Landforms 5.7B What are landforms? • The natural shapes or features on the Earth’s surface are called landforms. • Many different types of landforms can be found on the Earth. Journal Jam #1 canyon A canyon is a deep valley with very steep sides. Rivers often flow through canyons. Journal Jam #2 coastline A coastline is the area where the ocean touches the land. Journal Jam #3 delta A delta is a large, flat area of land where a river flows into an ocean or sea. Journal Jam #4 hill A hill is a rounded area of land higher than the area around it (not as high as a mountain). Journal Jam #5 island An island is land that is completely surrounded by water. Journal Jam #6 mountain A mountain is a place on Earth’s surface that is much higher than the land around it. Journal Jam #7 sand dune A sand dune is a hill of sand that is deposited by the wind. Journal Jam #8 valley A valley is a long, low area of land that is surrounded by higher land. Journal Jam #9 True or False: The Earth’s surface has stayed the same for thousands of years. Think about the statement in the box above. Do you think it is a true statement or a false statement? Circle True or False on Journal Jam #10. True or False: The Earth’s surface has stayed the same for thousands of years The Earth’s surface is CONSTANTLY changing! Changing Landforms Let’s look at a large rock (called a sea arch) by the seaside over a period of years. 1890 1910 The rock changed over this 80 year period. In fact, it almost disappeared! 1920 1970 Changing Landforms What do you think caused these drastic changes in the rock? 1890 What could possibly make rock break down into smaller pieces? 1970 Weathering The breakdown of the materials in the Earth’s crust into smaller pieces. Journal Jam #11 Moving water can cause weathering. What evidence of weathering do you see in this picture? Journal Jam #12 Wind can cause weathering. Why wasn’t this mass of land weathered away? What evidence of weathering do you see in this picture? Ice can cause weathering. Water can get into cracks in rocks. If the water freezes, it can push the sides of the crack farther apart, making the crack larger and larger. Plants CAN CAUSE weathering Journal Jam #13 Erosion The process by which water, ice, wind or gravity moves fragments of rock and soil. What evidence of erosion do you see in this picture? Erosion is the movement of sediments! • Erosion gradually wears down the surface of the earth. • Erosion carves the Earth's surface creating canyons, gorges, and even beaches. • Erosion is the process by which weathered rock and soil (sediments) are moved from one place to another. What do you think has caused this rock to look this way? Journal Jam #14 Wind Erosion • As the wind blows it picks up small particles of sand/sediment and blasts large rocks with the abrasive particles, cutting and shaping the rock. • The intensity of wind erosion is determined by: • The amount of wind • The speed of the wind • The slope of the land • The surface of the land Evidence of Wind Erosion Moving water causes erosion! Moving water causes erosion. When rain falls to the Earth it can evaporate, sink into the ground, or flow over the land as Runoff. When it flows over land, erosion occurs. Runoff picks up pieces of rock and "runs" downhill cutting tiny grooves (called rills) into the land. Moving water causes erosion. How much erosion takes place is determined by the: • Amount of water • Slope of the land • Speed of the water • Surface of the land Moving ice causes erosion. Glaciers wear down the landscape by picking up and carrying debris that moves across the land along with the ice. Ice Causes Erosion Glaciers can pick up and carry sediment that ranges in size from sand grains to boulders bigger than houses. Moving like a conveyor belt and a bulldozer, a single glacier can move millions of tons of material! Moving ice causes erosion. How much erosion takes place is determined by the: • Size of the glacier • Slope of the land • Speed of the glacier • Surface of the land Gravity causes erosion Landslides and Avalanches. Slower Faster These are examples of mass movement (also called landslides) Gravity causes Erosion How much erosion takes place is determined by the: • Amount of falling debris • Slope of the land • Speed of the falling debris • Surface of the land Journal Jam #15 Plants CAN PREVENT erosion Deposition Rock particles that are picked up and transported during erosion will ultimately be deposited somewhere else. Deposition is the process by which sediments (small particles of rock) are laid down in new locations. • Together, Erosion and Deposition build new landforms. • Deltas • Canyons • Sand dunes • Hills Journal Jam #16 Deposition and erosion together form deltas. Where rivers meet the ocean is called the mouth of the river. Soil and dirt carried by these rivers is deposited at the mouth, and new land is formed. The new, soil-rich land is known as a Delta Weathering and erosion together form canyons. This simple animation provides you with a visualization of how the Colorado River has "downcut" into the rock layers of the Grand Canyon. How long it took to carve the Grand Canyon is debated by geologists. Canyons are large valleys created by a river or stream. Some estimates are between 6 and 8 million years, which is very recent by comparison. Erosion and deposition together form sand dunes. Wind can move erode and deposit sediments, especially when it blows across open areas with no vegetation. Wind tears down landforms when it erodes sediments. Sand dunes are hills of sand deposited by the wind. Wind builds up landforms when it deposits sediments.