2.1 Exploring the 2.1 Exploring the OceanOcean

• The water in Earth’s oceans varies in The water in Earth’s oceans varies in salinity, temperature, and depthsalinity, temperature, and depth

• The ocean is made up of salt water NOT The ocean is made up of salt water NOT fresh waterfresh water

• The ocean is made up of 96.5% water and The ocean is made up of 96.5% water and only 3.5% salt.only 3.5% salt.

• salinitysalinity – the total amount of dissolved – the total amount of dissolved salts in a sample of watersalts in a sample of water

• Sodium chloride (table salt) makes up most Sodium chloride (table salt) makes up most of the salt in ocean & sea water (85.6%) of the salt in ocean & sea water (85.6%) – chloride = 55% – sodium = 30.6%chloride = 55% – sodium = 30.6%

• There is less salinity near the surface of There is less salinity near the surface of the ocean due to the fresh water from the ocean due to the fresh water from precipitationprecipitation

• There can be more salinity on a hot day There can be more salinity on a hot day due to evaporation – salt is left behind due to evaporation – salt is left behind when the water evaporateswhen the water evaporates

• There can also be more salinity near the There can also be more salinity near the poles. Water freezes leaving the salt poles. Water freezes leaving the salt behindbehind

• Salt acts like an anti-freeze by interfering Salt acts like an anti-freeze by interfering with the formation of ice – meaning the with the formation of ice – meaning the more salt the water has, the colder it has more salt the water has, the colder it has to be in order to freeze to be in order to freeze

• Which has a higher density – salt water or Which has a higher density – salt water or fresh water?fresh water?

• Salt water has a higher density than fresh Salt water has a higher density than fresh waterwater

• Temperatures at the surface of the ocean Temperatures at the surface of the ocean vary with location and the seasonvary with location and the season

• Water near the equator is about room Water near the equator is about room temperaturetemperature

• As you travel away from the equator (in As you travel away from the equator (in either directions) the water gets coolereither directions) the water gets cooler

• Why is this?Why is this?

• Direct sunlight VS indirect sunlightDirect sunlight VS indirect sunlight

• Direct sunlight is stronger and warmer Direct sunlight is stronger and warmer than indirect sunlight than indirect sunlight

• As you descend through the ocean, the As you descend through the ocean, the water temperature decreases.water temperature decreases.

• Why?Why?

• Further away from the sun’s radiation.Further away from the sun’s radiation.

• water columnwater column – a vertical section of the – a vertical section of the ocean that lowers in temperature the ocean that lowers in temperature the deeper one goesdeeper one goes

• 3 zones in the ocean’s water column:3 zones in the ocean’s water column:1.1. surface zonesurface zone – smallest zone, near the – smallest zone, near the

surface, warmest zone, affected most by surface, warmest zone, affected most by sun and weathersun and weather

2.2. transition zonetransition zone – in the middle of surface – in the middle of surface and deep, has the greatest and most rapid and deep, has the greatest and most rapid change in temperaturechange in temperature

3.3. deep zonedeep zone – biggest zone, bottom of the – biggest zone, bottom of the ocean, coldest zoneocean, coldest zone

• As you descend through the ocean, the As you descend through the ocean, the water pressure increases.water pressure increases.

• A scuba diver can only descend 40 A scuba diver can only descend 40 meters due to the immense pressuremeters due to the immense pressure

• After 40 meters a submersible is needed After 40 meters a submersible is needed (an underwater vehicle built of material (an underwater vehicle built of material to resist pressure)to resist pressure)

• On average the ocean floor is more than On average the ocean floor is more than twice as deep as the Grand Canyon (a twice as deep as the Grand Canyon (a little less than 2 ½ miles deep).little less than 2 ½ miles deep).

• The bottom of the ocean floor is very The bottom of the ocean floor is very dark, cold, and has extreme pressure.dark, cold, and has extreme pressure.

• sonarsonar – SOund NAvigation Ranging – uses – SOund NAvigation Ranging – uses sound waves to calculate the distance to sound waves to calculate the distance to an objectan object

• sonar was used to map the bottom of the sonar was used to map the bottom of the ocean floorocean floor

• The biggest mountains in the world are The biggest mountains in the world are underwaterunderwater

• There are 6 ocean floor features that are There are 6 ocean floor features that are created due to plate movement:created due to plate movement:

• trenchtrench – a long, deep valley on the ocean – a long, deep valley on the ocean floor where old ocean crust sinks back toward floor where old ocean crust sinks back toward the mantle (example: Marianas Trench)the mantle (example: Marianas Trench)

• mid-ocean ridgesmid-ocean ridges – long chains of underwater – long chains of underwater mountains on the ocean floors – lava erupts mountains on the ocean floors – lava erupts through them and forms new ocean crustthrough them and forms new ocean crust

• seamountseamount – a volcanic mountain rising from – a volcanic mountain rising from the ocean floor that doesn’t reach the surfacethe ocean floor that doesn’t reach the surface

• What is its name once it reaches the surface?What is its name once it reaches the surface?

• Island Island

• continental slopecontinental slope – the steep edge of the – the steep edge of the continental shelfcontinental shelf

• continental shelfcontinental shelf– a shallow area that – a shallow area that extends outward from the edge of each extends outward from the edge of each contientcontient

• abyssal plainabyssal plain – a smooth, nearly flat – a smooth, nearly flat region of the ocean covered with thick region of the ocean covered with thick layers of mud and siltlayers of mud and silt