Transcript Fresh and Saltwater Systems

Fresh and Saltwater Systems
Topic 4: The Oceans
Ocean Water is Salty
• 1 Kg of sea water contains 35 g of
dissolved salts. This works out to 3.5% of
ocean water being salts.
• Salinity is a measure of how much salt is
dissolved in water. Eg. Dead Sea. Salinity
also measure in parts per trillion (PPT).
• Where does the salt come from?
Freshwater rivers and streams move salts
and earth into the sea making ocean salty.
The Ocean Floor
• Oceans make up the largest ecosystems
on Earth, however, they’re so deep we
cannot see beyond 100 m.
• To map the ocean floor scientists use
technologies such as radar and sonar that
allow them to ‘see’ the floor.
• They’ve discovered underwater mountain
ranges called ocean ridges and valleys
called ocean trenches.
• The formation of the ocean basins is due to the
movement of tectonic plates.
Continental Shelf
• Is the submerged part of a continent and
stretches out 30-300 km from the
shoreline. At the end of the shelf the land
drops down at a steep angle to meet up
with the ocean floor.
• The part of the shelf that slopes down is
called the Continental Slope. The ocean
floor is also called the abyssal plain.
Ocean Waves
• Waves are a disturbance which transmits
energy from one point to another.
• Waves are caused by winds or tsunamis.
The stronger the disturbance, the larger
the wave amplitude.
• Water travels in a circular motion in a
wave, but does not actually move from its
position.
• Storms that produce strong waves are
called storm swells.
Tsunamis
• Are massive tidal waves caused by
underground earthquakes or volcanic
eruptions. Major tsunamis occur every 515 years and can kill thousands.
• A tsunami which began off the coast of
Indonesia killed up to 230’000 people in
2004.
• A graphic of the 2004 Tsunami
Breakers
• Waves that make it all the way and break or
collapse on the shore are called breakers. These
are the waves that surfers ride on.
• HW: Worksheet questions. Use the notes and
text-book.
How Waves Change Shorelines
• The force of waves crashing against a
shoreline causes the shape of the
shoreline to change as erosion takes
place.
• The angle that waves crash against the
shore is called the longshore current.
• Beaches are only formed if there is a
gentle slope to the shore. If the rocks form
a cliff, all sand will be washed back into
the sea. No beach will be formed.
Tides
• Are the water level along the coast of a
continent. The highest point is high tide
and lowest point is low tide.
• There are two high and two low tides per
day.
• The largest tides are called spring tides
and the smallest are called neap tides.
• The difference between high and low tide
is called the tidal range.
What Causes Tides? What Causes
Currents?
• The gravitational force from the moon and the
rotation of the Earth causes tides.
• Tides in Action
• Currents are the movement of the tides. Wind
patterns determine the direction of currents.
There are 3 factors that determine the direction
of these winds:
• 1. Uneven heating of the atmosphere.
• 2. Rotation of the Earth
• 3. The position of the continents.
Current Cont’d
• If the current arrives from the poles, it will
bring colder water, if it comes from the
Equator it will bring warmer weather.
• Despite the fact that Europe and North
America inhabit the same latitudes,
Europe is traditionally warmer because it
receives currents from the equator (the
Gulf Stream) while we get currents from
the North.
Water as a Heat Reservoir
• Because water has a higher heat capacity
than earth, it can store heat produced in
the summer and release it gradually over
the winter. This explains why coastal areas
such as Vancouver tend to be more
temperate in temperature versus the
extremes in the Prairies.
• However, if cold air currents dominate in
an area the weather can still be cold in a
coastal area (the Maritimes).