or log in
Waterfalls form where the river flows over a steep precipice in its course.
Lightning is a sudden electrostatic discharge accompanied by a sound known as thunder.
The weather can be forecast with different meteorological instruments.
On a geological time scale lakes are short-lived.
Plate tectonics is a theory dealing with the movement of plates.
One third of the continents is covered with desert. Today, desertification is a growing problem.
Sea and land breeze form because of the differing warming of land and sea.
Groundwater and aquifers are types of underground waters.