Download Earth`s Interior

Plate Tectonics and
Volcanoes
Plate Tectonics
•The Earth’s crust
is broken into
large pieces
called plates that
move in different
directions.
TECTONIC PLATES
***EARTHQUAKES HAPPEN AT TECTONIC PLATE
BOUNDARIES***
Asthenosphere convection currents
cause the continental plates to move
There are three types of plate
boundaries.
Convergent Plate Boundaries
•Converge = come together
•Location where two plates collide
•One plate (the more dense one) subducts (goes
under) the other one
•Responsible for large earthquakes
Subduction Zone
• When two tectonic plates meet and one slides underneath the other
• Responsible for earthquakes, volcanic activity, and formation of mountains
Divergent Plate Boundaries
•Diverge = to (go) separate (ways)
•This is when the plates separate
Transform Boundary
•When plates slide by each other
•Can cause valleys to form
California’s San Andreas Fault is a
Transform Boundary
•The plates slide against
each other, but get
stuck
• Tension builds in these
stuck areas (like a spring)
• When the rocks break or
slip, an earthquake
ensues
Oceanic - Continent Convergence Example: Andes, Cascades
At an ocean-continent collision, the ocean subducts,
and the continent rides high. Volcanoes are built on
the continental side due to melt which comes off the
subducting plate. Nazca-South America is an excellent
example.
Oceanic - Oceanic Convergence Example: Japan
At an ocean-ocean collision, one plate subducts beneath
the other, leaving a trace of the process in volcanoes
and earthquakes. At the fast collisions (Fiji-Tonga) the
subducting plate gets as deep as 700 km while still cool:
Continent - Continent Convergence Example: Himalayas
A continent-continent collision is like a train wreck both sides end up taking severe damage. Neither side
wants to subduct. The entire Alpine-Himalayan
mountain system from Spain to Thailand is behaving
this way.
Earthquakes and Faults
• An earthquake is caused by the sudden release of energy
stored in rocks along a fault
• Fault is a crack in a mass of rock along which there has
been movement of rock layers on either side of the crack
• Focus – where earthquake starts below surface
• Epicenter – location directly
above on land or water
Volcanoes occur along the Ring of
Fire
Local and Global effects of
Volcanoes
Short term Mudflows –
volcanic ash mixed with
water – and potential loss
of life.
Long Term – possible
global cooling due to ash
in the atmosphere
(less sunlight)
“Hot Spots”
•Hot places where magma rise out of volcanoes
(usually deep inside the mantle of the earth)
•Most occur over ocean plates
• Responsible for formation of Hawaiian and Galapagos
Islands
•Also found on land (i.e., continental), such as
Yellowstone National park
•Does not occur on or at plate boundaries
“Hot Spot”
Tsunamis
•A series of large waves caused by plate
boundary interactions or volcanic activityS
1. A mid-ocean ridge where two plates are spreading away from each other,
would be referred to as:
a.
b.
c.
d.
e.
A Divergent Plate boundary
A Transform Fault boundary
A Subduction Plate boundary
A Convergent Plate boundary
A Geologic Plate boundary
2. Which of the following parts of the Earth is responsible for causing the
continental plates to move?
a.
b.
c.
d.
e.
The inner core
The lithosphere
The mantle
The outer core
The asthenosphere
3. The majority of earthquakes and volcanoes occur:
a.
b.
c.
d.
e.
In the middle of the ocean
At the North and South poles
Along plate boundaries
In the middle of continents
Randomly, there is no discernible pattern to the occurrence of earthquakes and
volcanoes
4. What is the strongest evidence that supports the Theory of Plate Tectonics?
a.
b.
c.
d.
e.
The annual change in ocean currents and ocean temperatures
The fact that the outer core is molten
The fact that rocks and fossils of similar origin show up on different, now separated
continents
The fact that sedimentary rocks have been laid down in progressive layers
The fact that metamorphic rock forms from both igneous and sedimentary rock
5. The edge of the Pacific Plate is characterized by a circular string of
volcanoes and earthquakes. This circular string is known as:
a.
b.
c.
d.
e.
The Crown of Vulcan
The Shake and Bake Belt
The Ring of Fire
The Pacific Fire Belt
The Magma Ring
Geologic Time
Relative Dating: Putting geologic events into proper
order (oldest to youngest), but without absolute ages.
We use a number of principles and laws to do this:
• Law of Original Horizontality – Sedimentary
units and lava flows are deposited horizontally.
• Law of Superposition – the layer below is older
than the layer above.
• Law of Cross-cutting Relationships - A rock is
younger than any rock across which it cuts.
The Rock Cycle
Three basic rock types:
igneous - form from
magma/lava
sedimentary - form from
sediment and chemical
precipitation from seawater
metamorphic - form from other
rocks that recrystallize under
higher pressures and/or
temperatures.
A number of geological processes
can transform one rock type into
another.