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Geological phenomena resulting from erosion and weathering processes
2023-02-14
Researcher Alaa Yasseen Mohammed – Master of Remote Sensitivity, University of Baghdad
Definition of the weathering process: -
It is a number of surface processes that result in the preparation of rocks for the transport process and is done by breaking up rocks or decomposing them on or near the surface of the earth by the prevailing weather factors in the atmosphere and the hydrosphere, while erosion is defined as the process of eroding the surface layer of the earth's crust (rocks and soil) and moving them from one place to another by wind or water. One of the most important geological phenomena (weathering).
Weathering:-
The weathering process occurs when part of the rocks on the surface of the earth disintegrates as a result of exposure to certain conditions, most notably; rainwater, high and low temperatures, and vital activities, which do not result in any removal or change of the elements of the internal rocks. Rocks expand when exposed to high temperatures during the day, and shrink when exposed to low temperatures during the night, and therefore with the recurrence of this process, the rock crust disintegrates and decomposes into what is known as (Crumbs), causing the occurrence of the weathering process, which in turn is divided into two main types:
A- Freeze-thaw.
B- Exfoliation.
Chemical weathering:
Chemical weathering occurs when rainwater reacts with mineral elements in rocks, resulting in the formation of new minerals such as clay and dissolved salts, and these reactions usually occur when rainwater is acidic. Chemical weathering is one of the stages of soil formation, which includes several processes, including:
1. Hydrolysis.
2. Oxidation.
3. Erosion, transportation, and sedimentation.
Erosion: One of the geological factors that occur due to the effects of rainwater, wind, or water flowing on rocks and sediments, and with the continuation of this process, the rocks break and break, and thus shrink in size and change their external features.
Transportation: is the means by which small sediments are transported after erosion occurs, and this transport occurs by wind, currents of water, or glaciers.
Sedimentation: is the stage through which small rock particles are deposited, after the rocks are exposed to erosion and transport, and these particles are known as sediments, and these sediments usually collect in estuaries and areas of seas and oceans.
The most prominent factors that contribute to the occurrence of transport, erosion and sedimentation processes
A- Rain: Rainfall is one of the main factors affecting the process of formation of the terrain and features of the earth's surface, for example, landslides are formed as a result of rainwater reaching the lower mud layers in the slopes, making them slippery, when rain falls heavily, in addition to the formation of grooves known as rough terrain.
B- Wind: Winds work to transfer and deposit small rock particles from one place to another, so that new terrain and features are formed in the other site, while those terrains in the original site change, as well as strong winds break up the rocks, and transfer the crumbs to the new site, so that new hills arise, or settle the old hills.
Figure 1 (Impact of atmospheric phenomena)
One of the most important geological phenomena resulting from erosion and weathering processes:
1. The phenomenon of rock crusting (Exfoliation): The phenomenon of rock peeling is one of the results of one of the mechanical weathering factors, which is the thermal factor or the exposure of rock surfaces to the action of successive heating and cooling in hot regions, when rock surfaces are exposed to extreme high heat according to the fall of strong sunlight on them during the day, for example, and then exposed to rapid cold during the night (as happens in dry hot desert areas that are characterized by high both thermal and qualitative range) . This results in the formation of faults, cracks and widening This process continues to occur day after day the rock fragments and breaks down into small fragments, and this process is sometimes called weathering due to thermal change. Weathering due to thermal change may be aided by heavy rainfall or runoff rains, which also divide the rock along the cracks and joints, and transport rock fragments from the areas from which they were derived and sent to other areas that may be several miles away from the original centre of the rocks.
Figure 2 (rock crusting)
As a result of the successive occurrence of the action of heating and cooling on the surfaces of the rock, the rock crumbles in the form of rock crusts in which the rock erodes from top to bottom gradually, and this process is known as rock crusting, the impact of this last process is intensified when the climate of the region is characterized by a high daily and seasonal temperature range, and when this rock is heterogeneous such as granite, which consists of a group of minerals, it cracks in the form of circular rings, but if the rock is homogeneous such as limestone, which consists of one mineral, calcite, it cracks horizontally, when the peeling process occurs in large rock formations, this may result in huge oval-shaped rocks called round rocks or oval domes resulting from the action of crusting rocks.
2. Foothill rubble: It is the rock debris that accumulates under the mountain slopes as a result of the gravitational transport of rock crumbs resulting from the physical weathering process, and these crumbs are characterized by the sharpness of its angles, which when fused with each other can be solid rocks known as Breccia.
3. Boulder fields: They are large areas spread over them round boulders due to the reason for their formation due to physical and chemical weathering.
4. Soil composition: One of the most important products of weathering is the formation of soil, and soil is the fragmented outer surface layer that contains a mixture of minerals and rock crumbs in addition to air, water and decomposing organic materials.
Geological phenomena of the seas and oceans:
A. Winding beaches: Such winding beaches are formed as a result of the different hardness of the rocks, the hard rock's resist the impact of the waves, while the less hard rock's erode and retreat back, which results in the meandering of the beach, and if the beach rocks are similar in hardness, they retreat and the beach is almost straight.
B. Beach caves: The impact waves capture boulders, gravel and grains of sand and throw them into the lower parts of the rocks that fall under the influence of the waves, causing their erosion and fragmentation. Also, if these waves find cracks or gaps in these rocks, the mechanical movement of water that hits the surfaces of the rocks facing them, causes the air to suddenly compress inside the cracks or gaps, and by repeating this process, the gaps and cracks expand and beach caves are formed.
