A volcano is an opening in the earth’s crust through which gases, molten rock components (lava), ash, steam, and other substances are ejected during an eruption. Such vents or holes are found in areas of the earth’s crust where the rock layers are relatively weak. Volcanoes are one example of an endogenic process. Depending on the explosive nature of the volcano, various land shapes such as a plateau (if the volcano is not explosive) or a mountain can form (if the volcano is explosive in nature).
Types of Volcanoes
· Shield Volcanoes: They are not exceedingly steep, but they are long and wide. They reach vast heights and distances. They are the world’s biggest volcanoes, with lava flowing for a long distance. The most well-known examples are the Hawaiian volcanoes.
· Cinder Cone Volcanoes: Cinders are igneous rocks that extrude. Scoria is a more recent word for cinder. These volcanoes are virtually exclusively made up of loose, grainy cinders, with very little lava.
· Composite Volcanoes: Cone-shaped volcanoes with relatively steep sides and tiny craters in their tops. They are distinguished by the eruption of lavas that are colder and more viscous than basalt.
· Caldera: The most explosive volcanoes in the planet. They are generally so explosive that when they erupt, they collapse on themselves rather than erecting a lofty edifice. Calderas are the collapsed depressions.
· Flood Basalt Provinces: These volcanoes spew very fluid lava that travels considerable distances. The Indian Deccan Traps, which currently comprise the majority of the Maharashtra plateau, are a considerably bigger flood basalt province.
· Mid-Ocean Ridge Volcanoes: These volcanoes can be found in marine environments. A network of more than 70,000 km long mid-ocean ridges runs through all of the ocean basins. The centre section of this ridge is prone to eruptions.
Why are the volcano’s eruptions so highly explosive?
· If magma rises into sea water slowly, even at temperatures of about 1200 degrees Celsius, a thin film of steam forms between the magma and water. This provides a layer of insulation to allow the outer surface of the magma to cool.
· But this process doesn’t work when magma is blasted out of the ground full of volcanic gas. When magma enters the water rapidly, any steam layers are quickly disrupted, bringing hot magma in direct contact with cold water.
· Volcano researchers call this ‘fuel-coolant interaction’ and it is akin to weapons-grade chemical explosions. Extremely violent blasts tear the magma apart.
· A chain reaction begins, with new magma fragments exposing fresh hot interior surfaces to water, and the explosions repeat, ultimately jetting out volcanic particles and causing blasts with supersonic speeds.
How to structure
- Give an intro about volcanoes
- Explain why some volcanoes erupts explosively than others- give different tpes and use figures and maps- use recent example