ciencias

The internal forces of Earth

Earth changes: the relief of earth’s surface has not always been the same.

For example:

Islands and mountains have formed throughout time. Millions of years ago, there were plains where today there are mountains, and vice versa. Land now on the surface used to be under the ocean.

These changes occur as a result of the internal and external forces of earth.

Internal forces: create the surface relief.

External forces: erode the surface little by little.

Earthquakes: occur when internal forces break or move rocks inside earth. The rocks knock against each other and cause very intense and destructive seismic waves.

Earthquakes begin inside earth at a point called focus.

This point is called the epicenter on the surface.

The size or force of an earthquake is measured by a sale called richer scale and goes from 1 to about 9. The most intense earthquakes can change the lanscape.

Volcanic eruptions:

There are very hot substances inside earth. Sometimes these substances break through to the surface. They come out through to the surface. They come out through volcanoes.

The hot materials form magma. Internal forces put pressure on the magna and it rises through the central vert and comes out of the crater.

The substances that the volcano expels can be solid, like ash. They can also be liquid like lava. Volcanoes can also expel gases, which can cause explosions inside the volcano.

These expelled substances build up on the outside of the volcano and form volcanic cones. Sometimes volcanic eruptions can even create islands, such as the Hawaiian Islands.