InsightsUnveiled

A) Collapse Calderas:- they result from the collapse of the superstructure of the volcano due to withdrawal of the underlying support when the rapid large volume of the eruption of the ash may lower the magma level reservoir to an extent such that a potential void is left. Example- ‘Krakatau’ type. B) Resurgent Calderas:- Develop where collapse is followed by the doming of central block. Example-‘Valleys Caldera’, New Mexico. C) Erosion Calderas :-they are the result of the enlargement of craters or the calderas by the erosional processes. D) Pit craters or the volcanic sinks:- they are the typical exposed in Hawaiian Islands. It has the steep walls and the great depth. The pit may be widened by the faulting or the landslide after long periods. At periods of quiescence pit is floored by solid lava. At the racks magma works upwards by the stopping and fluxing to form a cylindrical chamber occupied by the magma.

When tectonic plates converge or slide past each other the continental margins are called Active margins/Pacific type margins(as they are common around Pacific ocean's rim).Active margin is divided into 2 sub-types:- 1)Steady-state margins;& 2)Collision-state margins. Subduction is deemed to create steady-state margins in the sense that oceanic crust is subducted indefinitely while a continent or island arc resists subduction.Steady-state margins produce 2 major landforms:- a)Intra-oceanic island arcs;& b)Continental magin orogens. Intra-oceanic island arcs result from the oceanic lithosphere being subducted beneath another oceanic plate.The subducted portion of that plate starts getting heated up & melts,as we know temperature decreases with depth.Subduction causes fracture. The molten portion of the subducted plate causes pressure inside the crust which is equated & released when volcanic eruption occurs through the fracture follow

The word Isostasy is derived from the german word ‘isostatios’ meaning to be ‘in equipoise’ and was first proposed by the American geologist Dutton. It simply means a mechanical stability between upstanding parts and the low lying basins on a rotating earth. The theory is developed out of the discrepancy that arose during the geodetic surveying of the Indo-Gangetic plain for the latitude determination under the supervision of Sir G.Everest,the then Surveyor General of India . The problem gave rise to several explainations to the problem proposed by – Sir G.Airy,Pratt,Hayford and Bowie and so on. However,the problem that arises with the theory of isostasy is that in all the concepts proposed ,all the aforementioned people considered different landforms (like the plateau,plain,mountain etc.) as coloumns while in reality it’s not so.Moreover the critics of this theory pointed that there is no complete isostasy over the globe due to constant endogenetic forces.Critics have also

Seismicity is the frequency and intensity of an earthquake (a shock or a series of shocks due to a sudden movement of crustal rocks , generated at a point called focus within the crust or mantle in an area. The term ‘ plate ’ is coined by Canadian Geo-physicist J.T. Wilson. The evolution,movement and destruction of the plates at the trenches are tectonically termed as plate tectonics . Earthquakes are classified into 5 types depending on the mode of generation:- 1)Tectonic earthquakes; 2)Volcanic earthquakes; 3)Collapse earthquakes; 4)Explosion earthquakes;& 5)Plutonic earthquakes. Tectonic earthquakes which occur from structural adjustments inside the earth are the result of the plate tectonic mechanism. Tectonic earthquakes are sub-divided into- Inter-plate earthquakes( occurring at plate edges) and Intra-plate earthquakes( occurring within the plates other than the edges) . Earthquakes occurring at where the plate boundaries converge such as trenches contrib