Understanding Landforms: A Geomorphology Primer
Relief: A set of forms which results in a terrestrial surface. It is a geological structure caused by the internal forces of the Earth and the modeling done on it by external forces and processes: air, water, living things, and so on. Geomorphology is the scientific discipline that studies relief.
Morphostructural Units
These are internal layout forms adopting the relief, resulting from tectonic movements that originate within the Earth. These movements give rise to uplift, subsidence, and displacement of the Earth’s crust, and the subsequent action of erosion and sedimentation. Both processes are conditioned by the nature of the rocks.
Erosion
Erosion is the attack, modification, and tearing of relief by certain erosive agents of different types:
- Climatic or atmospheric: water, ice, and wind
- Biological: animals, plants, and humans
The forms derived from the activities of different erosive agents are called modeling.
Sedimentation
Sedimentation is the deposit on the Earth’s crust, continental or marine, of solid materials from the disintegration of rocks (detrital sedimentation) or dissolved substances (chemical sedimentation).
Marine Transgression
Marine transgression is the advance of the sea over a territory not previously occupied, occurring due to the sinking of the coast or by rising sea level. The transgression is accompanied by the deposition of marine sediments over that territory.
Fractures and Faults
A fracture is a break in the crust without separation of fractured blocks. A fault is a break in the Earth’s crust where fractured blocks are separated. If separation is vertical and leads to one block rising and another sinking, it is a normal fault. If separation is horizontal, it is a tear fault.
Folds
A fold is a deformation of geological strata in the form of waves resulting from tectonic pressure. This occurs in sedimentary rocks with sufficient flexibility.
Lithology
Lithology is the science that studies the physical and chemical characteristics of rocks. It is a part of geology.
Granite
Granite is a plutonic igneous rock that is formed inside the Earth and solidified from a molten state when forced to ascend to the surface. It is light in color, gray, and consists of coarse-grained quartz, feldspar, and mica.
Limestone
Limestone is a sedimentary rock that is formed on the outside of the Earth from fragments of preexisting rocks or organisms deposited after being transported by rivers, oceans, wind, or ice. It consists mainly of calcium carbonate. Depending on its formation, there are three different kinds of limestone:
- Organic limestone: formed from fragments of dead organisms.
- Detrital limestone: formed from fragments of preexisting limestones destroyed by erosion.
- Limestones of precipitation: formed with the precipitation of calcium carbonate from the water.
Coastal Plains
Coastal plains are coastal fringes formed by sedimentary rocks from the alluvium deposited by rivers due to the erosive power loss near the mouth, or by the combined action of the sea and rivers.
Anticlines and Synclines
An anticline is the convex part of a simple fold. A syncline is the concave part of a simple fold. In a system of folds, it is between two anticlines.
Hanging Syncline
A hanging syncline is a form of relief inversion that occurs when the upper drive erodes away on the axis of the bordering anticlines, and erosion wears away the soft strata below until the altitude is superior to that of the anticlines. It is characteristic of Jurassic relief.