VHS+Science+Lesson+04

= Surface of Earth =

Today we are going to learn about how the surface of the Earth changes everyday.


How do you think this river is changing the surface of Earth? How did these rocks form? How is this river like ones you have visited? The surface of Earth changes every day. Wind, water, gravity, and even living things cause weathering, erosion, and deposition. These changes can be fast or slow. Weathering and Erosion: Over millions of years, the Colorado River slowly carved out the Grand Canyon.

Deposition: Wind carries sand and puts it down. On a windy day, the pattern in the sand can change quickly.

media type="custom" key="26363970"

Weathering breaks rocks apart. Erosion moves rocks from place to place. Deposition puts rocks down in a new place.



Water covers almost 75% of Earth's surface.



Oceans hold 97% of Earth's water. Each day ocean water moves tons of sediment.



A little more than 2% of Earth's water is frozen in glaciers. Glaciers change the surface of Earth when they move.



About 1% of Earth's water is the freshwater found in lakes and rivers underground.

Underground water may hollow out caves.

(start class plant, create job of giving water)

Part 2

(review part 1)

= The Changing Surface of Earth =

The surface of Earth changes by weathering, erosion, and deposition. Heat, cold, wind, water, and gravity cause these processes. The changes can happen quickly or slowly.

Weathering breaks rocks into pieces and can happen in two ways.

Chemical weathering changes the chemicals inside rocks. For example, salt is a chemical in some rocks. If water dissolves the salt, the rock starts to break apart. Some rock has iron in it. Iron will rust when water and air touch it. The rock falls apart if it gets too rusty.

Chemical weathering helps create soil. When water weathers rock, small pieces mix with the water and air. Plants grow in this mixture.

Mechanical weathering changes the size and shape of a rock. Heat, wind, water, ice, and living things can cause mechanical weathering.







= Fast Changes and Slow Changes =

Rivers and glaciers cause weathering, erosion, and deposition. These processes may be fast or slow.
Fast flowing rivers can wash away sediment. Fast moving water with rock in it cuts into the earth. It makes a V-shaped valley.





The steep valley may form in hundreds or thousands of years. This is a short time in the history of Earth.

Slow changes happen as well. Glaciers slowly dig into the surface of Earth. A glacier has time to make a U-shaped valley. It may take tens of thousands of years to make a glacier valley.







media type="custom" key="26364256"