The effects of the agents of weathering on rocks

ROCKS

Definition

These are naturally occurring solid aggregate of one or more minerals. There are three types of rocks. 

Igneous Rocks

These are rocks formed from molten lava(eruptions from volcanoes) when it cools down and solidifies. They contain primary minerals like quartz, feldspar, etc. Examples of igneous rocks are granite, quartz, gabbro, and diorite.

Sedimentary rocks

These are rocks formed from settling or sticking together of broken down particles of other rocks. Examples of sedimentary rocks include shale, sandstone, dolomite, and limestone.

Metamorphic rocks

These are rocks formed by subjecting any type of rock either igneous rocks or sedimentary rocks to different temperature and pressure conditions than those in which the original rocks were formed. Examples of this include marble, sandstone, schist, etc.

WEATHERING OF ROCKS

This refers to the gradual process that disintegrates, decomposes or crumbles rock into smaller rock particles by agents such as water, changes in temperature, pressure, chemicals, atmospheric oxygen, wind and roots of plants.

EFFECTS OF AGENTS OF WEATHERING

PHYSICAL AGENTS

This refers to the mechanical breakdown of rocks into smaller particles. In physical weathering, there is no change in the chemical composition of the rock. Examples of physicals include; effects of temperature, wind, water, moving ice and pressure.

     

Temperature

This refers to the degree of hotness or coldness of a place.

In hotter regions when the temperatures are high, rocks expand when heated and contract when cooled. The uneven expansion and contraction of rock minerals cause cracking and disintegration of rocks into smaller particles       

In colder regions when the temperature falls below freezing point, water in the crevices of rocks solidifies and expands in the process, causing the rocks to crack under stress.

       

CHEMICAL AGENTS

This refers to the breakdown of rocks into smaller particles as a result of various chemical processes. Some of the agents include:

Carbonation

This refers to the reaction of carbonic acid with rocks to break it down

Hydrolysis

This refers to the chemical reaction between a substance and water which leads to the breakdown of the bond between hydrogen and oxygen in water.

Hydration

This refers to the process by which water becomes attached to the surface of a substance

Reduction

This simply refers to the addition of hydrogen or removal of oxygen from a substance.

Oxidation

This means the addition of oxygen or removal of hydrogen

   

BIOLOGICAL AGENTS

This refers to the breakdown of rocks into smaller particles by activities of living things. Agents involved in biological weathering of rocks include the following:

a.       The pressure influenced by animals such as elephant

b.      The passage of the roots of plants through cracks in rocks

c.       The boring activities of organisms such as earthworms.