Name: _______________________________ Period: _________ Date: ____________
The 1964 Alaska Earthquake & Tsunami
Directions: Use the videos and this packet to analyze the Great Alaska Earthquake & Tsunami. Answer each
question in complete sentences.
Watch Videos Online:
https://www.youtube.com/watch?v=zZt9EZ3Q3qQ
https://www.youtube.com/watch?v=09xQ8n6GiTY
1. Where do most Earthquakes occur? Why do they occur there?
2. Plate Boundary of the Earthquake:
a. What plate boundary caused this earthquake?
b. What kind of a plate boundary is it?
c. Which plate is overriding?
d. Which plate is subducting?
3.
What other hazards to human safety exist OTHER THAN Earthquakes exist on the Aleutian islands?
a.
b.
4. List three things that caused damage in ALASKA.
a.
b.
c.
5. What caused the ground in Anchorage to both subside and be uplifted?\
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6. Why are there often fires and no water to fight them after an earthquake?
7. What is a tsunani?
8. Why are tsunamis so dangerous?
a.
b.
9. Why was the village of Valdez moved instead of being rebuilt in the same place?
10. List safety measures you can take.
a. Before an earthquake:
b. During an earthquake:
c. After an earthquake has occurred:
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1964 Alaska Earthquake
On Friday, March 28, 1964, the second largest
earthquake ever recorded struck near
Anchorage, Alaska. It was early evening, and
many people were already at home for the
holiday weekend of Good Friday and Easter.
The quake was a magnitude 9.2 earthquake,
which made it the largest quake that has hit
the United States in recorded history. The
earthquake also caused a large tsunami, which
affected areas all along the west coast of the
United States, and Hawaii, 2,800 miles away.
In Alaska, only 117 deaths were attributed to
the quake and tsunami combined, while the
widespread damage to man-made structures
was valued at 2.3 billion in today’s dollars.
The epicenter underneath a body of water
called Prince William Sound. The convergent
boundary between the Pacific Plate and the
North American plate slipped, which means it
moved a large distance in a short amount of time. Large areas near the plate boundary were uplifted, some as
far as 38 feet. Other areas subsided, or sank, some as far as 22 feet. Landslides occurred at the surface, as well
as beneath the surface of the ocean. Ground failure led to huge fissures in the ground and widespread
destruction of buildings, railroads, factories, mines, and homes. Seiche waves are waves that form in enclosed
bodies of water like lakes and ponds. Seiche waves and changes in water levels in drinking wells were
observed as far away as South America and Africa after the Earthquake.
Cause of the Earthquake
The Great Alaskan Earthquake was the result of the movement of huge plates of the earth's surface. This
process of plate tectonics causes quakes when neighboring plates interact. In this case the Pacific Plate
containing the Pacific Ocean is being pushed under the North American Plate. This kind of subduction causes
the largest and deepest earthquakes known. As the more dense, thinner Pacific Plate dives under the thicker, less
dense continental crust, it also pushes up portions of the ocean crust which rise as mountain ranges. In Alaska,
this subduction zone has created the Aleutian Islands, a chain of volcanic islands that stretch along the cost of
Canada, Alaska, and trail across the Pacific nearly to Russia. All along the islands, volcanoes erupt as the
descending ocean plate heats up in its descent towards the earth's mantle. Under tremendous heat and pressure,
the rock melts and magma rises to the surface in periodic eruptions.
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Description
The earthquake started with a few seconds of small tremors called foreshocks. The Primary Waves arrived in
Anchorage only about 30 seconds after the earthquake began at the epicenter. When the Secondary Waves
arrived, they quickly built into intense shaking that knocked people down, caused trees to whip back and forth,
started building collapses and destroyed water, sewer, gas, and phone lines. The shaking lasted for a full 5
minutes. Anchorage is built on soft ocean sediements, and the shaking cause liquefaction, or in other words,
the solid ground began to ripple like quicksand. The longer the ground shakes, the more damage will occur as
structures first weaken and then collapse under the strain. The long period of shaking in this quake caused much
of the ground failure that was observed.
Downtown Anchorage was especially
hard hit. Building facades crashed
into the street. In some places, one
side of the street dropped down over
10 feet, leaving the facing buildings
towering above. In places the ground
rippled in waves that peaked at 3 feet
high. Fissures opened up as blocks of
earth dropped and tilted. Cliffs
collapsed in huge landslides. Other
landslides into bays near Valdez and
Seward sent 35 foot waves sloshing
back and forth like water in a bathtub.
In Seward, an oil tanker was
wrenched loose from a pipeline,
which erupted in flames, spreading to
the nearby oil tanks. Burning oil on
the water washed inland and set fires
on the land. Ships were battered against piers, tossed up onto the shore by tsumani waves, and left stranded far
above the normal water line.
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Tsunamis
A tsunami is a large wave caused by an sudden push of the crust on the ocean water, very similar to the ripples
from a rock thrown into the water. Unlike normal ocean waves, tsunamis have a very long period between the
waves. While normal waves on the beach might come in every half minute or so, a tsunami's waves will be
separated by many minutes or hours. Not only are crests of the waves very high, but the troughs between the
waves will be very low. Usually as the tsunami comes onshore, the wave trough arrives first, causing the sea
level to drop, exposing the seabed. Soon however, the crest arrives, flooding coastal areas. Anybody living near
the coast should be aware of tsunamis and ready to move to higher ground immediately after an earthquake or
when tsunami warnings are in effect.
Tsunami waves can travel very rapidly across thousands of miles of ocean. In deep water the tsunami may only
raise the ocean level by a few inches, hardly enough to notice. But as it approaches land, the shallower water
causes the wave to build much higher and suddenly flood coastal areas. Tsunamis carry a lot of energy and
when they hit the coast. Strong currents can cause massive erosion of the coastline as well as tearing apart
buildings it encounters. Typically a tsunami will last for a period of hours with successive waves drastically
lowering and raising the sea level. Although scientists now understand the causes of tsunamis, there are many
local factors including the slope of the seafloor at a given location, the distance and direction of travel from the
earthquake that will determine the severity of the resulting wave.
Most tsunamis are too small to be noticed but the Tsunami Warning Center in Hawaii tracks them and sends out
warnings when there is a chance of a large one. Unfortunately, some of the worst tsunamis occur near the
epicenter of the originating earthquake and therefore give little warning.
In 1964, Tsunami waves were
recorded as high as 219 feet in
Shoup Bay, near the village of
Valdez. Another small fishing
community mostly populated by
native Innuit people, Chenga, lost
1/3 of its 75 residents to the
tsunami. In Hawaii, waves were
more than 12 feet high and killed
119 people. In both Chenga and
Hilo, HI, the water drew away from
the shore, leaving fish flopping
around on the tidal flats. As the
water went out, residents went out
to gather the fish, then getting
caught in the waves of incoming
water. In the village of Valdez, the
tsunami damage was so complete
that the entire village was moved to a new location instead of being rebuilt. In Hilo, a break water was built and
a large part of the shore front area converted into a park instead of being re-built after the destruction.
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Be Prepared
There are a number of factors that affect how much damage a given earthquake will cause. A quake that occurs
in a populated area will be more damaging than one in the wilderness. Soft soils will shake a lot more than
bedrock, and cause a lot more damage. Building methods will also affect how well a building will ride out the
quake. Some earthquakes that have had extremely high death tolls took place in areas of the world where
buildings were not well-engineered to withstand earthquakes like Haiti, Sumatra, and Indonesia. There are a
number of things that you can do before, during and after an earthquake that will help you be safe in an
earthquake.
Before
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Know your risks. Different places have a different chance of a big earthquake. Some areas might not be
in danger of having an earthquake, but could be in a tsunami zone.
Prepare your House.
o Make sure that your house is bolted to the foundation to prevent it from being knocked off its
foundation.
o Secure furniture such as bookcases and picture frames to the wall.
o Install cabinet latches to prevent heavy or breakable items from spilling out during a quake.
o Make sure that beds are not located in hazardous positions. Windows and heavy objects should
not be located where they can fall on you, especially on your head, while you are sleeping.
Prepare Your Emergency Supplies
o Have enough food and water on hand to last several days. You may be on your own for that long,
or longer, before authorities can get a relief system set up.
o Have your emergency supplies in one place so you can get to them quickly after the earthquake.
Many people use a large storage box
o Check your supplies periodically, to make sure that everything is still there and useable. Put
fresh food, water and batteries into the kit and use the old ones.
o Water - allow one gallon per person per day. Remember that water mains may be broken,
contaminating the water supply or cutting it off entirely.
o Food - choose items that are compact, nutritious, do not need refrigeration, and can be prepared
under adverse conditions with a minimum of cooking.
o Keep a fire extinguisher that has been recently serviced and is ready to use. Know how to use it!
o Portable Radio and extra batteries - So you can hear official bulletins and news.
o Flashlights and extra batteries.
o First Aid kit.
o Camp stove with fuel and matches.
o Blankets, warm clothing and sturdy shoes.
o Large, sturdy plastic bags.
Have an Emergency Plan
o Make sure that all family members know what to do in an earthquake.
o Decide on some safe places at home, work or school where you can ride out the quake.
o Plan an evacuation route if you are in a tsumani zone. Know where you will meet if you get
separated from your family while evacuating.
o Arrange an emergency phone contact. Phone lines might be out or your cell phone battery might
be dead, so make sure the phone numbers are written down somewhere besides your contacts on
your phone or computer.
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During
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Stay Calm - remember your earthquake or tsunami plan and follow it.
Take shelter in an interior doorway or under a sturdy table or in an area protected from falling objects
and breaking glass.
Do not run out of a building. Outside, you could be exposed to falling glass, bricks, or power lines.
If outside, move away from buildings or power lines. Be careful about standing in the street. Drivers
could panic or lose control of their cars during a quake.
If you are driving, slow down and pull over if it is safe to do so. Watch out for overpasses, bridges and
other objects that might collapse. Avoid these if possible.
After
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Help Injured People.
Check for fires
Check for damaged gas or electrical lines. Notify emergency personnel of any problems you find.
Turn off the gas if you have reason to believe that there is a leak in your house.
Keep people away from downed power lines.
Aftershocks are common. They may be strong enough to cause further damage, especially to already
weakened buildings. Stay away from anything that could fall in an aftershock.