What are Landforms?
Landforms are the natural features and shapes existent on the face of the earth. Landforms possess many different physical characteristics and are spread out throughout the planet. Together, landforms constitute a specific terrain and their physical arrangement in the landscape forms what is termed as topography. The physical features of landforms include slope, elevation, rock exposure, stratification and rock type.
Oceans and continents illustrate the largest grouping of landforms. They are they further subcategorized into many different landforms based on their physical features and shapes. Examples of distinctive landforms include mountains, valleys, plateaus, glaciers, hills, loess, deserts, shorelines, and plains. Features such as volcanoes, lakes, rivers, mid-ocean ridges, and the great ocean basins are also part of landform features.
Wikipedia define Landform as,
“A landform is a natural feature of the solid surface of the Earth or other planetary body. Landforms together make up a given terrain, and their arrangement in the landscape is known as topography. Typical landforms include hills, mountains, plateaus, canyons, valleys, as well as sho
reline features such as bays, peninsulas, and seas, including submerged features such as mid-ocean ridges, volcanoes, and the great ocean basins.”
Different Major Landforms on Earth
Major types of landforms on earth include mountains, valleys, plateaus, glaciers, hills, loess, plains and desserts.
Mountains are lands physical features protruding high beyond the hills and very high up the land surface with steep top commonly shaped up to a peak. They are created through the action of incredible forces in the earth such as volcanic eruptions. Often, mountains occur in the ocean compared to land and some are seen as mountain islands as their peaks protrude out of the water. Mountain formation result from the forces of erosion, volcanism, or uplifts in the earth’s crust.
The forces of heat and pressure within the earth’s interior are the main influencing factors to these forces as stated by geologists. These forces can be summed up as the plate tectonic movements – theoretically defined as the division of the earth’s outmost layer into several plates which are in constant motion. Hence, the uplifts are cause by collision or pulling apart of the plates that also triggers other various geologic activities such as the ejection of magma onto the surface or volcanic eruptions.
The movements also contribute to horizontal compression that is the deformation of crustal strata which gives rise to folds. The Himalayas and the Europe’s Jura and Alps mountains are examples of mountains formed as a result of horizontal compression. Some mountain ranges are also formed as a result of wind, water, and ice erosion. Other mountains are created from volcanism.
Examples of volcanic mountains include Mount Fuji in Japan, Mount Vesuvius in Italy, Mount Erebus in Antarctica, and Mount Saint Helens in the United States. Majority of volcanic mountains have summit craters that still expel debris and steam.
A valley is a lowland area or surface depression of the earth between higher lands such as mountains or hills. In simple terms, it can be defined as a natural trough bounded by mountains or hills on the surface of the earth sloping down to the lake, ocean or stream, which is created because of water or ice erosion. On this basis, the rivers or streams flowing through the valley empty the land’s precipitation into the oceans.
The lowest parts of the valleys are very fertile and make very good farmlands. Majority of the valleys on land are made up of running streams and rivers and nearly all their floors slope downstream. Valleys within the mountains normally have narrow floors. The sides of a valley are termed as valley slopes or valley walls and the section of floor along riverbanks are referred to as flood plains.
Valleys physical features include U-shaped and V-shaped caused through the forces of erosion by the flowing masses that persistently widens and deepens the valley. The flowing masses are either water or glacier that carries away huge amounts of debris. Very narrow and deep valleys are known as canyons.
Plateaus are fairly flat areas higher than the land surrounding it. The surrounding areas may have very steep slopes. Some plateaus such as the Tibet are situated between mountain ranges. Plateaus cover wide land areas and together with their enclosed basins they cover approximately 45% of the entire earth’s land surface.
Some plateaus, for instance the Columbia Plateau of the United States and the Deccan of India are basaltic and were created because of lava flows spreading to thousands of square kilometers thereby building up the fairly flat land surfaces. Other plateaus form as a result of upward folding while some are due to the erosion of the nearby land that leaves them elevated. Because plateaus are elevated, they are subject to erosion.
Low plateaus make up good farming regions whereas high plateaus are considered great for grazing livestock. Most of the world’s high plateaus are deserts. Other typical examples of plateaus include the Bolivian plateau in South America, the Colorado plateau of the United States, the Laurentian Plateau and the plateaus of Iran, Arabia, and Anatolia.
Glaciers are the perennial ice sheets on the planet. They are huge masses of ice that slowly move over the land surface, predominant in high mountains and the cold Polar Regions. The very low temperatures in the regions are the enabling factor for the buildup of snow and densification into ice at depths of 15 meters or even more. Most glaciers have density thickness in the ranges of 91 to 3000 meters.
The movements begin when the compaction is so dense that it moves under the pressure of its weight. It is estimated that more than 75% of the world’s fresh water is currently locked away in these frozen reservoirs. The glaciers include the Greenland Ice Sheet and the Antarctic Ice Sheet. The Antarctic Ice sheets outlet glaciers comprise the steep and extensively long and narrow depression Beordmore Glacier, which is one of the longest outlets in the world. The gradual rice in continental temperatures has seen the glacial density grow smaller owing to melting.
Hills are raised areas on the surface of the earth with distinctive summits, but are not as high as mountains. Hills are created as a result of accumulation of rock debris or sand deposited by wind and glaciers. They can also be created by faulting when the faults go slightly upwards. Hills are generally present in low mountain valleys and plains.
The Black Hills are the most known. Deep erosions of areas previously raised by the earth’s crust disturbances carry most of the soil away leaving behind a hill. Human activities may also create hill when soils are dug and piled giant masses. Volcanic eruptions as well create hills after the eruption when the molten materials or lava cools and hardens in a pile.
Loess is a fine-grained unstratified accumulation of clay and silt deposited by the wind. It appears brown or yellowish in color and is brought about by past glacial activity in an area. In precise, it is sedimentary deposits of clay and silt mineral particles which take place on land in some parts of the world. The thickness of loess deposits are just a few meters and one of their basic feature is known as the ‘cat steps’.
It’s held together by few clay particles and is mostly composed of quartz crystals which readily slide against each other. This property makes it highly susceptible to erosion which leads to the ‘cat steps’ feature. Loess formed after the ice age when the glaciers covering a relatively large portion of the earth melted and was carried away, exposing the vast plains of mud.
Upon drying of the mud, the forces of wind blew away the mud and exposed sediments and eventually deposited them as silt in stacks on top of each other to create bold steep banks. Regions made of loess are witnessed in eastern China and the northwestern region of the United States.
Plains are broad flat areas on the earth’s surface stretching over a wide area. Plains are lower than the land in their surrounding and can be found both inland and along the coast. Coastal plains rise from the seal level up to the point they meet raised landforms such as plateaus or mountains. The Atlantic Coastal plain is a prime example of a substantially populated and fertile coastal plain.
On the other hand, inland plains are generally found at high altitudes. Thick forests normally flourish on plains in humid climates. A fairly large portion of plains are covered by grasslands, for instance, the Great Plains in the United States. Human populations prefer settling on plains because of the soil and the terrain which is good for farming and building settlements such as cities, residential areas, and transportation networks. Flood plains are also in this category and they are formed as a result of continuous accumulation of sand, silt, and mud when rivers overflow its banks.
Deserts are the hot and dry areas of the world. They are the arid and semi-arid lands with little or no vegetation. Deserts constitute approximately 20% of the earth’s total land cover and are distinguished by little or no rainfall. The deserts are divided into four major categories including the Semi-Arid Deserts, the Hot and Dry Deserts, the Cold Deserts, and the Coastal Deserts.
These deserts are located in different areas of the world. Deserts experience very high temperatures, less cloud cover, low humidity, low atmospheric pressure, and very little rain, which makes them have very little vegetation cover. The soil cover is also rocky and shallow and with very little organic matter and as such, it only supports a few plants adapted to the conditions.
Plants such as cacti and short shrubs are the ones adapted to the desert conditions because they can conserve water and tolerate the high temperatures. Animals in the deserts include insects, small carnivores, snakes, lizards, and birds adapted to survive with very little water. These animals hide during the day till nightfall to avoid the heat. An example of a desert is the Sahara of North Africa.