Plains

Flat areas with absolute altitudes below 200 m are called lowlands. They are mostly located along the coast or in the estuaries of large rivers, such as the Amazon, Mississippi, Indus-Ganges lowlands. Lowlands are mostly formed in areas where the ground sinks and where wind and water have, over time, carried sediment from higher areas.

Most of the lowlands have been formed by the subsidence of the earth's crust, which has resulted in flooding of the area and the accumulation of sediments at the bottom of the formed water bodies. Any region of the globe can sink and rise once during a very long geological history. Therefore, the bottom of a water body once filled with sediment may rise again later. Estonian topography has also developed in this way.

The limestone plateau and sandstone areas that formed in the sea hundreds of millions of years ago have, over time, risen above the level of the world's oceans, and there are various valleys, depressions and terraces on their surface. The lowlands of the Central Danube in Hungary, Austria, Slovakia, Romania and Serbia are part of the bottom of the former Thetis Ocean. Today, this lowland with a very flat surface is surrounded by the Alps and the Carpathians.

There are large areas in many parts of the world that are below sea level but are not flooded. These are called depressions. On the maps, the height of the depressions is indicated by a minus sign. For example, the Caspian Basin is up to 28 m below the world's sea level. However, the area around the Dead Sea in the Middle East is almost 400 m below sea level.

A plain can also form in places where the crust gradually rises or where a high area has worn down over a long period of time.

Only the valleys of rivers and the terraces split the flat surface of a plateau. They can also be found in Estonia, for example, the land of Harju and Viru, which is bordered in the North by Estonian limestone bank as a high step on the sea side.

The flat area rising several hundred meters above sea level is a remnant of the former mountains and highlands and is called high plain. For example, the Mexican capital Mexico City in Central America is located on a plain more than 2,000 m above sea level. The Sahara Desert in North Africa is located on a plain between 500 and 1000 m. It is part of a large high plains across the African continent, the only mountainous terrain of which has survived to this day.

Plain areas, especially lowlands, depressions and plateaus, are densely populated and have the most diversified economic activities on earth. The most densely populated areas are concentrated on the coasts of the seas and oceans. But there are also many cities inland, mainly by rivers and lakes.

It is much easier for people to live on the plains than in the mountains, because the climatic conditions are mostly more favorable there, there is more agricultural land, it is easier to build roads, rivers are mostly navigable, and so on.

How a person can manage in an area depends largely on nature. The tundra peoples hunt, fish and breed reindeer, in the forests there is a lot of forestry, but also agriculture. Grasslands have the most productive soils in the world for growing grains and many other crops. There are many sedimentary mineral resources on the plains, such as oil, natural gas, coal, salt.