chapter 13 exploring the oceans. i. earth’s oceans a. global ocean contains most of the water that...

Chapter 13Exploring the Oceans

I. Earth’s OceansA. Global Ocean• Contains most of the water that covers 71% of

the Earth• Divided by the continents into five main oceans

1. Pacific Ocean- Largest ocean- Flows between Asia and the Americas

2. Atlantic Ocean- Second largest ocean; half the volume of the Pacific- Flows between the Americas and Africa

3. Indian Ocean4. Southern Ocean

- Extends from the coast of Antarctica to 60° south latitude

5. Arctic Ocean- Smallest ocean- Much of its surface is covered by ice

B. How Did the Oceans Form?• 4.5 billion years ago, there were no oceans• Volcanoes spewed lava, ash, and gases• Volcanic gases formed Earth’s atmosphere and

caused temperatures to decrease by blocking the sun• Earth cooled enough for water vapor to condense

and fall as rain

•When all the landmasses were collected into Pangia, the surrounding ocean was called Panthalassa• As Pangaea broke apart, the North Atlantic and

Indian Ocean began to form

C. Characteristics of Ocean Water1. Salty• Sodium chloride (NaCl) – same salt you

flavor food with

2. Salinity• The amount of dissolved solids in a given

amount of liquid• Places with hotter, drier climates typically have

a higher salinity because heat increases the evaporation rate• Places with cooler, more humid climates

typically have a lower salinity• Slow-moving areas of water develop high

salinity

3. Temperature Zones• Temperature decreases as depth

increases•Water can be divided into three

zonesa. Surface Zone

- warm, top layer- Can extend to 300m below

sea level- Sunlight heats the top 100m

and surface currents mix the heated water with cooler water below

b. Thermocline- Can extend from 300m to about 700m below

sea level- Temperature drops faster with increased

depth than it does in the other two zonesc. Deep Zone

- Extends from the bottom of the thermocline to the bottom of the ocean

- Temps range from 1°C to 3°C

D. The Water Cycle• A continuous movement of water from the

ocean to the atmosphere to the land and back to the ocean

1. Evaporation- Sun heats liquid water, causing it to rise into

the atmosphere as water vapor

2. Condensation- Water vapor in the atmosphere cools and

interacts with dust particles- Water vapor eventually turns to liquid water

3. Precipitation•Water droplets eventually become heavy

enough and fall back to Earth’s surface as precipitation

E. A Global Thermostat•Water has a high specific heat

- It takes a lot of energy to raise the temperature of a large body of water by 1°C

- It also has to release a lot of energy for the temperature to drop

• Dry land has a low specific heat- Land can change temperature quicker than

water because it does not require as much energy

• Air temperature remains steady due to the thermal energy between the ocean and the atmosphere• The air temperature would change drastically if

land made up a larger percentage of Earth’s cover (>30%)

II. The Ocean FloorA. Studying the Ocean Floor• Sending people to the ocean floor can be

risky so other method’s of surveying it from above water are needed

1. Seeing by Sonar- Sonar stands for Sound Navigation

And Ranging- Sound pulses from a ship are sent

down into the ocean- The sound moves through the

water, bounces off the ocean floor, and returns to the ship

- The deeper the water is, the longer the round trip

- The travel time is divided by two and then multiplied by the speed of sound (1,500 m/s)

2. Oceanography via Satellite- Seasat allowed scientists to measure the

direction and speed of ocean currents-Geosat measures slight changes in the height

of the ocean’s surface

B. Revealing the Ocean Floor1. Regions of the Ocean Floor

a. Continental Margin•Made of continental crust• Consists of the continental shelf, the

continental slope, and continental rise

i. Continental Shelf- Begins at the shoreline and slopes gently

toward the open oceanii. Continental slope

- Begins at the edge of the continental shelf and continues down to the flattest part of the ocean floor

iii. Continental Rise- The boundary between the continental margin

and the deep-ocean basin lies underneath the continental rise

b. Deep-ocean basin- Made of oceanic crust- Consists of the abyssal plain, mid-ocean

ridges, rift valleys, and ocean trenches- Most of these features form near the

boundaries of Earth’s tectonic plates

i. Abyssal Plain- The broad, flat part of the deep-ocean basin

ii. Mid-ocean Ridges- Mountain chains that form where tectonic

plates pull apart and magma rises to fill in the rift zones

iii. Rift Valley- Forms between mountains in the rift zone

iv. Ocean Trenches- Form where one oceanic plate is pushed

beneath a continental plate or another oceanic plate

C. Exploring the Ocean with Underwater Vessels• Some vessels contain the air that explorers

need to breathe and all the equipment they need to study the ocean

• Exploring the deep ocean by using piloted vessels is expensive and can be very dangerous due to the extreme pressure• Robotic vessels are designed to withstand

pressures much greater than those found in the deepest parts of the ocean and are “flown” by a pilot at the surface

III. Life in the OceanA. The Three Groups of Marine Life

1. Plankton• Organisms that float or drift freely near the

ocean’s surface•Most are microscopic

a. Phytoplankton - plantlikeb. Zooplankton - animal like

2. Nekton• Organisms that swim

actively in the open ocean• Include mammals as

well as many varieties of fish

3. Benthos• Organisms that live on

or in the ocean floor

B. The Benthic Environment “Bottom Environment”1. The Intertidal Zone• Shallowest benthic zone• Located between the high-tide and low-tide

limits

2. The Sublittoral Zone• Starts at the low-tide limit and ends at the edge

of the continental shelf• The temperature, water pressure, and amount of

sunlight remain fairly constant• The kind of sediment on the ocean floor

influences where organisms live in the sublittoral zone

3. The Bathyal Zone• Extends from the edge of the continental

shelf to the abyssal plain• Plant life is scarce because of the lack of

sunlight

4. The Abyssal Zone• Largest ecological zone of the ocean• No plants and very few animals live in the

abyssal zone•Many of these organisms live around hot-water

vents called blacksmokers5. The Hadal Zone• Deepest zone that consists of the floor of the

ocean trenches

C. The Pelagic Environment• The zones near the ocean’s surface and at the

middle depths1. The Neritic Zone• Covers the continental shelf•Warm, shallow zone• Contains the largest concentration of marine

life

2. The Oceanic Zone• Covers the entire sea floor except for the

continental shelf• The water temperature is cooler and the

pressure is greater• Organisms are more spread

IV. Resources from the OceanA. Living Resources

1. Fishing the Ocean• Almost 75 million tons of fish are harvested

each year• Overfishing reduces fish populations• People have begun to raise ocean fish in fish

farms to help meet the demand

B. Nonliving Resources1. Oil and Natural Gas• Found under layers of

impermeable rock• Petroleum engineers must

drill through this rock in order to reach these resources• Seismic equipment is used

to indicate how rock layers are arranged below the ocean floor and which layers contain oil

2. Fresh Water and Desalination• Desalination is the process of removing salt

from sea water• Found in drier parts of the world such as

Saudi Arabia and Kuwait

3. Sea-Floor Minerals• Nodules of manganese, iron, copper, nickel,

and cobalt are found on the ocean floor

4. Tidal Energy• Generated from the movement

of tidesa. As the tide rises, water enters

a bay behind a damb. The gate of the dam closes at

high tidec. The tide lowersd. At low tide, the gate opens

and the water behind the dam rushes out, moving through turbines, which in turn, generates electrical energy

V. Ocean PollutionA. Nonpoint-Source Pollution• Pollution that comes from many sources

rather than just from a single site• Human activities on land can pollute

streams and rivers, which then flow into the ocean and bring the pollutants they carry with them

B. Point-Source Pollution• Pollution that comes from a specific site1. Trash Dumping

- Dumping trash in the deeper parts of the ocean

- Trash thrown into the ocean can affect the organisms that live in the ocean and those organisms that depend on the ocean for food

2. Sludge Dumping- Raw sewage, or the liquid and solid wastes

that are flushed down toilets and poured down drains

- Settles on the ocean floor but can be stirred by currents and moved closer to shore

3. Oil Spills• Large tankers that transport billions of barrels

of oil across the oceans can be disastrous• Oil spills can harm plants, animals, and

people

C. Saving Our Ocean Resources• A treaty was passed 64 countries in 1989 that

prohibits the dumping of certain metals, plastics, oil, and radioactive wastes• The U.S. has passed an act that prohibits the

dumping of any material that would affect human health or welfare, the marine environment or ecosystems, or business that depend on the ocean