Presentation on theme: "Chapter 9, Section 3. The Shore Ocean Shoreline Where land meets the ocean. Surface waves, tides, and currents cause shorelines to constantly change."— Presentation transcript:
Chapter 9, Section 3
The Shore Ocean Shoreline Where land meets the ocean. Surface waves, tides, and currents cause shorelines to constantly change.
The Shore Shoreline Forces There are 3 major shoreline forces: Waves Currents Tides
The Shore Waves Caused by winds blowing across the water. Break rocks into tiny pieces. Can erode and move large amounts of material in a short amount of time.
The Shore Currents Longshore current Formed when waves collide with the shore at a slight angle. Causes water to run parallel to the shore. Act like rivers of sand in the ocean. Carry many metric tons of loose sediment. Cause abrasion.
The Shore Tides Create currents that move at right angles to the shore. Called tidal currents Move sediment into deeper waters. Bring new sediment to the shore.
Rocky Shorelines Features of Rocky Shorelines Have rocks and cliffs About 14,000 waves crash onto the shore each day. As waves crash into the cliffs, the rock is worn away. Rock fragments are ground up by waves and transported as sediment by longshore currents. Softer rocks erode quicker than harder rocks, leaving islands of rock in the water.
Sandy Beaches Beaches Deposits of sediment that are parallel to the shore. Made of different materials. Quartz and shell fragments are common. Hawaii has black basalt beaches and green olivine beaches. Grains range in size from.06 mm to 2 mm in diameter. Grains tend to be smooth from collisions with other grains.
Sand Erosion and Deposition Erosion and Deposition Storms and wind cause waves that erode sediments. These sediments are later deposited as features such as barrier islands, spits, and sandbars.
Sand Erosion and Deposition Barrier Islands Sand deposits that lay parallel to the shore but are separated from the mainland. Start as underwater sand ridges formed by breaking waves. When the barrier island becomes big enough, loose sand is blown into dunes. Have a life-time from a few years to a few centuries.