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The Ocean
15.1 The Composition of Seawater
Make-up
Salinity
The Composition of Seawater
Salinity is the total amount of solid material
dissolved in water.
Because the proportion of dissolved
substances in seawater is such a small
number, oceanographers typically express
salinity in parts per thousands.
Most of the salt in seawater is sodium
chloride, common table salt.
The rain that falls on the land contains some dissolved carbon dioxide from the surrounding air. This causes the
rainwater to be slightly acidic.
The rain physically breaks down the rock and the acids chemically break down the rocks. Rain then carries the
dissolved salts and minerals along as it flows. The salts in the runoff are carried to the streams and rivers and then to the
ocean. http://www.classzone.com/books/earth_science/terc/content/visualizat
ions/es1303/es1303page01.cfm?chapter_no=visualization
Many of the dissolved salts are used by organisms in the ocean and are removed from the water. Others are not used
up and are left for long periods of time where their concentrations increase over time.
Hydrothermal vents are recently-discovered features on the ocean seafloor that
contribute dissolved minerals to the oceans.
These vents are the “exit points” on the ocean floor from which sea water that has seeped into the rocks of the oceanic crust has become hotter, has dissolved some of
the minerals from the crust, and then flows back into the ocean.
http://www.youtube.com/watch?v=D69hGv
CsWgA&list=PL88CB33C02CCF3D39&index=1
Similar to the previous process, during an
underwater volcano eruption, seawater
reacts with hot rock and some minerals are
dissolved into the sea water.
http://www.youtube.com/watch?v=U5
1cY6iod3U&index=5&list=PL88CB33C02
CCF3D39
Salinity
15.1 The Composition of Seawater
Sources of Sea Salt
• Chemical weathering of rocks on the continents
is one source of elements found in seawater.
• The second major source of elements found in
seawater is from Earth’s interior.
Salts in Seawater
Natural Processes Affecting Salinity
Salinity Processes Affecting Salinity
The Composition of Seawater
• Processes that decrease salinity:
• Processes that increase salinity:
- Precipitation
- Runoff from land
- Icebergs melting
- Sea ice melting
- Evaporation
- Formation of sea ice
Ocean Temperature Variation The ocean’s surface water temperature
varies with the amount of solar radiation
received, which is primarily a function of
latitude.
The Composition of Seawater
• The thermocline is the layer of ocean water
between about 300 meters and 1000 meters where
there is a rapid change of temperature with depth.
Temperature Variation with Depth
• The thermocline is a very important structure
because it creates a barrier to marine life.
Ocean Density Variation
Density is defined as mass per unit volume.
It can be thought of as a measure of how
heavy something is for its size.
The Composition of Seawater
• Seawater density is influenced by two main
factors: salinity and temperature.
Factors Affecting Seawater Density
Aunt
Patty
Seldom
Ate
Inchworms
What?
The 5 Oceans on Earth
Atlantic
Southern
Artic
Indian
Pacific
The 5 Oceans on Earth
Fun Fact about the 5 Oceans
Atlantic
Southern
Artic
Pacific
Indian
Create a mnemonic sequencing the oceans from largest to smallest
Variations in Ocean
Surface Temperature