Constructive and Destructive Forces The physical features on the Earth’s surface are called landforms. Some examples of landforms include deltas, canyons, beaches, and cliffs. Rapid and slow changes affect the landforms on Earth. Construct means to make or form. So, a constructive force would be a force that would build something! Examples: The formation of mountains, beaches, deltas, and islands The deposition of sediment (laying down small pieces of rock). Deposition is the process by which sediments (small particles of rock) are laid down in new locations. (happens slowly) Landforms made by deposition: Deltas Beaches Sand Dunes The mouth of the river is where the river meets the ocean. Soil and dirt carried by the river is deposited at the mouth, and new land is formed. The new, soil-rich land is known as a Delta. Beaches are formed when sand is picked up by the waves and deposited at the shoreline. Sand Dunes are formed as wind moves mountains of sand from one place to another. Are formed by allowing molten rock from the depths of the Earth to force its way to the surface. As the magma flows from the volcano it begins to cool and eventually will become new rock covering the existing rock and building up the land. Volcanic eruptions can dramatically and quickly changes the surface of the land surrounding it. Natural Arches are rock formations that have changed over time until the rock forms an arch. Formed by erosion and extreme temperature changes. A destructive force breaks things down. Examples: Flooding-happens fast Weathering- happens slowly Erosion-happens slowly Earthquakes- happens fast Landforms made by destructive forces include ushaped valleys, canyons, arches, and floodplains. Large amounts of rain or the overflow of water from a large body of water can cause flooding. Floodplains form along the banks of mid-sized streams and larger rivers. These are low-lying areas along the sides of a river which become flooded when there are large amounts of water. Weathering breaks apart existing rocks, forming sediment. No matter how slowly, sooner or later, every rock that is in water or air will be weathered away. Mechanical or Physical Weathering takes place when rocks are broken apart by a physical force. Pieces of rock are called sediments. This type of weathering can be caused by water, wind, ice, and plants. Ice can cause rocks to break apart into smaller pieces. This is referred to as ice wedging. Erosion occurs when sediment is picked up and moved to new locations. Moving water, ice (glaciers), wind, or gravity can cause erosion. When rain falls to the Earth it can evaporate, sink into the ground, or flow over the land as Runoff. When water flows over land, erosion occurs. Runoff picks up pieces of rock and "runs" downhill cutting tiny grooves into the land. Glaciers can pick up and carry sediment that ranges in size from sand grains to boulders bigger than houses. Glaciers can cause u shape valleys. Moving like a conveyor belt and a bulldozer, a single glacier can move millions of tons of material! 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. Abrasive particles are able to grind or polish another substance. Gravity can move rocks and sediments. Mass movement is the downhill movement of rock and soil because of gravity. This happens very quickly. A mudslide, landslide, and a sinkhole are examples of mass movement. Earthquakes caused by plates on the Earth’s crust crashing into each other sometimes causing the ground to violently move for a short period of time. This happens quickly. Weathering is the breaking down of rocks and minerals. Erosion is the movement of those particles (sediments). Deposition is where it ends up or stops.