Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 16 The Marine Environment BEACHES • SLOPING BAND OF LOOSE SEDIMENTS • THAT IS MOVED AND DEPOSITED BY WAVES. – BEACH DIFFERENCES: • HAWAII - BLACK BEACHES FROM VOLCANIC ROCKS • FLORIDA - FINE GRAINED WHITE/PINK FROM CORALS • LARGE RIVER MOUTHS - SMALL GRAINS OF QUARTZ AND FELDSPAR Estuaries • Area where the lower end of a fresh water river or stream meets the ocean Longshore currents • Waves usually • approach the beach at an angle Water recedes parallel to the beach. Longshore currents • This repetitive wave • • • motion creates a flow of water in one direction along the shore. The waves do deflect depending on the shape of the coast. The larger the waves the stronger the current. Waves produce erosional and depositional landforms on beaches. Groins will catch sand carried by the Longshore current. Which way is the Longshore current flowing in this picture? Erosional landforms • Water crashing on the • beach as surf will erode material away even solid rock. Headlands receive most of the wave force because of wave refraction. Erosional landforms • • • • Sea stacks Wave cut platform Wave cut cliff Sea caves Beaches • Beaches can be mud, • sand, pebbles, cobbles, gravel, or rocky. Color of the sand depends on material eroded. Beaches • Hawaii has black • sand beaches in some locations. The eroded material is dark volcanic rock. Beaches • Florida and the Bahamas white and pink sand beaches are bits of local coral and sea shells. Estuaries • Occur where a river • • • meets the sea. Formed by rising sea level flooding a river valley. Water is brackish These areas provide an excellent environment for wildlife. (protection, quiet water, food) Depositional landforms • Spit • Which way is the current flowing? Depositional landforms • Tombolo Depositional landforms • Baymouth bar Depositional landforms • Lagoon • Bay Depositional landforms • Barrier Island *** Coastal landforms • • • • • • • • Depositional Beach Spit, Baymouth bar Tombolo Bay or Lagoon Barrier Island Longshore bar Sand bar • • • • • • • Erosional Beach Sea stack Wave cut platform Wave cut cliff Sea cave Estuary Rd Section 16.2 • Open to figure 16-12 • on pg 422. Proceed with ppt Oceanic and Continental Crust • Continental margins (Figure 16-12) – – – – Continental shelf (avg. width 60 km) Continental slope (10% drop off, edge of continent) Continental rise (gentle slope of sediment) Abyssal Plains (the smooth parts of the ocean floor 5-6 km below sea level) – Trenches ( the deepest part of the ocean basins) Ocean Basins • Abyssal plains - large flat areas covered by (hundreds of meters thick) sediments • Deep sea trenches (most on the edges of the Pacific Ocean). Trenches are 100 km wide and extend thousands of km. Ocean floor bumps • Mid-ocean ridges – 1500 m tall – Thousands of km wide – Many thousands of km long • Rifts extend along the ocean ridges in many places • Volcanic activity and earthquakes are common at the mid-ocean ridges