Page 162 - General Knowledge

GENERAL KNOWLEDGE 2019

ROCKS

A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is
categorized by the minerals included, its chemical composition and the way in which it is
formed. Rocks are usually grouped into three main groups:
I. Igneous rocks
II. Metamorphic rocks and
III. Sedimentary rocks
Igneous rock
 Formed due to the cooling, solidification and crystallisatiioin of hot and molten magma.
 They are called as the Primary rocks as all the other rocks are formed directly or
indirectly from the igneous rocks.
 They are hard, granular and crystalline rocks, less affected by chemical weathering.
 Moreover, it does not have any fossil or does not form any strata or layers of lava, eg, of
Igneous rocks – Granite, Loccolith, Batholiths, Sills, Basalt, Gabbro.

Metamorphic rocks

 Metamorphic rocks are formed by subjecting any rock type—sedimentary rock, igneous
rock or another older metamorphic rock—to different temperature and pressure
conditions than those in which the original rock was formed.
 This process is called metamorphism, meaning to "change in form".
 The result is a profound change in physical properties and chemistry of the stone.
 The original rock, known as the protolith, transforms into other mineral types or other
forms of the same minerals, by recrystallization.
 The temperatures and pressures required for this process are always higher than those
found at the Earth's surface: temperatures greater than 150 to 200 °C and pressures of
1500 bars.
 Metamorphic rocks compose 27.4% of the crust by volume.

Sedimentary rocks

Sedimentary rocks are types of rock that are formed by the accumulation or deposition of
small particles and subsequent cementation of mineral or organic particles on the floor of
oceans or other bodies of water at the Earth's surface.
LANDFORM

Many different types of landforms make up Earth‘s topography. Several major categories of
landform define that smaller portion of the planet not covered by water, including mountains,
plains, plateaus and valleys. These can be formed by a variety of natural forces, including

erosion from water and wind, plate movement, folding and faulting, and volcanic activity.
Mountain

The most common type of mountains arise where the Earth‘s crust experienced folding or
faulting, such as the Canadian Rockies and the Alps. Fault-block mountains, such as
California‘s Sierra Nevada, are formed when Earth‘s crust cracked and was pushed upward.
Volcanic mountains form when hot magma from deep in Earth‘s interior breaks through the

158 | P a g e shop.ssbcrack.com