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 general objective of geology section of the physical environment course unit is to introduce you to the basic concepts of geosciences.