Oceanography - Chapter 4

Tectonic forces

the energy or the movements that cause a change in the Earth's crust; shapes the Earth’s crusts

Continental margins

seaward extensions of the adjacent continents and are usually underlain by granite

Deep ocean basins

deep sea floor; usually made up of basalt

What is Earth’s most prominent feature?

Mid-Ocean Ridge

How long does it take for Earth’s water to circulate?

10 million years

Where does the Earth’s water circulate?

Through the hot oceanic crust of ridges

Bathymetry

the study of ocean floor topography

Echo sounder

a device to measure the depth of water. sends out sound waves and measures how long it takes for the sound wave to return (bounces back)

How can satellites be used to map seabed topography?

They can measure small variations in elevation of surface water

Passive margin

a type of continental margin which conducts very little activity. found at every ocean and continent boundary that is not marked by a strike-slip fault or a subduction zone

Active margin

a type of continental margin which conducts lots of activity. these are more prevalent in the Pacific

Continental shelf

the area of seabed around a large landmass where the sea is relatively shallow compared with the open ocean. it’s width is determined by it’s proximity to the plate boundary. greatly influenced by changes in sea level

Why is most ocean life found at the continental shelf?

The photic zone is the first 100 feet of water and allows sunlight to penetrate the water

Continental slope

the transition between shelf and deep-ocean floor. formed of sediments, very steep slope

Submarine canyons

a steep-sided valley cut into the seabed of the continental slope, sometimes extending well onto the continental shelf, having nearly vertical walls, and occasionally having canyon wall heights of up to 5 km (3 mi). carved out by turbidity currents (underwater landslides)

Turbidity currents

a rapid, downhill flow of water caused by increased density due to high amounts of sediment

Continental rise

a low-relief zone of accumulated sediments that lies between the continental slope and the abyssal plain

Ocean ridges

a mountainous chain of young basaltic rock at an active spreading center

Fracture zones

seismically inactive areas that show evidence of past transform fault activity

Hydrothermal vents

superheated, chemically active water circulating around mid-ocean ridges

Abyssal plains

flat, featureless expanse of sediment on ocean floor. abyssal hills extend out of sediment

Seamount

pointed-topped underwater mountain ranges that were likely volcanic

Guyot

a flat-topped underwater mountain. formerly an island that was eroded and sank into the ocean 

Mid-Ocean Ridge

an underwater mountain range where new oceanic crust is formed as tectonic plates move apart. these ridges can cause sea levels to rise and fall dramatically

Trench

arc-shaped depressions in deep-ocean floor. formed from convergent boundaries where one plate dives beneath another (subduction zone). deepest place in Earth’s crust. have the most pressure

Island arc

curving chain of volcanic islands and seamounts

• found parallel to trenches

Littoral zone

the band of coast alternately covered and uncovered by tidal action; the intertidal zone

Neritic zone

zone of open water near shore, over the continental shelf

Pelagic zone

the realm of open water over the ocean bottom

Vertical divisions of the pelagic zone, in order

Epipelagic, mesopelagic, bathypelagic, abyssopelagic, hadal zone (EMBAH)

Clastics

sand, silt, mud, and clay found on continental shelf make up the thickest sediments

Biogenic sediments

calcium carbonate and silica from organisms like forams and diatoms leave oozes on the ocean floor that form Chert (Silica from diatoms) and Chalk (Calcite from forams).  Also limestone (calcite)

Chemical sediments

nodules of manganese, copper, iron, and nickel can form and be found scattered on the ocean floor