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Ocean Floor Makeup

• The ocean floor has higher mountains, deeper canyons, and larger flatter plains. Earthquakes occur more often.

• The rocks are very different.• The crust is thinner

Edges of the Continents• The shoreline is a boundary between where the

land and the ocean meet.• The topography of the ocean floor is different

from the topography of the continents

Continental Margin

• The area where the underwater edge of a continent meets the ocean floor is called a continental margin.

• A continental margin consists of a continental shelf, a continental slope and a continental rise.

Continental shelf• The flat part of a continental margin that is

covered by shallow area of the ocean floor that extends outward from the edge of continents is called a continental shelf.

Continental shelf

• Depth of 130 meters and gets steeper• A continental shelf slopes gently from

the shoreline.• The width of the continental shelf varies.• Large mineral, oil and natural gas

deposits are found here.

Continental Slope

Continental Slope

• The steep edge of the continental shelf • At the edge of the continental shelf, the

ocean floor plunges steeply 4 to 5 kilometers.

• A continental slope marks the boundary between the crust of the continent and the crust of the ocean floor

Continental Rise

• Separating a continental slope from the ocean floor is a continental rise.

• A continental rise is made of large amount of sediments, rocks, plants and animals.

• Sometimes the sediments are carried down the slope in masses of flowing water called turbidity currents, like an underwater avalanche.

Abyssal Plain

Abyssal Plains

• Large, flat areas on the ocean floor are called abyssal plains.

• The abyssal plains are larger in the Atlantic and Indian than in the Pacific due to the deposition of sediments by large rivers.

• The Pacific Ocean has large cracks that trap sediments and result in smaller abyssal plains.

Abyssal Plains

• Abyssal plains close to the continent are made of mud, sand and silt.

• Farther out on the abyssal plains, some of them contain the remains of tiny organisms that form ooze.

• Where ocean life is not abundant, the floor of the ocean is covered with red clay

Plates• Pieces of earth’s crust along with parts of the upper

mantle are called plates.• The plates move at an average speed of several

centimeters per year-barely faster than your fingernails grow

• This is what shaped the dramatic features of the ocean, such as mountains and trenches

Seafloor Spreading• Mid ocean ridge is along

boundaries of plates that are moving apart or diverging adding a new strip of rock to the ocean floor

• Magma squeezes up through cracks

• Magma hardens• Seafloor spreading is what

produced our ocean floor• When plates come together or

converge, one plate sinks under the other

Mid Ocean Ridge

Mid Ocean Ridges

• The mid ocean ridges form an almost continuous mountain belt that extends from the Arctic Ocean down through the middle of the Atlantic Ocean around Africa into the Indian Ocean and across the Pacific Ocean , much as the line of stitches winds around a baseball.

• In the Atlantic it is called the mid-Atlantic Ridge and in the Pacific, the Pacific-Antarctica Ridge.

Formation of Mid Ocean Ridges

• Mountain ranges on land are formed when the Earth’s crust folds and is squeezed together.

• Mid ocean ridges are areas where molten material from deep within the Earth flows up to the surface and cools and forms new crust.

• Has 2 parallel chains of mountains separated by valley and trenches

Submarine Canyons

• In many areas, submarine canyons cut through a continental shelf and slope.

• They are deep, V-shaped valleys that have been cut in the rock, possibly by turbidity currents.

• The Monterey Submarine Canyon (2000 meters) is deeper than the Grand Canyon.

Rifts

• Running along the middle of the mid ocean ridges between the rows of parallel mountains are deep crevices or rifts.

• Rifts are areas of great earthquake and volcanic activity.

Trenches• Trenches are the

deepest parts of the ocean found along the edge of the ocean floor.

• Is a steep sided canyon in the ocean floor

• The Mariana Trench in the Pacific Ocean contains the deepest spot on Earth- the Challenger Deep.

Mariana Trench

• The Mariana Trench is 2, 542 km (1,580 miles) long (more than five times the length of the Grand Canyon) and 69 km (43 miles) wide

• The Challenger Deep is 11,033 meters (36,201 feet), almost 7 miles

• If Mount Everest, which is the tallest point on Earth at 8,850 meters (29,035 feet), were set in the Mariana Trench, there would still be 2,183 meters (7,166 feet or about 2 miles) of water left above it.

MarianaTrench

Seamounts and Guyots• Seamounts are underwater volcanic mountains that

rise more than 100 meters above the ocean floor. Most have been found in the Pacific Ocean.

• Some seamounts reach above the surface of the water to form islands, like the Azores in the Atlantic and the Hawaiian islands in the Pacific.

• Guyots are flat-topped seamounts.

Properties of Ocean Water

• Ocean water is a mixture of gases and solids dissolved in pure water.

• Oceanographers have found all of earth’s natural elements in seawater, though some are in extremely tiny concentrations.

Major Elements in the Ocean

• Ocean water is 96% pure water.• Chlorine (1.9) and sodium (1.1) make up the

next largest concentration of elements.• Sodium chloride is table salt.

Salinity

• Salinity describes the amount of dissolved salt in the ocean.

• Salinity is expressed in parts per thousand.• The average salinity of the ocean is 35 parts

per thousand.

Sources of Salt in the Ocean

• When volcanoes erupt, rock materials and gases, such as chlorine, spew forth.

• As rivers, streams and glaciers move over rock and soil, they dissolve salts in them, such as magnesium, sodium and potassium.

• As waves pound the shoreline, they dissolve salts from the rocks.

Gases in Ocean Water

• The most abundant gases in ocean water are nitrogen, carbon dioxide and oxygen.

• The amounts of these elements vary with depth. They are more abundant at the ocean’s surface where sunlight causes more plant life.

Temperature of Ocean Water

• Warm water holds less dissolved gas than cold water.

• When ocean water is cold, like in polar regions, it sinks and carries oxygen rich water to the ocean depths.

• As a result, fish and other animals can live in deep parts of the ocean.

Temperature of Ocean Water

• Sun is the major source of heat for the ocean.

• Motions of the ocean, such as waves and currents, mix the surface water and transfer the heat downward.

Thermocline

• The zone of rapid temperature change is called the thermocline.

• The thermocline does not occur at a certain depth.• The season and flow of ocean currents alter the

depth of the thermocline.• The thermocline exists because warm, surface water

does not mix easily with colder, denser water.

Surface Zone

• The zone where the water is mixed by waves and currents is called the surface zone.

• The surface zone extends 100-400 meters downward.• The temperature remains constant with depth.• Temperature in a surface zone changes due to

seasons and locations.

Deep Zone• The thermocline forms a transition between the

surface zone and the deep zone.• The deep zone is an area of extremely cold water

that extends from the bottom of the thermocline to depths of 4000 meters or more.

• Within the deep zone, temperatures decrease only slightly.

• At depths greater than 1500 meters, the temperature is about 4 degrees C (49 degrees F).

• The three ocean zones are not found in the polar (Arctic and Antarctica) regions since the surface waters are always cold.

Major Groups of Ocean Life• Plants and animals in the ocean are classified

into three major groups based on their habits and the depth of the water in which they live.–Plankton–Nekton–Benthos

Ocean Life- Plankton

• Plankton float at or nearthe surface wheresunlight can penetrate.• Most of the plankton are very small, such as

algae.• These organisms drift with the currents or tides.• Plankton are the main food for many larger

organisms. They account for most of the organisms in the ocean.

YT Video: The Invisible Watery World of Plankton

Ocean Life- Nekton• Whales , seals , dolphins,

squid, octopus, barracuda and other fish are all nekton.

• Nekton are free-swimming organisms that feed on other nekton as well as plankton.

• Many have adaptations enabling them to function at depths that have great pressure and no light.

Ocean Life- Benthos• Organisms that live on the

ocean floor are benthos.• The forms of these animals

include crustaceans and shell fish.

• The deep bottom environments are sparsely populated with benthos.

• Some benthos are plants that live on the ocean floor in shallow waters where sun can penetrate.

Ocean Life Zones• The plant and animal life in the ocean is affected

by several factors.– the amount of sunlight that penetrates the

ocean.– the temperature of the ocean water.–Water pressure

• The classification of the ocean into life zones is based on the conditions in the ocean. These conditions vary widely.

• The classification includes the intertidal zone, the neritic zone and open-ocean zones.

Ocean Life Zones

• Intertidal Zone (Splash Zone)• Neritic Zone (Continental Shelf)

Open Sea Zones• Bathyal Zone (Continental Slope) • Abyssal Zone (Ocean floor)

Intertidal (Splash) Zone• This region is the most

changeable in the ocean– includes estuaries.

• Anemones, crabs, clams, mussels and plants such as seaweed live here.

• They must beable to exist withoutwater for periodsof time.• They must be ableto anchor to keepfrom being washed out to sea.

Neritic ( Shelf) Zone• This zone extends to a depth of 200

meters and receives plenty of sunlight.• The water pressure is low and the

temperature and salinity stay constant.• The shallow water over the continental

shelf receives sunlight and a steady supply of nutrients washed from land into the ocean.

• Water also receives nutrients from a wind-driven process called upwelling: the rising of deeper, colder, nutrient-rich water up to the surface

• Supports more organisms than any other zone.

• Can form only in shallow tropical ocean waters

• Produce a hard material around their soft bodies

• When they die, the hard material is left behind

Coral Reefs

• Grow in cold neritic waters where the ocean has a rocky floor

Kelp Forests

Open Ocean Zones• There are two open-ocean zones: Bathyal & Abyssal

Bathyal (Slope)• The bathyal zone begins at the continental

slope and extends down about 2000 meters.• Sunlight cannot penetrate the bottom of this

zone and plants do not grow at the bottom.• Many forms of nekton, such as squid, octopus

and large whales live in this zone.

Abyssal (Ocean Floor) Zone• At a depth of about 2000

meters, the abyssal zone begins.

• The abyssal zone extends to a depth of 6000 meters.

• This zone covers the large flat plains of the ocean. No sunlight can penetrate and food is scarce. The water pressure is great.

• Most of the animals here are small.

• Many deep sea fishes produce their own light called bioluminescence.

• Located in the deep zone• Is an area in which

heated ocean water rises through the cracks of ocean floor• Chemical nutrients

in the heated water support unique organisms.

Hydrothermal Vents

Methane Cold Seeps• Located in the deep zone• The rising of methane

from marine sediment• Not actually “cold”, but

not heated like hydrothermal vents

• Provide methane, hydrogen sulfide and hydrocarbons for chemosynthetic bacteria

YT Video: Cold Seeps and Methane Hydrates

Studying the Ocean Floor• In 1872, the first expedition to explore the ocean

began when the Challenger sailed from England.• Scientists used wire to measure the ocean depth.• Scientists aboard used nets to collect animals and

plants from the ocean floor.• Special thermometers measured the temperature.

Samples of water were collected.

Present Oceanographers• Today oceanographers have modern

instruments.• Underwater cameras provide pictures of the

ocean floor. Corers bring up samples of mud and sand from the ocean bottom.

• Bathyspheres, bathscaphs and other submersibles are able to dive deep under the surface to explore

Mapping the Ocean Floor• One of the most important goals is to map the

ocean floor.• This is done by indirect methods such as echo

sounding, radar, sonar and seismographic surveys.

Echo Soundings

• All of these methods are based on the same principles.

• Energy waves are sent down to the floor are reflected and return to the surface, where they are recorded.

• Knowing the speed of sound, 1500 m per second, oceanographers can determine the depth.

• The most complete picture was gathered from information from a satellite, the Seasat, launched in 1978

Sonar• Stands for Sound

Navigation and Ranging

• Is a system that uses sound waves to calculate the distance to an object

YT Video: Scientists "See" Ocean Floor Via Sonar