The circumference of the Earth has already been calculated in ancient Egypt. The calculations turned out to be rather accurate, considering the conditions of the time.

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Mountain climate zones

The decisive factor that determines the climate zones of mountains is the altitude above sea level.

Factors of warming

The duration of solar radiation, the angle of the Sun's rays and the surface albedo all have an...

Formation of stratovolcanoes

Stratovolcanoes consist of layers of volcanic ash, debris and lava.


Tsunami waves are very high waves of immense destructive power.


The dissolution of limestone results in the development of karst formations.

Snow line

Above a certain altitude snow does not melt, not even in summer.

Karst region (basic)

Karst formations include dolines and dripstones.

The Gregorian calendar

Developed nearly 500 years ago, it is a variant of the Julian calendar. Today it is the most...

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