Geology and Earth Structure

• 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.

A rift valley is a lowland region that forms where Earth's tectonic plates move apart, or rift. This is a direct result of tectonic forces, unlike V-shaped valleys (river erosion) or U-shaped valleys (glacial erosion).

Percentage of fresh water in the hydrosphere is 2.5%. Out of this, about 68% of the fresh water is found in icecaps and glaciers and about 30% is found in ground water. About 98.5% of water in the hydrosphere is salt water.

Convergent plate boundaries are known as destructive boundaries because tectonic plates collide, leading to the subduction or destruction of lithospheric material.

• The surface of the earth is still irregular in spite of millions of years of gradation, because— material re-elevates the land. Parts of the crust have been uplifted.
  
• Delamination of the lithosphere has two major geologic effects. First, because a large portion of dense material is removed, the remaining portion of the crust and lithosphere undergo rapid uplift to form mountain ranges. 
  
• Second, the flow of hot mantle material encounters the base of the thin lithosphere and often results in melting and a new phase of volcanism.
  
• Delamination may thus account for some volcanic regions that have been attributed to mantle plumes in the past.

• The shape of the Earth is classified as an ellipsoid or an oblate spheroid.
• The Earth is not considered a true sphere because it has a larger circumference and diameter at the equator.
• The poles of the Earth are squished, which creates a slight bulge around the equator.
• The Earth's polar diameter is about 43 kilometers shorter than its equatorial diameter, a difference of about 0.3%.
• This is due to the equatorial bulge caused by the Earth's rotation.

• The outer core of the Earth is a fluid layer about 2,300 km (1,400 mi) thick and composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle.

• The core is 2900-6376 kms in thickness.
  
• It is composed of dense and heavy substances like iron and nickel.

The crust is the outermost solid shell of the Earth where human beings and other life forms reside.

The mantle is the layer of the Earth located between the crust and the core, extending from a depth of approximately 100 km to 2900 km.

• So, even though it is hotter in the inner core, the pressure in the core is also higher, and you can have solid iron-nickel instead of liquid.
  
• It is made of iron and nickel. 
  
• This is above the Earth's solid inner core and below the mantle. Its outer boundary is 2,890 km (1,800 mi) beneath the Earth's surface..
  
• Convection of liquid metals in the outer core creates the Earth's magnetic field.
  

Large and continues land masses on surface of the earth are termed as continents. This division on the earth as continents are done by us. Our planet is divided into seven large continental masses, these are, Asia, Europe, Africa, North America, South America, Australia and Antarcatica. Among them Asia is the largest and Australia is the smallest continent.

The lithosphere is broken into several large and small segments known as tectonic plates, which move over the asthenosphere.

At a divergent boundary, tectonic plates move away from each other, often leading to the formation of new crust.

Tectonic plates are part of the lithosphere, which floats on the semi-fluid, ductile layer of the Earth known as the asthenosphere, located within the upper mantle.