Landforms: Mountains, Valleys, Plains, and Other Features
Landforms
Valleys
A valley is an elongated depression of land, more or less wide, crossed by a stream or a glacier.
- Longitudinal Valley: A valley whose course is parallel to the general direction of a mountain range.
- Transversal Valley: A valley that cuts at right angles to a mountain range.
- U-Shaped Valley (Trough): A flat-bottomed glacial valley with steep slopes resulting from glacial erosion.
- V-Shaped Valley: A river valley formed by the flow of a river.
Plateaus and Mountains
A plateau is a slightly hilly region with level peaks of fairly constant height, elevated compared to neighboring regions.
A mountain range consists of large elevations formed by the collision of two tectonic plates. Mountain ranges are characterized by high, steep slopes and are relatively young (less than 200 million years old), showing minimal erosion. Recent examples include the Alpine ranges, extending over 15,000 km across Eurasia (including the Betic, Pyrenees, Alps, and Himalayas) and 19,000 km along the western coast of the Americas (including the Rockies and Andes).
Plains
A plain is a region of low relief, whose average height is close to sea level, formed by erosion and sedimentation.
- Coastal Plain: Lowland bordering a sea or ocean, gently sloping towards the sea. It can result from material accumulation, relative sea level decrease, or human activities.
- Lake Plain: The bottom of an old lake, filled with materials transported by rivers. The soils are often suitable for agriculture, but may require drainage.
- Abyssal Plain: A plain landscape at depths between 3,600 and 5,500 meters below sea level, occupying about 2/3 of the ocean floor.
- Alluvial Floodplain: A valley where a river overflows during floods, depositing alluvium.
- Alluvium: Fragmentary material transported and deposited by a river on its floodplain.
- Peneplain: A gently rolling plain formed after a long process of erosion over millions of years.
Geological Terms
- Exogenous: External agents.
- Tectonic Movements: Internal forces of the Earth that raise, sink, or move parts of the crust, creating landforms (endogenous forces).
- Xeric: Organisms thriving in dry steppes.
- Thermophilic: Organisms requiring high temperatures for development.
- Hygrophilous/Hydrophilic: Species needing high humidity for development.
- Latitude: The angle of a location with the equatorial plane.
- Longitude: The angle formed by a location’s meridional plane and a prime meridian.
- Sedimentary Basin: Formed by the sinking of a shield, often invaded by the sea, accumulating sedimentary material from rivers.
- Shield/Craton: Oldest structural units of continents, occupying 3/4 of the surface, characterized by flat topography (plateaus or low-rise plains) due to their age and erosion.
- Isthmus: A narrow neck of land connecting two continents or a peninsula to a continent.
- Fold: Deformation of geological layers related to orogeny; a set of folds.
- Fault: Geological fracture with vertical, oblique, or horizontal displacement of blocks.
- Erosion: Degradation of relief, transport, and accumulation of eroded material.
- Orogeny: The study of mountain formation and crustal movements.
- Folding: Tectonic deformation (folds, faults) in rocks caused by orogenic forces. The final stage in geosyncline development.
- Fault: Fracture surface implying dislocation and displacement of the crust. Fractures depend on the age of the materials.
- Map Projection: Projecting the Earth’s surface onto a flat plane. Common types include cylindrical and conical projections.
- Scale: Ratio between actual distance and distance on a map, expressed numerically or graphically.
- Contour Lines: Lines connecting points of equal elevation.
- Isobar: Line connecting points of equal atmospheric pressure.
- Isotherm: Line connecting points of equal temperature.
- Isohyet: Line connecting points of equal precipitation.
- Cenozoic: Tertiary and Quaternary periods.
- Glacier: Accumulated ice, moving slowly, covering vast areas in polar regions (Inlandsis or continental glacier), flowing through valleys (valley glacier), or extending from mountains (piedmont glacier).
- Mesozoic: Triassic, Jurassic, and Cretaceous periods (Secondary Era).
- Paleozoic: Primary Era (before the Mesozoic).
- Pangaea: Hypothetical supercontinent during the Carboniferous period, surrounded by Panthalassa.
- Gondwana: Large landmass during the Paleozoic Era, comprising present-day Madagascar, Australia, Africa, South America, and Antarctica.
- Laurasia: Paleozoic landmass comprising North America, Europe, and Asia.
- Tethys Sea: Sea between Gondwana and Laurasia.
- Anticline: Upward-convex fold.
- Batholith: Intrusion of plutonic rocks.
- Scree: Accumulation of large stones.
- Gully: Series of gullies separated by ridges, formed by water erosion on slopes.
- Washout: Rock fragments accumulated on slopes and valley bottoms.
- Doline/Sinkhole: Funnel-shaped depression in bedrock, characteristic of karst topography.
- Soil Science: Study of the physical, chemical, and biological properties of soils.
- Metamorphic Rocks: Rocks changed in composition and structure due to high temperatures or pressures.
- Polje: Broad, temporarily closed and flooded depression in karst regions.
- Sedimentary Rocks: Rocks formed by diagenesis of sediments.
- Sima: Example: limestone and clay. Deep natural crevices in the bottom of a sinkhole.
- Syncline: Downward-convex fold.
- South: Opposite of North.
- Endogenous: Internal agents.
- Erosion Agents: Natural agents like wind and rain that shape the Earth’s crust.
- Cirque Glacier: Mountain depression where snow accumulates and forms firn.
- Igneous Rocks: Rocks formed by the solidification of magma.
- Eogene: Sediments from the first two parts of the Tertiary period.
- Detritus: Sediments formed by the disintegration of rocks.
- Páramos: Large flat surfaces with alternating materials. Limestones form the exterior, while clays erode underneath, creating slopes.
- Campiñas: Clayey areas with gentle hills and valleys, terraced levels accompanying rivers. The lower terraces are suitable for irrigated agriculture.
- Cerro-Witness/Mesa: Highest zones of a flat area.
- Horst: Uplifted blocks.
- Graben: Down-dropped blocks.
- Depression: Deep ravine or valley in a mountainous area or a lower level of land.
- Parallel: Curve connecting points of equal latitude.
- Escarpment: Steep slope or cliff.
- Frogs: Inclined erosion surfaces covered with quartzite boulders.
- Lapiaz/Karren: Grooves and cavities in limestone, separated by sharp peaks.
- Rías: Deep grooves perpendicular to the coast, where the sea enters.
- Tombolo: Narrow strip of sand connecting an island to the mainland.
- Abrasion Surface: Land extension caused by mechanical wear, often by friction against rock materials transported by waves.