Test- Plate Tectonics
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Western University *
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Course
CGF3M
Subject
Geology
Date
Jan 9, 2024
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doc
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4
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Name: ____________________________
Date: _____________________________
KNOWLEDGE
1. Name the type of tectonic plate boundary associated with each of the following:
CGF 3M1 Test: Plate Tectonics
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A.Iceland ______________________________________
B.Mt. St. Helens_________________________________
C.San Andreas Fault______________________________
D.Marianas Trench______________________
E.Folding_____________________________
F. Sea Floor Ridges______________________
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2.
TRUE / FALSE
A.
Earthquakes are most frequent along ridge axis plate boundaries _________________________
B.
Volcanoes occur most often along transform plate boundaries____________________________
C.
Earthquakes, volcanoes, folding & faulting occur at subduction zones_____________________
D.
The further a tectonic plate edge is located from the coastline of the continent under which it is
being subducted, the deeper the source of the earthquake_______________________________
E.
Mt. St. Helen’s is an extinct volcano_______________________________________________
F.
The only seismically active region in Canada is along the West Coast_____________________
G.
Tectonic plate subduction along the Rim of Fire has produced volcanoes in Canada__________
3.
Identify the name of the tectonic plate represented by each of the following letters:
A.
___________________________
B.
___________________________
C.
___________________________
D.
___________________________
E.
___________________________
Source:
http://wrgis.wr.usgs.gov/docs/usgsnps/misc/pdfdocs.html#dynamic
4.
Choose from the following list of terms to identify the process or feature
best
represented by each
diagram below. Write your answer in the space provided below each:
vulcanism, thrust fault, normal fault, folding, transform fault, subduction
i______________________ ii
_____________________
iii _____________________
Choose from the following list to identify the features represented by each letter:
block mountain, rift valley, syncline, anticline, volcanoe
a
. ______________________
b.
_________________________
c.
__________________________
a
b
c
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Refer to the diagram below and match each number with the corresponding descriptions that follow.
Write the appropriate number in the space provided.
_____ Beneath the lithospheric plates lies a layer semi-molten rock called the ASTHENOSPHERE. The asthenosphere is more dense than
either continental or oceanic lithosphere. This means that the plates are floating on top of the asthenosphere.
_____The 'gap' between these diverging plates fills with molten rock from below. Sea water cools the molten rock, which quickly solidifies,
forming new oceanic lithosphere. This continuous process builds a chain of volcanoes and rift valleys called a MID-OCEAN RIDGE or
SPREADING RIDGE.
_____ Deep within the asthenosphere the pressure and temperature are so high that the rock softens and partially melts. This softened, dense
rock can flow very slowly (think of Silly Putty). Where temperature instabilities exist near the core/mantle boundary, slowly moving
CONVECTION CURRENTS may form within the semi-fluid asthenosphere
_____Convection currents bring hot material from deeper within the mantle up toward the surface.
_____ Convection currents diverge where they approach the surface. The diverging currents exert a weak tension or "pull" on the plate above
it. Tension and high heat flow weakens the floating, solid plate, causing it to
break apart. The two sides then move away from each
other in opposite directions, forming a DIVERGENT PLATE BOUNDARY.
_____
The sinking leading edge of the oceanic plate actually 'pulls' the rest of the plate behind it. ‘Evidence suggests this is the main driving
force of SUBDUCTION. Geologists are not sure how deep the oceanic plate sinks before it melts, but we do know that it remains solid
far beyond depths of 100 km beneath the Earth's surface.
_____ There are two basic types of lithosphere, CONTINENTAL and OCEANIC. Continental lithosphere is made of relatively light-weight
minerals, so it has a low density. Oceanic lithosphere is more dense than continental lithosphere because it is composed of heavier
minerals. A single plate may be partly oceanic and partly continental lithosphere.
_____
The newly generated molten mantle is less dense than the surrounding rock, so it rises toward the surface. On its way upward, dense
minerals solidify from the magma and are left behind, making the magma increasing less dense as it approaches the Earth's surface.
Most of the molten rock cools and solidifies in magma chambers far below the Earth's surface. Large INTRUSIVE rock bodies that form
the backbones of great mountain ranges such as the Sierra Nevada form by this process.
_____
As you know, denser materials sink, and that's exactly what happens to the oceanic plate starts to sink into the asthenosphere!
Where
one plate sinks beneath another a SUBDUCTION ZONE forms.
_____
Some molten rock may break through the Earth's surface, instantly releasing the huge pressure built up in the gas-rich magma
chambers below. Gasses, lava and ash explode out from the surface breach. Over time, layer upon layer of erupting lava and ash build
volcanic mountain ranges above the simmering cauldrons of crystals and magma below
_____ Little by little, as new molten rock is extruded at the mid-ocean ridge, the newly created oceanic lithosphere moves away from the ridge
where it was created
_____ As distance from the hot spreading ridge increases, the oceanic plate cools down. The colder the oceanic plate gets, the denser
('heavier') it gets. Eventually the edge of the plate that is farthest from the spreading ridge cools so much that it becomes more dense
than the asthenosphere beneath it.
_____
When the subducting oceanic plate sinks deeper than about 100 kilometers below the Earth's surface, huge temperature and pressure
increases cause water and other volatile gasses trapped in the minerals of sinking plate to be released. These gasses work their way
upward, MELTING THE MANTLE above the subducting plate.
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