TEACHING CLUES AND CUES
Students may be aware
that the flooding of the
Mississippi and Missouri
Rivers in the summer of
1993 caused mud boils in some
places. Explain that these eruptions,
somewhat similar to sand boils, were
caused by extreme saturation of
muddy soils in combination with the
force of the torrential rains. Mud
boils, like sand boils, can also be
caused by earthquakes over
magnitude 5.0.
VOCABULARY
Consolidated:
tightly
packed, composed of
particles that are not
easily separated.
P ROC E DUR E
Teacher Preparation
Read Master 2.4a, Teacher Background Reading: Liquefaction, and
Master 2.4b, New Madrid Narrative. Decide how you will share this
information with your students. Students who like to read will find
New Madrid Narrative delightful.
Gather enough materials so you can have two students per station.
Before class, cover work areas with newspapers, set up the stations,
and practice each activity at least once to be sure everything works.
A. Introduction
Tell students that an earthquake with a magnitude of 5.0 or greater
may cause saturated sand or clay soils to liquefy. During the winter
of 1811 and 1812, a series of earthquakes affected the central por-tions
of the United States that we now know as Missouri, Arkansas,
Kentucky, Illinois, and Tennessee. As the soft sediments along the
rivers were violently shaken, tremendous volumes of sand were lique-
fied and ejected onto the Mississippi River flood plain. These sand
boils, as they are called, are still visible in the rural countryside today.
Fortunately the area of the earthquakes was not heavily populated in
1811-12, so loss of life, injuries, and loss of property were minimal.
During the 1989 World Series in San Francisco, a 7.1 earthquake
struck the Bay Area. Millions of people viewed firsthand the fires and
severe damage to buildings in the Marina District. Some of this
damage occurred because soil liquefaction caused lifelines to rupture
and buildings to collapse.
B. Lesson Development
1. Write the word
liquefaction
on the board, and ask student to
identify its root work (
liquid
). Emphasize that liquefaction does not
cause an earthquake, but is the result of an earthquake. Liquefaction
occurs only in highly saturated sand or clay soils. An earthquake with
a magnitude of 5.0 or greater is usually needed to cause liquefaction.
Earthquake vibrations cause soil particles to lose contact with each
other, so the soil takes on the characteristics of a liquid.
2. Assign a partner to each student and designate a work station for
each team. Give these directions:
a. Cut off about 5 mm from the bottom portion of the plastic cup.
b. Invert the cup and place it in the middle of the pie pan.
c. Holding the cup firmly, slowly pour the sand into the bottom of the
cup to a level of 10-20 mm from the top. (One student may hold while
another pours.) Level the sand with your fingers.
Do not shake the cup
to settle or level the sand.
d. Lightly place the sinker, model house, or other weight onto the
leveled surface of the sand.
Ground water:
subsurface or
underground water.
Lifeline:
a service that is vital to the
life of a community. Major lifelines
include transportation systems,
communication systems, water
supply lines, electric power lines,
and petroleum or natural gas
pipelines.
Liquefaction:
the process in which
a solid (soil) takes on the
characteristics of a liquid as a result
of an increase in pore pressure and
a reduction in stress.
Sand boil:
a forcible ejection of sand
and water from saturated soil,
caused by an earthquake or heavy
flooding.
Saturated:
having absorbed water
to the point that all the spaces
between the particles are filled, and
no more water can enter.
Unconsolidated:
loosely arranged,
not cemented together, so particles
separate easily.
A G U
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F E M A
90
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