“Earthquake/volcano Study Guide”
1. Why do earthquakes take place? Completely explain the entire process.
Applying stress to a rock will cause it to bend or stretch. Stress causes the rock to deform. When
the rock can’t handle the stress it eventually breaks. The area in which a rock breaks is called a
fault. When the break occurs energy is released. The energy causes the crust to vibrate.
2. How is each of the seismic wave types different? List two differences.
1. Primary Waves (P waves) - Energy waves that move through the ground in a back and forth
.
motion P waves are the fastest moving earthquake waves. (6km/s).
2. Secondary Waves (S Waves) - Move through the ground in an up and down motion. * S
waves move half as fast as P waves. (3 km/s)
3. Surface Waves (L Waves) - Energy waves that travel along the surface of the earth like waves
do in the ocean. (Rolling motion)
* L waves move the slowest. (1 km/s)
3. How could seismic waves be used to find the epicenter of an earthquake?
Completely explain the entire process!
When an earthquake occurs P waves will reach the seismograph station before the S waves. The
further the epicenter, the higher the interval between the P wave and the S wave arrival time.
When seismic wave information is obtained by at least three stations, the epicenter of an
earthquake can be found. P waves travel 6 km/s and S waves travel 3 km/s. When the waves
arrive at the station we can calculate the distance to the epicenter. Scientists at each station draw
a circle on a map The radius of each circle is the distance away the earthquake epicenter was.
The place where all three circles cross is the epicenter.
4. Explain how the Richter scale works.
Magnitude is measured using the Richter Scale.
A 1 magnitude earthquake is the weakest and a 10 magnitude is the strongest.
There has never been a reading over 9.5 (1960, Chile).
An earthquake that is 1 magnitude higher than another releases over 30 times more energy.
EX> How much more energy is released from an 8 mag. earthquake than a 6 mag. earthquake?
32 squared = 1024 times more energy released.
5. Why do we get Tsunami? (List three ways)
Under water earthquake, volcanic eruption, landslide, and meteorite impact will cause the
ocean water to displace. This will generate a large series of waves that will push inland.
6. What can be done to increase earthquake safety and reduce earthquake damage? List
and describe three examples.
1. Buildings and highway over passes are being reinforced with alternating layers of steel and
rubber. 2. Highways are built with concrete reinforced with steel 3. Some building
foundations are built on rollers that can slide on steel beams a few millimeters to ease stress.
7. If the P and S wave arrival differences for three stations here 3 minutes and 20
sec, 5 minutes and 45 sec, and 7 minutes and 20 seconds what are the distances way
from those earthquakes? Using the chart on page 2 of the epicenter lab you should find the
three distances are: 2000 km, 4000km, 5500 km.
8. What happens to the difference in P and S wave arrival differences if you get
further away from the earthquake? The difference will continue to increase as the distance
to the epicenter of the earthquake increases.
9. Where do most earthquakes take place in the contiguous United Sates, and why
do they take place there? Most of the take place in California. They occur there because of
the San Andreas fault and all of the faults that were caused because of the curve in the plate
boundary in California.
10. List and define the 3 types of faults. (Make sure to mention the stress involved
with each).1- normal –hanging wall goes down—caused by tension 2-reverse—hanging wall
moves up—caused by compression 3-strike-slip—walls move laterally—caused by shearing
---------------------------------------------------------------------------------------------------------1. What causes a volcano?
1. Rock has to melt into magma.
2. Magma is forced upward because it is less
dense than the rock layers around it.
3. When magma and other gases reach the surface it
turns to lava or volcanic ash.
4. Thais forms the volcano
2. Where do volcanoes occur?
Rift Zones, Subduction Zones, and Hot Spots
3. What causes a volcano to erupt violently?
A.) The amount of water and gas trapped in the magma. The more gas and water, the more
pressure
that can build up. B.) The type of magma. The higher the viscosity the thicker
the magma is. Thick magma can build up much more pressure because gases trapped in magma
can not escape.
4. What are the 3 types of volcanoes? Describe each.
-Shield Volcanoes - a broad volcano with gently sloping sides, built by nonviolent eruptions of
basaltic magma.
-Cinder Cone - Volcano that forms from volcanic material that is violently erupted and piles up
into a steep sided cone mountain
-Strato / Composite Volcano - Volcano that alternates between violent tephra (ash cinder, block,
bombs) eruptions and nonviolent lava eruptions.
5. Name (ex. MT. Pinatubo) an example for each of the volcano types.
Shield = Mt. Kilauea
Cinder Cone = Paricutin in Mexico (Corn Field Volcano)
Composite = Mt. St. Helens, Mt. Pinatubo
6. What is the life cycle of a volcano? (Explain the 3 stages of life/activity).
Active-currently showing signs of possible eruption, Dormant-not showing signs of
erupting, but still in an active zone, Extinct-no longer in active zone, little chance of
future eruption.
---------------------DRAW AND LABEL PARTS OF A VOLCANO------------------------