You're right, the continents are moving.
Actually, the continents are parts of larger
plates that make up the Earth's crust. These
plates are shifting around at rates on the order
of millimeters per year.For example, here in
southern California, the plate under the Pacific
Ocean is sliding north along the edge of North
America. Because the rates of movement are so
slow and the Earth's surface is so large, it takes a long, long time for a super continent like
Pangaea to form. Tens of millions or hundreds of millions of years in fact.
There are some places on Earth today where continents are colliding. You've heard of the Himalayas? The Himalayan Mountains are forming as India moves north into Asia, causing the Earth's crust there to fold and
push up into mountains. It's possible that more continents will collide to form a super continent sometime in the far, far future.
The continents are continuously moving at the rate your fingernails grow--a few centimeters a year.
Pangaea is the name of the most recent super
continent. Take a look at a map of the word that includes topography of the oceans, and you'll see what looks like a submerged mountain range in the middle of the Atlantic. This is one region where the continents are spreading apart from each
While the continents will probably never
look exactly like Pangaea again, they will
inevitably form a super continent again, and
scientists predict that the next super continent will form in the next 200-300 million years (it's hard to predict, since we have to assume that the current movement of the plates will not change with respect to each other).
Earth's tectonic plates are constantly moving -- just like you heard -- at about the same rate our fingernails grow. That amounts to, at most, a few inches per year.
Geologists think that sometimes the continental crust is all pretty much in the
same part of the globe (like Pangaea) or split
into a lot of different continents (like now).
They call this the Super Continent Cycle.
The last time Earth had a super continent was ~200 million years ago when Pangaea broke up. The time before that was ~580 million years ago
--geologists call that one Rodinia. In another ~250 million years the Earth will probably have another super continent.
Check out the Paleomap Project to see pictures of what geologists think
the Earth looked like through time and how it will
look in the future.
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.
So, the continents are not reforming back into another super continent,they are constantly moving around on the surface of the earth, carried along by the motion of the larger tectonic "plates." If you want to learn more about this, you can go to the web page of the Geology Department at UCSB,
Geology animations; look at these animations of plate tectonics by Professor Tanya At water.
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
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,
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!
They will never form the same Pangaea that existed 200-250 million years ago, because the continents will be attached to each-other in different places. Antarctica and South America are currently moving away from other continents, not toward them, and east Africa is splitting off into the Indian Ocean. However, the rest of Africa, Europe, Asia, Australia, and North America will be a continuous land mass within the 25 million years.
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