Optionals IAS Mains Geology: Questions 72 - 79 of 126

Lithosphere and Asthensophere

Lithosphere

• The earth is divided into four major layers.
  • The crust
  • Mantle
  • Outer core and
  • Inner core
• The lithosphere is outermost layer of the earth crust. The upper mantle consists of crust and lithosphere which is rigid in nature.
• The lithosphere consists of 95 % of igneous rocks, 4 % shale and 0.75 % limestone. It mainly com…

Different Types of Plate Boundaries and Their Characteristic Features

Introduction

• Depending on the relative motions of the various plates the plate boundaries are classified into three groups,
  • Divergent boundaries
  • Convergent boundaries
  • Transform fault boundaries
• The zone of motion between two plates is called plate boundary. Two plate margins meet at a …

Spectral Significance

• The energy reaching the surface of a material is called irradiance and the energy reflected by the surface is called radiance. Earth material has its specific reflectance which is the fraction of incident radiation and is reflected as a function of wavelength.
• Spectral signatures are the combination of reflected, absorbed, and t…

Plate Boundaries

• Plate boundaries are the surface trace of the zone of motion between two plates.
• The marginal part of two plates that is a plate - margins meet at a common plate boundary.

Depending upon the relative motion of adjacent plates, the plate boundaries are classified into three groups: -

Divergent Plate Boundary

• Accor…

Satellite Orbits

• The satellites always move in a plane called the orbital plane, which passes through the centre of the earth. If the orbital inclination is 0 or 180 degrees, the orbital plane lies in the equatorial orbit. When the inclination is close to 90 degrees, the satellite moves over the poles, i.e.. , the centre of the earth and the North a…

Meteorites

• A meteorite is a term given to a piece of a comet or asteroid that falls into the Earth՚s atmosphere and survives to hit the surface. There are presumably millions of meteorites of all sizes in the solar system, from the finest dust particles up to those that are miles in diameter.
• Meteorites consist essentially of a nickel-iron alloy, of …

Unconformities

• An unconformity is a break in the stratigraphic sequence, it records a major line gap and it is caused by erosion or non – deposition.
• They are typically buried erosional surfaces that can represent a break in the geologic record of hundreds of millions of years or more.
• The shorter gaps are known as Diastems.

Three Commonly Recognized U…

Shear Zones

• The term Shear zone is a general term for a relatively narrow zone with sub-parallel boundaries in which shear strain was localized. The relatively unreformed wall rocks on opposite sides of the zone have been displaced relative to one another in a direction parallel to the plane of the shear zone.
• Shear zones form under a variety of defo…