MadSci Network: Earth Sciences
Query:

Re: WITH ALL THE TRUCKS AND CARS GOING N,S,E,AND WEST IS THERE ANY INFLUENCE

Date: Thu Jul 5 15:36:53 2001
Posted By: Carol Stein, , geology/geochemistry, Gannett Fleming, Inc.
Area of science: Earth Sciences
ID: 993612544.Es
Message:

Paul -

You've posed some interesting problems!  I am a geologist/geophysicist, and 
have worked with some dimensions of these sorts of problems, but cannot 
answer all of your questions knowledgeably.  

Magnetics:  This one is the farthest afield for me, but my guess is that 
moving large masses of magnetic materials around (for example, moving iron 
from ore deposits to end uses like building cars, and then having them move 
around on Earth's surface) will cause measurable perturbations to the 
magnetic field you measure locally.  That is, a magnetometer will sense the 
proximity of large metallic bodies.  However, in the "big picture," these 
changes will do virtually nothing to the global magnetic field, as it is a 
consequence of processes in Earth's core --- things happening on a vastly 
greater scale and involving vastly greater masses of material than anything 
mankind can perturb significantly.  

Earthquakes and volcanoes:   Again, I doubt that vehicle activity could 
ever be correlated with natural hazards.  You might think that earthquake 
and volcanic activity are controlled by stresses within Earth's crust --- 
that is, what is the pressure (due largely to the weight of overlying 
rocks) on a fault plane or a magma body, what kind of shearing are these 
areas subjected to, etc.?   The disturbance due to cars moving around is 
very tiny compared to the stress levels in the Earth's crust.  Moreover, it 
turns out that those loads on the surface don't affect things very deep, so 
they don't do much to deep crustal areas where earthquakes and volcanoes 
are originating.  However, interestingly enough, there is mounting evidence 
that very tiny stress changes can indeed "push the crust over the edge" and 
cause failures like earthquakes and eruptions.  For example, I worked with 
a researcher in Washington who found that Mt. Rainier apparently erupted 
shortly (geologically short, anyway!) after the last glacial retreat, and 
he speculated that the removal of the ice load on top of the mountain was 
enough to "uncork" the mountain, and trigger an eruption.  If that proves 
to be true, your instincts about cars may be on the right track!

One other thing about moving cars....  Years ago, I heard of speculation 
that cars passing each other on the highway tend to create vortices 
(spinning counterclockwise in the US where we drive on the right) that 
might then grow and increase tornado activity.  Someone tested this idea by 
looking at the frequency of tornadoes during World War II, when there was 
strict gasoline rationing, and driving was way down from pre- and post-war 
levels.  This study did find that tornado frequency seemed to be up in that 
era.  However, I believe that serious scientists doubt the significance of 
this result ---- That is, people who understand the fluid dynamics of 
atmospheric vorticity don't buy the idea that cars can change things 
significantly;  also, statisticians would point out that the data are too 
few to conclude with confidence that the correlation of amount of driving 
with number of tornadoes is meaningful.

I hope this helps some with your questions.... You have good insight into 
what makes nature work!  Keep it up!

Best of luck, Dave


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 | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci


MadSci Network, webadmin@www.madsci.org
© 1995-2001. All rights reserved.