1964 Good Friday
Great Alaskan Earthquake
LIQUEFACTION and LANDSLIDES
Landslides and ground subsidence
caused the greatest damage to structures, not ground vibration.
Water mains, gas, sewer, telephone and electrical systems were
all destroyed in Anchorage, Alaska, which was the site of three
- Turnagain Heights
- A layer of clay lost its strength causing
200 acres of land
to slide toward the ocean.(3)
- The bluffs Turnagain Heights was built on were 22 meters
(72 feet) high.
- They collapsed
inland 300 meters (984 feet) from the bluffs' edge.
- 2800 meters (1.74 miles) of coastland were destroyed.(1)
- The displacements
caused by the landslide broke the
ground into blocks that collapsed
and tilted at all angles.
- 75 homes were destroyed.(6)
- The spreading was so intensive that two houses that
were originally more than two football fields apart
collided within the landslide area.
- The entire area suffered total destruction.
- Parts of it were never rebuilt, and have been
preserved in an area named "Earthquake Park".(4)
Another landslide took out Government Hill Grade School,
which was reported as a total loss.(6)
- Another huge slide caused the main business district to drop
3 meters (10 feet).(3)
- Fortunately the businesses were closed because it was a holiday.
Anchorage, Alaska sits on an ancient clay
deposit known as Bootlegger Cove Clay. This deposit
is what is known as a quick clay
. Quick clays exist
under ground as a solid gel. This gel turns to a
liquid when it is shaken. This process is known as liquefaction.
Liquefaction occurs in two forms.(4)
- Quick clay
- Sandy Soil
Sandy soil liquefaction happens when the spaces between the grains
of a sandy soil are saturated, completely filled up with water.
When this soil is shaken the grains compact, squeeze together,
and take up less space. The soil on top of the sand is then mostly
water, and can not hold up the buildings that are on it, so the
buildings sink, usually one corner at a time. Sometimes this
causes buildings to fall over on their sides.
Sandy soil liquefaction can also cause huge chunks of land to
slump, slide in one piece down a slope.
This happened in Valdez, Alaska.(4)
- In Valdez, Alaska 31 people died
while standing on a
dock waiting for a ship to come to shore.(3)
- The land above them slid into the sea because of sandy soil
- The water there was 10 meters (33 feet) deep then.
- The water there is 30 meters (100 feet) deep now.
- The landslide caused a seiche
to form, which continued
all night long.
- When Valdez was rebuilt, it was moved
7 kilometers (4.3 miles) away, to a location on more stable ground.(3)
Learn more about the 1964 Good Friday Great Alaskan Earthquake
Other sites of interest:
Windows to Arizona Geology
United States Geological Survey Report on
Slides, links to earthquake maps and location of
With many thanks to the following sources:
Macklin, T. for
photos by his brother.
1) Bolt, B., 1993, Earthquakes. W.H.Freeman and Company.
2) Christensen, D.
3) Lutgens, F. and Tarbeck, E., 1995, Essentials in Geology. Prentice Hall.
4) Pipkin, B. and Trent, D., 1997, Geology and the Environment. West/Wadsworth.
5) Sokolowski, T.
6) United States Geological Survey.
Page by Nievita Bueno Hartness
Last Updated 12/06/2001
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