What you heard is only partially true. The
continents are not reforming Pangaea, but the
tectonic plates are in constant motion. In some places there is new material coming up from
beneath the crust - in the mid-ocean ridges. In
other places there is crust that is being pulled
down under another piece of crust - we call those
"subduction zones" such as under Japan. In still other places, plates are just slipping past each other -we call those transform faults. The San Andreas Fault is an example of this.
The part that you heard about the rate I believe is true. The rate at which new material is forming in the oceans, which translates into the rate at which continents are moving, is about 6
centimeters/year in the Pacific, and about 3
centimeters/year in the Atlantic. I think this is comparable to the rate at which your fingernails grow, but on that part I'm not totally
sure.
Take a metric ruler, and hold it up to your hand. Imagine your fingernails if they
were sticking out 3 cm from the end of your
finger, or as much as 6cm. That looks pretty long,
doesn't it?
You can try an experiment to see if your fingernails, in fact, do grow at rate between 3 and 6 centimeters/year. Every time you cut your fingernails, choose one finger - say the index finger on your left hand. Every time you cut your fingernails, save the clipping of your left index finger; measure the widest part of the piece of nail you cut, and write it down. Write down the measurement in millimeters (1 mm is one tenth of a centimeter) and write down the date. Keep this in a table. Make 4 columns: the date, and the measurement, in the first two columns. In
the next two columns keep a running total - add
the days, and add up the measurements.You could do
this for a full year, and see if your cuttings
amount to somewhere between 3 and 6 centimeters.
Or, you could do this for a portion of a year, and
then "extrapolate," that is, assume that the rate
of growth would be the same for the whole year,
and make a graph, and extend the graph. You can
determine the rate at which your nails grow per
day, per month, and per year.
Hey - this would be a totally cool science experiment for a science fair!I would be willing to meet with you and help you design the experiment, if you are interested.
All the best to you, and keep asking those great questions!