Super Slow Motion (with answers)
PURPOSE:
To understand that given enough time, an extremely slow rate of drift can produce
significant distances.
MATERIALS:
Metric ruler
Calculator
Cardboard cutout of California
Scissors
PROCEDURE:
1. Cut out the California map along the San Andreas Fault.
2. Scientists estimate that continents drift on top of the Earth’s mantle at about the rate
of a growing fingernail. Estimate how many centimeters your fingernails grow in one
year.
3. Assume that two places on the Earth’s surface which were once next to each other
drifted apart 5,000km. How many centimeters is that?
4. If these two places began separating 100,000,000 years ago, how many centimeters
per year did they move? Draw a line at #5 on your answer sheet to indicate this
distance.
5. If San Francisco and Los Angeles are moving toward each other at the rate you
determined, and if they are now 500 kilometers apart, how long will it take for the cities
to become next door neighbors?
ANSWERS:
1. ____5______ cm/year
2. _____500,000,000_*____ cm
*since 100cm = 1m and 1000m = 1km, then 5,000km 5,000X1000X100=500,000,000cm
*Solve using the formula, d = rt. If the distance between these two places lengthen 5 x
108cm over 1 x 108(100 million) years, then they moved at a rate of 5 x 10 8cm ÷ 1 x
108yrs. = 5cm/year
4. ____10,000,000*______ years
*Solve using the formula, d = rt. Since the different plates (and the cities on them) are
moving toward each other at the rate of 5cm/year, and their present distance is 500km,
then it will take 5 x 10-6km/year ÷ 500km = 1 x 107 or 10,000,000 years.
5. Draw here:
Actual measurements taken at observatories in the U.S. and in Sweden indicate that the
North Atlantic is separating at a rate of 1 – 2 cm/year. Some areas in the Pacific Ocean
are widening as fast as 17cm/year.
HINTS:
1. Your fingernail grows about 5cm per year.
2. All of the Earth’s plates are not moving at the same rate. Some are moving at 2cm a
year while others travel at 18-20cm a year.
3. These problems are all variations on the familiar formula d=rt.
4. There are 100,000 centimeters in a kilometer.