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Texture is defined as the size, shape and arrangement of the grains of crystals in a rock.  Igneous rock can have different textures depending on different bases: On the basis of degree of crystallization:       All of the minerals present in the rock may be distinctly crystallized and may be easily recognized by unaided eye or they may be very poorly crystallized or even glassy (i.e. non crystallized) Polycrystalline (Phaneric/ Phanerocrystalline) : When all the minerals are distinctly crystallized.    Holohyaline (Aphanitic): when the component minerals are very fine in size and glassy or non-crystalline in character. Merocrystalline : intermediate type of texture i.e. some minerals are crystallized and others are of glassy characters. b ) On the basis of granularity: Granularity defines the grain size of rocks taking into account the average dimensions of different component minerals. The rock is described as:   Coarse grained : If the average size of the minerals of the rock

  Internal Structure of the Earth and Plate Tectonics Division of Earth The internal structure of earth is divided into:     (a) Crust      (b) Mantle and      (c) Core  The division is based on physical and chemical properties,  thickness,  depth,  density,  seismic data,  pressure-temperature and  availability of metals. Ad: https://happyshirtsnp.com/ Types of Seismic Waves seismological data shows us that the earth has a layered structure. Seismic waves with varying velocities that depend on the type of wave and physical properties of medium for the wave travelling. Therefore, it is necessary to understand different types of waves.   Wave type Description 1. Body wave (2 types)     (a) Primary wave/ P-wave/Transverse wave          (b) Secondary wave/Shear wave/Longitudinal wave Body waves travel through the body of the earth. The particles move forward and backward to the direction in which the wave is travelling. Can travel