Physical Geography

Continental Drift Theory – Tectonics

  The continental drift theory is the theory that once all the continents were joined in a super-continent, which scientists call Pangaea. Over a vast period of time, the continents drifted apart to their current locations. Alfred Wegener first supported continental drift. Wegener’s explanation of continental drift in 1912 was that drifting occurred because of the earth’s rotation. Fossil records from separate continents, particularly on the outskirts of continents show the same species.

Orogenic or the mountain-forming movements

  Orogenic or the mountain-forming movements act tangentially to the earth surface, as in plate tectonics. Tensions produces fissures (since this type of force acts away from a point in two directions) and compression produces folds (because this type of force acts towards a point from two or more directions). In the landforms so produced, the structurally identifiable units are difficult to recognise. In general, diastrophic forces which have uplifted lands have predominated over forces which have lowered them. Orogenic- mountain-forming movements Sudden Movements These movements cause considerable deformation over a short span of time, and may be of two ... Read more

Earth Movements – Endogenetic Movements

  The interaction of matter and temperature generates these forces or movements inside the earth’s crust. The earth movements are mainly of two types: diastrophism and the sudden movements. The energy emanating from within the earth is the main force behind endogenic geomorphic processes. This energy is mostly generated by radioactivity, rotational and tidal friction and primordial heat from the origin of the earth. This energy due to geothermal gradients and heat flow from within induces diastrophism and volcanism in the lithosphere. Diastrophism Diastrophism is the general term applied to slow bending, folding, warping and fracturing. Wrap == make or ... Read more

Earth’s Layers – Earth’s Composition

  The Crust of Earth It is the outermost and the thinnest layer of the earth’s surface, about 8 to 40 km thick. The crust varies greatly in thickness and composition – as small as 5 km thick in some places beneath the oceans, while under some mountain ranges it extends up to 70 km in depth. The crust is made up of two layers­ an upper lighter layer called the Sial (Silicate + Aluminium) and a lower density layer called Sima (Silicate + Magnesium).The average density of this layer is 3 gm/cc. The Mantle of Earth This layer extends ... Read more

Earth’s Interior – Earthquake Waves – Shadow Zone

  Most of the knowledge we have about Earth’s deep interior comes from the fact that seismic waves penetrate the Earth and are recorded on the other side.  Earthquake ray paths and arrival times are more complex than illustrated in the animations, because velocity in the Earth does not simply increase with depth. Velocities generally increase downward, according to Snell’s Law, bending rays away from the vertical between layers on their downward journey; velocity generally decreases upward in layers, so that rays bend toward the vertical as they travel out of the Earth . Snell’s Law also dictates that rays ... Read more