Tag: geography

Igneous rocks are of two types, extrusive and intrusive. Extrusive igneous rocks cool and solidify quicker than intrusive igneous rocks. They are formed by the cooling of molten magma on the earth's surface. The magma, which is brought to the surface through fissures or volcanic eruptions, solidifies at a faster rate.

• Rock cycle is the transition of rocks of 3 basic types viz igneous, sedimentary and metamorphic into each other in a cyclic manner.
  
• Primary rock is an igneous rock which is formed after solidification of lava. It may then get eroded and settled as various layers to form sedimentary rocks. The sedimentary rocks get metamorphosised under high pressure and temperature beneath the earth crust which forms metamorphic rocks.
• Finally, all types of rocks may get subducted deep inside the earth were under extreme temperatures they get melted leading to the formation of liquid magma and the cycle repeats.
• Thus all options are part of this cycle and option D is correct.

• Water and wind are the main agents of erosion and transportation which erode and carry the loosened material from one place to another
• Eg water - through streams and rivers
• Eg Wind - through dust storms.

Mass wasting, which is sometimes called mass movement or slope movement, is defined as the large movement of rock, soil and debris downward due to the force of gravity. In other words, the earth's outer crust is being 'wasted' away on a 'massive' scale and falling to lower elevations.

The decade between 1930 and 1940, saw long periods of severe droughts accompanied by extreme dust storms in North America 

Winds may erode, transport, and deposit materials and are effective agents in regions with sparse vegetation.

• Deposition of materials in lowlands which causes the filling up of the land and its upliftment is called Aggradation. Hence option A is correct.
• Degradation is the lowering of the land.
• Wethering is the breakdown and wearing away of rocks.
• Gradation is the levelling of the land.