Storm in A Jar
written by:
Cam Tsujita
Department of Earth Sciences,
The University of Western Ontario
Ingredients
1 large (2 litre or more) plastic jar (such as
a large peanut butter or pickle jar) or flat-bottomed plastic storage container
1 cup of sand
1 cup of mud (a well- mixed slurry of clay-rich
soil and water will do)
1/2 cup seashells or pebbles
water to fill jar to about 5 cm from top
Procedure:
Place all ingredients in the jar. Shake
jar vigourously (this simulates turbulent conditions during a tropical
storm). Let contents settle (this simulates settling process as storm
wanes) for about 1 hour. After contents have settled, observe the
sedimentation pattern in the jar.
Observations:
After contents of the jar settle, you will hopefully
note that the storm deposit is coarse-grained on the bottom (shells and
gravel concentrated at base of deposit) and finer-grained on top (gravel
overlain by sand and, in turn, by mud). This sedimentation pattern,
called "graded bedding" is evidence that can be used to recognize storms
in ancient rocks.
Additional Comments:
Next time you see an outcrop of marine sedimentary
rock containing fossils, look closely and see if you can recognize evidence
of storms .