GEOGRAPHY AND HISTORY

  Rock cycle is the cycle in which rocks tend to change from one type to another. For instance, igneous rocks may change to metamorphic rocks or sedimentary rocks ; sedimentary rocks to metamorphic or igneous rocks, etc. It is a relationship in which rocks tend to change from one type of rock to another.   Necessary conditions for rock cycle to take place 1. the molten rocks are erupted from the interior of the earth and then cool and solidify to form igneous rocks. 2. the igneous rocks are subjected to denudation process to form sedimentary rocks. 3. either igneous or sedimentary rocks undergo metamorphism, due to prolonged heat and pressure, to form metamorphic rocks. 4. metamorphic or igneous rocks can undergo weathering process through erosion and transportation of sediments which are further deposited in layers in the ocean or lake floors where they are cemented and consolidated to form sedimentary rocks and vice versa. 5. metamorphic or sedimentary rocks can be ...

  Sedimentary rocks are rocks composed of deposited minerals and rock fragments or sediments produced by mechanical or physical or chemical weathering of former rock masses of igneous rocks. They have therefore derived from already existing igneous rocks and because of this, they are sometimes referred to as derived rocks or secondary or laid down rocks. The weathered materials are then transported by erosion agents of water, ice, and wind and are later deposited in layers (strata) on either a dry land or in valleys or under water (in oceans and seas). The layers are separated by bedding plains which demarcate the end of one deposition cycle and the beginning of another. Layers can be horizontal, gently sloping or steeply dipping. Generally speaking, sedimentary rocks have the following characteristics; They contain fossils of dead plants and animals. They have layers i.e. strata (they are stratified) They are non-crystalline in nature Stratas are either horizontal or gently slopin...