The Earth's surface is the interface between the solid Earth's crust, together with the water on it, and the atmosphere. The Earth's surface covers approximately 510 million km² and can be divided into hemispheres or hemispheres in various ways.
About 365.5 million km² of the Earth's surface (71%) is covered by water against 144.5 million km² (29%) of land.
The study of the layout of the earth's surface is called geography or geography. Besides the design of the earth's surface by man (social geography), the natural state of the surface (physical geography) also falls under geography.
The shape and origin of the landscape and the landform is called geomorphology. The shape of the surface depends on an interplay of geomorphological processes such as erosion (degradation) and sedimentation. Tectonic processes can cause the Earth's crust to fall or move up. The natural processes that determine the landform are the sea (marine process), rivers (fluvial process), land ice (glacial process) and wind (aeolian process).
Measuring the Earth's surface is called geodesy. The geodesy tries to describe the shape of the surface as accurately as possible, including the surface of the seabed. One goal is to determine the shape of the Earth and to measure the gravitational field.
Finally, soil science studies the top layer below the surface. At the surface, the atmosphere acts on hard rocks causing weathering and erosion. Weathering reduces the size of the rock, so the top layer often consists of loose material called regolith. Plants can take root and various organisms live in it. A regolith in which biological activity arises is called a soil. Different soil types can be distinguished depending on the degree of weathering and the chemical composition of the original rock.
In geodesy, the surface is divided into a southern and a northern hemisphere, but depending on the geographical latitude (measured from the prime meridian), an eastern and a western hemisphere can also be distinguished.
These hemispheres are at once cultural and economic-political divisions, although they are chosen arbitrarily. At the time of the Cold War, the Southern Hemisphere more or less coincided with the Third World; the eastern hemisphere with the communist and real socialist countries of Europe and Asia. Due to the changed political situation, these terms are becoming obsolete.
In geomorphology, the surface is divided into a water hemisphere and a land hemisphere. The first contains the Pacific Ocean and surrounding continents, the second the Atlantic Ocean and Eurasia.
In the treaties of Tordesillas (1494) and Zaragoza (1529) the earth's surface was divided into colonial spheres of influence under Spain and Portugal.
Another division is that of an Old World (Eurasia and Africa) and a New World (both Americas).
Water and land
Geomorphologically, the earth's surface can be divided into mainland (continents), oceans and seas, lakes and islands. On land, the earth's surface is the interface between solid material and air, but on water two interfaces can be distinguished: the water surface (sea level) and the surface of the solid seabed (bathymetry). However, several areas can also be taken on the mainland: the top of the vegetation, the top of the built-up area (topography) or the top of the bottom (orography). In areas with land ice, the question is whether the ice should be counted as the surface or the bottom.
In plate tectonics, the surface of the solid Earth is divided into tectonic plates, which move very slowly relative to each other.
The average height of the land surface above sea level is about 700 m. The highest point above sea level is Mount Everest (8844 m), h