landform analysis

A mountain is a landform that rises prominently above its surroundings. Mountains are generally distinguished by steep slopes, a relatively confined summit, and considerable height. Most mountains are peaked, but many have flat tops.

Any region that supports very little life may be called a desert. However, the term desert is usually reserved for regions that are arid or dry -- they may or may not be hot. A desert is a barren area of land where little precipitation occurs and consequently, living conditions are hostile for plant and animal life.

A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river.

A valley has two characteristics: low land and being formed between hills or mountains. Valleys in low areas have an average slope; in the mountains, valleys are deep and narrow

An island is any area of land smaller than a continent and entirely surrounded by water. Islands may occur in oceans, seas, lakes, or rivers. A group of islands is called an archipelago.

Plains are any relatively level area of the Earth's surface exhibiting gentle slopes and small local relief. Plains vary widely in size. The smallest occupy only a few hectares, whereas the largest cover hundreds of thousands of square miles—as, for example, the Great Plains of North America.

A valley is a hollow or surface depression of the earth bounded by hills or mountains, a natural trough in the earth's surface that slopes down to a stream, lake, or ocean, formed by water and/or ice erosion. Erosion by rivers is a main valley-forming process. However, not all valleys are formed by rivers, other valleys were formerly occupied by glaciers. As the huge bodies of ice moved along, they carved the valleys as they passed, carrying away giant boulders and huge amounts of debris.

Desert areas differ greatly in their surface features, ranging from mountains to plateaus to plains. The ground may be bare rock or be covered with sand, scattered boulders, or coarse gravel and stones. Although sand dunes are spectacular features of deserts, they are not as common as generally believed.

Streams that rise in rainy regions outside deserts bring the most generous supply of water for irrigation. Desert soils are usually productive when given water. Humans have changed many desert environments. Irrigated lands have been extended by giant river-control systems. Oases once reached only by camel now have airports and gas stations for motor vehicles. Settlements have sprung up in deserts to obtain such valuable minerals as petroleum, copper and other metals.

Rainfall in deserts varies. Most deserts have at least a few days of rain a year, but some may get no rain at all for several years or receive a year's amount in one storm.

Temperatures range widely in deserts. In hot deserts, daytime air temperatures of 100° F occur regularly in summer. Winters are cold in temperate deserts, located far from the equator. The temperature drops sharply in the desert night.

Islands may be either continental or oceanic. Oceanic islands are those that rise to the surface from the floors of the ocean basins. Continental islands are simply un-submerged parts of the continental shelf that are surrounded by water. Islands often lack many natural resources and are forced to trade with other nations.

Their flat surfaces are easily cultivated and usually contain the most productive soil. Moreover, such areas of low relief present few obstacles to land transportation, and the rivers running across them are generally much easier to navigate than are those of rougher terrain.

Mountains have played a major role in human history, forming boundaries between countries and natural barriers to migration and transportation. They also have formed refuge areas for distinctive mountain cultures and economies. Mountainous terrain is often both an asset and a hindrance to humans. Mountains have provided protection from war-minded neighbors.

Mountain dwellers also have to contend with avalanches, landslides, earthquakes, and glacial bursts. The cold temperatures and low oxygen levels, along with difficulties with the construction and maintenance of engineering works have prevented the development of many modern highland cities.

Rivers carry the water that people, plants, and animals must have to live. They also provide transportation and waterpower. Rivers are also a principal natural force in shaping land surfaces. They drain surplus water to the sea, deposit soil and rocks to build new acreage, and erode land formations.

Today people are also dependent upon rivers for much of their water supply. Spreading cities need huge amounts of water every day for industrial and home use. Hydroelectric dams generate millions of volts of electricity that serve the energy needs of modern urban and rural areas. In dry and semiarid lands, water from rivers is used to irrigate acreage for farming.

Mountains regions along the coasts are often associated with special weather conditions. Here moist air masses move inland and are cooled by forced ascent over these mountains, producing heavy rainfalls on the windward slopes. This is called the orographic effect.

In many ways rivers helped give rise to human civilization. The earliest people built their towns and villages beside rivers. Here they found water and food supply, a means of transportation, and protection from enemies. These settlements often developed into major urban centers of trade and commerce. Most of the great cities of the world arose beside large rivers and the settlement of new lands throughout the world followed the course of rivers.

Human activities can also be harmful to rivers. Waste products and heated water discharged from plants pollute rivers and streams they are also polluted by sewage or commercial fertilizers and pesticides that drain into the water from the surrounding land. The destruction of grass and forests have added to the flood problem in some states, muddied the streams, and filled the lakes with silt. In some areas levees or dams built to control flooding have actually made the condition worse.

Occupying slightly more than one-third of the terrestrial surface, plains are found on all continents except Antarctica. They occur north of the Arctic Circle, in the tropics, and in the middle latitudes. Corresponding to their broad geographical distribution, the lains of the world show considerable variation in vegetation. Some are tree covered and others are grassy. Still others support scrub brush and bunch grass, while a few, which are nearly waterless deserts, have only the most sparse and scanty plant life.

Systems of valleys extend through plains, hills, and mountains. Rivers and streams flowing through valleys drain interior land regions to the ocean. At the bottom of many valleys is fertile soil, which makes excellent farmland. The bottom of a valley is called its floor. Most loors slope downstream. Mountain valleys usually have narrow floors. The part of the floor along riverbanks is called flood plain.

Mountains have furnished valuable resources of minerals, timber, water, and scenery. Some mountain slopes, along volcanoes have unusually fertile soils for agriculture. The short growing seasons at high altitudes, however, often restrict agriculture to specialized crops such as tea and coffee in lower altitudes and to grazing in higher ones.

Potential waterpower and mineral deposits are commonly found in mountains but are frequently expensive to develop.

With certain exceptions, plains have become the sites of major centers of population, industry, commerce, and transportation.

The major plains of North America, South America, Europe, and Asia occur in the continental interiors, but broad extensions of some of these flat lands reach the Atlantic coast. The largest plains of Africa occupy a vast portion of the Sahara and extend southward into the Congo and Kalahari basins. Most of the interior of Australia, from the mountains along the eastern margin to the plateaus in the far west, is one vast desert plain.

Islands everywhere have to provide for their populations from restricted ranges of resources (including available land) and economic opportunities. Today, tourism is the major economic industry for many island nations.

A river starts as a tiny trickle on a slope. Rainfall, snowfall, a spring, or the melting of glacial ice may be its source. As it flows downhill it form streams, then creeks, and finally it becomes a river. Rivers are also fed by groundwater—water that has soaked into the earth instead of running off the surface.

Like other landforms, river valleys are always changing. At the same time that the river is deepening its bed, other forces— rain, frost, wind, and the atmosphere—are loosening material on the valley walls. This material falls into the stream and is carried away. While most valleys supply fertile soil and water for irrigation and consumption, some may be too steep to be suitable for settlement of farming.

Large cities located in a valley may increase air pollution and create health concerns due to air being trapped in the valley.

Islands are home to approximately 550 million people, including the entire population of 43 independent states. They are found in all parts of the world and vary greatly in terms of size, climate, resources, and political power. Although the variety among islands is great, they share some common characteristics and effects on human civilization – some positive, others negative.

Islands often act as a barrier to both cultural diffusion (spread of ideas and technology) and invasion. Most island nations need to develop good forms of sea travel. Islands have been used as stepping-stones to cross the major oceans (in many cases this has created a history of political domination by outside nations).

Plants and animals living in the desert need special adaptations to survive in the harsh environment. People have struggled to live in deserts and the surrounding semi-arid lands for millennia. Nomad have moved their flocks and herds to wherever grazing is available and oases have provided opportunities for a more settled way of life. Sand and dust storms are natural events that occur in arid regions where the land is not protected by a covering of vegetation. Humans have long made use of deserts as places to live, and more recently have started to exploit them for minerals and energy capture.

Deserts are much less densely populated than other land areas. People can live and grow crops in the desert only at places where they can get water, called oases or by using underground water reached by wells.