Weathering, Erosion and Deposition! By: Ms. Moya

True or False The Earth’s surface has stayed the same for thousands of years? FALSE The Earth’s surface is always changing !

Earth’s Surface: A Historical Look What do you observe about each picture? 1890

20 Years Later…. 1910

30 Years Later…. 1920

80 Years Later…. 1970

100 Years Later… 1990

What Caused These Changes? Weathering Erosion Deposition

Weathering Weathering happens when the Earth’s crust is broken down into smaller pieces. This process causes soil to form over time. There are two types of weathering: physical weathering and chemical weathering.

Physical Weathering Physical weathering is caused by other rocks, water, wind and ice. Water Wind Ice

Let’s Physically Weather Rocks! Observe the properties of the chalk at your table. Place the chalk in to the empty soda bottle. Draw a diagram of the bottle just as it appears and write your observations. Shake the bottle as hard as you can for 1 minute. Use the stop watch at your table to measure the time. Observe the inside of the bottle and record what you see. Every table member must get a chance. How has your piece of chalk changed over time?

Weathering By Organisms! Animals step on rocks causes them to break down. As this plant grows it splits the rock apart.

Chemical Weathering Chemical weathering happens when a rock is changed through a chemical process and becomes easier to break down. (It is a chemical change of matter) Chemical weathering can be caused by air, temperature and acid rain.

Modeling an Example of Chemical Weathering Observe and record the properties of the steel wool at your table. (Tug on it) Draw a diagram of it in your book. Table monitors – place the steel wool into the container at your table. Then sprinkle the water in your measuring cup over the entire piece of wool. Make a prediction! What do you think will happen to the steel wool.

Erosion Erosion happens when sediment is moved from one place to another with the help of gravity. Erosion carves the Earth’s surface creating canyons, gorges and beaches.

Erosion By Wind: As the wind blows it picks up different types of sediments and moves it to another place.

Erosion By Water: Most of the changes to the Earth’s surfaces is caused by water. Rivers and Streams erode the Earth’s surface. The Water Cycle – Runoff picks up soil and pieces of rock, and “runs” downhill cutting tiny grooves into the land.

Erosion by Ice: Glaciers wear down landscapes by picking up sediment and moving it across the Earth’s surface. Glaciers can pick up sediment as small as sand grains and as big as boulders. Glaciers are nature’s bulldozers. They can move over a million tons of Earth’s materials.

Modeling Erosion of the Earth’s Surface! Table monitors use the sand at your table to create a sand dune in the middle of container. Observe and draw a diagram of the sand dune at your table. Another table member take the “glacier” and press it into the sand dune. Follow the path of gravity and drag the glacier to the bottom of the sand dune. Observe and record the changes to the sand dune. Next table member, turn the sand dune carefully to a “clean” side and use the straw to gently blow on the sand dune for 30 seconds. Use your stop watch to measure time. Observe and record the changes to the sand dune. Last table member, take the bottle of water and gently pour it onto a “clean” side of the sand dune. Observe and record the changes to the sand dune.

Humans and Erosion! Humans affect the process of erosion when they:  Build highways  Destroy forests  Unsuccessful landfill projects

Plants Prevent Erosion Plants roots help keep soil in place so new plants can grow!

Deposition Deposition is the process by which sediments (small particles of rock) are laid down in new locations. Together deposition and erosion create deltas, canyons and meanders. Delta Canyon Meander