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Exploring the Oceans

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Most scientists prior to the 1900's thought the ocean floor ... Surface Temperature Changes Surface-zone temperatures vary with latitude and the time of year. ... – PowerPoint PPT presentation

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Title: Exploring the Oceans


1
Exploring the Oceans
  • Chapter 13

2
The Earths Oceans
  • Chapter 13
  • Section 1

3
Divisions of the Global Ocean
  • The largest ocean is the Pacific Ocean.
  • The other oceans, listed from largest to
    smallest, are
  • Atlantic Ocean
  • Indian Ocean
  • Southern Ocean
  • Arctic Ocean

4
Section 1 Earths Oceans
Chapter 13
5
How Did the Oceans Form?
  • About 4.5 billion years ago, there were no
    oceans.
  • Sometime before 4 billion years ago, water vapor
    in the atmosphere condensed and fell as rain.
  • The rain filled the deeper levels of Earths
    surface and the first oceans began to form.

6
How Did the Oceans Form?, continued
7
Exploring the Ocean Floor
  • Until recently, the ocean floor was unexplored.
  • The darkness, cold, and extreme pressure required
    new technology.
  • Most scientists prior to the 1900s thought the
    ocean floor was flat, covered with layers of
    sediments washed in from the land.

8
HMS Challenger
  • First dedicated exploration of the oceans (1872).
  • Used a weighted line to find the depth of the
    water as they sailed.
  • Slow and inaccurate, but it gave scientists an
    idea of the ocean floor.

9
Sonar
  • Sound Navigation and Ranging.
  • Invented in WWI to hunt submarines.
  • Sound is bounced off the ocean floor to find the
    depth.
  • The closer the bottom is, to quicker the echo
    returns.

10
Studying the Ocean Floor
  • Seeing by Sonar Scientists use sonar to
    determine the oceans depth.
  • Oceanography via Satellite Scientists use
    images from the satellite Seasat to study ocean
    currents.
  • Studying the Ocean with Geosat Scientists use
    the Geosat satellite to measure slight changes in
    the height of the oceans surface.

11
Ocean Floor Mapping with Sonar
12
Revealing the Ocean Floor
  • Regions of the Ocean Floor The two regions of
    the ocean floor are the continental margin and
    the deep-ocean basin.
  • Underwater Real Estate The continental margin
    and the deep-ocean basin are subdivided into
    different areas and have different features, as
    shown on the next two slides.

13
Submersibles
  • Specially designed submarines used by scientists
    to explore more than 1-km below the surface.
  • Thick metal hulls protect the scientists from
    being crushed by the immense pressure.

14
The Ocean Floor
Mid-ocean Ridge
Trench
15
Continental Shelf
  • Gently sloping, shallow part of ocean floor that
    extends outward from the continent.
  • Varies from a few kilometers to over 1300-km from
    shore.
  • Provides nutrient rich home to large numbers of
    fish.

16
Continental Slope
  • Steeply slanting portion after the shelf.
  • Bottom marks the edge of the continental crust.

17
Turbidity Currents
  • Rapid moving currents that carry large amounts of
    sediments.
  • Similar to landslides on land.
  • Often cut canyons in the continental slope.

18
Continental Rise
  • Gentle slope at base of continental slope formed
    by accumulation of sediments that wash down.

19
Abyssal Plain
  • Smooth parts of the deep ocean floor.
  • Covered with fine grained muddy sediments (silt).
  • Cover large areas of the ocean floor.

Mid-ocean ridge
20
Mid-ocean Ridge
  • Divergent boundary underwater, where new crust is
    being formed from magma deep in the mantle.
  • Form underwater mountain ranges that seldom break
    the surface.
  • Can be 1000s of km wide, and over 80,000-km
    long.
  • Passes through all the Earths oceans.

21
Seamount
  • Underwater volcanoes.
  • If they reach the surface they form islands.

22
Volcanic Island
  • These once underwater volcanoes grow so large
    they break the surface of the ocean.

23
Deep SeaTrenches
  • Deepest part of the ocean.
  • Many kilometers deeper than the surrounding
    abyssal plain.
  • Very long (1000s of km), but fairly narrow
    (100-km across).
  • Place where old crust is being subducted back
    into the mantle.

24
Characteristics of Ocean Water
  • Dissolved Gases Nitrogen, oxygen, and carbon
    dioxide are the main gases dissolved in ocean
    water.
  • Solids Sodium chloride, or table salt, is the
    most abundant dissolved solid in the ocean. Other
    solids are also found in ocean water.
  • Ocean water is 3.5 salt.

25
Characteristics of Ocean Water, continued
  • Salinity is a measure of the amount of dissolved
    salts in a given amount of liquid.
  • Changes in Salinity Climate and water movement
    affect salinity. Coastal water in cool, humid
    places has a low salinity. Slow-moving bodies of
    water have higher salinity than other parts of
    the ocean do.

26
Ocean Salinity
Salinity varies in different parts of the ocean
because of variations in evaporation,
circulation, and freshwater inflow.
27
Characteristics of Ocean Water, continued
  • Temperature Zones The temperature of ocean water
    decreases as depth increases.
  • Zones based on the amount of temperature change.
  • Thermocline shows rapid temperature change.

28
Characteristics of Ocean Water, continued
  • Surface Temperature Changes Surface-zone
    temperatures vary with latitude and the time of
    year.
  • Surface temperatures range from 1ºC near the
    poles to about 24 ºC near the equator.
  • The surface zone is heated more in the summer.

29
The Ocean and the Water Cycle
  • The water cycle is the continuous movement of
    water from the ocean to the atmosphere to the
    land and back to the ocean.
  • The ocean is an important part of the water
    cycle because nearly all of Earths water is in
    the ocean.

30
A Global Thermostat
  • The ocean regulates atmospheric temperatures.
  • A Thermal Exchange The ocean absorbs and
    releases thermal energy much more slowly than dry
    land does.
  • The circulation of warm water causes some
    coastal lands to have warmer climates than they
    would have with the currents.
  • Ocean currents moderate the temperature of the
    planet by carrying warm water from the equator to
    the poles.

The Gulf Stream moderates the climate of Northern
Europe, making England and Scandinavia warmer
than you would expect from their latitude.
31
Oceans and Pressure
  • As you increase depth the pressure increases.
  • Increases at a rate of 10 times the air pressure
    at sea level per 100 meters of depth.
  • Humans can safely dive to about 40 meters.
  • Modern submarines can safely dive to only about
    600 meters (0.6-km).
  • The average ocean depth is 3.8-km.

32
Oceans and Sunlight
  • Sunlight will barely reach 150-m deep into the
    ocean.
  • Below this it is always dark as night.
  • Since plankton need sunlight, most sea life will
    be in this first 150 meters.
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