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PLATE TECTONICS PRODUCING
OCEAN PROCESSES
• Warm Water is LESS dense, so it RISES.
• Colder Water is MORE dense, so it SINKS.
Convection- transfer of heat
Earth and Convection
ABYSSAL PLAINS





Flat areas of ocean floor
Between ocean trenches and
continental rises
Formed by Mantle Convection
Uneven rock surface becomes covered
with fine-grained sediment
Depth between 3000 & 6000 m below
sea level
PLATE BOUNDARY DYNAMICS
1. Divergent
3 Boundaries:
2. Convergent
3. Transform
EFFECTS OF DIVERGENT
BOUNDARY:

Mid-Oceanic Ridges
Underwater Mountain
Ridges
 Formed by upward
movement & spreading of
underlying magma
 Sea Floor Spreading

This is an eruptive fissure that
was found several kilometers
from the mid-ocean ridge.
DIVERGENT BOUNDARY: ICELAND (MID-ATLANTIC
RIDGE)
Mid-Atlantic
Ridge, Iceland
ICELAND PLATE BOUNDARY
The East Africa
Rift Valley is in a
very early stage of
development; above
ocean, has created
lakes
 The Red Sea is an
example of a more
completely
developed rift. The
plates have fully
separated and the
central rift valley
has dropped below
sea level

EVOLUTION OF DIVERGENT BOUNDARIES
EFFECTS OF CONVERGENT
Zone of progressively
deeper earthquakes
 Chain of Volcanoes
 Tsunamis
 Ocean Trench

(OCEAN-CONT)
OCEANIC/OCEANIC
Magma is less dense than basalt so it melts/fractures its way to
surface causing eruptions
 Eventually islands
form
EX: Japan,
Newer;
less
Aleutian Islands,
Older; denser plate
dense
plate
E. Caribbean Islands
 When 2 Oceanic plates collide; ______________________________
beneath the newer plate

OCEANIC/OCEANIC
EFFECTS
Cleveland Volcano, Aleutian Islan
DEEPEST PLACE ON EARTH
• One plate is forced
under another
(Subduction)
• Convergent
Boundaries
• Long and narrow
Left: Trieste:
bathyscaphe
January, 1960
Right: James
Cameron
Green Machine
March, 2012
DIVE TO CHALLENGER
DEEP IN THE MARIANA
TRENCH

http://youtu.be/Y2tm4
0uMhDI
EARTHQUAKE

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Sudden release of energy in Earth’s
crust, creating seismic waves
Arises from Convergent , specifically
Transform Boundaries
If two plates are unable to slip past
each other they LOCK, strain
(energy) builds up
When the plates start moving again,
stored energy gets released
TRANSFORM BOUNDARY
Plates slide past one another
 EX:

1. San Andreas Fault
 2. Alpine Fault in New Zealand
 3. Along the Mid-Atlantic Ridge

TSUNAMI
Long wavelength wave produced by the sudden
movement of a very large volume of water
 Convergent plate boundary, abrupt slippage of
one plate against another results in an
underwater earthquake and then a tsunami

Deep Water= wave (small) travels quickly
 Shallow Water (coastal waters)= slows down and
forms large, destructive waves

Japan Tsunami 2011
VOLCANO

Opening in Earth’s crust


Hot gases and molten rock to escape
Thinning of the crust= Divergent
Mainly under the sea
 New sea floor
 Mid-ocean ridges



If these rise above sea level, volcanic islands may be formed
(ICELAND)
Also form when plates move towards each
other=Convergent
HYDROTHERMAL VENTS
WHERE DO THEY
OCCUR?
Discovered 1977
 Divergent Boundary
 Deep Ocean
 Rift Valley/spreading
center

HOW DOES IT WORK?
HOW DOES IT WORK?
1.
2.
3.
4.
Cold seawater (2OC) seeps into cracks and fissures
along boundaries
Seawater continues to seep deeper into crust.
Water heats by underlying magma under the ocean
floor
Hot Water is forced back up to ocean floor, carrying
dissolved minerals
•


All oxygen is removed
Water becomes acidic
Water picks up dissolved metals (Fe, Cu, Zn) & Hydrogen
sulfide
HYDROTHERMAL VENTS FORM:
1.
2.
Hot hydrothermal fluid (less dense) (water),
carrying dissolved metals & hydrogen sulfide.
Hydrothermal liquids exit vent/chimney & mix
w/ cold seawater.
a)
3.
4.
Metals carried in fluid combine w/ sulphur to form
black minerals (metal sulfides; AKA “black
smokers”)
As it cools, the dissolved minerals starts to
precipitate out
Precipitates form the chimney
HYDROTHERMAL VENTS
Found at depths of over 2000 m
 Pressure is HIGH (over 200 atmospheres
 High Pressure= super heated water= reach
temperatures higher than 100 degrees Celsius

Discovering Hydrothermal Vents