Geological agents

As we have seen in other articles such as the internal structure of the Earth, our planet is continually modified. There are a series of processes both internal and external that make the Earth is constantly transforming. In this case we are going to talk about geological agents. The internal geological agents are those that modify the internal structure of the planet as well as are responsible for the movements of tectonic plates.

In this post, we'll focus on external geological agents and their impact on the Earth's crust. Would you like to learn more about geological processes and fine-tune your notes with extra knowledge? You'll find it all in this article.

Earth transformations

Unlike what happens with internal geological agents, external ones do not create depressions, mountain ranges or volcanoes. They are those who level the ground and who are modifying the forms it has.

The main external geological agents they are erosion, transport and sedimentation. Weathering is also a very important geological agent since they are phenomena that take place in the atmosphere and affect the landscape. We will also see the types of existing weathering.

The shapes that terrain acquires through these processes are very varied. It's not that a mountain is formed or deformed, but rather its relief and composition. For example, erosion eventually flattens mountain peaks after millions of years of continuous action. For example, one indicator of a mountain's age is the altitude of its peak. If it has a pointed shape, it's young, and if it's already flattened, it means erosion has been taking effect for millions of years. In this sense, the sedimentation plays an important role in long-term changes.

External geological agents can be both physical and chemical. These first ones are in charge of modifying the form, while the second ones modify the chemical composition of the places where they are acting. A key example is the chemical weathering that rocks undergo over time.

Landscapes are the result of the interaction of all geological processes, in addition to the action of flora and fauna. Let's not forget that a landscape is composed of the action of many living beings that are also in continuous development and have a certain impact on the environment. And of course, the human being is another very conditioning factor in the diversity of landscapes today.

Everything you need to know about weathering

Weathering

Physical weathering

Physical weathering is a process that breaks or modifies rocks depending on its action and environmental conditions. They are capable of fragmenting and disintegrating them. They also act on minerals. The most frequent causes of physical weathering are rain, ice, thaw, wind, and continuous changes in temperature between day and night.

It is thought that these changes are not conditioning factors in the modification of rocks and their shapes, but they are. Especially in places where the thermal amplitude is large (such as in deserts) the physical weathering caused by temperature changes is much greater.

There are three types of weathering. The first is the one we have mentioned about temperature changes. Over the years, these continuous changes cause the materials to break. It also occurs frequently in areas that have a climate of low humidity and large temperature variations.

The second type is biogenic weathering. This is caused by the action of microorganisms and organisms such as mosses, lichens, algae, and other mollusks that impact the surfaces of rocks. This action constantly weakens them and makes them more vulnerable to other influences. In this context, it is interesting to observe how these phenomena relate to the petrogenesis from the rocks.

Chemical weathering

What we have left is chemical weathering. This is what occurs mainly in humid climates and causes chemical reactions that take place between gases in the atmosphere and minerals present in the rocks. In this case, what takes place is the disintegration of these particles. Water and the presence of gases such as oxygen and hydrogen become triggers for chemical reactions causing weathering.

One of the main reactions that takes place in this case is oxidation. It is the combination of oxygen from the air dissolved in water with minerals from rocks. This is when the oxides and hydroxides are formed.

Sedimentary rocks

Erosion and transport

Erosion is the process that occurs when rain, wind, and water flows are continuously acting on rocks and sediment. They cause the fragmentation and deformation of the rocks And it is an ongoing process. As the rocks are eroded, they lose volume and their appearance and structure are deformed.

Transportation is the process that results from the action of erosion. The sediments and fragments divided from the action of erosion in the rocks are transported by the wind, torrents of water, glaciers, etc. Sediments do not have to be detached from the ground to be transported. They can be transported in three ways:

Crawling, in which they crawl along the surface of the ground.
Suspension. Here are the sediments suspended both in the water and in the air. For example, small particles or leaves both in water currents and in gusts of wind.
Diluted. They are part of the composition of water or air.

Understanding these processes is fundamental to the study of the reliefs and its evolution.

As mentioned in some articles, the age of the Earth is thought to be between 4.400 and 5.100 billion years. This theory is determined through the use of radiometric dating techniques thanks to the information and material that can be extracted from meteorites. The evidence for this is consistent, so it can be said that this is the origin of the Earth. In order to explain all the events that have occurred on our planet, actualism is used. It is the law that is based on the conviction that the events that have occurred throughout history are the same as those that occur in the present. In this article we are going to point out what actualism is, what its characteristics are and how important it is. What is actualism? It is a principle issued by James Hutton and further developed by Charles Lyell (link) in which it is established that the processes that have occurred throughout the history of the Earth are similar to those that take place in the present. Hence this theory is called actualism. This actualism is also considered catastrophizing. It is that today's geological characters are suddenly formed in the past thanks to transformations and evolutions. Some of the most important tools by which actualism and uniformism serve to extract information from our past is the superposition of strata, the faunal succession and the succession of events both in the past and in the evolution of the present. This law was confirmed in the XNUMXth century and at the beginning of the XNUMXth century. It was naturalists who were able to verify the facts by examining the Earth's surface. These naturalists affirmed and supported themselves on these facts in order to understand the genesis of the planet and all its evolution. Logically it makes sense. Why are the processes going to change over time? The patterns of atmospheric changes, soil, geological agents (link), etc. They are the same ones who acted at the beginning of everything. You have to notice that before the atmosphere did not have the same composition. But it is that, to this day, its composition is also being altered. Perhaps it is the geological time scale (link) that makes us think that before there were other geological events than there are now. Wind, sea currents, rainfall, storms, etc. They also occurred when the Earth originated. For this reason, what currentism defends is that it is these same events that have been transforming the planet and causing it to evolve, but to this day, they are still having an effect and acting. Genesis The genesis of landforms and sediments were explained in this way by the actions of the water, the wind, and the waves that they monitored and of which they could measure the effects every day. Those who supported catastrophism, opposed the ideas of actualism, since they defend that great valleys, geological formations and marine basins have taken place through impressive cataclysms that occurred in the past. They can be found in religious texts such as the Bible and its Deluge that can be explained as responsible for large alluvial layers that flooded the valley floor. Uniformity also has a place in all this. It is a geological science whose theories say that the processes that currently exist have occurred gradually. In addition, they are the cause of the geological characteristics that our planet has. What uniformism defends is that these processes have been maintained until today without alterations. Biological actualism It is a principle that sustains the relationship between the living creatures of today and those of the past. Basically, what biological actualism does is affirm that the processes that living beings carry out today were also carried out in the past. That none of that has changed so far. To make it clearer and easier to understand. If a species breathes and reproduces, it is very likely that these processes also did millions of years ago. So, if we combine this with geological processes, we will be affirming that the same processes have always been happening and that none of that has changed today. It is true that these processes have had their nuances, given that living beings have had to adapt to new environments and conditions that geological agents themselves have transformed over the years. However, although the nuances are changing, the base of the process is respected, that is, it is breathed and they reproduce. Biological actualism applies to processes such as reproduction and metabolism. Things are already beginning to change when we talk about the behavior of living beings. In this case, the processes are more complicated to apply biological actualism. As individuals adapt to new conditions, we cannot guarantee that it is the same behavior that they have at all times. Furthermore, it is impossible to deduce the behavior of extinct species and to know if it was similar to those of now, millions and millions of years ago. For example, before an ice age (link), living beings must modify their behavior in order to adapt to the conditions and survive. Migration is one of the behaviors that has been maintained throughout the evolution of living beings, since it is a survival instinct to want to find a habitat where they can reproduce and have good living conditions. Geological history of actualism In order to acquire all the information about what happened throughout history, actualism and uniformitarianism are used, which are defended in the faunal succession, the succession of events and the superposition of strata. According to the information that can be obtained from the different fossil strata, we have the following: • The position they had with respect to sea level • The temperature at which they lived • The flora and fauna present at that time • The moment when there were large tectonic movements As you can see, science tries to explain how the Earth evolved today.

Actualism

Sedimentation

It is the last external geological agent that we lack. It corresponds to the deposition of solid particles that have been transported by erosion. These particles are called sediments. The areas with the highest amount of sediment They are the mouths of rivers and in places like seas and oceans.

The sediments once deposited are, in turn, removed by other geological agents such as erosion and weathering. If these sediments acquire large size and compaction over the years, they form sedimentary rocks.