Plate Tectonic Theory
BC Science 10 (pg. 510-514)
Today’s Objectives:
 Define plate tectonics, spreading ridge, hot spot
 Explain how plate movement produces the following features: spreading ridges;
mountain ranges and mid-ocean ridges; hot spot chains
 Relate the following to plate tectonic theory: world distribution of volcanoes,
earthquakes, mid-ocean ridges; hot spot and; magnetic reversals and age of rocks
relative to spreading ridges
Plate Tectonics
 In Wegener’s time, scientists did not know that Earth’s surface was broken up into large,
moveable ______ of rock
 These slabs are called ______________ ____________
 These rigid, solid plates ________ on top of a layer of _________ rock
 The movement of these plates result in the movement of the _______________
How do we know the Plates are Moving?
There are 4 main pieces of evidence:
1. Existence and patterns of ______________ and ______________
2. Existence of _________ __________
3. ______________________, the existence of magnetic striping
4. Existence of ____________ ___________ _____________
#1: Earthquakes and Volcanoes
•
only occur at plate _______________ (the edges of plates)
•
appear to occur when adjacent plates ________
•
_______________ objects cannot collide
•
suggests that plates must be _________
#2: Ocean Ridges
 These are under water mountain ___________
 A well known example of the _____ ___________ ________ which runs north to south
down the entire length of the Atlantic Ocean.
How is this proof???
 Can be best explained as a formation made by two plates moving ___________ from
one another
 As the plates move apart, they form a ________
 The hot magma rises through the gap, _______ and forms new rocks/mountains
Paleomagnetism
 This is the study of the magnetic properties of ____________ _____________
 Like Earth itself, its magnetic field is continually ____________
 In the last 10 million years the poles have shifted 4-5 times per million years!
#3- Magnetic Striping
 Scientists have discovered that Iron grains in rocks align with the _____________ _____
 They call this pattern ______________ ______________
 Can be explained if the plates are moving apart as the Earth’s magnetic field is ________
Stripes of rock at the
bottom of the ocean
that have alternating
magnetic patterns
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Seafloor Spreading
 Ocean ridges and magnetic striping both suggest that the sea floor is
_____________ or moving
 In other words “the plates” are moving
#4- Volcanic Island Chains
 Are chains of islands that are formed when ___________ reaches the Earth’s
surface and cools
HOT SPOTS
 ____________ = an area where ________ rock rises through the Earth’s surface,
________, and forms ______ rock
 _____________ __________ ____________ can be explained by Hot Spots
 Hot spots are ____________________ spots located BELOW the tectonic plates
 Hot Spots do not move, rather the _________ ______ _________ the hot spots!
 As the plates moves, the islands move as well.
 As a new portion of the plate moves over the hot spot a new island forms until
eventually you get a ________ of islands
For example, the Hawaiian Islands
They formed when the Pacific Plate moves North East
over a hot spot
 Typically the smaller islands = the _________ islands. Why?
 As time goes by the islands get __________ away by the ocean ________
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Plate Direction
 Not only does the existence of Volcanic chains and hot spots prove that plates are
moving...they can show the _______________ of plate movement!
Summary of Evidence that Prove that Plates can MOVE
1. _____________ ______ ____________ = occur as plates move and collide
2. ___________ ____________ = form as plates move apart
3. _____________ _____________ = form as plates move apart
4. _____________ _______________ = form as plates move over hot spots
The Theory of Plate Tectonics
 Is a unified ___________ that came out of the above evidence
 States that the Earth’s surface is made up of large ________ of rock that
________ and continually move on top of a ___________ layer.
 Came about __________Wegener’s Continental Drift Theory
 Supported Wegener’s theory as it explained how continents could move
PLATE FACTS
 There are 7 major plates and 5 minor plates – 12 plates total.
 It is on the edges of the plates – near the borders of plates where all the action is!
(earthquakes, volcanoes, mountain building!)
 These tectonic plates move approximately 1 inch per year due to CONTINENTAL
DRIFT!!!
›
That is the same rate as your fingernails grow!!!
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