Chapter 13 Exploring the Oceans

I. Earth’s Oceans A. 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 Ocean 4. 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 Water 1. 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 zones a. 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 zones c. 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 Floor A. 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 Floor 1. 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 ocean ii. 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 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 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

Life in the Ocean A. The Three Groups of Marine Life 1. Plankton Organisms that float or drift freely near the ocean’s surface Most are microscopic a. Phytoplankton - plantlike b. 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 blacksmokers 5. 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 depths 1. 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 Ocean A. 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 Resources 1. 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 tides a. As the tide rises, water enters a bay behind a dam b. The gate of the dam closes at high tide c. The tide lowers d. 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 Pollution A. 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 site 1. 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