Probing beneath Earth surface to understand what's there
MAIN ACTIVITY
Because many geological features like craters are buried, geologists must find
ways of probing beneath Earth's surface to understand what's there. Since it
would be too expensive to simply dig one big hole, geologists do the next best
thing--they drill long, slim holes and correlate the sections. In this activity, you can try your hand at unmasking a hidden geological structure.
Materials
- a cardboard shoe box
- 4 or 5 colors of plastic modeling clay, about 1 lb of each
- 25 wide plastic straws
- small, sharp scissors
- a metric ruler
- 2 blank pieces of paper and a pencil
- Before starting this exercise, someone must create a geological
structure in the shoe box.
Begin by placing layers of clay, each a different
color, one on top of each other in the box.
Vary the thicknesses of the layers.
In the middle of the box, either create a crater by cutting out a circular
depression or make a dome by burying a big ball of one clay color in the
different layers.
Once the structure has been completed, give it to the
students doing the drilling.
- To "drill" the structure, slowly insert one plastic straw into the top
and push it down all the way to the bottom of the box.
Before removing the
straw, measure the exact location of the core relative to two sides of the box
and mark that point on the blank paper.
Label it "core 1."
- After marking the core location, slowly remove the straw.
The clay should
stay inside.
With the scissors, carefully cut the straw lengthwise, starting
at the bottom.
Try not to disturb the clay inside. Using the ruler, start at
the bottom of the straw and measure the thickness of each color of clay.
Draw
this on the second piece of paper and label it "core 1."
- After marking the first core, take a second straw and repeat steps 2 and
3 in a second location.
Continue until you have drilled, located, and
measured 20 cores.
Based on the location of the cores and the clay layers in
each one, see if you can reconstruct a three-dimensional model of the geology
in the shoe box.
When you think you have done it, peel away the sides of the
box and see how close you came.
Questions
- Based on this exercise, how might increasing or decreasing the number of
straws you use change the accuracy of your coring model?
- When you are cutting open your straws, what error factors must you
consider?
- Besides coring, what other methods might geologists use to "look inside"
Earth?
- What hazards might a drill team encounter if they were drilling rock
instead of clay?