the type of rock. The rocks are defined by the viscosity of the magma. Let’s say that the magma is very thick or viscous gives rise to a highly functional volcano explosive eruption of its major characteristics.

On the other hand, if we were to define volcanoes that are made of magma that is thin or non-viscous, the volcano would turn out to be non-functional. It would result in effusive eruptions. 

There are times when the magma does not come out on the surface and remains inside. In such cases, it mostly solidifies. When the magma does not hit the surface or even come in contact with it, it is likely to form a crystalline structure that is formed by the solidification of the lava or magma. These form intrusive structures. 

What are Intrusive Landforms? 

The intrusive landforms are formed when the magma does not reach the Earth’s surface and starts solidifying inside the Earth’s crust. In such a case, the magma cools down underneath the surface of Earth and starts solidifying there to form different structures. During the whole process, it is underground. It never hits the surface. These structures are known as plutons. 

These structures have no way of being exposed on the Earth’s surface unless years and years of soil erosion have corroded the topmost layer of Earth. Only then the other layers can be revealed. It is one of the differences between extrusion force and intrusion force.

The different types of intrusive landforms that are formed by the action of intrusive and extrusive force values are:

• Batholiths

These are granite rocks. They can not occur on the Earth’s surface unless the layer has been washed away by soil erosion for centuries. They are the core material for many strong mountains.

• Laccolith

They are a minor part of a dome-like batholith. They also have a pipe-like conduit present underneath their surface. 

• Lapolith

The magma can move in several directions that affect its shape and form. If it takes the form of a saucer, it is a lopolith.

• Phacoliths 

They are wavy structures. They are the wavy counterparts of the intrusive landforms.

• Dykes 

When the lava forms a wall-like structure while it is cooled, it results in a dyke.

• Sills

When the intrusive rocks develop into horizontal structures or sheets, they are known as sills.

What are Extrusive Landforms? 

When the intrusive and extrusive force values are so much that the magma is forced out of the surface of Earth, it results in extrusive landforms. It is one of the differences between extrusion force and intrusion force. 

• Caldera 

As its name suggests, the caldera is a cauldron-like structure that can be seen when the magma has been emptied due to a volcanic eruption.

• Geysers 

When hot water is ejected from the surface of Earth, it is a geyser of steam.

• Hot Springs 

When the groundwater that has been heated geothermally occurs on the Earth’s surface, hot springs are formed.

• Composite Cones

When the cooled lava forms mountains, they are composite cones. 

Conclusion 

In this article, we learnt about volcanism and the process of volcanism. We discussed that the process of volcanism takes place when the tectonic plates of the Earth shift in a way that they can override each other. In simple words, it means that one plate can come over the other.  We then discussed how the magma is stored under the surface of Earth. The magma or lava is stored in reservoirs under Earth’s surface. There is a network with several pathways or conduits in between them. The solidification of the magma inside or outside the surface of Earth determines the action of intrusive and extrusive forces. The major difference between extrusion force and intrusion force is the solidification of magma on the surface (extrusive) and solidification under the surface of Earth (intrusive).