Life on an Ocean Planet

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

Chapter Topic Menu
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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
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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 coast is one that can be both
  primary and secondary.

Coastal Classification
Chapter 13 Pages 13-3 to 3-5
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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
• EstuaryAn 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
  estuaries and
• Highly stratified estuaries.

Coastal Classification
Chapter 13 Pages 13-5 to 13-8
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Primary Coasts (continued)

• 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).

Coastal Classification
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Secondary Coasts

• Secondary coasts result from marine processes
  that 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.

Coastal Classification
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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 drift occurs as the current moves
  material down the coast.

Coastal Dynamics
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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.
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Beach Dynamics

• 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.

Coastal Dynamics
Chapter 13 Pages 13-13 to 13-15
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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?

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Large Scale Sand Features

• Spits form when a longshore current slows and
  cant carry as much sediment. Sand settles out of
  the water, forming the spit. (Why does the
  current slow?)
• Tombolos are 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.

Coastal Dynamics
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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
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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 deltas have strong rivers and
  mild wave and tidal action (Mississippi River
  delta).
• 2. Tide-dominated deltas occur 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
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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
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Coral Reefs
Biological Processes and Human Activity
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• Fringing reefs lie along an island or mainland
  coast.They have a fore reef the outer ocean
  side with most biological activity.
• A reef crest is the top of the reef that takes
  most of the wave energy.
• A back reef is on the land side and has less
  biological activity.

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Coral Reefs
Biological Processes and Human Activity
Chapter 13 Pages 13-21 13-22

• Barrier reefs have a similar structure as
  fringing reefs, but lie further from shore.
• A barrier reef has a lagoon between it and the
  main coast

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Coral Reefs
Biological Processes and Human Activity
Chapter 13 Pages 13-21 13-22

• 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.

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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.

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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
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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
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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.
• Jetties are 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.
• Seawalls stand 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.

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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.

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Human Activities (continued)

• Beach renourishment is 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
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