Srinivasa ramanujan

Srinivasa ramanujan

• 1.
  S.S.T LITHOSPHERE The lithosphere (Greek:for "rocky" +[ sphaira ] for "sphere") is the rigid. outermost shell of a rocky planet. On Earth, it comprises the crust and the portion of the upper mantle that behave In the Earth the lithosphere includes the crust and the uppermost mantle, which constitute the hard and rigid outer layer of the Earth. The lithosphere is underlain by the as lithosphere, the weaker, hotter, and deeper part of the upper mantle. The boundary between the lithosphere and the underlying as the lithosphere is defined by a difference in response to stress: the lithosphere remains rigid for very long periods of geologic time in which it deforms elastically and through brittle failure, while the asthenosphere deforms viscously and accommodates strain through plastic deformation. The lithosphere is broken into tectonic plates. The uppermost part of the lithosphere that chemically reacts to the atmosphere, hydrosphere and biosphere through the soil forming process is called the pedosphere. elastically on time scales of thousands of years or greater. There are two types of lithosphere: 1. Oceanic lithosphere, which is associated with oceanic crust and exists in the ocean basins. Oceanic lithosphere is typically about 50–100 km thick 2. Continental lithosphere, which is associated with continental crust. Continental lithosphere has a range in thickness from about 40 km to perhaps 200 km, of which about 40 km is crust.
• 2.
  3. The lithosphereis divided into tectonic plates, which move gradually relative to one another. 4. Oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge. This thickening occurs by conductive cooling, which converts hot asthenosphere into lithospheric mantle, and causes the oceanic lithosphere to become increasingly dense with age. Oceanic lithosphere is less dense than asthenosphere for a few tens of millions of years, but after this becomes increasingly denser than asthenosphere. 5. When a continental plate comes together with an oceanic plate, at a subduction zones, the oceanic lithosphere always sinks beneath the continental. 6. New oceanic lithosphere is constantly being produced at mid-ocean ridges and is recycled back to the mantle at subduction zones. As a result, oceanic lithosphere is much younger than continental lithosphere: the oldest oceanic lithosphere is about 200 million years old, while parts of the continental lithosphere are billions of years old. 7. Another distinguishing characteristic of the lithosphere is its flow properties. Under the influence of the low-intensity, long-term stresses that drive tectonic motion, the lithosphere responds essentially as a rigid shell and thus deforms primarily through brittle failure, whereas the asthenosphere (the layer of the mantle below the lithosphere) is heat-softened and accommodates strain through plastic deformation. change