Chapter 3: Marine Provinces Flashcards
What three main provinces can the ocean floor be divided into?
- Continental Margins
- Deep-ocean Basins
- Mid-ocean Ridges
Shallow water areas close to continents
Continental Margins
Deep water areas further from land
Deep-ocean Basins
Shallower areas near the middle of an ocean
Mid-ocean Ridges
The measurement of ocean depths and the charting of the shape, or topography of the ocean floor.
Bathymetry
The letting out of line before the heavy weight on the end of the line touches the bottom.
Sounding
The standard unit of ocean depth; equal go 1.8 meters (6 feet)
Fathom
What did the first systematic bathymetric measurements indicate?
The measurements indicated that the deep ocean floor was not flat but had significant relief (variations in elevation), just as dry land does.
Sends a sound signal (called a ping) from the ship downward into the ocean, where it produces echoes when it bounces off any density difference.
Echo Sounder
How is the echo sounder useful?
The time it takes for the echoes to return is used to determine the depth and as a result, the corresponding shape of the ocean floor.
Developed in the 1950s; uses a high frequency sound beam to measure depths to a resolution of about 1 meter (3.3 feet)
Precision Depth Recorder (PDR)
Use multiple frequencies of sound simultaneously and side-scan sonar (an acronym for sound navigation and ranging).
Multibeam Echo Sounders
The first multibeam echo sounder; made it possible for a survey ship to map the features of the ocean floor. Uses sound emitters directed away from both sides of a survey ship, with receivers permanently mounted on the ship’s hull.
Seabeam
Why are multibeam surveys useful?
They provide incredibly detailed imagery of the seabed.
Tall volcanoes on the sea floor
Seamounts
Strong low-frequency sounds produced by explosions or air guns penetrate beneath the sea floor and reflect off the boundaries between different rock or sediment layers, producing what?
Seismic Reflection Profiles
Continental Margins can be classified into what two groups?
Passive Margins or Active Margins
Embedded within the interior of lithospheric plates and are therefore not in close proximity to any plate boundary.
Passive Margins
Associated with lithospheric plate boundaries and are marked by a high degree of tectonic activity.
Active Margins
What two types of Active Margins exist?
- Convergent Active Margins
2. Transform Active Margins
Associated with oceanic-continental convergent plate boundaries. From the land to the ocean, features include an on-shore arc-shaped row of active volcanoes, then a narrow shelf, a steep slope, and an offshore trench that delineates the plate boundary.
Convergent Active Margins
Less common and are associated with transform plate boundaries. At these locations, there are usually offshore faults that parallel the main transform plate boundary fault and create linear islands, banks (shallowly submerged areas), and deep basins close to shore.
Transform Active Margins
Defined as a generally flat zone extending from the shore beneath the ocean surface to a point at which a marked increase in slope angle occurs, called the shelf break.
Continental Shelf
A marked increase in slope angle on a continental shelf.
Shelf Break
For Transform Active Margins such as along California, the presence of offshore faults produces a continental shelf that is not flat. Rather, it is marked by a high degree of relief (islands, shallow banks, and deep basins) called a what?
Continental Borderland
Lies beyond the shelf break, and is where the deep ocean basins begin.
Continental Slope
Narrow but deep submarine valleys that are V-shaped in profile view and have branches or tributaries with step to overhanging walls. These are exhibited amongst the continental slope, and to a lesser extent, the continental shelf.
Submarine Canyons
Underwater avalanches of muddy water mixed with rocks and other debris. The erosive power of these have suggested they are responsible for carving submarine canyons.
Turbidity Currents
Transition zone between the continental slope and the deep-ocean floor comprised of a huge submerged pile of debris.
Continental Rise
What is responsible for the creation of continental rises and how?
The existence of turbidity currents suggests that the material transported by these currents is responsible for the creation of continental rises.
When a turbidity current moves through and erodes a submarine canyon, it exits through the mouth of the canyon. The slops angle decreases and the turbidity current slows, causing suspended material to settle out in a distinctive type of layering called what?
Graded Bedding
These stacks of graded bedding, which make up the continental rise, are called what?
Turbidite Deposits
The deposits at the mouths of submarine canyons are fan, lobate, or apron shaped. Consequently, these deposits are called what?
Deep-sea fans, or submarine fans
How do deep-sea fans create the continental rise?
They merge together along the base of the continental slope.
Why are these no continental rises alongside convergent Active Margins?
The steep continental slopes leads directly into a deep-ocean trench. Sediment from turbidity currents accumulates in the trench.
Extending from the base of the continental rise into the deep-ocean basins are flat depositional surfaces with slopes of less than a fraction of a degree that cover extensive portions of the deep-ocean basins.
Abyssal Plains
How are abyssal plains formed?
By fine particle of sediment slowly drifting onto the deep-ocean floor. Over millions of years, a thick blanket of sediment is produced by SUSPENSION SETTLING as fine particles (analogous to “marine dust”) accumulate on the ocean floor.
Where do most abyssal plains occur?
Atlantic and Indian Oceans
Why are there few abyssal plains in the Pacific Ocean?
The deep ocean trenches found on the convergent Active Margins of the Pacific Ocean prevent sediment from moving past the continental slope.
If a volcano has a flattened top, it is called a what?
Tablemount
Poking through the sediment cover of the abyssal plains are a variety of what?
Volcanic Peaks
Volcanic features on the ocean floor that are less than 1,000 meters (0.6 mile) tall -the minimum height of a seamount- are called what?
Abyssal hills, or seaknolls
Created by stretching of crust during the creation of a new sea floor at the mid-ocean ridge.
Abyssal Hills
In the Pacific Ocean, the abundance of deep trenches along the margins of the Pacific helps trap land-derived sediment, and so the rate of sediment deposition is lower. Consequently, extensive regions dominated by abyssal hills have resulted. These are called what?
Abyssal Hill Provinces
Deep linear scars in the ocean floor, caused by the collision of two plates along convergent plate margins.
Ocean Trench
The landward side of an ocean trench rises as a what?
Volcanic Arc
Volcanic Arc may produce islands called a what?
Island Arc
Volcanic Arcs may produce a volcanic mountain range along the margin of a continent called a what?
Continental Arc
Where are the majority of ocean trenches found?
The margins of the Pacific Ocean
Specifically occurs along the margins of the Pacific Ocean. It is home to the majority of Earth’s active volcano a and large earthquakes because of the prevalence of convergent plate boundaries along the Pacific Rim.
The Pacific Ring of Fire
A central downdrop created by sea floor spreading (rifting) where two plates diverge.
Rift Valley
Sediments of the mid-ocean ridge that have a prominent Rift Valley and steep rugged slopes
Oceanic Ridges
Slopes that are gentler and less rugged
Oceanic Rises
When hot basaltic lava spills onto the sea floor, it is exposed to cold seawater that chills the margins of the lava. These creations are smooth, rounded lobes of rock that resemble a stack of bed pillows.
Pillow Lavas or Pillow Basalts
Sea floor hot springs created when cold seawater seeps down along cracks and fractures in the ocean crust and approaches an underground magma chamber.
Hydrothermal Vents
Have water temperatures below 30C (86F) and generally emit water that is clear in color.
Warm-water Vents
Water temperatures from 30C to 350C (86 to 662F) and emit water that is white because of the presence of various light-colored compounded, including barium sulfide.
White Smokers
Water temperatures above 350C (662F) and emit water that is black because of the presence of dark-colored metal sulfides, including iron, nickel, copper, and zinc.
Black Smokers
A compound containing one or more metals and sulfur.
Metal Sulfide
Shows the relationship between the height of the land and the depth of the oceans
Hypsographic Curve
The dissolved metal particles often come out of solution when the hot water mixes with cold seawater, creating coatings of mineral deposits on nearby rocks.
Precipitate
A fault with side-to-side motion that offsets segments of a mid-ocean ridge. Occur wholly on the ocean floor.
Transform Fault
What two reasons do transform faults occur?
- To accommodate spreading of a linear ridge system on a spherical Earth
- Different segments of the mid-ocean ridge spread apart at different rates.
Extension away from the mid-ocean ridge
Fracture Zones
What are the three basic types of oceanic islands?
What is the exception?
- Islands associated with volcanic activity along the mid-ocean ridge
- Islands associated with hotspots
- Islands that are island arcs and associated with convergent plate boundaries
Exception: Islands that are part of continents, but these occur close to shore and thus are not considered a true type of oceanic island.
