Transcript Chapter 4 Marine Provinces Today, we're going to drain the ocean.

Chapter 4
Marine Provinces
Today, we're going to drain the ocean.
History
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Posidonius: The first known to attempt at
measuring the ocean's depth. (Mediterranean
Sea 85 B.C.)
Soundings were done by dropping weighted
rope. Depth measured in Fathoms.
1 Fathom = 1.8 Meters = 6 Feet
History
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HMS Challenger: First systematic
measuring of depth. (1872)
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Still using rope.
Notable for determining variation in ocean
depth.
History
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Echo Sounders: Early 1900's. Sends a ping to
the ocean floor and records the echo.
Precision Depth Recorder(PDR): WWII tech.
More focused, and accurate sonar. Used in the
1960's to produce the first reliable maps of sea
floor.
Today
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Multibeam Echo Sounder: Multiple frequencies
of sound used to provided detailed images.
Can be attached to sides of a ship to survey
sea floor (SeaBeam, 1st Multi-beam echo
sounder).
Side Scan Sonar: Mult-beam echo sounders
towed behind the ship, provide better resolution
images due to proximity to the sea floor. (Sea
MARC and GLORIA)
Today
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Satellites, like those you saw in Chapter 1, can
map sea floor by measuring gravity field
Echo sounding using explosions or air guns can
give Seismic Reflection Profiles. <-this is where
the money is, guys.
Important Formula:
Depth = Velocity x (Time/2)
Ocean Provinces
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Three Major Regions:
1. Continental Margins: Shallow land close to
the continents.
2. Deep-Ocean Basins: Deep land far from the
continents.
3. Mid-Ocean Ridge: Shallower areas near the
middle of ocean basins.
Continental Margins
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Passive Margins:
Areas that are not near a plate boundary.
Characterized by low tectonic activity.
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Active Margins:
Opposite of Passive.
- Convergent Active Margins
-Transform Active Margins.
Continental Margins
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The continental margins are all characterized by
the following features, in order.
-Continental Shelf
-Shelf Break
-Continental Slope
-Continental Rise
Submarine Canyons
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Submarine Canyons: On continental slopes.
They are V-shaped canyons formed by
Turbidity Currents (Avalanches of accumulated
sediment and rock).
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As the sediment and rock falls, it lands on the
Continental Rise, forming a Deep Sea Fan.
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The Deep Sea Fan exhibits Graded Bedding.
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Multiple layers of graded bedding are called
Turbidite Deposits.
Deep Ocean Basins
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Abyssal Plains: Deepest, flattest land on earth.
Sediments here are deposited by
Suspension Settling.
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Peaks of the Plains: If there is a volcanic
formation at least 1 Km above the sea floor, it is
a Sea Mount.
-If its top is flat, it is called a Tablemount or
Guyot.
Deep Ocean Basins
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Volcanic Features >1Km are called
Abyssal Hills or Seaknolls.
Very common feature of the sea floor.
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Very active areas may lack in sediment
deposition, resulting in Abyssal Hill Provinces.
Volcanism
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Flood Basalts: Large, flat surfaces of basalt
rock formed by some volcanic release of
magma.
If found near a continent, they're called
Continental Flood Basalts.
Trenches
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Ocean Trench: Found near Ocean-Continent
Convergent Boundaries. Deep scars in the sea
floor where the ocean crust is subducted.
Can produce a Volcanic Arc on landward side.
These include:
-Island Arc: Forms islands.
-Continental Arc: Forms mountains on land.
THE Trench
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The deepest point in the ocean is found in
Challenger Deep, which is found in
The Mariana Trench.
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11,022 meters!
The Ring of Fire
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A ring of volcanoes surrounding the Pacific
Ocean Basin.
Also, the majority of ocean trenches are found
in the pacific ocean.
Mid-Ocean Ridge
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World's largest land formation. Continuous, and
running through all the ocean's basins.
Within the center of its mountain ranges are Rift
Valleys. That's where the ocean floor tears
open and spits fire.
Common features:
Seamounts, Abyssal Hills, Fissures, Pillow
Basalts, and Hydrothermal Vents.
Hydrothermal Vents
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Formed by sea water seeping into the crust and
rising back up when heated by magma.
Comes in 3 flavors:
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Warm-Water Vents: below 30C and clear.
White Smoker: 30C<T<350C. Water is white
due to light colored compounds.
Black Smoker: T>350C. Water is black due to
metal sulfides.
And one more thing!
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The mid-ocean ridge does not spread equally
along its length.
Mid-Ocean Ridges: Spread slow
Mid-Ocean Rise: Spread Fast
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Because of this, there are many Transform
Faults along it, surrounded by Fracture Zones.