The earths surface is basically covered by rocks and sediments


Rocks and sediments are the materials covering the earth’s surface. The earth is comprised of the basic layers. The inner one is called the core and it is basically made up of fluid and very hot material that is molten rock. The middle layer is the mantle basically made up of semisolid and solid rock. Then there is the outer layer that is the crust and is made up of purely solid material/ rock. Rocks are solid materials made up of various minerals and these minerals are natural and have chemical constituents. Sediments on the other hand are very tiny pieces of rocks that have been Brocken down through weathering and are easily transported by fluids such as water. Keywords: rock, mineral, sediment, weathering.

The Earth

The earth’s surface is basically covered by rocks and sediments. The rocks are of different types which include igneous, metamorphic and sedimentary rocks. These different types of rocks are formed in different ways. For instance, igneous rocks are formed through the solidification of a naturally occurring mass of rock that is mobile and it is known as magma. Rocks such as granite are formed when magma crystallizes below the earth’s surface. These rocks that are formed below earth’s surface are called intrusive igneous rocks whereas those that are formed on the earth’s surface through the escape of magma to the surface through volcanoes are called extrusive igneous rocks.

According to Rana (2007), sedimentary rocks are formed through a process whereby there is weathering of rocks mainly by water or wind. This weathering leads to the formation of small to very tiny rock particles that are easily transported by water or wind. These particles are transported and deposited probably on sea beds and other water bends where they are naturally cemented, and compressed to form sedimentary rocks. There are two types of sedimentary rocks and these are detrital and chemical sedimentary rocks. Detrital rocks are formed through the weathering of previously existing rocks whereas chemical rocks are formed through biochemical and chemical processes that are able to remove materials that are carried in solutions containing these chemicals. Examples of sedimentary rocks include, limestone, salt, sand stone and shale.

Metamorphic rocks are basically changed rocks in the sense that pressure, heat or chemically active liquids may interfere with the chemical composition of rocks thus changing their texture and mineralogy. Metamorphic rocks has two types namely foliated rocks that appear in layers like the pages in a book and non-foliated rocks that has no particular alignment or segregation. Examples of metamorphic rocks include marble, quartzite, gneiss and slate.

According to Katie (2007), Granite is an igneous rock that is formed from cooling magma. Granite forms from magma that is in cooling pockets that occur below the earth’s surface. Granite has characteristic colors of gray, shiny black and white crystals. Economically, it is usually used for decorative purposes such as decorating buildings, bridges and making stone carvings. Sometimes granite may contain pink crystals which are basically crystals of quartz rocks. According to Robert (1933), granite is able to form some king of veins that are able to pierce into the superincumbent rocks. This fact has been found to be of geological significance because it shows that the granite has undergone a state of fusion. Here the heat produced by the granite is able to soften the rocks lying on top of it and thus is able to penetrate through these rocks even though it is in a melted state. Thus they form fissures.

Another explanation is whereby at the time of formation of these structures, the granite and the rocks lying above it were is liquid state and thus was able to mix and create these structures. This would mean that the granite and the rocks resting immediately on it were not only in the fluid state but also were contemporaneous. Properties of Granite include strength, or basically resistance to breakage. This means that the rock can withstand forces of extension, compression or cross-strain. The rock is also very hard capable of resisting shocks. It is also known to be very durable because it has resistance t o weathering, chemical constituents, atmosphere and extremes of heat. Because of these properties, granite has been used in various ways especially economically in the making of building stones, carvings, and decorative structures.

Thus granite is important geologically because it shows how the rocks formed against other resting rocks on top of them and posses important questions on how the formation occurred. It may also help in determining when these formations came into place.


Katie, K. & Niki, M. (2007). Rocks and Minerals. USA: HOCPP 1205.

Robert, B. (1933). An introduction to Geology: intended to convey a practical knowledge of the science. Hezekiah Howe & co. USA.

Rana, S. (2007). Essentials of Ecology and environmental science. New Delhi. India: Jay print pack private limited.

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