1. 12.2 Features of Plate Tectonics
Earth is over _______ km thick and has ___ distinct layers.
These layers are the ____________, ____________________ (upper and lower), outer ________________, and inner ________________.
Crust – outer ____________________layer (granite on land, basalt in oceans)
Mantle –____________________layer, mostly________________except for upper mantle being able to flow like “thick toothpaste”
Outer core – composed of liquid __________________
Inner core – mostly _____________, at tremendous
temperature and pressure
___________________make up the lithosphere,
which floats on the asthenosphere.
The lithosphere is the _________________ and upper portion of the upper ____________________.
The asthenosphere is the ____________________________of the upper mantle.
Heat to keep the asthenosphere molten comes from _________________________________________.
Earth’s layers
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2. Plate Motion (continued)
_________________, attached to the tectonic plates,
float in the magma of the _________________.
As magma is heated in the asthenosphere,
_________________________________form.
Rising magma can reach the surface at __________
(in the oceans) or __________________ (on land).
The magma ___________ when it reaches the surface, _______________, and is ______________________________as new magma pushes from below. This is called ridge push.
Tectonic plates are all ____________________at the same time.
There are _________ large tectonic plates and many smaller ones.
Where continental and oceanic plates meet, subduction occurs.
The denser oceanic plate __________ under the lighter continental plate.
By “slab pull,” the rest of the plate follows.
Large earthquakes and volcanoes are found in
_______________________________________.
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3. A _____________________an area where two plates are in contact.
Plate Interactions
A _____________________an area where two plates are in contact.
The way the plates interact is based on the_____________of plate and the ______________________ the plates are moving relative to each other.
_______________ plate boundaries – areas where plates are spreading apart
___________________ Plate boundaries – areas where plates meet
_____________ plate boundaries – areas where plates move past each other
Tectonic plate boundaries, and their relative movement to each other.
See page 523
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4. Plate Interactions (continued)
Divergent plate boundaries are areas where plates are _______________________.
________________________________and continental rifts are examples.
The _____________________________is the longest mountain range on Earth.
Convergent plate boundaries are areas where plates __________________.
Oceanic-continental plate convergence
The oceanic plate ______________ under the continental plate, forming a ____________________________.
Cone-shaped _____________ can form from magma seeping to the surface.
This is how the volcanic belt of the
North America’s west coast has formed.
Mountain ranges like the ___________________
range also form from the collision.
Earthquakes can occur when subduction,
ridge push, and slab pull __________________.
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The convergence of an oceanic and a continental plate.
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5. Plate Interactions (continued)
Oceanic-oceanic plate convergence
The ______________, ______________ plate will subduct
under the ______________________plate.
Convergence may produce a __________________,
such as those found in Japan, Indonesia, and
Alaska’s Aleutian islands.
Continental-continental plate convergence
Since both are continental plates, their ___________________ are similar.
As they collide, their edges fold and crumple, forming ____________________________.
The _____________________ are the world’s youngest (and tallest) mountain range, formed as Asia and Africa plates collided 40 million years ago.
They are still ______________________________ today.
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6. Plate Interactions (continued)
Transform plate boundaries are where plates move past each other.
Usually are found ________________________________
Since rock slides past rock, _______ mountains
or volcanoes form.
______________________________ are very common.
__________________ often form from the friction between moving tectonic plates.
This accounts for ____ percent of all earthquakes.
The Juan de Fuca convergent plate boundary west of
__________________________has many earthquakes.
Large earthquakes hit this region every
_____________________years.
Transform boundary
San Andreas fault
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7. Describing Earthquakes
Earthquakes are very difficult to __________________.
Scientists understand _________ they happen, but it is very difficult to predict their ________________, exact ___________________, and ________________.
Their pressure build-up happens underground, over very __________________of time.
What we do understand has helped us to prepare structures to survive them.
The _____________ of the earthquake is where the pressure is finally released.
The _________________ is the point on the surface directly above the focus.
Earthquakes occur at various ____________, depending on the plates involved.
Earthquakes at the ____________________ tend to cause more damage.
See page 528
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8. Describing Earthquakes (continued)
Earthquakes produce ________________________.
______________________________ is the study of these waves.
These waves reveal the _____________ and ____________ of an earthquake.
They also help us learn about the_________________________and _______________________ of the Earth’s interior.
Types of earthquake waves:
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9. Describing Earthquakes (continued)
Seismic waves behave differently in different __________________.
Knowing this, scientists can learn about earthquakes and Earth’s ___________.
______________________ are used to measure seismic wave energy.
Early seismometers just measured whether the _______________________.
Some seismometers measure ________________ movement, others _______________ movement.
A _______________ is produced, showing
when an earthquake started, how _______
it lasted, and the ____________________.
___ increase in magnitude = ____ stronger
A magnitude 6 earthquake is
_______ more powerful than a 4.
Since seismic waves travel at different speeds,
a __________________________ graph can reveal the focus.
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10. The ________________ of tectonic plates causes volcano formation.
Volcanoes
The ________________ of tectonic plates causes volcano formation.
___________________ volcanoes – found along plate boundaries
Layers of ash and thick lava form _________________________
As magma reaches the surface, it cools, hardens, and _______________________below.
_________________________; eventually,
there is an eruption.
____________ volcanoes – these are not found at plate
boundaries but instead form over _______________.
Thin magma/lava flows out from a hot spot
and forms a ______________________________.
The _____________________________are an example of a chain of shield volcanoes.
_____________ eruptions – occur along long ___________ in the lithosphere
These are not explosive, but they release massive amounts of __________.
Mount St. Helens is composite volcano.
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