Re: Is continental drift caused by earth expansion?
Date: Thu May 7 10:04:03 1998
Posted By: Bill Raatz, Ph.D., Exploration geologist, Stratigraphy/sedimentology, ARCO International Oil & Gas Co.
Area of science: Earth Sciences
Dear A. Compton,
Thanks for your interesting question on the idea of an
expanding earth as the driving mechanism of continental
drift. In short, almost no one subscribes to the
expanding earth hypothesis. A very few free thinkers in
Australia support the idea, and I think one professor at
either the Univ. of Texas or Texas A&M.
As you rightly observe, on the surface the idea has some
merit. A reconstruction based on a small earth composed
entirely of land which then breaks apart due to
expansion would fit our observations that continents
were at one time all connected. There are some
problems, however, and today almost all scientists
believe that the earth has retained pretty much the same
size through time and that land masses float atop a
liquid mantle and move due to mantle convection.
I have not made a study of the small earth hypothesis,
but the following general points against it come to
Cranky feeling ideas that are contrary to present
thinking are incredibly valuable both because they force
us to reexamine our assumptions and because when true,
they revolutionize our views of the earth. Therefore I
wouldn1t pass absolute judgment against the idea,
especially when I haven't investigated the subtleties of
the expanding earth people's arguments. That being said
it is very very unlikely to be true. I encourage you to
investigate it further.
- The earth, like all rocky planets, is cooling
through time. Cooling creates contraction rather than
- A smaller earth implies that the earth either had
less mass or was more dense in the past. If it had less
mass, it could only gain more through meteor
bombardment, which is quite a small source of material.
If it was more dense, this implies that it was cooler
which goes against point number 1.
- Modern measurement techniques are so sophisticated
that I think if the earth were actually expanding we
could detect it. It is true that the
subtly changes through time (the study of this is called
geodesy) but the absolute volume does not change.
- The small earth hypothesis predicts that all of the
continents were together at the earth's beginning (say 5
billion years ago), and as expansion occurs through time
they drift further and further apart. Although the
earth's land mass has been connected in the past, the
timing of this supercontinent (called
Pangea) is very
precisely known from both fossil and magnetic evidence
to be only about 250 million years ago. In fact,
detailed reconstructions of plate movement through time
shows that the early earth had lots of small
microcontinents that randomly collided and accreted.
This is why large continents have their oldest rocks in
the center with successively younger rock outward.
Landmasses have come together and broken apart many
times in earth's history without following the predicted
pattern of less interaction through time as supposed by
the expanding earth model. What we see today as far as
the earth's continents fitting together like a puzzle is
simply the result of the latest break up. In the
future, continents will again collide and break apart.
India's collision with Asia forming the Himalayas is a
Current Queue |
Current Queue for Earth Sciences |
Earth Sciences archives
Try the links in the MadSci Library for more information on Earth Sciences.
MadSci Home | Information |
Random Knowledge Generator |
MadSci Archives |
Mad Library | MAD Labs |
MAD FAQs |
Ask a ? |
Join Us! |
Help Support MadSci
© 1995-1998. All rights reserved.