Choose to view chapter section with a click on the section heading. Coastal Classification

1. Choose to view chapter section with a click on the section heading. • Coastal Classification • Coastal Dynamics • Biological Processes and Human Activity Chapter Topic Menu

2. Two Classification Systems • Without coastal dynamics, the processes that create and shape the oceans’ coastlines, history would be significantly different. • This first classification system is based on geology and processes that take place over very long periods of time. • Active Coasts: These are close to plate collisions that result in volcanic activity and earthquakes (the Ring of Fire). West Coast California • Narrow Continental shelf for active margin • Passive Coasts: These lie far away from active plate boundaries with little volcanic activity and few earthquakes. East Coast North America • Broad continental shelf – no subduction Coastal Classification Chapter 13 Pages 13-3 to 3-5

5. Two Classification Systems • Oceanographers believe that many other coastal processes occur. This second classification system is based on short-term coastal dynamics. • Primary Coasts: Formed by geologic processes not directly related to the ocean over an extended period of time. • Secondary Coasts: Formed by marine action, process takes much less time. • A combination coastis one that can be both primary and secondary. Coastal Classification Chapter 13 Pages 13-3 to 3-5

9. Primary Coasts • Scientists attribute primary coast development to nonmarine forces. These include land-based erosion (from running water, wind or land ice), sedimentation, volcanic activity and tectonic activity. • Land-based Erosion Coasts – include • fjord coasts – Glacier gougingdrowned river valleys. River flow & erosion then water backflow • Both fjord coasts and drowned river valleys can form estuaries • Estuary–An estuary is a partly enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. salt wedge estuaries, • vertically mixed estuaries,slightly stratified estuariesand • Highly stratified estuaries. Coastal Classification Chapter 13 Pages 13-5 to 13-8

17. Sedimentation Coasts– form when materials carried by rivers flow into the ocean, deposit and accumulate. Often sediments accumulated form a wide triangular shape – a delta (Nile deltain Egypt). Volcanic Coasts– formed by volcanic activity (Hawaiian Islands). Tectonic Activity Coasts– formed by tectonic activity. Primarily includes fault coasts which form as plates collide. Results when the collision uplifts the seafloor above the water surface, allowing the sea to flood the new area (Tomales Bay, California). Primary Coasts (continued) Coastal Classification Chapter 13 Pages 13-8 & 13-9

23. Secondary coasts result from marine processesthat include wave erosion, material deposited by seawater motion, and marine life. Wave-erosion Coasts– constant pounding by waves erodes and changes a coastline, wearing away land protrusions. Can result in spectacular formations like sea caves, arches and sea stacks. Marine-deposition Coasts– form when sea action causes ocean sediment to accumulate in one place. Involves ocean sediments moved by water motion in the sea. Barrier islands, beaches, salt marshes, and mud flats are all types of deposition coasts. Marine Organism Coasts– marine organisms build coasts by providing a structure that reduces the effects of waves and currents. Best known of these is the Great Barrier Reef of Australia built by coral. Secondary Coasts Coastal Classification Chapter 13 Pages 13-9 & 13-10

26. Longshore Drift • One of the most significant forces shaping the coast is longshore drift. • The tendency for materials to move along the coastline due to a longshore current. • Waves arrive on shore at somewhat of an angle, but the water recedes at nearly a 90º angle to the beach. Sand and sediment flow back with the water at this angle. The net motion of this backwash combines with the net motion imparted by the waves to cause a longshore current. • Longshore driftoccurs as the current moves material down the coast. Coastal Dynamics Chapter 13 Pages 13-12 & 13-13

27. Longshore Drift Longshore Current: This is the overall movement of the water along a beach based on the angle of wave approach and then the backwash of the water returning to the ocean. Waves do not approach the beach perfectly parallel to the shoreline. The return of the water is nearly 90 degrees to the shoreline. Longshore Drift: This is the process of when the wave breaks on the beach and due to the energy of the wave lift sediment and sand and takes it back out to the waters. Longshore Drift can cause immense beach erosion.

28. Sand comes from erosion. It may be from the effect of waves pounding the shoreline or inland erosion. In tropical regions sand also comes from biological sources, like the erosion of coral reefs. A beach is composed of three sections: 1. Foreshore – region from the high- to low-tide mark. 2. Backshore – region rarely touched by seawater. Includes dunes and grasses. 3. Offshore – beyond the low-tide terrace. Factors that shape a beach: They are grain size of beach sediments, wave energy and the degree of beach slope. Beach Dynamics Coastal Dynamics Chapter 13 Pages 13-13 to 13-15

29. Beach Dynamics • Factors that shape a beach: They are grain size of beach sediments, wave energy and the degree of beach slope. • Why is grain size important? What if I increase grain size of the sand? • Are there other factors that affect beach shape? • Can Man affect beach shape unintentionally?

30. Spitsform when a longshore current slows and can’t carry as much sediment. Sand settles out of the water, forming the spit. (Why does the current slow?) Tombolosare spits that extend between two islands or from an island to the mainland. These are actually two spits that extend and meet in the middle. Large Scale Sand Features Coastal Dynamics Chapter 13 Page 13-16

31. Large Scale Sand Features (continued) • Barrier Islands: there are currently two theories on how they form. • 1. Sediment accumulates offshore, eventually building up into an island. • 2. They were giant sand dunes that became islands with the last major sea-level rise. • Typical barrier islands share five features: • 1. Ocean beach • 2. Ocean dune • 3. Barrier flat • 4. Salt marsh • 5. Lagoon Coastal Dynamics Chapter 13 Pages 13-17 to 13-19

32. Large Scale Sand Features (continued) • Deltas: there are three types. All are developed from the sediments discharged from a river mouth accumulating and creating new nutrient rich land. • 1. River-dominated deltashave strong rivers and mild wave and tidal action (Mississippi River delta). • 2. Tide-dominated deltasoccur in areas with strong tidal changes (Essex Riverin Massachusetts). • 3. Wave-dominated deltas have significant wave energy that redistributes river sediments (Senegal delta in west Africa). Coastal Dynamics Chapter 13 Pages 13-17 to 13-19

33. Coral Reefs • Coral is perhaps the most significant of all biologicalprocesses that affect the coast. Coral reefs can be massive, but only the outside layer, the coral polyps, is alive. • Individual polyps create a calcium carbonate externalskeleton as they grow. It is this part of its structurethat creates coral reefs. Biological Processes and Human Activity Chapter 13 Pages 13-21 & 13-22

34. Coral Reefs • Fringing reefslie along an island or mainland coast.They have a fore reef – the outer ocean side with most biological activity. • A reef crestis the top of the reef that takes most of the wave energy. • A back reefis on the land side and has less biological activity. Biological Processes and Human Activity Chapter 13 Pages 13-21 & 13-22

35. Coral Reefs • Barrier reefshave a similar structure as fringing reefs, but lie further from shore. • A barrier reef has a lagoonbetween it and the main coast Biological Processes and Human Activity Chapter 13 Pages 13-21 & 13-22

36. Coral Reefs • Atolls are ring-shaped coral reefs that encircle a shallow lagoon. These are the last stages of the fringe reef and then the barrier reef. Biological Processes and Human Activity Chapter 13 Pages 13-21 & 13-22

37. Mangroves A wet, spongy area of land in tropical climates and along coastal regions that is dominated by mangrove trees and shrubs, particularly red mangroves (Rhizophora), black mangroves (Avicennia) and white mangroves (Laguncularia). • Mangrove ecosystem act as Buffer Zone between the land and sea. • Mangroves protect the coast against erosion due to wind, waves, water currents • and protect coral reefs, sea-grass bed and shipping lanes against siltation. • They are also known to absorb pollutants.

40. Plant Communities • In areas where the waves have generally low energy, plant communities can dominate the coast. • Seagrasses for example live entirely underwater, but most marine plants live partly out of the water. • Among the most important of the plant-dominated shorelines are the mangrove swamps. • Mangroves affect the coast directly by holding sediment in place and absorbing wave energy. Human Activities • There are two primary motivations for humans to modify the coastline: • 1. To create new coastal structures. • 2. To protect building and structures already on the coast from naturalcoastal changes. Biological Processes and Human Activity Chapter 13 Pages 13-23 & 13-24

41. Plant Communities Human Activities • There are two primary motivations for humans to modify the coastline: • 1. To create new coastal structures. • 2. To protect building and structures already on the coast from natural coastal changes. (How successful are man-made attempts to stop natural processes?) Biological Processes and Human Activity Chapter 13 Pages 13-23 & 13-24

42. Human Activities (continued) • Human-built coastal structures include: • Groins(No not that one)are artificial protrusions jutting out perpendicular to the shore. These may be built to create an area relatively protected from longshore current, or for recreation. • Jettiesare the same as a groin, except they are built to reinforce a harbor entrance. • Breakwaters run parallel to shore or start on shore and curve into the sea. They are used to create an artificial lagoon for use as a harbor or beach. • Seawallsstand either at the water along the shoreor at the top of a beach. They act as a barrier toblock the waves from eroding the land. Biological Processes and Human Activity Chapter 13 Pages 13-24 & 13-25

46. Human Activities (continued) • All of these man-made structures can create problems: • Jetties and groins block longshore drift. This tends to cause sand to accumulate on the upside drift and to become depleted on the downside drift. Spits may form at the top of jetties. • Seawalls effectively absorb energy but create problems at their ends. The unprotected land next to the seawall tends to suffer from increased erosion. Biological Processes and Human Activity Chapter 13 Pages 13-24 & 13-25

47. Human Activities (continued) • Beach renourishmentis the process of bringing in sand or sediment from somewhere else to replenish eroded sand. • It is expensive and is only a temporary fix as the sand beach will again erode. Taking sand from somewhere else effects that environment also and may damage biological communities. • The likely solution to problems created by human structures is a change in coastal attitudes and management. In the long run it is more effective and less costly to work with nature instead of against it. (Should we be building structures on barrier reefs or right on the beach) Biological Processes and Human Activity Chapter 13 Pages 13-24 & 13-25