Transcript Plate Tectonics - NagelBeelmanScience

By : Lily Ganote
History of Pangaea
Alfred Wegener originated the theory of Pangaea. Pangaea means “ All
Lands” and existed during the Carboniferous period and is believed to have
started to separate late into the period, about 300 million years ago. His theory
was controversial because of the fact that it didn’t explain why the continents
moved. There was also another theory about the continents movement. This
theory was that the Earth was going through cycles of heating and cooling. The
heating and cooling causing expansion and contraction of the land masses.
People who believed this theory were called anti - mobilizes.
While Alfred was a German geologist, he also was accomplished in other
sciences. Of the few he went and got a Ph. D in astronomy. I believe this helped
him because he knew a lot about the other planets and how they have changed
over time. Because of this knowledge he could make a better hypothesis about
the Earth and it has changed over time as well. Alfred also had an interest in
meteorology and climatology.
Their were to major people that helped in the recognition of Wegener’s
theory. The South African geologist Alexander Du Toit supported Wegener's
theory because it was an explanation for the close similarity of fossils between
Africa and South America. The Swiss geologist Émile Argand also agreed
because she saw continental collisions as the best explanation
for the folded and buckled strata that he observed in the
Swiss Alp.
Convergent Boundaries
Convergent boundaries occur all over the world but mainly along coast lines. A
convergent plate boundaries are places where the lithosphere plates are moving
towards one another. An example of a convergent boundary would be on the
Washington – Oregon coastline. The Juan de Fuca oceanic plate is being subducted
underneath the westward moving North American plate. Seduction is when an oceanic
plate is forced down into the mantle by a thicker but less dense continental-land-plate.
Convergent boundaries can cause many hazards to our environment Some of
these hazards are earthquakes, volcanoes and crustal deformation. Earthquakes and
volcanoes can then cause trenches to form in the earths crust.
Divergent Boundaries
Divergent plate boundaries are places where plates are moving away from
another plate. This occurs above rising convection currents, the rising current than
pushes up on the bottom of the lithosphere, lifting it and flowing laterally beneath it. The
flow causes the plates materials that are above to be dragged along in the direction of
the flow. At the crest of the uplift, the overlying plate is than stretched thin, and ends up
breaking and pulling apart.
When a divergent boundary occurs beneath the oceanic lithosphere, the rising
convection current below lifts the lithosphere producing a mid-ocean ridge.
Divergent boundaries can cause many harms to our planet. Divergent
boundaries cause trenches, mud and landslides and volcanoes because of the forming
hole in the earth .
One well known divergent boundary is the Mid-Atlantic Ridge. This submerged
mountain range, that extends from the Arctic Ocean, and beyond the southern tip of
Africa, it is one segment of the global mid-ocean ridge system that encircles the Earth.
The Mid-Atlantic Ridge moves about 2.5 centimeters each year or 25 centimeters every
decade.
Transform boundaries
Transform Plate Boundaries are places where two plates slide past one another.
The gap or “fracture zone” created by the plates sliding is known as a transform fault.
Most transform faults are found in the ocean basins and connect offsets in mid-ocean
ridges. A smaller number connect mid-ocean ridges and subduction zones.
there are to types of faults, transform and strike-slip faults. Transform faults can
be distinguished from the typical strike-slip faults because the sense of movement is in
the opposite direction then the other. A strike-slip fault is a simple offset. While a
transform fault there are two plates moving away from the spreading center of a
divergent boundary.
The most famous example of transform boundary is the San Andreas Fault Zone
in North America. The San Andreas causes many earthquakes and mud/ landslides.
Real World Connections
We live on the North American Plate. We are surrounded by the Juan De Fuca
Plate, the South American Plate, the Caribbean Plate, the Eurasia Plate, and the
African Plate. Here in Ohio we are not in much danger, being in the middle of the plate
with no volcanoes or mountains, although the Appalachian Mountains are close. In the
middle of the North American Plate there are no transform, convergent, or divergent
boundaries.
The last earthquake in Ohio was on April 18, 2008. The United States Geological
Survey reported the earthquake occurred at 5:36 a.m. The earth quake didn’t start in
Ohio it started in Illinois near the Indiana Border. It was centered six miles from West
Salem, Illinois. It was a 5.2 magnitude earthquake.
Columbus, Ohio is raked one of the highest places in the U.S, of the 50 most
populated, at risk of a natural disaster , according to a 2009 study. Why you may ask? It
is because of it high risk of floods, winter storms, tornadoes and the occasional
earthquake. Five cities in California are on the top 10 list.
In the very distant future I think the San Andreas Fault
will be even larger and it earth quakes will be even
worse. I also think that the mountains will move
from the spots they are in now.
Cites
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http://scign.jpl.nasa.gov/learn/plate2.htm
http://www.ucmp.berkeley.edu/geology/techist.html
http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/description_plate_tectonic
s.html
http://geology.com/nsta/convergent-plate-boundaries.shtml
http://science.howstuffworks.com/environmental/earth/geology/landslide3.ht
m
http://pubs.usgs.gov/gip/dynamic/understanding.html
http://geology.com/nsta/transform-plate-boundaries.shtml
http://www.city-data.com/forum/city-vs-city/608032-most-least-dangerousus-cities-natural-3.html
http://ema.ohio.gov/kids_page/index.htm