Geology has several branches that deepen the studies of different parts. One of the branches of geology is lithology. This is the science that studies rocks, including their origin, age, composition, structure, and distribution across the planet. This branch of science has its origins in ancient times, beginning with various contributions from the Greeks, Chinese, and Arabs, among other civilizations. The contributions from the western world are best known, those of Aristotle and his disciple Theophrastus in his work On Rocks.
In this article we are going to tell you about all the characteristics and importance of lithology.
Characteristics of lithology
Lithology is a discipline that classifies rocks based on the study of both their physical and clinical properties. They are also classified according to the processes that give rise to the rocks. Based on this, they are divided into three major rock types: igneous, sedimentary, and metamorphic. Although the terms lithology and petrology are generally considered synonymous, some people establish subtle differences. For example, when we refer to lithology, we are focusing on the study of the composition of rocks within a defined area. That is, we take an area and study the different types of rocks that exist within that area.
On the other hand, Petrology is restricted to the study of each type of rock in particular. According to those who consider them separate terms, the study of the sequence of rocks found in a given region is lithology. However, the study of the mineral composition of rocks is technology. Although both are considered synonyms, they encompass all of these aspects.
The object of study of lithology is the physical and chemical properties of rocksMechanisms are also used to study the mineral aggregates of each. This includes studies of chemical composition and mineralogy. The structure, or how the components are arranged together, is also the subject of lithology. If you'd like to learn more about this topic, you can visit the following link: minerals and rocks.
Lithology and rock types
We know that rocks are found in the Earth's crust and are classified according to the processes that gave rise to them. This leads to the formation of three possible types of rocks: igneous, sedimentary, and metamorphic. Let's define the different types of rocks studied in lithology.
Igneous rocks
They are those that are formed as a result of the fusion of magma. Magma is the molten material that makes up the Earth's mantle. These materials are nothing but molten rock with gases and liquids. Magma is found at great depths and rises to the surface due to mantle convection currents and volcanic eruptions. When this magma has emerged to the earth's surface, it loses gases and cools until it forms igneous rocks. This type of rock is called volcanic rocks.
Magma can slowly solidify midway between deep cracks and form plutonic igneous rocks. These rocks form more slowly. They are called igneous rocks because they are considered to be of endogenous origin. two general types of igneous rocks according to their compositionAcidic igneous rocks are those formed with a high proportion of silica and contain free quartz and little iron and magnesium. On the other hand, basic igneous rocks are those with a lower proportion of silica and no quartz, but abundant magnesium and iron. For more information on this topic, you can consult the article on igneous rocks.
Sedimentary rocks
These are rocks formed from sediments deposited on the Earth's surface and come from the erosion of existing rocks. They are also called rocks of exogenous origin, since they are formed from materials on the surface of the Earth's crust. The formation of many of these rocks is organic. For example, there are numerous rocks composed of seashells that contain large amounts of calcium and form calcareous rocks. Sediments are nothing more than mineral particles produced during the erosion of existing rocks. That is, Sedimentary rocks are rocks that form from existing rocks through the process known as sedimentation.
The particles that form sedimentary rocks are loosened by a combination of water, temperature changes, wind, drag, and deposition. This causes all the sediments deposited through all geological processes to form layer upon layer, with the upper layers compressing the lower ones until rock is formed. As expected, this process takes millions of years. After millions of years, the sediments will have silted up and settled to form fixed sediment layers. The layers accumulate because they are acted upon by the pressure of the upper layers. The resulting high temperatures and the depression of cementing substances also play a role in the formation of sedimentary rocks.
It is then tectonic movements that bring these rocks to the surface. Furthermore, the sediments that form these rocks also contain the remains of living organisms, such as shells and organic carbon. Typically, these types of rocks, which also contain the remains of living organisms, are characterized by being stratified. That is, the rocks show layers or strata. Examples of the best-known sedimentary rocks are: they are limestone with the rest of shells, sandstones and shales. To learn more about them, you can visit the following article on sedimentary rocks.
Metamorphic rocks
These are rocks formed from the two previous types of processes. These processes occur at great depths in the Earth's crust or more superficially. They are rocks formed from sedimentary formations that have been subjected to great pressure and high temperatures. The action of magma gases is also present, resulting in deep metamorphosis. Let's look at an example of this. One type of contact metamorphism is when magma that has a high heat comes into contact with the surface rock. This contact causes gases and heat to be transmitted.
Dislocation metamorphism is also another variant. In this case, pressure is exerted on sedimentary or igneous rocks due to the movement of tectonic plates. This pressure exerted on the rock ultimately forms a metamorphic rock. To learn more about this process, you can read about Metamorphic rocks.
I hope that with this information you can learn more about lithology and what it studies.