JNTU B.Tech II GENERAL GEOLOGY Previous Question Paper (October - 2020 - R18)

Tectonic earthquakes are the most common type of seismic events, resulting from the sudden release of accumulated strain energy within the Earth's lithosphere. They occur primarily along plate boundaries or active fault lines where tectonic plates interact.

The process is driven by the continuous movement of tectonic plates due to mantle convection currents. As plates move, they experience friction and resistance at their boundaries, causing stress to accumulate in the crustal rocks. When the accumulated stress exceeds the frictional strength or the shear strength of the rocks, the crust undergoes brittle failure. This sudden rupture causes the rocks to slip along a fault plane, releasing the stored elastic energy in the form of seismic waves that propagate through the Earth, causing ground shaking.

The Earth is chemically differentiated into three primary layers: the crust, the mantle, and the core. The crust is composed mainly of silicate rocks, with the continental crust being granitic and the oceanic crust being basaltic. The mantle, which makes up the bulk of the Earth's volume, consists of ultramafic rocks rich in magnesium and iron, such as peridotite. The core is divided into a liquid outer core and a solid inner core, both composed primarily of iron and nickel.

Regarding its origin, the Earth formed approximately 4.54 billion years ago from the solar nebula, a rotating disk of gas and dust surrounding the young Sun. Through the process of accretion, planetesimals collided and merged, generating immense heat. This heat caused the early Earth to become molten, allowing for planetary differentiation: denser materials like iron and nickel sank to the center to form the core, while lighter silicate materials rose to form the mantle and crust. Subsequent cooling and volcanic outgassing contributed to the formation of the atmosphere and oceans.