Earth’s Relief and Geological Processes: A Detailed Study
Earth’s Relief Classification
- Mountain: Relief over ten degrees with a large gap between the top and its base.
- Hill: Relief with little unevenness.
- Gorge or Throat: Narrow valley featuring steep walls on its sides.
- Plateau: Relief with a flat top.
- Terraces: Graduated relief.
Interpretive Rating of Relief Forms
Some terms are:
- Mountain: Relief that stands out from contiguous areas, formed by the folding of materials or volcanic activity.
- Witness Hill: Relief that, at peak height, is not at the same level as the surrounding area.
- Terraces: Fragmented and graduated zone, formed by successive incasements of a river.
- Anthropic Modeling: Produced by human activity.
Characteristics of the Oceanic Crust Relief
- Abyssal Plains: Very extensive submarine plains with an average depth of 4500 meters.
- Oceanic Ridges: Alignments of volcanoes with intense volcanic fissure activity.
- Volcanic Relief: Volcanoes resulting from concrete volcanic activity. When islands protrude from the water, they are volcanic.
- Ocean Trenches: Elongated trenches where great depths are reached.
- Island Arcs: Volcanic mountain ranges that emerge from the sea and form archipelagos.
Relief Characteristics of the Continental Crust
- Peneplains: Extensive plains resulting from erosion caused by geological agents.
- Mountain Ranges: Alignments of mountains formed by the folding of materials, or by volcanic activity.
- Rifts: Elongated depressions formed by the breaking, bloating, and sinking of the continental crust along large fractures.
- Continental Platforms: Part of the continental crust covered by the sea. Epicontinental seas can be found in them.
- Continental Slopes: Represent the levees between continents and areas encompassing the continental shelf located between the oceanic crust and the continental crust.
Weathering
The fragmentation and disintegration of rocks occur in several ways:
Mechanical Weathering
It is the breakage of rocks due to tensions that originate from different processes:
- Gelifraction: It is the wedging action that makes the water freeze and increase in volume within the cracks of the rocks.
- Thermoclasty: It is the breaking of rocks exposed to intense insolation.
- Decompression: It is the cracking and expansion that occurs in rocks that formed at great depths.
Chemical Weathering
It is the disintegration of rocks due to the chemical alteration of their minerals. It can occur by:
- Oxidation: Oxygen from the air, or that which is dissolved in water.
- Carbonation: It is the reaction that occurs when some minerals are hydrolyzed.
- Hydrolysis: It is the reaction or alteration of minerals with the H+ and OH- ions of water.
Formation of Sediments
Sediments accumulate and can be produced by two processes:
- Decanting: Precipitation or falling to the bottom of clasts where they were found. It occurs when the current that carries them stops.
- Kinetic Accretion: It occurs when transported clasts encounter a barrier that stops them, and they accumulate on top of each other.
Management of Clasts
During sedimentation, the management of clasts can produce sedimentary structures:
- Stratification: It is the arrangement of sediment in layers of some centimeters or meters thick.
- Lamination: Layering of a few millimeters thick. It occurs when sedimentation is produced in a low-energy current.
- Graded Sedimentation: Sorting by size of clasts. The thickest ones are at the bottom.
- Cross-lamination: Disposition in sheets that are cut into each other.