|Demand of the question |
Introduction. What is volcano?
Body. Types of volcanoes and various associated landforms.
Conclusion. Way forward.
A volcano is a vent or fissure in Earth’s crust through which lava, ash, rocks, and gases erupt. An active volcano is a volcano that has erupted in the recent past. Material that flows to or reaches the ground comprises lava flows, volcanic bombs, pyroclastic debris, dust, ash and gases. The gases maybe sulphur compounds, nitrogen compounds, and trace amounts of argon, hydrogen and chlorine.
Major types of volcanoes: Volcanoes are classified on the basis of nature of eruption and the form developed at the surface.
- Shield Volcanoes: The Shield volcanoes are the largest of all the volcanoes on the earth, which are not steep. These volcanoes are mostly made up of basalt. They become explosive if in some way water gets into the vent, otherwise, they are characterized by low-explosivity. Eg: Hawaiian shield volcanoes
- Composite Volcanoes: Composite Volcanoes are characterized by outbreaks of cooler and more viscous lavas than basalt. They are constructed from numerous explosive eruptions. The major composite volcano chains are Pacific Rim which known as the “Rim of Fire”.
- Caldera: Calderas are known as the most explosive volcanoes of Earth. They are generally explosive in nature. When they erupt, they incline to collapse on themselves rather than constructing any structure. The collapsed depressions are known as calderas.
- Flood Basalt Provinces: Flood Basalt Province volcanoes discharge highly fluid lava that flows for long distances. Many parts of the world are covered by thick basalt lava flows.
- Mid-Ocean Ridge Volcanoes: These volcanoes are found in the oceanic areas. There exists a system of mid-ocean ridges stretching for over 70000 km all through the ocean basins. The central region of this ridge gets frequent eruptions.
Various Volcanic Landforms are:
- Batholiths: These are large rock masses formed due to cooling down and solidification of hot magma inside the earth. Batholiths form the core of huge mountains and may be exposed on surface after erosion.
- Laccoliths: These are large dome-shaped intrusive bodies connected by a pipe-like conduit from below. These are basically intrusive counterparts of an exposed domelike batholith. Karnataka plateau is spotted with dome hills of granite rocks. Most of these, now exfoliated, are examples of laccoliths or batholiths.
- Lapolith: As and when the lava moves upwards, a portion of the same may tend to move in a horizontal direction wherever it finds a weak plane. It may get rested in different forms. In case it develops into a saucer shape, concave to the sky body, it is called Lapolith.
- Phacolith: A wavy mass of intrusive rocks, at times, is found at the base of synclines or at the top of anticline in folded igneous country. Such wavy materials have a definite conduit to source beneath in the form of magma chambers (subsequently developed as batholiths). These are called the Phacoliths.
- Sills: These are solidified horizontal lava layers inside the earth.The near horizontal bodies of the intrusive igneous rocks are called sill or sheet, depending on the thickness of the material. The thinner ones are called sheets while the thick horizontal deposits are called sills.
- Dykes: When the lava makes its way through cracks and the fissures developed in the land, it solidifies almost perpendicular to the ground. It gets cooled in the same position to develop a wall-like structure. Such structures are called dykes. These are the most commonly found intrusive forms in the western Maharashtra area. These are considered the feeders for the eruptions that led to the development of the Deccan traps.