Plate Boundaries, Bathymetry, Ocean Basins

Oceanic Ridge

- is an underwater mountain system formed by plate tectonics -form islands -youngest rock=center oldest rock= distance from center

Passive Margins

- is the transition between oceanic and continental lithosphere that is not an active plate margin. -forms by sedimentation above an ancient rift, now marked by transitional lithosphere. -little earthquakes+ volcanic activity is now associated w/them -surround the Atlantic, "Atlantic-type margins"

Ocean Basin

- the regions below sea level -can be active, with a lot of new structures being created -can be inactive, only collecting sediments

Shelf Break

-An area of increasing slope that marks the edge of a continental shelf -depth of water is constant

Continental Margin

-They are the drowned edges of continents. - Covered by the oceans -continental margins are part of the same crust (thin, solid outermost layer of Earth) that forms the continents. -They are covered in sediments that have been eroded from dry land. (Erosion is the gradual wearing away of Earth surfaces through the action of wind and water.)

Continental Margins have 3 main divisions

-a shallow, continental shelf -steep sloped continental slope -apron of sediment the continental rise

Continental Slope

-a usually steep slope from a continental shelf to the ocean floor -are formed of sediments,transported over the side -at active margins -may also include marine sediments scraped off a descending plate during subduction

Trench

-an arc-shaped depression in the deep-ocean floor. -occur when a converging oceanic plate is subducted -are old,cold ocean crust sinking into the upper mantle -steeper w/depth

Active Margins

-are commonly the sites of tectonic activity: earthquakes, volcanoes, mountain building, and the formation of new igneous rock. - is found on the leading edge of the continent where it is crashing into an oceanic plate.

Abyssal Plains

-are flat,featureless of sediment-covered ocean floor -A plain below sea level which is made up of rocks and sediment, and covered by little hills -common in the Atlantic Ocean -less in the Indian Ocean -lie between the continental margins,oceanic ridges,below the surface -most is terrestrial or shallow water origin

Transform Faults

-are fractures along which lithospheric plates slide horizontally -shallow earthquakes -active part of fracture zones -show evidence of past transform activity

Hydrothermal Vents

-are hot springs on active ocean ridges

Island Arcs

-curving chains of volcanic islands and seamounts -curving series of volcanic islands that are created through the collision of tectonic plates in an ocean setting. -The particular type plate boundary island arcs is called a subduction zone -formed by tectonic+volcanic activity

Guyots

-flat-topped seamounts that were once tall enough to approach or penetrate the sea surface -the flat top is because it was eroded by wave action -formed near spreading centers

Submarine Canyons

-is a valley cut into the seabed of the continental slope, sometimes extending well onto the continental shelf -created by erosion

Continental Shelf

-is the edge of a continent that lies under the ocean -are influenced by changes in sea level -extension of continents, are underlain by granitic continental crust

Turbidity Currents

-landslides or sediment triggered by earthquakes that sometimes causes an "avalanche" of sediments -occur when turbulence mixes sediments into water above a sloping bottom

The Deep-Ocean Floor

-oceanic ridge systems+sediment covered plains - includes continental shelves and slopes, oceanic ridges, trenches, fracture zones, abyssal hills, abyssal plains, volcanoes, and seamounts. -sediments reflect the history of the continents

Black Smokers

-rock chimneys blasting water -not all vents form chimneys -Underwater volcanoes at spreading ridges and convergent plate boundaries produce hot springs

Continental Rise

-sloping transition between the continental slope and the deep ocean floor -covered in sediment-->from the shelf that slowly go into the ocean floor -most of the sediments that form are transported to the area by turbidity currents

What is Bathymetry? and what are the methods of determining?

-the earliest known studies in the Mediterranean by Posidonius----> let out 1.25m of rope until it reached the bottom Methods: -Echo Sounder: a boat that directs a powerful underwater sound pulse,wasn't perfect because of temp,pressure and salinity Multi beam system: bounces sound off the seafloor to measure ocean depth,has 121 beams radiating Satellites: can't measure ocean depths but can measure small details in the elevation of surface water,average height of ocean Robots: can manipulate valves,lift, and reposition equipment, and examine shipwrecks

Seamounts

-volcanoes that don't rise above the surface of the sea. -are circular or elliptical -form at hotspots submerged inactive volcanoes that formed at spreading centers

Types of Plate Boundaries and features

Divergent: two plates move apart from each other Convergent: two plates move toward each other Transform: two plates slide laterally past each other

Rift valley

is a linear-shaped lowland between highlands or mountain ranges created by the action of a geologic rift or fault