Ocean BasinsChapter 11.1

By: Elena Grace Emika

The Ocean

• 2/3 of Earth’s surface covered by ocean

• Exist on Earth for more than 3 billion yrs.

• 5 major oceans: Pacific, Atlantic, Indian, Southern, Artic

• Control Earth’s temperature

• Create weather patterns

• Water source - Support all life form

The Ocean Basins• Ocean Basins =low points on the Earth’s surface

• Water flows into basin =create ocean

• Hundreds of millions of years for oceans to fill up to present levels from water that ran off the continents

The Origin of the Ocean water• Planet first formed hot ball of molten rock• Outside of Earth cooled down• Heat released from deep within the planet

through volcanoes• Water inside volcanic materials also

released into the atmosphere form of water vapour

• Water vapour cooled & condensed = fall on to Earth’s surface as rain

• Gravity causes water to fall downhill water that fell collected in the lowest parts of Earth’s surface- the ocean basins

• Original water on planet came from ice in comets that hit the young Earth

•Has interesting & varied landscape like Earth’s continents

•Features found on land: mountain ranges, valleys, flat plains, canyons, and volcanoes also exist on ocean floor

•2 distinct parts-Largest: middle part (general ocean basin)-Rising outside edges (continental margins)

Ocean Floor

The Tectonic Process• Tectonic plates =large sections of rock that the entire surface of Earth is

made up of• Sections of rock are solid but float over a layer of molten rock (magma)• Magma heats up =molten rock rises • Pressure =force 2 plates apart• 2 types of tectonic plates -Continental: lie under continents -Oceanic plate: lie under oceans, dense

• Plates pushed apart magma oozes up into the empty space

• Under ocean =mid-ocean ridge

• Magma cools at mid-ocean ridges becomes newest rock on planet

• Rising & hardening of magma forces plates to continually move apart ocean floors grow wider & wider

• Plates moving apart from mid-ocean ridge must come in contact with other plates.

Mid-Ocean Ridges

SUBDUCTION• Subduction =process where oceanic plate collides with continental

plate the denser oceanic plate forced to slip underneath continental plate• When subduction occurs ocean trench is formed• Trench =long V-shaped groove that marks boundary between oceanic plate & continental plate • Ridges =develop usually in middle of ocean basin• Trenches = tend to develop near outer edges

Trench

Abyssal Plains• Abyssal plains =wide, flat areas that are stretching between areas of trenches & mid-ocean ridges• Make up 30% of Atlantic ocean floor & more than 75% of Pacific ocean floor• These flat areas broken by occasional underwater peak called a seamount• Seamount = an old inactive volcano that once developed near a mid-ocean ridge

CONTINENTAL MARGINS • Continental margins = regions of the ocean floor that lie underwater along the edge of the

continents• These margins are made up of: - continental shelf =flat area that extends from continent’s shoreline to ocean basin - continental slope =steep area that drops off rapidly to the ocean basin from edge of the continental shelf• During last ice age continental shelves in northern hemisphere =not under water• More ocean water became locked up as ice water level fell leaving the shelves exposed

Turbidity Current• Sediments carried into the ocean by rivers flowing off the continents• Sediments build up along the steep continental slope• Build-up becomes too big =gravity suddenly causes slope to give way• Resulting collapse =turbidity current• Turbidity current =underwater landslide that can travel hundreds of km down the continental slope & out along ocean floor• Turbidity currents deposit piles of sediment that form the continental rise• Continental rise =between continental slope & abyssal plain.

Submarine Canyons

• Some turbidity currents powerful enough to carve out large sections of continental shelf & continental slope =creates submarine canyons• Result =underwater landscape• Submarine canyons also found in regions where large rivers reach ocean

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