Transcript PLATE TECTONICS - Los Alamos Public Schools / Home

PLATE
TECTONICS
Inside
Earth
Geologists are
scientists who study
the forces that make
and shape the Earth.
Geologists study
constructive and
destructive force.
Geology is the study
of the planet Earth.
Constructive
forces shape
the surface by
building up
mountains and
landmasses.
Destructive
forces slowly
wear away
mountains or
other features.
Journey to the Center of the Earth
If you were to take a journey
into the center of the
Earth…the closer you get
to the inside the HOTTER
you would get!
Also, the deeper you go into
the earth the more
pressure you would feel.
As you travel to the center of
the Earth you would pass
through several different
layers.
The 3 MAIN layers are:
1. Crust
2. Mantle
3. Core
Earth’s Interior
Lithosphere and Asthenosphere
• Lithosphere- all of the crust and upper part
of mantle
• Asthenosphere- the rest of the
“flowable/liquidy” part of the mantle
THE CORE!!!
• There are currents (because of
temperature and pressure) that cause the
outer core to move, because it is more
fluid than the SOLID inner core, they move
at different rates.
• This provides our Earth with a MAGNETIC
FIELD! Our planet works like a bar magnet
which is why compasses point NORTH
Evidence for the Theory of Plate
Tectonics
• Pangea
• Fossils
• Seafloor Spreading
• Let’s talk about each!
Drifting
Continents
Alfred Wegener
came up with a
hypothesis about
the continents
moving…..He
stated all
continents were
once joined
together in one
landmass
“Pangaea” and
since that time
they have drifted
apart.
Continental Drift was Wegner’s
idea that the continents slowly moved
over Earth’s surface
EVIDENCE:
1. landforms
2. fossils
3. climate
Unfortunately, Wegener could not
prove his theory…so scientist did not
believe him.
Fossil Evidence Map
What do you think the words “Sea
Floor Spreading” mean?
How do you think this “sea floor”
could spread?
Mid-Ocean Ridge: the under sea
mountain chain where new ocean
floor is produced
At the mid ocean ridge, molten
material rises from the mantle and
erupts. The molten material then
spreads out, pushing older rock to
both sides of the ridge.
Sea Floor
Spreading:
the process
by which
molten
material
adds new
oceanic
crust to the
ocean floor
EVIDENCE:
1.Molten material
2.Magnetic strips
3.Drilling samples
Subduction at Deep Ocean
Trenches
• Deep Ocean
Trenches: a deep
valley along the
ocean floor through
which oceanic crust
slowly sinks towards
the mantle
• Subduction: the
process by which
oceanic crust sinks
beneath a deepocean trench back
into the mantle
At deep-ocean trenches, subduction
allows part of the ocean floor to sink
back into the mantle, over tens of
millions of years.
Plate Tectonics
• Plate Tectonics is
the theory that
pieces of Earth’s
lithosphere are in
constant motion,
driven by
convection
currents in the
mantle
• The theory of plate
tectonics explains
the formation,
movement, and
subduction of
Earth’s plates.
Convection Current?
• Convection currents is what cause the
plates to move. Rocks closer to the center
get hot and rise, rocks further away get
colder and sink- a cycle/ current is
created.
• There is also RADIATION- like heat from
the Sun and CONDUCTION- heat by
contact= other ways heat tranfers
Plate Boundaries
• Faults: a break
in Earth’s crust
where slabs of
rock slip past
each other
• Faults form
along plate
boundaries
• There are 3 types of
Plate Boundaries
• Transform
• Divergent
• Convergent
Transform Boundaries
• A plate
boundary
where two
plates move
past each other
in opposite
directions
Divergent Boundaries
• A plate boundary
where two plates
move away from
each other
• A deep valley
called a rift valley
can form along a
divergent boundary
Convergent Boundaries
• A plate boundary
where two plates
move toward
each other
• The collide or
crash
Earthquakes
• Is the movement of rock beneath earth’s
surface which causes the Earth to shake
STRESSED OUT!!! (force that changes shape or volume)
- Shearing- pulls rock in opposite directions,
sliding
- Tension- Stretches rock apart, thins in
middle
- Compression- squeezes rock together
until folds or breaks
It’s all your FAULT!!!
• Occurs along plate boundaries
• Strike-slip- SHEARING force, TRANSFORM
boundary, San Andreas fault
• Normal- TENSION force, DIVERGENT
boundary- Rio Grande Rift Valley
• Reverse- COMPRESSION force,
CONVERGENT boundary- Glacier Natl. Park
• *thrust fault- type of reverse
Hanging and Foot Walls
• Normal and reverse can cause
MOUNTAINS and PLATEAUS
• Normal- Fault Block Mountains
• Reverse- Folding forces, mountain range
• Anticlines and Synclines- folding forces
that creates arches
Types of Waves
• Focus- where rocks break underground
• Epicenter- point on surface above focus
• Seismic Wave- p, s, and surface waves
Primary Waves- Compression/ Longitudinal
Waves, first set of seismic waves, fastest
Secondary Waves- Transverse (horizontally and
vertically)
Surface Waves- seen on surface, slowest,
transverse
AFTERSHOCK!
Measuring
• What tool do we use to measure these?
• 3 Scales- Mercalli (damage/intensity) ,
Richter (size of waves, MAGNITUDE) and
Moment Magnitude Scale (total energy
released)
Volcanoes
What is it?
• A volcano is a weak spot in the crust
which allows magma to break through
• Most forms in lines/ belts- ex Ring of Fire
• Magma- in the mantle
• Lava- let loose on the surface
• Most common at DIVERGENT plate
boundaries or SUBDUCTION zones
• Divergent boundary- Mid Ocean Ridges,
like Iceland and Azores Islands, most stay
underwater
• Convergent boundary- Subduction zones,
or 2 oceanic plates converging. (In this
case- whichever plate is denser due to
age, sinks)
• Hot spot- a superheated section of magma
blasts through the crust and creates a
volcano- exception to rule, not at boundary
Parts of a volcano
How different is lava?
• Temperature and amount of silica (Si +O2)
• More silica  THICK LAVA
• Less silica  THIN LAVA
• And this determines type of volcano and
how it erupts
Eruptions and Stages
• 2 types of eruptions- quiet or explosive,
depends of composition and temperature
• Slow eruptions- pahoehoe or aa
• Fast eruptions- pyroclastic flow- ash,
cinders and exploding chunks of lava,
tephra
• Active, Dormant and ExtinctErupting, now or soon, might erupt and probably never.
Volcano types
• Shield Volcanoes- thin lava, erupts in
layers, low sloped side- ex- hot spots that
created Hawaii
Cinder Cone volcanoes
• Steep sided, explosive, thicker lava-exParicutin, Sunset Crater (AZ)
Composite Volcanoes
• Alternates thick and thin lava- therefore
explosive or calm eruptions, very tall,
generally what you see in pics or
diagrams, ex- Mt. Fuji, Mt St. Helens
Lava Plateaus
• Instead of forming a mountain, a plateau is
formed instead, thin/ runny lava forms in
flat layers- ex- Columbia Plateau
Calderas
• Once a vent runs out of magma, it can
become an empty shell-like opening and
the mountain collapses in on
itself…hmmm…example?
Other weird things
volcanoes can do!
• Hot springs- water is heated underground
by magma and collects as a pool
• Geyser- water is heated, but let through a
small opening which causes pressure and
the water sprays out
• Can be utilized for geothermal energy
Also…
• Volcanic Neck- magma hardens in the
pipe, jagged landform,
• Batholith- massive chunk of rock forms
when magma cools inside of the crust,
Yosemite
• Dome Mountain- magma is blocked by
rock but it can’t break through, so the rock
bends upward, Black Hills, SD
Unique to New Mexico
• Rio Grande Rift
The Earth’s crust thins and pulls apart, a
fault. A rift, such as the one here in NM, is
considered a continental rift. There are
only around 7 on Earth. The Rio Grande
helped to make this rift deeper as the
Basin and Range Province pulled away
from the Colorado Plateau. Where the
crust thins- volcanoes form.