Earth Processes Lecture series for Bachelor of Science (Geology) and Bachelor of Science (ODL)

Mulwa JK. Earth Processes Lecture series for Bachelor of Science (Geology) and Bachelor of Science (ODL). Nairobi: Nairobi University Press; 2003.


The Earth Processes course unit is one of the three core courses in Geology. The other two core courses are SGL 101 – Materials of the Earth and SGL 103 - Introduction to Paleontology. Geology is a science of the study of the earth with reference to its evolution, composition and processes that have prevailed from the time of its evolution to the present time.

The earth is a dynamic body that has undergone various changes. These changes are both of internal and external origin. The internal processes are referred to as diastrophism and they tend to elevate the earth’s surface. They are counterbalanced by the external processes that wear down the land surface. The constant interaction between these two processes determines the configuration of the earth’s surface. The external processes are as a result of solar energy and gravitational forces whereas the internal processes are as a result of the earth’s internal heat.

Weather pattern, for example, is to a large extent due to the solar energy on the one hand. Along the equator there is a substantial amount of heating because the sun is always overhead and therefore this results in the rising up of hot air. The rising hot air is replaced by cold air from the colder regions. This cyclic process is closely related to ocean waves and currents generated by solar heating. Waves are effective forces for determining the shape of the landscape along shorelines of oceans and seas.

The force of gravity on the other hand is due to mutual attraction between bodies. The greater the attracting bodies the greater the gravitational force. Because the mass of the earth is greater than any other body on its surface, materials are attracted towards the earth’s center. Rain and snow precipitate due to gravitational attraction of the earth. Water moves towards the oceans because of gravitational force. Glaciers on higher mountains are normally pulled down by the force of gravity.

Internal earth processes are due to heat energy which keeps rocks in the mantle below the earth’s crust in a molten state. This break forth as a volcanic flow during volcanic eruptions. Heat energy is also responsible for large-scale processes such as earthquakes and mountain building, and small scale processes such as geysers, hot springs, steaming ground and hydrothermal processes.

We can therefore conclude that all earth processes are manifestations of energy and these processes are responsible for sculpturing the land surface.

The Earth Processes course unit begins with an overview of the types of energy which contribute to earth processes. These are discussed in Lecture 1. The unit is thereafter subdivided into two parts. Lectures in Part I of the course unit discusses the External Earth processes where else lectures in Part II of the unit discusses the Internal Earth Processes.

The general objective of the Earth processes course unit is to introduce you to the basic concepts of geosciences. More specifically, at the end of this course unit you should be able to:

 describe the internal and external processes which shape the earth;
 explain the present configuration of the earth and attempt to reconstruct its original form;
 explain the natural processes of the earth;
 categorize hazardous and non-hazardous processes of the earth;
 outline the contribution of the earths natural fields in exploration of natural resources;
• propose measures of minimizing hazards due to earth processes.

You are required to have writing materials e.g. books or foolscaps, pens, lead pencils, coloured pencils or crayons, a scientific calculator, a ruler and a mathematical set. Although every effort has been made to provide you with an up-to-date lecture notes, you are expected to do further reading for a better understanding of Geology, Geological concepts and Processes.

Practicals are compulsory in this course unit and a separate practical manual will be availed to you.

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