Volcanic Landforms

The structures and terrestrial landforms created by the explosion of volcanoes can be defined as volcanic landforms. These landforms are ever-changing and the transformation in the structure of these landforms depends on the volcanic eruptions.

Some of the basic structures formed by the eruption of volcanoes are cinder cones, calderas, volcanic domes and stratovolcanoes. Generally, volcanic eruption activities occur throughout hundreds and thousands of years; hence, people have settled civilisations across volcanic landforms due to a sense of security.

Volcanic landforms can be differentiated into two categories that are extrusive volcanic landforms and intrusive volcanic landforms. 

Landforms associated with volcanoes

The molten Magma stored below the surface of the Earth finds its way to the surface through the volcanic network system. As soon as it reaches the surface through the process of a volcanic explosion, the Magma, along with other volcanic matters, starts solidifying. 

The Magma finds its way to the Earth’s surface through a channel of network known as conduits and this network is commonly known as the “volcanoes’ plumbing system”. This plumbing system beneath the surface of the crust extends for miles.The emptied conduit after a volcanic explosion collapses into the formation of a “caldera” or retains the structure of lava tubes or volcanic caves. The cooling and settling of Magma are known as “pluton”, and the rocky structure around the pluton is known as “country rock”.The cooling and settling of the Magma on the Earth’s surface create various landforms and other terrestrial structures, categorised into mainly two types, i.e., intrusive volcanic forms and extrusive volcanic forms.

Intrusive volcanic features

The intrusive volcanic structures are formed when the Magma cools down within the crust. The intrusive volcanic activities lead to batholiths, sills and dikes, monadnocks, stocks and laccoliths.

Intrusive volcanic landforms

• Batholiths: Batholiths can be described as plutons which have solidified over the surface of the crust through the process of uplifting and erosion
• Sills and Dykes: Sills form tabular chambers that intrude the body or layer of older sedimentary rocks. On the other hand, Dykes are similar intrusive structures that do not intrude or overlap the older layers of sedimentary rocks
• Monad nocks: They are isolated hill-like structures formed by the deposition of Magma over the crust’s surface which makes it appear in the form of a solid isolated rock structure. They are also commonly known as Inselbergs
• Laccoliths: These are mushroom-shaped intrusive structures that are formed by deforming the initial host rock by the process of folding. The structure of a laccolith is formed when older sedimentary rock layers are intruded in a sheet-like formation
• Stocks: The cooling of intrusive igneous plutonic rocks beneath the crust’s surface or within the crust of the Earth is known as stock or pluton
• Phacolith: These are wavy igneous rock structures parallel to the foliation of the folded country rock or the bedding plane
• Lopolith: These are structures of intrusive igneous rocks shaped in the form of pipes or lentils and have a depressed central cavity chamber

Extrusive volcanic landforms

The extrusive volcanic structures are formed when the volcanic matter and substances are thrown over on the Earth’s surface. They solidify, forming various types of volcanic landforms.The volcanic matter and substances that find their way to the Earth’s surface are composed of lava, volcanic bombs, ash, dust, gases, nitrogen and sulphur compounds, pyroclastic debris and more minor compositions of chlorine hydrogen and argon.

The types of landforms formed due to extrusive volcanic activities are:

• Fissure vent: The fissure vent allows the flow of lava to the Earth’s surface through a narrow channel that generally does not involve any explosion
• Conical vent: Violent volcanic structures explode violently during an eruption; here, the Magma flows out through a conical chamber
• Mid-ocean ridges: The mid-oceanic ridges can extend up to almost 70,000 KMS. Since the lava contains lesser quantities of silica, it is less explosive and it spreads across the ocean floor
• Shield type volcanoes: These volcanoes explode or erupt only when water enters their vent. They are structurally not steep and they are composed of basaltic lava. Hawaiian volcanoes are the perfect examples of shield-type volcanoes
• Lava plateaus: When the Magma from beneath the Earth’s surface finds its way to the surface through cracks and fissures and solidifies on the surface of the Earth’s crust, it forms lava plateaus. Since these plateaus are formed due to the spreading of the lava, they cover vast spaces
• Caldera: When the conduit chamber collapses after a volcanic explosion, the structure formed is called a caldera
• Cinder cone: These structures are built around a lava vent over some time and they resemble the shape of an oval or circle
• Lava dome: The name of this structure is pretty self-explanatory for its shape; the lava domes are formed due to the accumulation of Magma around the vent of a volcano

Conclusion

Years of volcanic explosions and volcanic activities cause the formation of volcanic landforms which are composed of solidified Magma over or under the surface of the crust.The volcanic landforms are divided into two major categories such as intrusive volcanic landforms and extrusive volcanic landforms. The fundamental difference between the two is the location where the volcanic magma solidifies, i.e., over or within the earth’s crust.