Ch. 2.3 Flashcards
continental margins
boundaries between continental and oceanic crust. Shallow and close to shore
continental shelf
portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea
Submarine Canyons
narrow steep sided valleys that cut into continental slopes and continental rises of the ocean.
Formed by turbidity currents
shelf break
steepening of the bottom that marks the seaward limit of the continental shelf which begins the continental slope.
continental slope
closest to the exact edge of the continent. Begins at shelf break and descends to deep sea-floor
continental rise
closest to the exact edge of the continent. Begins at shelf break and descends to deep sea floor.
continental rise
sediment moving down a submarine canyon accumilates at the canyon’s base in a deposit called a deep sea fan.
deep ocean basin
deep water area, further from land
turbidity currents
a rapid downhill flow of water caused by increased density due to high amounts of sediment
underwater avalanche of sediment
mid ocean ridges
shallow waters close to the middle of deep ocean basins
Why is the Southern Hemisphere referred to as the water hemisphere?
80% of the Southern Hemisphere is ocean as compared to only 61% of the Northern Hemisphere is earth.
Active Margin
zone where tectonic plates either converge with or shear past one another
-subduction and volcanic activity occurs
-think of the cliffs on the coast
Passive Margin
transition between oceanic and continental lithosphere that is not an active plate margin
-adjacent to where seafloor spreading occurs
-flat long coasts
trenches
formed by subduction of a tectonic plate
- parallel to margin
-located on deep ocean floor
Abyssal plains
flat region of ocean floor usually at base of continental rise; slope of less that 1 degree toward mid ocean ridge
abyssal hills
small submarine hills
seamounts
a submarine mountain
guyots
seamount with flat top used to be islands that sunk below the sea cause of island weight
central rift valley
center of ridge system divergent boundary with magma rising up through the oceanic crust
hydrothermal vents
result of seawater percolating down through fissures in the ocean crust in the vicinity of spreading centers or subduction zones the cold sea water is heated by magma and reemerges to form the vents
black smokers
solidified minerals in the water that build up around the vents forming chimney-like structures.
mantle plume
stationary channel of magma usually far from any plate boundary that rises towards the surface from deep within the mantle
hotspot
area of volcanic activity due to the mantle plume
Why are hotspots and mantel plumes considered an intraplate feature
they tend to be far from plate boundaries
Which of the Hawaiian Islands is the youngest and which is the oldest??
youngest is the Big Island
oldest is kauai
What do coral reefs need to survive?
- shallow clear water for sunlight
- warm water 68 F - 90 F
- a site for attachment since coral are sessile organisms
Stages of a coral reef in order
- fringing reef
- barrier reef
- atoll
Fringing coral reef
grows at base of islands
ex. Carribean
Barrier Reef
Island begins to sink as coral grows. The coral is seperated from the island by a wide channel
Ex. French Polynesia and Australia
Atoll
Completely surrounded by coral and island is completely submerged
Ex. Pacific and a few in Indian and Caribbean Oceans
Other less important factors for growing coral
PH, salinity, and a turbidity of 0
bathymetry
measurement of the ocean depths and the charting of the shape or topography of the ocean floor.
fathom
measure of depth, 6 feet
sonar
a type of electronic depth sounding equipment/ echo sounding. transmits sound waves to the very bottom of the ocean. From the speed of the sound waves and the time required for the energy pulse to reach the ocean floor and come back up they can calculate the depth.
satellites
they measure the ocean floor from space by bouncing microwaves off the ocean surface.
submersibles
a small underwater craft used for deep sea research. They collect data deep down where humans can’t go.
What are the two main marine regions?
continental margins and deep ocean basins
Which of the two main marine regions contains the most biological activity
continental margins; specifically in the continental shelf.
Characteristics of active margins
steep continental slopes, narrow continental shelves, little to absent rises, continental volcanic arcs, coastal mountain ranges, volcanic island arcs mountain building, and trenches; high in seismic activity(earthquakes)
Characteristics of passive margins
gentle continental slopes, wide continental shelves, built-up rises(build-up of sediment), not much seismic activity.
On the continental margin where are most submarine canyons located?
continental shelf
List two ways in which submarine canyons are formed
- Turbidity currents
- river systems adjacent to the current
Why are abyssal plains so flat?
Over time, a thick layer of sediment builds up by suspension settling.
What is the difference between a seamount and a guyot (tablemount)?
Seamounts are underwater pointed-topped volcanic peaks; guyots are seamounts that rose above sea
level to become an island. Then, due to erosion by wind and waves, their peaks have been flattened and they have sunk beneath the surface.
What geographical features are associated with nearby ocean trenches?
Volcanic islands arcs, continental volcanic arcs, seamounts
What creates a rift valley?
Divergent plates
Where are hydrothermal vents found?
commonly around mid-ocean ridges
