​The crust lies on the mantle. The mantle is made partly of melted rocks. Therefore, there is always constant movement in the layer.

​Fast Changes in the Earth's Crust

- causes large blocks of rocks in the crust to either slide or shake forming cracks.

Earthquake

New faults are formed when an earthquake takes place.

The cracks are called faults.

Seismologists - scientists who study earthquakes.

Seismic Waves

- movement of an earthquake

Seismograph

- an instrument used to identify the strength and point of origin of the earthquake.

- when magma is pushed up forcefully to the earth’s crust through a mountain with a hole or crater.

Volcanic Eruptions

Magma is melted rock inside the mantle.

Lava is magma that flows out of a volcano.

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Lava will harden and form solid rock after some time.

Tsunami

- giant ocean waves that are caused by underwater earthquakes, eruptions of underwater volcanoes, or sudden movement of the ocean plates.

First, a trigger will cause changes to the sea floor creating a vast energy displacing large volumes of water.

Then progressive waves will propagate and will travel outward. In a short time, it can reach the shore creating impact that can bring death and destruction of property.

Fast Changes in the Earth’s Crust are destructive and beyond human control. Therefore, instruments or apparatuses are developed in order to predict these phenomena, to warn people to be ready and follow the precautions imposed.

​Slow Changes in the Earth's Crust

Weathering

The breaking up, crumbling, and wearing away of rocks.

During winter, water freezes and expands in between rocks. When it melts, it leaves a crack in the rocks. With many repeated cycles, the rock will eventually crack.

Weathering due to Frozen Water

Rainwater mixing with gases in the air creates acid which can turn rocks into soft clay. Hollow gaps are then formed.

This can take thousand of years.

Chemical Weathering

Erosion

Broken pieces of rocks are carried away by water or wind to new places

Rocks and soil were deposited from higher ground. As time passes, continually flowing water widens a stream thus creating a river. The deposited materials form a triangular landform called a delta.

Water Erosion

The wind carries pieces of soil and sand to other locations to form sand dunes.

This usually happens in deserts.

Wind Erosion

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