Properties of Ocean WaterProperties of Ocean Water

Chapter 17

How do we learn about the ocean floor?

How do we learn about the ocean floor?

• Echo sounding – sound waves are sent down from a ship, hit the ocean floor, and return to the ship• Measure the time it takes for a round trip and

you can calculate the depth

• Sound travels at 1500 meters per second

• Watch out for round trip times!

How do we learn about the ocean floor?

How do we learn about the ocean floor?

• Direct Observation• Mini-submarines like Alvin

• Drawback – too much time going up and down

Origin of the OceansOrigin of the Oceans

1. Many Volcanoes Erupted.

2. They released gases, including water vapor.

3. The vapor condensed into liquid water.

4. The water rained from the sky and collected in large basins, forming the oceans.

Ocean FormationOcean Formation

Water Condenses

Water vaporreleased

Rain

SalinitySalinity

• Dissolved salts give ocean water a property called salinity. 100 x

waterof mass

salt of mass Salinity %

100 x waterof mass

salt of mass Salinity %

SalinitySalinity

• High salinity occurs:• In regions of high evaporation• In regions of low rainfall

• Low salinity occurs:• Where rivers flow into oceans (Estuaries)• In regions of high rainfall• In regions with melting ice

TemperatureTemperature

• Only the top of the ocean is directly warmed by the sun. (Mixed Layer)

• Downward to a depth of 300 m.

TemperatureTemperature

• Just below this surface zone, the water temperature changes rapidly.

• This zone of rapid change is called a thermocline.

TemperatureTemperature

• Below a thermocline, most of the water is about the same cold temperature

• This layer is called the “Bottom Layer”

DensityDensity

• High-salinity water is more dense than low-salinity water.• Why?

• Salt is heavy

• Cold water is more dense than warm water.• Why?

• Molecules are closer together