Presentation on theme: "Wave action is the primary means of erosion along coastlines."— Presentation transcript:
1 Wave action is the primary means of erosion along coastlines.
2 Exploring the OceanHow do conditions in the ocean change with depth?Light and temperature decrease with depth, whereas pressure increases.
3 Ocean water is a mixture that includes dissolved salts and gases. Exploring the OceanOcean water is a mixture that includes dissolved salts and gases.Salinity is the proportion of dissolved salts in water.The most abundant salt in ocean water is table salt, sodium chloride (NaCl).
4 Exploring the Ocean Changes With Depth Conditions in the ocean change as you move from the surface to the ocean floor.Sunlight decreases with depth in the ocean. The deep ocean is totally dark.Water temperature decreases with depth. Deeper water is much colder and denser.Pressure increases continuously with depth in the ocean.
5 Exploring the Ocean The Ocean Floor The continental shelf is a gently sloping plain that forms an apron of shallow water along the edges of most continents.The continental slope descends more steeply to the floor of the deep ocean.In places, you would see deep canyons cutting through the continental shelf and slope.
6 Exploring the OceanThe ocean floor itself is a vast, flat plain dotted with volcanic peaks.The mid-ocean ridges wind through the ocean basins, and there are deep trenches along the edges of some oceanic plates.
7 Exploring the OceanKelp forests occur in coastal waters swept by cold ocean currents.Light can penetrate to the floor of the continental shelf, allowing the long strands of kelp to grow in nutrient-rich waters.
8 Ocean CurrentsWhat causes surface currents, density currents, and upwelling?Winds blowing across the surface of the ocean cause the continuous flow of surface currents.
9 Ocean CurrentsIn upwelling, winds blow warm surface water aside. This allows cold water from the deep ocean to rise and take the place of the warmer water.Deep ocean currents are caused by differences in the density of ocean water.
10 Ocean CurrentsOcean currents are the patterns of flow in Earth’s oceans.Ocean currents are affected by winds, Earth’s rotation, and the positions and shapes of the continents.
11 Ocean CurrentsPrevailing wind patterns drive the ocean’s surface currents.
12 Ocean CurrentsSurface CurrentsA surface current is a large stream of ocean water that moves continuously in about the same path.Global surface currents reflect the effects of wind patterns in the atmosphere.
13 Ocean CurrentsIn general, currents of warm water flow away from the equator along the east side of continents.Currents of cold water flow away from the polar regions along the west side of continents.
14 Ocean CurrentsThis satellite image of the Atlantic Ocean shows the Gulf Stream, which carries warm water northward from the Gulf of Mexico toward the British Isles. The image has been enhanced so that red indicates warmer water and blue indicates cooler water.
15 Ocean CurrentsDeep CurrentsUnlike surface currents, deep currents are not caused by winds.Denser water results from colder temperatures or higher salinity.
16 Ocean CurrentsBecause deep ocean currents are affected by density, they are called density currents.Density currents are responsible for a slow mixing of water between the surface and deeper ocean.
17 Ocean Currents Upwelling The movement of water from the deep ocean to the surface is called upwelling.Much upwelling occurs along the western coasts of continents.Upwelling brings nutrients from deep in the ocean to the surface.
18 Upwelling of deeper ocean water occurs along some coastlines. Ocean CurrentsUpwelling of deeper ocean water occurs along some coastlines.Surface windWarm surface waterCold water upwelling
19 Wave Erosion and Deposition How do waves erode rock and deposit sediment?Two physical processes, hydraulic action and abrasion, are responsible for much wave erosion.
20 Wave Erosion and Deposition Waves can pound a coastline with a tremendous amount of energy, so waves are the major cause of erosion along coastlines.On a rocky coast, wave erosion creates cliffs, arches, caves, and tall rock towers called sea stacks.Over time, wave erosion and deposition work together to straighten a coastline.
21 Wave Erosion and Deposition A sea cliff with a sea stack and arch in Etretat, France
22 Wave Erosion and Deposition A sea cliff with a sea stack and arch in Etretat, FranceA barrier beach in South Carolina
23 Wave Erosion and Deposition A sea cliff with a sea stack and arch in Etretat, FranceA barrier beach in South CarolinaA sand spit along the Red Sea in Egypt.
24 Wave Erosion and Deposition How Waves Cause ErosionThe process of hydraulic action occurs when waves pound on cracks in rocks.First, a wave fills a crack with water.Another wave forces more water into the crack.This pressure causes the crack to get bigger.Eventually, the rock breaks apart into smaller pieces that are further eroded by waves.
25 Wave Erosion and Deposition Abrasion also breaks up rocks into smaller pieces. The sediment carried by waves acts like sandpaper, rubbing away at the rocks.Sand is continuously eroded and deposited along the shore by waves and currents.
26 Wave Erosion and Deposition Longshore drift is the process that moves sand along a shore.Currents move large amounts of sediment parallel to the shore. When these currents meet a bend in the shoreline, they slow down and deposit the sediment. This deposit is called a spit.
27 Wave Erosion and Deposition Longshore drift can carry sediment great distances along the shore, creating long sandbars or spits that grow parallel to the shoreline.Movement of sand grainsDirection of longshore drift
28 Wave Erosion and Deposition Deposition by Currents and WavesThe sediment that is eroded from a coastline or brought to the ocean by rivers is also deposited.Currents and waves deposit sediment in bays and inlets as the water slows down.
29 Wave Erosion and Deposition A shoreline covered with sand or other sediment is a beach.In many areas, rivers that discharge into the ocean are the main source of the sand on ocean beaches.
30 Which of the following increases with depth in the ocean? Assessment QuestionsWhich of the following increases with depth in the ocean?temperaturepressurelighterosion
31 Which of the following increases with depth in the ocean? Assessment QuestionsWhich of the following increases with depth in the ocean?temperaturepressurelighterosion ANS: B
32 What causes surface currents? Assessment QuestionsWhat causes surface currents?convection currentsplate tectonic movementdifferences in densitywind
33 What causes surface currents? Assessment QuestionsWhat causes surface currents?convection currentsplate tectonic movementdifferences in densitywind ANS: D
34 Assessment QuestionsHydraulic action is the process that moves sand along a shore. True False
35 Assessment QuestionsHydraulic action is the process that moves sand along a shore. True FalseANS: F, Longshore drift