Chapter 13: The Ocean Floor Flashcards
How much of the earth’s surface is covered with bodies of water?
71%
How much of the earth is covered with continents and islands?
29%
What are the nicknames for the Northern and Southern Hemisphere?
N= Land Hemisphere S= Water Hemisphere
What is Oceanography?
interdisciplinary study of the oceans that draws on geology, biology, chemistry, and physics
The four basic ocean basins?
1) Pacific (largest and deepest)
2) Atlantic (half size of Pacific)
3) Indian (southern hem ocean… smaller than Atlantic)
4) Arctic (only 7% size of Pacific)
What is the measurement of the ocean depths and the charging of the shape or topography of the ocean floor?
Bathymetry
What is a Echo Sounder?
also known as a sonar.
- invented in 1920’s
- instrument measuring water depth
- reflects sound from ocean floor, measures time required for acoustic wave to travel from ship to the sea floor and back
When was the Sidescan Sonar developed?
after WWII
What is a Multibeam Sonar?
improvement from sidescan sonar and DOES provide depth.
What device bounces microwaves off sea surface from space to measure surface irregularities present due to gravity?
Radar altimeter
What is a Passive Continental Margin?
Found along coastal areas that surround Atlantic.
Margins that are not associated w/ tectonic plate boundaries
-experience very little volcansim and few earthquakes
The five components to Passive Continental Margins?
1) Continental Shelf
2) Continental Slope
3) Submarine Canyons
4) Turbidity Currents
5) Continental Rise
What is a Continental Shelf?
A flooded extension of the continent.
- varies greatly in width
- gentle sloping
- contains rich oil and mineral deposits
- consist thick deposits of shallow-water sediments
What is a Continental Slope?
Marks seaward edge of the continental shelf.
- relatively steep
- boundary between continental crust and oceanic crust
What is a Submarine Canyon?
A deep, steep-sided valleys cut into continental slop by rivers.
- seaward extensions of river valleys that once were above sea level, now flooded by ocean
- appear to have further eroded by turbidity currents
What is a Turbidity Current?
A downslope movement of dense, sediment-laden water; type of mass wasting event
- underwater landslides
- deposits formed from this mass wasting is called turbidtides
What is Continental Rise?
Composed of thick sediment.
- located at base of continental slope
- found in regions of subduction trenches are absent
- continental merges into a more gradual incline (continental rise)
What is an Active Continental Margin?
Accumulations of deformed sediments and scraps of ocean crust from accretionary wedges.
- located primary around Pacific “ring of fire”
- occurs when continental slope descends abruptly into a deep-ocean trench
Bathymetry reflects what?
Tectonic plate boundaries
Mid-ocean ridges mark what?
divergent boundaries
Oceanic transform faults trace what?
strike-slip boundaries
Deep-ocean trenches signify what?
convergent boundaries
Deep-Ocean Trenches
- Long, narrow features
- Created due to subduction moving lithoshoeric plates plunge into mantle
- Trenches are DEEPEST part of ocean
- Associated w/ volcanic activity
Mariana Trench
Deepest location anywhere in the ocean.
Result of 2 oceanic plates colliding together. (subduction)
The Challenger Deep Canyon
Named after HMS Challenger a British Royal Navy Ship.
-the deepest point within the deepest trench
What is a Abyssal Plain?
A deep, flat ocean feature -most level place on earth -thick layer of sediment -found in ALL oceans EX: abyssal plain off coast of Argentina
Seamount
An isolated submarine volcano that rises at least 1,000 m above the ocean floor.
- many grow large enough to become an island
- may erode to from flat-topped seamounts called guyots or tablemounts
What is a Guyot?
a submerged flat-topped seamount (“gee-oh”)
Oceans Preserve what?
Hot-spot sediments.
-volcanoes for islands over hot spots
EX: Hawaiian Islands and Emperor Seamount Chain
A ring of coral reef that builds up to surround a central lagoon is called what?
Coral Atoll
What is the Mid-Ocean Ridge?
An elevated ridge in the center of each ocean w/ faulting where new sea floor is always forming.
-Longest topographic feature on Earth! (not narrow)
What are some sediment sources for the ocean floor?
Turbidity currents (underwater landslides) Sediment that slowly settles to the bottom from above. (thickness of sediment will vary)
Types of seafloor sediments?
1) Terrigenous (land-based) sediments (material weathered from continents)
2) Biogenous Sediment (shells and skeletons of marine animals and plants)
3 Hydrogenous Sediment (minerals that crystallize directly from seawater)
How much of the world salt is extracted from seawater?
30%
