Shaping Earth’s Surface Lesson 2: Shaping Earth’s Surface

The surface of the earth is continually being changed by geological forces and processes. Some changes happen very quickly, but other slower changes can take thousands of years.

Major forces that shape our planet’s surface include: Erosion and Deposition Volcanic Eruptions Earthquakes

Erosion is the process in which wind, water, ice, or other things move pieces of rock and soil over Earth's surface.

Discovery Education Video: Erosion Looks at the role wind and water play in erosion and defines three types of weathering: mechanical, chemical, and organic.

Discovery Education Video: Erosion The process of rocks and soil moving from one place to another is called erosion. There are two forms: water erosion (can also be in the form of ice) and wind erosion.

Deposition occurs when sediments and soil are added to a land mass.

A delta formed at the mouth of a river is an example of deposition.

Discovery Education Video: Deposition During its journey the river carries eroded materials such as sand and small pebbles. At slow points, these materials are deposited and form sandbanks.

An earthquake is the sudden shaking of the ground caused by the movement of rock underground. Earthquakes commonly occur along fault lines – the boundaries along Earth’s tectonic plates – as they rub together.

Discovery Education Video: Earthquake Explores how the movement of tectonic plates create earthquakes along fault lines.

Discovery Education Video: Earthquakes Claire and Nisha tour a Lawrence Hall of Science geology exhibit and then walk the fault lines in San Francisco to learn how the earth moves in an earthquake.

A volcano is an opening in the Earth's surface through which magma and gases erupt.

When magma beneath Earth's surface is forced up due to pressure, it flows out to Earth's surface through volcanoes.

Discovery Education Video: Volcano Establishes why volcanoes often form along plate boundaries, and describes the differences between composite, shield, and cinder cone volcanoes.

Discovery Education Video: Volcanoes: The Structure Delves into the structure of volcanoes, a rock formation with a magma chamber deep underground. Magma rises from the chamber and exits the volcano through vents at the surface, resulting in a volcanic eruption. Magma is formed when rock is melted in the asthenosphere as a result of change in temperature or pressure.

Discovery Education Video: Volcanoes: Hot Spots and Eruptions Explains hot spots, volcanic regions found both near to and far from plate boundaries, and eruptions. Hot spots account for the quantity of volcanoes on the Hawaiian Islands. There are two kinds of eruptions, explosive eruptions and non-explosive eruptions. Volcanoes erupt as a result of gas expanding rapidly in the magma chamber.

Key Questions: Describe positive and negative effects of erosion. What can humans do to control or prevent erosion? How do earthquakes and the movement of Earth's tectonic plates change earth's surface? Describe the positive and negative effects of volcanic eruptions. Why can volcanic eruptions sometimes be difficult to predict?