Unit 4 The
Restless Earth
Part II Lessons
4, 5 & 6
http://wondrouspics.com/volcano-photos/
The Big Idea: The
movement of tectonic
plates accounts for
important features of
Earth’s surface and for
major geologic events.
Unit 4 Lesson 4 Volcanoes
Magma Magic
 Volcano-
any place where
gas, ash, or melted rock
come out of the ground
•
•
Magma -melted rock is less
dense than solid rock, so it
rises to the surface.
Lava - magma that has
reached Earth’s surface. Lava
and ash erupt from a vent, or
an opening of a volcano.
•
•
Viscosityresistance to flow;
shape and
explosiveness of a
volcano depend on
the lava’s viscosity.
Pyroclastic
material- hot ash
and bits of rock,
may also be ejected
into the
atmosphere.
http://www.studyblue.com/notes/note/n/how-the-earth-worksfinal/deck/1690726
Volcanic Flow
http://www.zeitnews.org/node/3350
Unit 4 Lesson 4 Volcanoes
Volcanic Landforms
Shield volcanoes -broad
bases and gently sloping
sides.
1.
•
They are the result of mild
eruptions.
Cinder cones -small
volcanoes with steep
slopes.
2.
•
They form from ash and
pieces of solidified lava
that fall around a small
vent.
Unit 4 Lesson 4 Volcanoes
Composite volcanoes- built from
alternating layers of hardened
lava flows & pyroclastic material.
3.

4.
Volcanic Landforms continued
They generally develop into large,
steep mountains. Have violent
eruptions
Lava plateau-fissure
eruptions produce flattened
layer of cooled lava
Unit 4 Lesson 4 Volcanoes
5.
Volcanic Landforms continued
Caldera – magma chamber empties, the roof
of the chamber can collapse, leaving a large
basin-shaped depression
 Magma chamber-expanded area of magma
Unit 4 Lesson 4 Volcanoes
Eruption! Where
do Volcanoes
come from?
 Tectonic
plates -giant sections of lithosphere on
Earth’s surface. Volcanoes can form at plate
boundaries or within the middle of a plate.
1. Divergent boundaries-creates fissure eruptions &
shield volcanoes, crust stretches & gets thinner.
Most occur on ocean floor, creating undersea
volcanoes, long underwater mtn range known as
mid-ocean ridge. On land the crust stretches
until a rift valley is formed.
http://ajs-geo-blog.blogspot.com/2012/03/rift-valley.html
Unit 4 Lesson 4 Volcanoes
2.
3.
4.
http://www.eclp.com.na/demo/geography/mod1page24.html
Convergent boundaries- composite volcanoes or
calderas can occur. Magma has high concentration of
fluids, which form gas bubbles
Hot spots-far from any plate boundary, shield
volcanoes, fissure eruptions & cinder cones can occur.
Ring of Fire –numerous explosive volcanoes that form
on convergent boundaries surrounding the Pacific
Ocean.
http://volcanoworld.wordpress.com/2011/12/12/what-is-a-hot-spot-and-what-is-a-mantle-plume/
Unit 4 Lesson 5 Earthquakes
Let’s Focus
•
Earthquakes are ground movements
that occur when blocks of rock in Earth
move suddenly and release energy.
The energy is released
as seismic waves that
cause the ground
to move.
http://www.fhmindia.com/tag/earthquakes/
Unit 4 Lesson 5 Earthquakes
What Causes Earthquakes?
1.Faults
-release of energy that accompanies the
movement of rock along a fault causes an earthquake.
2.Deformation-process
by which the rock becomes
deformed and changes shape caused by stress
As the stress on rock increases, the energy stored in it increases.
When the stress is released, the rock may return to its original shape.
When rock returns to nearly the same shape after the stress is removed, its called
elastic deformation.
3.Elastic
rebound- return of rock to its original shape
after elastic deformation
Unit 4 Lesson 5 Earthquakes
http://pmikecolumbus.wordpress.com/2012/02/29/ripples-in-the-water/
What is an Earthquake?
Focus-place
w/in Earth
along a fault where the
first motion of an
earthquake occurs.
Seismic waves flow
outward in all directions
Epicenter- place on
Earth’s surface directly
above the focus
http://geomaps.wr.usgs.gov/parks/deform/geqepifoc1.html
Unit 4 Lesson 5 Earthquakes
Where do Earthquakes happen?
 Divergent
boundaries- tension stress causes
normal faults to form. Earthquakes tend to be
shallow because the crust is thin.
 Convergent boundaries- rock is squeezed, &
the stress is called compression. Reverse faults
are formed, and earthquakes can be strong and
deep.
 Transform boundaries- shear stress pushes
tectonic plates in opposite directions.
Earthquakes tend to be relatively shallow.
Unit 4 Lesson 6 Measuring Earthquake Waves
Shake, Rattle & Roll
Seismic
waves vibrations that cause
different types of
ground motion. Their
speed depends on
what they travel
through
1. Surface wavestravel along Earth’s
surface
Unit 4 Lesson 6 Measuring Earthquake Waves
Seismic Waves continued
2.
Body waves- travel through Earth’s
interior
A.
B.
P waves – pressure waves or primary
waves are the fastest
S waves- shear waves secondary, move
side to side
Unit 4 Lesson 6 Measuring Earthquake Waves
Wave Action!
Seismogram
-tracing
of earthquake motion.
It also records the
arrival times of
seismic waves at a
seismometer station.
Page 259 to see triangulation.
http://www.qrg.northwestern.edu/projects/vss/docs/navigation/1-what-is-triangulation.html
Unit 4 Lesson 6 Measuring Earthquake Waves
http://www.panorama.am/en/society/2012/10/08/mes-az/
Earthquake Measurement
Magnitude-
measure of the energy
released by an earthquake, larger
magnitude = stronger earthquake
 Richter
scale-measures ground motion
from an earthquake to find the strength
 Moment Magnitude scale-more accurate
for large earthquakes, based on area of
moving fault, avg distance the fault
moves & rigidity of rocks in the fault.
Unit 4 Lesson 6 Measuring Earthquake Waves
Did you feel that?
 Intensity-effects
of an earthquake and how the
earthquake is felt by people
Effects of an Earthquake
1. Magnitude
2. Local geology
3. Distance from the epicenter
4. Type of construction used
http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/
Notes/earthquake_effects.html
http://www.ga.gov.au/ausgeonews/ausgeonews200606/sediments.jsp