Oceanography Ch. 3 Marine Provinces

Fracture Zones

*No plate boundary *movement in the same direction *very few earthquakes *occur beyond offset mid-ocean ridge segments *mendocino Facture

transform faults

*have a plate boundary *movement in opposite directions *lots of earthquakes *occur between offset mid-ocean ridge segments *San Andreas Fault, Alpine Foult, Dead Sea Fault

lead-weight soundings

Rope or wire with heavy weight that "bounces" off the ocean bottom

abyssal plains

Very flat (< 1° slope) - flattest place on Earth Very deep; average depth of 4500 - 6000 m Depositional surfaces extending seaward from the base of the continental rise Sediment comes from suspension settling of very fine particles (sedimentation rate very slow) Sediments cover ocean crust irregularities Well-developed in Atlantic and Indian oceans

submarine canyons

cut into the slope Narrow, deep, v-shaped in profile Steep to overhanging walls Extend to base of continental slope Carved by turbidity currents, they erode the continental margin to enlarge the canyons.

Ways of measuring bathymetry

echo sounder, multi-beam sonar, side-scan sonar, and satellites

multi-beam

echo sounders use many sonar beams to survey a wide swath

echo sound

sends a ping how long it takes for the sound to travel indicates the depth of the ocean. Reflection of sound signals off the ocean floor German research vessel, Meteor, used it make 14 profiles across the Atlantic Ocean between 1925 and 1927, revealing the Mid-Atlantic Ridge system

margin

the boundary between a continent and an ocean (NOT ALWAYS a plate boundary)

Bathymetry

the measurement of the ocean depths and charting of the shapes or topography of the ocean floor. Measures the vertical distance from the ocean surface to the mountains, valleys, plains, and other sea floor features.

Pillow lava or Pillow Basalt

*which are smooth rounded lobes that resemble a stack of bed pillow *created when hot basaltic lava spills onto the sea floor and is exposed to the cold water

What are the 3 types of islands

1) islands associated with volcanic activity along the mid-ocean ridge 2)islands associated with hot spots 3)islands that are island arcs and associated with convergent plate boundaries. 4)...islands that are part of continents

different types of hydrothermal vents

1)warm-water vents: emit water clear in color 30 degrees C 2) White Smokers-have water temps from 30 degrees C-350 C emit white water because of various light colored compounds such as, Barium sulfide 3) Black Smokers water temp 350 degrees C and up. black because of dark-colored metal sulfides like iron, nickel, copper, and zinc

oceans 3 major provinces

1. continential margins, which are shallow-water areas close to the continents 2. deep-ocean basins, which are deep water areas farther from land 3. Mid-ocean ridge, which is composed of shallower areas near the middle of an ocean

continental borderland

California's transform active margin has it. characterized to have a high degree of relief, ( islands, shallow banks, and deep basins). Continental shelf that is not flat.

Continental Shelf

Extends from the shoreline to the shelf break Shallow, low relief, gently sloping (~1-2°) Similar topography to the adjacent coast Geologically part of continent Average width of 70 km (43 miles) but can extend to 1500 km (930 miles) Average depth of the shelf break is 135 m (443 feet)

hydrothermal vents

Heated subsurface seawater migrates through cracks in the ocean crust Warm-water vents: less than 30°C (86°F) White smokers: between 30°C and 350°C (662°F) Black smokers: greater than 350°C Black smokers emit water through chimneys Associated with metal sulfide deposits and unusual life forms Foster unusual deep-ocean ecosystems able to survive without sunlight

transform active margin

Less common Transform plate boundary Linear islands, banks, and deep basins close to shore Example: Coastal California along San Andreas fault

Mid-Ocean Ridge MOR

Longest mountain chain on Earth; circles the globe like the seam of a baseball Mostly traverses the middle of ocean basins On average, 2.5 km above the surrounding seafloor Entirely volcanic - basaltic lava Divergent plate boundary (spreading centers) Contains a central down-dropped rift valley In the Atlantic, called the Mid-Atlantic Ridge In the Pacific, called the East Pacific Rise

abyssal hill or seaknolls

Ocean crust that pokes through abyssal plain sediment cover Below sea level: Seamounts are at least 1 km above the seafloor Abyssal hills are less than 1 km above the seafloor Above sea level: Volcanic Islands (Bermuda, Canary Islands, Azores, Hawaiian Islands)

convergent active margin

Oceanic-continent convergent plate boundary Active continental volcanoes Narrow shelf Offshore trench Example: Western South America

continental margins classification

Passive:embedded within the interior of the lithospheric plates therefore not in close proximity to any plate boundary Active: marked by a high degree of plate tectonic activity two types: 1) convergent: associated with oceanic-continental converging plate boundaries 2: Transform active margins: less common, create linear island banks (coastal California)

continental slope

Steeply sloping area extending seaward from the shelf break to the deep ocean floor Change in slope from the shelf (average slope is 4° but varies from 1-25°) Depth range from 200 - 3000 meters

Key Ideas

The general shape of the ocean floor: continental margins vs. ocean basins. Most ocean floor features are generated by plate tectonic processes. Different sea floor features exist in different oceanographic locations.

Global sea surface elevation map from satellite data

This new high-resolution map of the sea floor was produced in 2014 using satellite data of Earth's gravity field, which, when adjusted using measured depths, closely corresponds to ocean depth.

continental rise

Transition between the continental margin and the deep ocean Also transition between continental crust and oceanic crust Marked by turbidite deposits from turbidity currents Submarine fans Graded bedding Distal end of submarine fans become the flat abyssal plains

active margin

a continental shoreline that is a plate boundary (more common in the Pacific). Associated with convergent or transform plate boundaries Lots of tectonic activity Examples: Western South America; Coastal California. Associated with earthquakes, volcanoes and ocean trench.

passive margin

a continental shoreline where there is NO plate boundary (more common in the Atlantic). Not close to any plate boundary No major tectonic activity Example: East coast of the United States. Associated with continental shelf, slope, rise and abyssal plain.

Transform faults

are active transform plate boundaries that occur between the segments of the mid-ocean ridge

deep-sea fans

are composed of turbidity deposits, which consist of sequences of graded bedding.

Fracture zones

are inactive intraplate features that occur beyond the segments of the mid-ocean ridge.

what is the standard unit of measurement for ocean depth?

fathom 1=(1.8 m=6ft)

Posidonius:

first record of attempt to measure the oceans depth was in the Mediterranean sea 85 B.C., used a founding line 1.2 miles long (2km)

GLORIA Sea MARC

geological Long-Range Inclined Acoustical Instrument Sea Mapping and Remote Characterization used to map the sea floor

Topography

is the study of the Earth's shape and features, including the ocean floor

turbidity currents

underwater avalanche mixed with muddy water with rocks and debris. Move under the influence of gravity. Sediments deposited at base of slope.

seismic reflection profiles

use air guns explosion with very low frequencies to see beneath the ocean floor,to determine the structure beneath the seafloor. use this to look for mineral and petroleum exploration

Precision depth recorder (PRD)

uses a high-frequency sound beam to measure depths to a resolution of about 1 meter.

side-scan sonar

uses a tow fish to send sonar beams to each side to make a picture of the seafloor

seabeam (sonar)

uses multi echo sounders to make a picture of the sea floor.

satellite altimetry

uses satellite measurements Measures seafloor based on gravitational "bulges" in sea surface height Indirectly reveals bathymetry. Has an increased detail compared to echo sounder.

Pacific Ring of Fire

where most of the active volcanoes and earthquakes occur on earth, this is on the boundary of the pacific plate. Marked by convergent boundaries