The geological cycle depends on a series of effects set in motion by internal geological processes acting upon rock types. While not as readily apparent as external geological processes, the importance of these internal processes is undeniable, as they have a profound impact on the composition and structure of rocks.
Therefore, in this article we are going to tell you what internal geological processes are, their characteristics and importance.
What are internal geological processes
Internal geological processes refer to the natural movements and activities that take place within the Earth's crust and mantle. These processes can include volcanic eruptions, earthquakes, and tectonic plate movements. For more information on these phenomena, you can consult the entry on what geology is.
Geological processes that occur within the Earth are considered internal, as they originate from mechanisms located beneath the Earth's crust, despite having external manifestations. These processes are not as dynamic as other agents, and their development spans millions of years. As a result, the causes behind these processes cannot be directly observed, although their effects are often evident.
The degree to which land is affected by a geological force originating from within is of greater importance. Although the easterly wind affects a certain stretch of the coastline (an external force), the lithologies of the entire peninsula are influenced by the movement of tectonic plates (an internal force). As a result, they play a significant role in shaping the region's topographic features.
The geological processes that occur internally are fueled by the natural heat generated by the Earth's radioactive elements, which dissipate towards the planet's surface. These processes are responsible for the formation, structure and arrangement of lithologies. In contrast, external geologic agents act to refine rocks through weathering, weathering, and sedimentation, as well as through diagenesis.
Characteristics of internal geological processes
Orogenesis
Mountain ranges, commonly referred to as orogenies, are formed by deformation processes resulting from the interaction of tectonic plates during various geological periods. As a result, orogenesis affects vast regions of land and influences the distribution of external geological features. Furthermore, orogeny encompasses a series of events that can have a global impact and give rise to other internal geological processes.
Due to their susceptibility to intense tectonic pressures and diverse origins, geologically active zones of convergent margins host orogens. These orogens can be classified into several types based on the way they are created.
- Subduction orogens: Mountain ranges, known as subduction orogens, are created at the point of convergence between two tectonic plates where one plate slides beneath the other. This collision can produce island arcs, which can occur when two oceanic plates come together, or a thermal orogen if an oceanic plate collides with a continental one. In the first scenario, the steep subduction slope and high level of volcanic activity give rise to deep trenches. In the latter, the slope is not as steep, allowing sediments to accumulate in the accretion prism. Additionally, the presence of water and friction can cause the formation of seismic and volcanic events.
- Accretion orogens: They result from the merger of smaller continental microplates with a larger orogen, leading to size expansion. The Rocky Mountains serve as an excellent example of this category of geological formations.
- Collision orogens: When two tectonic plates with a mix of characteristics meet in an orogenic collision, their continental portions push together as subduction progresses. This collision results in the presence of oceanic plate materials in the center of the orogen, which has important academic implications.
- Intraplate orogens: They form when a sedimentary basin is compressed as a result of tectonic reversal. This often occurs as internal geological forces take advantage of areas of weakness, such as fractures, which offer less resistance during the change in force directions. An example of an intraplate orogen can be found in the Iberian System located in Spain.
Magmatism
The genesis of this phenomenon dates back to the generation of internal heat, and its effects are felt in the rock formations it comes into contact with. It is worth noting that a decrease in pressure can alter the equilibrium of the magma chamber and trigger an eruption. Furthermore, the circulation and bubbling of magma can cause fracturing of the surrounding rock and lead to seismic activity. In addition, a sudden increase in temperature and various compositional factors also play a significant role in shaping the environment.
The impact of volcanism on the land is strongly influenced by the specific type of volcanic activity involved. After an eruption, the landscape is transformed, and the arrangement of its features reflects this transformation. The resulting igneous rocks will be either volcanic or plutonic, depending on the particular event that occurred. These internal geological processes can manifest at divergent boundaries, where mantle materials, such as continental ridges and rifts, are uplifted, or at convergent margins, where layers experience friction during subduction. Intraplate zones can also be affected by the presence of hotspots.
metamorphism
Metamorphism is a process that occurs within a rock, characterized by physicochemical changes caused by a combination of higher temperatures, increased pressure, and the introduction of fluids during burial. Melting is not a factor in this process, which leads to changes in mineral properties through means such as rearrangement, recrystallization, transformation, and an increase in mineral density.
Metamorphism can be classified according to the scale or factors considered. Regional metamorphism is characterized by an increase in pressure and temperature with depth, making it typical in orogenic and subduction zones. On the other hand, dynamic metamorphism places greater emphasis on pressure as the main determining factor, while temperature plays a secondary role in creating fractures. In practice, distinguishing between diagenesis and metamorphism can be complex.
Structural deformation
Structural deformation refers to the process by which a substance undergoes a change in its shape due to an external force or pressure. This can occur at a macro or micro level and can result in alterations to the substance's physical characteristics.
Rocks can undergo deformation for two reasons: lithostatic pressure or tectonic stress. Lithostatic pressure is caused by the thickness of the sedimentary layer, which exerts pressure on the rocks beneath it equally in all directions, resulting in deformation. Additionally, within this category the fluid pressure of substances within the pores of the rock is also examined.
I hope that with this information you can learn more about the internal geological processes and their characteristics.
