2. Ocean Water is constantly in motion, powered by many different forces: Winds, Density differences, etc.

3. Winds generate surface currents which influence coastal climate. Winds produce waves, which carry energy to distant shores where their impact erodes the land.

4. Ocean currents are masses of ocean water that flow from one place to another. Currents can be surface level or deep below.

5. The creation of the currents can be simple or complex. In all cases, however, the currents that are generated involve water masses in motion.

6. Surface currents are movements of water that flow horizontally in the upper part of the ocean’s surface.

7. Surface currents develop from friction between the ocean and the wind that blows across its surface.

8. Some currents do not last long and only affect small areas. These water movements are responses to local or seasonal influences.

9. Other currents are more permanent and extend over large portions of the ocean. These are related to the general circulation of the atmosphere.

10. Huge circular-moving current systems within an ocean basin that dominate the surfaces of the ocean.

11. There are five main ocean gyres: North Pacific South Pacific North Atlantic South Atlantic Indian Ocean

12. Another factor that influences the movement of ocean waters is the Coriolis Effect.

13. The Coriolis Effect is the deflection of currents away from their original course as a result of Earth’s rotation.

14. Because of Earth’s rotation, currents are deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

15. The two different deflections from the Coriolis Effect is why currents in the south rotate differently from that of the north.

16. There are four main currents within each gyre. The tracking of floating objects reveal that it takes about six years to go all the way around the loop.

17. Why do gyres in the Northern Hemisphere flow in the opposite direction of gyres in the Southern Hemisphere?

18. When currents from low-latitude regions move into higher latitudes, they transfer heat from warmer to cooler areas on the Earth.

19. The Gulf Stream, a warm water current brings water from the equator up to the North Atlantic.

20. This warmer water allows Great Britain and northwestern Europe to be warmer than one would expect.

21. The effects of the warm water currents are felt most in mid latitudes in winter. The influence of cold currents are felt most in the tropics during the summer months.

22. As cold water currents travel toward the equator, they help moderate the warm temperatures of adjacent land areas.

23. Ocean currents play a major role in maintaining Earth’s heat balance. They transfer heat from the tropics to the cold polar regions.

24. Ocean water movement accounts for about a quarter of the heat transport. Winds account for the remaining three quarters.

25. Winds can also cause vertical movements. Upwelling is the rising of the cold water from deeper layers to replace warmer surface water.

26. Upwelling is a common wind-induced vertical movement.

27. One type of upwelling, called coastal upwelling, is most characteristic along the west coasts of continents, such as California, western South America, and West Africa.

28. Coastal upwelling occurs when winds blow toward the equator and parallel to the coast.

29. Coastal winds combined with the Coriolis Effect cause surface water to move away from the shore. As the surface layer moves away from the coast, it is replaced with water from below.

30. The slow upward movement of water from depths of 50 to 300 meters brings water that is cooler than the original surface water.

31. Upwelling brings greater concentrations of dissolved nutrients, such as nitrates and phosphates, to the ocean surface.

32. The nutrients from upwelling promote the growth of microscopic plankton, which in turn support extensive populations of fish.

33. What is upwelling?

34. In contrast to horizontal movement of surface currents, deep-ocean circulation has a significant vertical component.

35. The vertical component of deep-ocean currents accounts for the through mixing of deep-water masses.

36. Density currents are vertical currents of ocean water that results from density differences of water.

37. An increase in seawater density can be caused by a decrease in temperature or an increase in salinity.

38. Density changes due to salinity variations are important in very high latitudes, where water temperature remains low and relatively constant.

39. Most water involved in deep-ocean density currents begins in high latitudes at the surface. When this water becomes dense enough it sinks, where its temperature and salinity remain largely unchanged.

40. By knowing the temperature, salinity, and density of a water mass, scientists are able to map the slow circulation of the water mass through the ocean.

41. Near Antarctica, surface conditions create the highest density water in the world. This cold, salty water sinks to the sea floor, where it moves throughout the ocean basins in slow currents.

42. After sinking from the ocean surface, deeps waters will not reappear at the surface for an average of 500 to 2000 years.

43. These currents can also result from increased salinity of ocean water due to evaporation.

44. One example of evaporation causing a density current is when Mediterranean waters, which have a salinity of 38 ‰, flow into the Atlantic, salinity of 35 ‰.

45. A simplified model of ocean circulation is similar to a conveyor belt that travels from the Atlantic Ocean through the Indian and Pacific oceans and back again.

46. In the conveyor belt model, warm water in the ocean’s upper layers flows toward the poles. When water reaches the poles it cools and drops to the bottom of the ocean.

47. The water returns to the equator, as cold, deep water that eventually upwells to complete the circuit.

48. As the conveyor belt moves around the globe, it influences global climate by converting warm water to cold water and releasing heat to the atmosphere.

49. Describe what the “Conveyor Belt” is.

50. Waves created by storms release energy when they crash along the shoreline. Sometimes this energy can be harnessed and used to generate electricity.

51. Ocean waves are energy traveling along the boundary between ocean and atmosphere. Waves can transfer energy from a storm far out at sea over distances of several thousand kilometers.

52. The power of waves is noticeable along the shore, the area between land and sea where waves are constantly rolling in and breaking.

53. Some waves can be low and gentle, others can be are powerful as they pound the shore.

54. When observing waves, remember that you are watching energy travel through a medium, in this case water.

55. Most ocean waves obtain their energy and motion from the wind.

56. When a breeze is less than 3 km/hr, only small waves appear. At greater wind speeds, more stable waves gradually form and advance with the wind.

57. Crest—The high point on a wave Trough—The low point on a wave Wave Height—The vertical distance between trough and crest

58. Wave Length—The horizontal distance between two successive troughs/crests Wave Period—The time it takes one full wave to pass a fixed position.

60. The height, length, and period that are eventually achieved by a wave depend on three factors: (1) wind speed (2) length of time wind has blown (3) Fetch

61. Fetch—The distance that the wave has travelled in the open water.

62. As the quantity of energy transferred from the wind to the water increases, both the height and steepness of the wave increases.

63. If enough energy is transferred into the wave, a critical point is reached where waves grow so tall that they topple over, forming breakers called whitecaps.

64. Waves can travel great distances across ocean basins. Waves were once tracked that formed in Antarctica, went through the Pacific Ocean.

65. After traveling through the Pacific Ocean for more than 10,000 km, the waves finally expended their energy a week later along the shoreline of the Aleutian Islands of Alaska.

66. The water itself does not travel the entire distance, but the wave does. As the wave travels, the water particles pass the energy by moving in a circle.

67. Observations of a floating object reveals that it moves not only up and down but also slightly forward and backward with each successive wave.

68. Circular orbital motion allows energy to move forward through the water while the individual water particles that transmit the wave move around in a circle.

69. The energy transmitted to a wave also is transmitted downward, where the circular motion diminishes until the movement of water particles becomes negligible.

70. As long as a wave is in deep water, it is unaffected by water depth. As a wave approaches shore the water becomes shallower and influences the wave behavior.

71. The wave begins to “feel bottom” at a water depth equal to half of its wavelength. Such depths interfere with the water movement as the wave slows its advance at the bottom.

72. As the wave advances toward the shore, the faster moving trailing waves catches up and decreases the wavelength and speed of the wave.

73. As the speed and length of the wave decrease the waves grows higher. A critical point is reached when the wave is too steep to support itself, and the wave front collapses.

74. The turbulent water created by breaking waves is called surf. The turbulent sheet of water from collapsing breakers, called swash, moves up the beach, then recedes back after it expends its energy

77. Tides are daily changes in the elevation of the ocean surface. Their rhythmic rise and fall along coastlines have been noted throughout history.

78. Although known for centuries, tides were not well explained until Sir Isaac Newton applied the law of universal gravitation to them.

79. Newton showed that any two bodies are attracted to each other, and because the oceans and atmosphere are fluids, free to move, both are changed by this force.

80. Ocean tides result from the gravitational attraction exerted upon the Earth by the moon and, to a lesser extent, by the sun.

81. The primary body that influences the tides is the moon, which makes one complete revolution around Earth every 29.5 days.

82. The sun also influences the tides, but much less so than the moon. The sun’s tide-generating effect is only about 46 % that of the moon’s

83. The force that produces tides on Earth is gravity. Gravity is the force that attracts the Earth and the moon to each other.

84. On the side of the Earth closest to the moon, the force of gravity is greater. At this time, water is pulled in the direction of the moon and produces a tidal bulge.

85. On the far side of the Earth, farthest from the moon, water is pulled from the Earth causing an equal bulge on the other side of the Earth, opposite the moon.

86. Because the position of the moon changes only moderately in a single day, the tidal bulges remain in place and the Earth rotates through them.

87. As the Earth rotates, the bulges produce high tide, and the troughs produce low tide. Most places on Earth experience 2 high tide times, and 2 low tide times.

88. Although the sun is farther away from the Earth than the moon, the gravitational attraction does play a role in producing tides.

89. The sun’s influence produces smaller tidal bulges on Earth. The influence of the sun on tides is most noticeable near the times of the full moon, and new moon.

90. During the new and full moon phases the sun, Earth, and moon are aligned, and their forces are added together. The combined forces result in higher high tides and lower low tides.

91. The tidal range is the difference in height between successive high and low tides.

92. Spring Tides are tides that have the greatest tidal range due to the alignment of the Earth, moon, and sun. They are experienced during new and full moons.

93. During first and third quarter moons, the sun and moon act at right angles of each other. The gravitational influence of the two bodies partially offset each other.

94. Neap Tides are the low tides near first and third quarter moons. Each month there are two spring tides and two neap tides, each one about one week apart.

96. What is the difference between neap tides and spring tides? How are each formed?

97. Beaches and shorelines are constantly undergoing changes as the force of waves and currents act on them.

98. A beach is the accumulation of sediment found along the shore of a lake or ocean. They are composed of whatever sediment is locally available.

99. Beaches may be made of mineral particles from erosion of beach cliffs or coastal mountains. This sediment may be relatively coarse in texture.

100. Some beaches have a significant biological component. Southern Florida beaches are composed of shell fragments and remains of organisms.

101. The sediment that makes up beaches doesn’t stay in one place. Waves are constantly moving the sediments.

102. Waves along the shoreline are constantly eroding, transporting, and depositing sediment. Many types of shoreline features can result from this activity.

103. During calm weather, wave action is minimal. During storms waves are capable of causing much erosion.

104. Each breaking wave may hurl thousands of tons of water against the land, sometimes causing the ground to tremble.

105. Cracks and crevices are quickly opened in cliffs, coastal structures, etc. Water is forced into every opening, causing air in the cracks to become highly compressed.

106. As the wave subsides, the air expands rapidly. The expanding air dislodges rock fragments and enlarges and extends preexisting fractures.

107. In addition to erosion caused by wave impact and pressure, erosion by abrasion is also important.

108. Abrasion is the sawing and grinding action of rock fragments in the water. Smooth, rounded stones and pebbles along the shore are evidence of continual grinding.

109. Waves are very effective at breaking down rock material and supplying sand to beaches.

110. Wave refraction, the bending of waves, plays an important part of shoreline processes.

111. Wave refraction affects the distribution of energy along the shore. It strongly influences where and to what degree erosion, sediment transport, and deposition takes place.

112. Waves seldom approach the shore at right angles. Most waves move toward the shore at a slight angle.

113. When they reach the shallow waters, of the smoothly sloping bottom, the wave crests are bent or refracted, and tend to line up nearly parallel to the shore.

114. The waves bend because as the wave approaches the shore the shallower bottom slows down that part of the wave, while the other part of the wave continues at full speed.

115. The change in speed causes the wave crests to become nearly parallel to the shore regardless of their original orientation.

116. Because of refraction, wave energy is concentrated against the sides and ends of headlands that project into the water, whereas wave action is weakened in bays.

117. As the waves enter into bays they reach the shallower areas near the headlands, and wave energy is concentrated more there than in the adjacent bays.

118. The refraction leads to erosion of the headlands, and deposition of sediments and the formation of sandy beaches in the bays.

119. Although waves are refracted, most still reach the shore at a slight angle. These angled waves produce currents with the surf zone.

120. The current flow parallel to the shore move large amounts of sediment along the shore. This type of current is called longshore current.

121. Turbulence in the surf zone allows longshore currents to easily move the fine suspended sand and to roll larger sand and gravel particles along the bottom.

122. Longshore currents can change direction because the direction that waves approach the beach changes with the seasons.

123. Longshore currents generally flow southward along both the Atlantic and Pacific shores of the United States.

124. What is wave refraction? What causes longshore currents?

125. An assortment of shoreline features can be seen along the worlds coasts.

126. The shoreline features vary depending on the type of exposed rock, the intensity of the waves, the nature of coastal currents, and what the coast is doing (stable, sinking, or rising)

127. Shoreline features that originate primarily from the work of erosion are called erosional features.

128. Sediment that is transported along the shore and deposited in areas where energy is low produce depositional features.

129. Many coastal landforms owe their origin to erosional processes. Such erosional features are common along the rugged irregular New England coast and steep shorelines of Western US.

130. Wave-cut cliffs result from the cutting action of the surf against the base of coastal land.

131. As the erosion progresses on the wave-cut cliffs, rocks that overhang the notch at the base of the cliff crumble into the surf, and the cliff retreats.

132. A relatively flat bench like structure, called a wave-cut platform, is left behind by the receding cliff.

133. The platform broadens as the wave attacks continue. Some debris produced by the waves remains along the water’s edge as sediment on the beach, as the rest is transported further out.

134. Headlands that extend into the sea are vigorously attacked by the waves because of refraction. The surf erodes the rock selectively and wears away the softer rock at the fastest rate.

135. At first, sea caves may form. When two sea caves from opposite sides of a headland meet, a sea arch results.

136. Eventually, the arch falls in, leaving an isolated remnant, or sea stack, on the wave-cut platform.

137. Beach shore of a body of water that is covered in sand, gravel, or other larger sediments.

138. Sediment eroded from the beach is transported along the shore and deposited in areas where wave energy is low. These processes produce a variety of depositional features.

139. Where longshore currents are active, several features related to the movement of sediment along the shore may develop.

140. A spit is an elongated ridge of sand that projects from the land into the mouth of an adjacent bay.

141. Often the end of a spit hooks landward in response to the dominant direction of the longshore current.

142. Baymouth bar is a sandbar that completely crosses a bay, sealing it off from the open ocean.

143. Bars tend to form across bays where currents are weak. This weak current allows a spit to extend to the other side and form a baymouth bar.

144. A tombolo is a ridge of sand that connects an island to the mainland or to another island. A tombolo forms in much the same way as a spit.

145. The Atlantic and Gulf Coastal Plains are relatively flat and slope gently seaward. The shore in these areas are characterized by barrier islands.

146. Barrier Islands are narrow sandbars parallel to, but separate from, the coast at distances from 3 to 30 km offshore.

147. From Cape Cod, Massachusetts, to Padre Islands, Texas, nearly 300 barrier islands rim the coast.

148. Some barrier islands begun as spits, that were later cut off from the mainland by wave erosion or by the general rise in sea level following the last glacial period.

149. Other barrier islands were created when turbulent waters in the line of breakers heaped up sand that had been scoured from the ocean bottom.

150. Other barrier islands may be former sand-dune ridges that began along the shore during the last glacial period, when sea level was lower. As the ice melted, sea level rose and flooded the area behind the islands.

151. Shorelines change rapidly in response to natural forces. Storms are capable of eroding beaches and cliffs at rates that far exceed long-term average erosion.

152. The bursts of erosion from storms effect the natural evolution of the coast and have a profound impact on people who reside in coastal areas.

153. Erosion along the coast causes significant property damage. Huge sums of money are spent anually to prevent erosion.

154. Groins, breakwaters, and seawalls are some structures built to protect a coast from erosion or to prevent the movement of sand along a beach.

155. Groins, barrier built at a right angle to a beach, are sometimes constructed to maintain or widen beaches that are losing sand.

156. A breakwater, protective structure built parallel to the shore, protects boats form the force of large breaking waves by creating a quiet water zone near the shore.

157. A seawall, designed to shield the coast and defend property from the forces of breaking waves, reduces energy of waves moving across an open beach, by reflecting the waves seaward.

158. Protective structures are often only temporary solutions. The structures themselves interfere with natural processes of erosion and deposition.

159. As structures are built, often new structures need to be built to counteract the new problems that arise. Scientists feel using these structures are more harmful than good.

160. Beach nourishment is the addition of large quantities of sand to the beach system.

161. Beach nourishment is an attempt to stabilize the shore without building protective structures. By building the beach seaward, both beach quality, and storm protection are improved.

162. The same processes that removed the sand in the first place will eventually wash away the replacement sand as well.

163. Beach nourishment can be very expensive, due to the massive amount of sand that needs to be transported. Beach nourishment can have detrimental effects, as well.

164. In Hawaii they replaced the natural coarse beach sand with softer muddier sand, which resulted in increased cloudiness, which killed the offshore coral reefs.

165. How do sea arches form? What is a barrier island?