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The Work of Waves

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What is the Effect of Refraction on a Coastline of Headlands and Bays? ... At end of ice age, rising sea level drowned river valleys and formed bays ... – PowerPoint PPT presentation

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Title: The Work of Waves


1
The Work of Waves
2
How do West and East Coasts Differ?
Atlantic
Gulf Coast
Why?
Differences in The landscape next to the ocean
3
What Causes Waves?
Wind
Push
Drag
4
How Does Water Move in Waves?
  • Wave form moves forward
  • Water particles move in circular orbits

5
What is the Depth of the Wave Base?
  • Wave base half a wave length
  • If wavelength 400 feet
  • Wave base 200 feet

6
Why Do Waves Break?
  • As waves approach the shore they feel bottom
  • Wave length shortens
  • Wave height increases
  • Circular motion ceases and wave falls forward

7
What is a tsunami?
  • A giant wave generated by movement of the sea
    floor
  • Generated by earthquakes or volcanoes
  • Tsunami waves reach heights of 50 feet near the
    shore
  • Travel up to 600 mph

8
Why Are Tsunami Hazardous?
  • Tsunami pile up in shallow water
  • Drown coastal property

9
How Do Waves Behave As They Approach the Shore?
10
Why Are Waves Refracted as They Approach the
Shore?
  • Waves slow down and bend in shallow water off
    headlands
  • Faster waves continue into the bay

11
What is the Effect of Refraction on a Coastline
of Headlands and Bays?
  • Wave energy erodes headlands
  • Sediments eroded from headlands are deposited in
    bays
  • Erosion straightens shoreline

12
Western Side of North America Coastline of
Headlands and Bays
  • At end of ice age, rising sea level drowned river
    valleys and formed bays
  • Higher land forms headlands
  • Waves attack headlands and form cliffs

13
How Do Waves Erode?
  • Hydraulic Action
  • Abrasion
  • Solution
  • Attrition

14
Softer rock form caves
  • Caves form as waves erode weak rock
  • Caves develop into arches
  • Stacks form when arches collapse

15
Cave Erode to Form arches
16
Changes Along a Shore
  • 1890
  • 1920
  • 1970

17
Point Reyes
18
Coastline of Headlands and Bays
19
Where Does Most Beach Sand Originate?
  • Rivers flowing down to the sea
  • Some erosion of cliffs

20
Why Does Sand Get Moved Along a Beach and in the
Surf Zone?
  • Most waves approach the coast at an oblique angle
  • Swash and backwash move sand up and down the
    beach in a zig-zag pattern
  • Longshore currents form in the surf zone
  • Currents move sediment parallel to the shore

21
What Coastal Features Are Formed By Longshore
Currents?
  • Longshore currents transport material across bays
  • Sandspits form across the open water of the bay
  • Eventually, sandspits grow across the bay to form
    a baymouth bar

22
Is There More Sand on the Beach at the end of the
Summer or Winter?
A
B
End of Summer
End of Winter
  • Which picture represents the end of the summer?
  • Gentle summer waves build up the beach
  • Plunging winter storm waves erode the beach

23
Barrier Island Beaches
Barrier island coasts develop where there are
  • Coastal plains next to the sea
  • Gentle offshore gradients
  • Slight tidal ranges

24
(No Transcript)
25
Barrier Beaches Dominate the Atlantic and Gulf
Coasts
  • Low-lying barrier islands are vulnerable to
    hurricanes
  • Should be left undeveloped

26
How Do Dams Affect Beaches?
  • Less sediment reaches the beach
  • Waves attack cliffs
  • Cliffs are eroded

27
What Are the Problems Presented by Sea Walls?
  • Sea walls built to protect coastal property
  • Waves bouncing back from sea walls erode sand
    away from the beach

28
  • Beach erosion continues after building on the
    shore

29
Santa Barbara Harbor
30
Groins
What is the direction of longshore transport
along this coast?
31
Can you tell the direction of longshore transport
along this coast?
32
Do you know your rivers and lakes?
33
Breakwaters
Breakwaters on Lake Erie
34
Artificial Beach Nourishment
  • Ocean City, Maryland
  • Note wider beach on left
  • Pipeline pumps sand collected offshore

35
Identify these Coastal Features
  • A
  • Tombolo
  • B
  • Seacliffs
  • C
  • Sandspit
  • D
  • Stack

36
Is America losing its beaches?
37
What is this?
  • A stack
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