bell ringer what is a continental slope and a continental shelf

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What is a continental slope What is a continental slope and a continental shelf.and a continental shelf.



Earth Science Earth Science Chapter 20Chapter 20

Earth Science Earth Science Chapter 20Chapter 20

20.1 The Water Planet20.1 The Water Planet

20.1 The Water Planet• ¾ of the earth’s surface lies submerged

beneath salt water called global ocean.• Earth alone is called the water planet.• 97 % of all the water on earth is

contained by the global ocean.• Mass of the ocean is 1/4000 of the mass

of the earth as a whole.• Volume is about 800 times greater than

the volume of water in the global ocean.

Divisions of the Global Ocean

• 3 major oceans-Atlantic, Pacific & Indian • Water at the polar regions are called

oceans.• They are really part of one of the major 3• Artic is really part of the Atlantic• Sea is a smaller area of an ocean.• Ex. Mediterranean, Caribbean, & Coral Sea

• Water in the Artic is less salty than the other oceans.

• Pacific is the largest and deepest• The 2nd is the Atlantic which contains

the Mediterranean, Caribbean, Gulf of Mexico and Baltic Sea.

• Indian is the 3rd largest and contains the Arabian and Red Sea.

Exploration of the Ocean

• Oceanography is the study of the physical characteristics, chemical, composition & life forms.

• American naval officer, Matthew Maury used records from navy ships to learn about ocean currents, winds, depths, & weather conditions.

Challenger• British Navy ship H.M.S. Challenger laid

the foundation for modern science of oceanography.

• Team crossed the big 3 oceans and collected the data of water temperatures, depth of oceans, and samples of ocean water, sediments, and 1000’s forms of marine life.

Joides Resolution• World’s largest and most sophisticated

scientific drilling ship.• Provided scientists with valuable data

about plate tectonics and the ocean floor.

• Floor is made up of continental crust and oceanic crust that lies beneath the ocean waters.

Submersibles• Underwater research vessels, that enable

oceanographers to study ocean depths.• These are referred to as submarine robots.• Jason Jr. • Perform tasks ranging from photographing

the ocean to collecting mineral samples.

Bathysphere• Spherical diving vessel that was

first used for deep-ocean exploration.

• Carried by an area of the ocean sphere, which carried scientists, but stayed connected to the research ship & life support.

Bathyscaph• Research ship self-propelled, free

moving submarine equipped for deep ocean.

• Alvin is a craft that holds a pilot and two scientists.

• Alvin has made over 2000 dives.• Found marine life in deep hydrothermal

water (hot water).

Robot submersibles• Study at great depths for long

periods of time.• Argo was a seeing-eye robot

vessel, that located the luxury ship called the Titanic.

Sonar• Research ships and submersibles are

equipped with sonar to aid in mapping the ocean floor.

• Sonar is an acronym for sound navigation and ranging.

• Consists of a transmitter an receiver.• Bounces off the solid ocean floor and reflected

back up to the receiver.• Measures the amount of time it takes to

bounce back

20.2 Features of the Ocean Floor

• Divide into 2 major areas: continental margins and deep ocean basin.

• Continental margins are shallower portions of the ocean floor. Consists of continental crust and thick wedge sediment.

• Deep ocean basin is made up of oceanic crust and thin sediment.

Continental Margins• Part of the continental shelf and

continental slope.• Real boundary lies offshore.• Part of the continent that is covered

by ocean water is called the continental shelf.

• Water above is shallow.

• Are affected by changes in sea level.• Continental shelf along the east

coast of the US has an average of 70 km in width.

• Shelf along the west coast has an average width of 170 km.

Continental Slope• At the seaward edge of the

continental shelf is a steeper slope called the continental slope.

• Boundary between the continental crust and the oceanic crust is found at the base of the continental slope.

• Continental shelf & continental slope may be cut by deep V-shaped valleys.

Submarine canyons• These are deep valleys.• Often associated with the mouths of

major rivers.• Other canyons may have been caused

by turbidity currents.• The turbidity currents are dense

currents that carry large amounts of sediments down the continental slope.

Continental Rise.

• Sediments that form a raised wedge at the base of the continental slope.

• These sediments are deposited as the turbidity currents slow down.

Deep Ocean Basins

• Distinctive features include: broad, flat plains, submerged volcanic mountains, gigantic volcanic mountain ranges, & deep trenches.

Trenches• Located in the deep ocean basin and

are the deepest features on the earth’s surface.

• Long, narrow places • Deepest in the world is the Mariana

Trench in the Pacific Ocean near the island of Guam.

• Most are located along the Pacific Ring of Fire.

Trenches continued• Trenches are associated with

earthquakes, volcanic mountain ranges, and volcanic island arcs.

• Deep trenches in the Pacific Ocean occur offshore from Japan.

• Also, there are trenches found in the Alaska’s Aleutian Islands, the Philippines, & the west coast of South America.

Abyssal Plains

• Extremely vast flat areas that lie in the deep ocean basins.

• They are found in ocean depths greater than 4 km.

• Cover about half of the deep-ocean basin.

• Flattest regions on earth.

Facts about abyssal plains

• Sonar reveals that the abyssal plains are made of sediments deposited in the deep ocean basin.

• The abyssal plains of the Atlantic Ocean are close to the continental margins.

Mid-Ocean Ridges• Most prominent features of the

ocean basin.• Continuous series of underwater

mountain ranges that run along the ocean floors.

• Only in Iceland, do mid-ocean ridges rise above sea level.

Facts of mid-ocean ridges

• Form when ridge plates pull away from each other.

• Have narrow depressions called rift.• A new crust separates and breaks

into a series of faults called fracture zones.

Seamounts• Submerged volcanic mountains at least

1000 m high.• Submerged volcanic mountains less

than 1 km are called abyssal hills.• Seamounts and abyssal hills are

generally associated with hotspots.• Those that rise above the surface of

the ocean form islands such as Hawaii & the Canary Islands.

Guyouts

• These flat-topped, submerged seamounts.

20.3 Ocean-Floor Sediments

• Differ from one part of the ocean to another.

• Continental slope and shelves are covered with sediments.

• Samples in the deep-ocean basins are obtained by taking core samples. (Scoops of sediments)

Sources of Deep Ocean-Basin Sediments• Materials may come from organic

or inorganic sources.

Inorganic Sediments• Most of these sediments are

deposited along the shore & on the continental shelf.

• Great quantities come from slides.• Some come from volcanic dust.• Icebergs provide some sediments.• Even meteorites contribute

Organic Sediments• Remains of marine plants and

animals.• 2 most common substances are

silica and calcium carbonate.• Silica comes primarily from

microscopic organisms (diatoms & radiolaria).

• Calcium carbonate comes from skeletons of tiny organisms called foraminifera.

• Animals like coral and clams also add calcium carbonate to ocean-basin sediments.

Chemical Deposits• Make up part of the ocean floor

sediments.• Potato-shaped lumps of minerals,

or nodules, form on the abyssal plains.

• Composed mainly of oxides of manganese, nickel, & iron.

others• Phosphorite are also formed

directly in the ocean water.

Physical Classification of Sediments

• Two types: Muds and ooze• 1st type is 40 % of ocean floor is

covered with a soft, organic sediment called Muds.

• 2nd type is ooze.• 30 % of the ooze is made up of organic

materials.

Two types of ooze• 1st type is Calcareous ooze and is

mostly calcium carbonate.• Never found in deep ocean water.• 2nd type of ooze is siliceous ooze.• Siliceous ooze is mostly silicon dioxide.• Most found in cool, nutrient-rich ocean

waters near Antarctica.

Test• Will come from power point notes,

worksheets, section questions, and chapter review questions.

• Test will be Thursday

bell ringer what is a continental slope and a continental shelf

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