Ocean Motions

1
Ocean Motions

• Chapter 4
• Section 1
• Wave Action

2
Anticipation Guide ResultsResults prior to
learning-Pretest

• True False
• Question 1 22 1
• Question 2 6 17
• Question 3 16 7
• Question 4 21 2
• Question 5 7 16
• Question 6 18 5
• Question 7 13 10
• Question 8 18 5
• Question 9 6 17
• Question 10 18 5

3
What we think we know about Ocean Motions.

• A wave is an ocean motion.
• A wave is caused by the moon pulling with
  gravity.
• The undertow of the ocean is motion.
• Waves crash at the shore lines.
• When you go surfing the waves pushes you forward.
• The ocean is cold and big.
• If you float in the ocean the waves can take you
  to a different place.
• Waves push seashells onto the shore.
• The ocean is a vast body of water.
• The ocean is a habitat for many living things.
• The water is salt water.
• Some waves can be big and some can be small.
• Waves push a lot of sea weed to land.
• The ocean is in many places in the world.
• There is more ocean than land in the world.
• Humans use the ocean for many different things
  (fishing, boating)

4
What we want to know about ocean motions.

• How do waves form?
• How many people per year use the ocean waves for
  surfing of something like that?
• What are the shortest and tallest parts of a wave
  called?
• How do waves start?
• How long is the ocean?
• What causes waves to get bigger and/or smaller?
• Do many sea animals get pushed by the ocean to
  the shore?
• How come there are currents that carry you deeper
  into the ocean or far away from where you set
  out?
• Are most waves caused by boating in the water?
• Are the biggest waves in the deepest or the
  shallowest part of the ocean?
• Are living sea animals killed by waves?
• Do sea shells get crushed under the pressure of
  the waves?
• Why does salt get into the ocean?
• What is the tallest wave on record?
• How do tsunamis form?
• Can sea animals create waves?

5
How Waves Form?

• Waves form from the wind. The wind gives energy
  to the wave. (p. 115)
• Stronger winds create larger waves. (p. 115)
• The longer the wind blows the larger a wave will
  become.
• Waves start in the open ocean.
• During storms some waves can become larger and
  more powerful.

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6
How Do You Describe Waves?

• The highest point of the wave is called a crest.
• The lowest point of the wave is called a trough.
• The horizontal distance (left to right) is called
  the wavelength.
• The vertical distance (top to bottom or crest to
  trough) is called the wave height.
• Frequency measures how many waves go by in a
  certain amount of time.
• Most waves are 2-5 meters high in the open ocean.

7
How Waves Change Near Shore.

• Near the shore the wave height increases (gets
  taller) and the wavelength decreases (gets
  skinnier).
• Once a wave gets too tall, the crest topples
  over. (breaker)
• When the shape of a wave changes, the speed
  decreases (goes slower).
• When the wave breaks on the shore, surf is
  formed.
• The energy of the wave breaking causes the wave
  to travel onto the beach.
• When a wave first starts its called a swell.
• When the water rushes back from the shore to the
  ocean an undertow is created.

8
How Waves Affect the Shore

• 1. Longshore Drift
• Carry sand from deeper waters and forms sandbars.
  Sand is dropped as the slope of the shore goes
  up.
• Sandbar- an underwater slope in a long ridge.
• Occurs when sand grains flow in and out from the
  beach.
• The water heads toward the beach at an angle and
  then changes to be parallel to the shore.
• Rip Currents- water that flows rapidly back out
  towards sea.
• As a sandbar gets larger is starts to trap more
  and more water along the shore.
• Rip currents can be so strong that they can pull
  things back out into the ocean. (Examplehumans
  that were swimming)
• To get out of a rip current a swimmer can swim
  sideways.
• In some places water breaks through a sand bar
  and flows back out into the ocean.

9
Waves and Beach Erosion

• Wave shape a beach by eroding (wearing away) some
  of the shore and dumping it in other places.
• Waves break down rocks (cliffs and hills) into
  sand (this takes thousands of years).
• A beach is always changing.
• If you go daily you would not notice it, but if
  you go yearly you would be able to notice a
  change.

10
Reducing Erosion

• Groins- A wall made out of concrete and rocks to
  stop erosion.
• Groins increase the amount of erosion further
  down.
• Sand that is carried by the ocean piles up along
  the groin and not the shore.
• Dunes-naturally formed sand hills that are made
  stronger with dune plants.
• Roots from the plants hold down the sand and help
  stop erosion.
• Dunes can be destroyed by people, cars, or bikes.
• Barrier Beaches-natural land forms that protect
  the shore from wave.
• Wave break along the barrier beach instead of the
  land.

11
Tsunamis

• A tsunamis is caused by an underwater earthquake.
• Some tsunamis have reached 20 meters high.
• A tsunami in deep waters can be 200 kilometer or
  more long.
• Mostly occur in Alaska, Hawaii and Japan.
• The wave height increases as water the water
  piles up.

12
Anticipation Guide ResultsResults prior to
learning-Pretestand results after learning.

• True
  False Answer
• Before After Before After
• Question 1 22 23 1 0 T
• Question 2 6 1 17 22 F
• Question 3 16 22 7 1 T
• Question 4 21 18 2
  5 F
• Question 5 7 9 16 14 T
• Question 6 18 0 5 23 F
• Question 7 13 1 10 22 F
• Question 8 18 22 5
  1 T
• Question 9 6 20 17 3 T
• Question 10 18 21 5
  2 T