Download Exploring the Ocean 2014

Chapter 13
Chapter 13
Section 1
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
Chapter 13
Section 1 Earth’s Oceans
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 Earth’s
surface and the first
oceans began to form.
How Did the Oceans Form?, continued
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.
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. Slowmoving bodies of water
have higher salinity than
other parts of the ocean
do.
Ocean Salinity
Salinity varies in different parts of the ocean
because of variations in evaporation,
circulation, and freshwater inflow.
Ocean Water and
Density
 Salt water is
denser than
fresh water.
 Cold water is
denser than
warm water.
 Water of
different
densities will not
mix easily.
In the resort town of Skagen you can watch
an amazing natural phenomenon. This city is
the northernmost point of Denmark, where
the Baltic and North Seas meet. The two
opposing tides in this place can not merge
because they have different densities.
Characteristics of Ocean Water, continued
further
• Temperature Zones The temperature of ocean
water decreases as depth increases.
• Zones based on the amount of temperature
change.
• Thermocline: shows rapid temperature change.
Characteristics of Ocean Water,
continued further still
 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.
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.
 Driven by the sun.
 The ocean is an
important part of
the water cycle
because nearly all
of Earth’s water is in
the ocean.
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.
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 without 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.
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.
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 1900’s thought the ocean
floor was flat, covered with layers of sediments washed
in from the land.
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.
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,
the quicker the echo
returns.
Studying the Ocean Floor
 Seeing by Sonar Scientists
use sonar to determine the
ocean’s 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 ocean’s surface.
Ocean Floor Mapping with Sonar
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.
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.
The Ocean Floor
Trench
Mid-ocean
Ridge
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.
Continental Slope
 Steeply slanting portion
after the shelf.
 Bottom marks the edge
of the continental crust.
Turbidity Currents
 Rapid moving currents
that carry large amounts
of sediments.
 Similar to landslides on
land.
 Often cut canyons in the
continental slope.
Continental Rise
 Gentle slope at base of
continental slope
formed by
accumulation of
sediments that wash
down.
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
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 1000’s of km wide, and
over 80,000-km long.
 Passes through all the Earth’s
oceans.
Seamount
 Underwater volcanoes.
 If they reach the
surface they form
islands.
Volcanic Island Arcs
 These once underwater volcanoes grow so large
they break the surface of the ocean.
 Associated with O-O convergent boundaries.
Deep Sea
Trenches
 Deepest part of the




ocean.
Many kilometers deeper
than the surrounding
abyssal plain.
Very long (1000’s of km),
but fairly narrow (100-km
across).
Place where old crust is
being subducted back
into the mantle.
Sign of convergent
boundary.