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Earth Systems, Structures and Processes Notes
6.E.2.2 Explain how crustal plates and ocean basins are formed, move and interact using
earthquakes, heat flow and volcanoes to reflect forces within the earth.
The earth's plates sit on a dense, hot, somewhat melted layer of the earth. The plates move very slowly,
pressing against one another in some places and pulling apart in other places, sometimes scraping
alongside each other as they do. Mountains form as two continental plates, or an ocean plate and a
continental plate, press together. There are worldwide patterns to major geological events (such as
earthquakes, volcanic eruptions, and mountain building) that coincide with plate boundaries. Lithospheric
plates on the scale of continents and oceans constantly move at rates of centimeters per year as a result
of movements in the mantle coupled with characteristics of the plates themselves. Major geological
events, such as earthquakes, volcanic eruptions, and mountain building, result from these plate motions.
The crustal plates range in thickness from a few to more than 100 kilometers. Ocean floors are the tops of
thin oceanic plates that spread outward from mid-ocean rift zones; land surfaces are the tops of thicker,
less-dense continental plates. Earth is made up of 4 different layers: inner core, outer core, mantle, crust.
Seismologists have studied how wave energy travels through the different layers of Earth. Waves have
characteristics: frequency, wavelength, amplitude and speed. During an earthquake, energy is released
into the Earth as: Primary waves, Secondary waves and Surface waves.
Drifting Continents (154-158)
Explain Alfred Wegener’s hypothesis about drifting continents:
Evidence that supports his hypothesis:
Land Features
Fossils
Climate
Explain why Alfred Wegener’s hypothesis
was rejected by other scientists.
Sea-Floor Spreading (159-165)
What is a mid-ocean ridge?
Explain how sea-floor spreading works:
Evidence for sea-floor spreading
Evidence from molten
material
Evidence from magnetic
stripes
How can the ocean floor keep getting wider?
Explain what happens during subduction?
Subduction at trenches:
Try these:
1.
Subduction of the ocean floor takes place at
a.
The lower mantle
Evidence from drilling
2.
b.
Mid-ocean ridges
c.
Rift valleys
d.
Trenches
In a process taking tens of millions of years, part of the ocean floor sinks back into the mantle at
a.
deep-ocean trenches
b.
Mid-ocean ridges
c.
The coast line
d.
The mantle
The Theory of Plate Tectonics (168-172)
What is the theory of plate tectonics?
Earth’s Lithospheric Plates:
Plate Boundaries:
Divergent Boundary
Convergent Boundary
Transform Boundary
Compare and Contrast:
Type of Plate
Boundary
Type of Motion
Effect on Crust
Feature(s) Formed
________________
Boundary
Plates slide past
each other.
_________________
_________________
_________________
_________________
________________
Boundary
_________________
_________________
Subduction or
mountain building
_________________
_________________
________________
Boundary
_________________
_________________
_________________
_________________
Mid-ocean ridge,
ocean floor
Try These:
1.
2.
The process that powers plate tectonics is
a.
Radiation
b.
Convection
c.
Conduction
d.
Subduction
Two plates collide with each other at
a.
A divergent boundary
b.
A convergent boundary
c.
The boundary between the mantle and the crust
d.
A transform boundary
Forces in the Earth’s Crust (180-186)
Explain stress:
3 Types of Stress
Tension
Compression
Shearing
Draw it
How does it work?
Results
Explain the difference between an anticline and a syncline.
Anticline
Syncline
Try These:
1.
2.
The force that causes part of the crust to become shorter and thicker is
a.
Tension
b.
Compression
c.
Shearing
d.
Normal force
_________________ usually occur along plate boundaries, where the forces of plate motion push or
pull the crust so much that it breaks.
a.
Compression
b.
Faults
c.
Footwalls
d.
Anticlines
Earthquakes and Seismic Waves (187-193)
What is an earthquake?
What do seismic waves do?
Types of seismic waves:
P Waves
S Waves
When do they arrive?
What happens?
Explain what the epicenter is and how it is located.
Try These:
Surface Waves
1.
2.
The largest waves on a seismograph are
a.
P waves
b.
S waves
c.
Surface waves
d.
Tsunami waves
Seismic waves carry energy from an earthquake away from the focus, through Earth’s interior and
across the ________________
a.
Mantle
b.
Inner core
c.
Outer core
d.
Surface
Volcanoes and Plate Tectonics (204-207)
What is a volcano?
Why do volcanoes form along the boundaries of Earth’s plates?
Explain why/how volcanoes form along diverging boundaries.
Explain why/how volcanoes form near converging boundaries.
Explain how hot spot volcanoes form.
Try These:
1.
Most volcanoes are located
2.
a.
In the ocean
b.
Along diverging and converging plate boundaries
c.
In Asia
d.
In the island arc
A volcano forms above _______________ when magma erupts through the crust and reaches the
surface.
a.
A hot spot
b.
The ring of fire
c.
A plate
d.
A convergent boundary
Volcanic Eruptions (209-216)
Draw and label a volcano and its 6 main parts. Use the figure on page 211 as a reference.
Explain how a volcano erupts.
Explain the two kinds of volcanic eruptions.
Quiet Eruption
Answer the questions below.
Explosive Eruption
1. Which is the basic composition of Earth’s core?
A. The solid inner core is surrounded by a liquid outer core.
B. The liquid inner core is surrounded by a solid outer core.
C. Both the inner core and the outer core are solid.
D. Both the inner core and the outer core are liquid.
2. Which best explains the movement of tectonic plates?
A. They move several miles each year because of convection within Earth.
B. They move several centimeters each year because of convection within Earth.
C. They move several feet each year because of convection within Earth.
D. They move several kilometers each year because of convection within Earth.
3. Lithospheric plates have moved to form land formations on the Earth's surface. Which land formation occurs as a
result of the plates folding upon one another?
A. an earthquake
B. a mountain range
C. a river
D. a volcano
4. What best describes the mantle of Earth?
A. a thin layer that is located on the surface
B. a solid layer made of iron and nickel
C. the largest layer between the crust and outer core
D. the smallest layer that is made up of molten rock
5. Due to extreme pressure, the inner core of Earth is
A. solid.
B. liquid.
C. gas.
D. Plasma.
6. Earth is made of different layers that have varying characteristics. Which is the thickest layer?
A. the mantle
B. the inner core
C. the outer core
D. the crust
7. Which event most likely takes place as the result of crustal movement along transform boundaries?
A. earthquakes
B. volcanic activity
C. mountain building
D. trenches