The Earth

Plate Tectonics Theory that states the earth’s outer shell is not one solid sheet of rock, but broken in to a number of moving plates. Plates vary in size and thickness. Plates are not anchored in place, but slide over a hot flexible layer of the mantle.

Plate Tectonics

Continental Drift Theory Theory that states there was once a single “supercontinent” called Pangaea. Began to break up about 180 million years ago. Continents look like puzzle pieces.

Plate Movement Scientists believe plates move because of convection occurring in the mantle-circular movement caused when a material is heated, expands, and rises, then cools and falls. When plates move, it can cause mountains and valleys to form, volcanoes, or earthquakes.

Weathering The breakdown of rock at or near the earth’s surface into smaller and smaller pieces. Two types of weathering- mechanical and chemical

Mechanical Weathering When rock is actually broken or weakened physically. One of primary processes involved in soil building. Most common type is frost wedging.

Chemical Weathering Alters a rock’s chemical makeup by changing the minerals that form the rock or combining them with new chemical elements. Water and Carbon Dioxide are most important factors. Acid Rain

Erosion Movement of weathered materials such as gravel, soil, and sand. Most common causes are water, wind, and glaciers.

Examples of Erosion