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The Ocean Floor
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Question 1: Three different plate boundaries and their outstanding features
There are three distinct types of plate boundaries. They are; divergent boundaries, transform and
convergent boundaries.
i.
Convergent boundaries
This is a boundary formed when two plates move towards each other and collide. The
boundary, otherwise known as destructive boundary, leads to subduction or lifting of plates. The
heavier plate undergoes subduction while the lighter one is uplifted. The boundary is
characterized by activities such as earthquakes and volcanicity. A common characteristic of a
convergent boundary is the ocean trench.
According to Stille (2007), collisions of plates lead to the mounting of pressure at the
boundaries and also on the crust. Pressure at the boundary triggers seismic reactions that cause
earthquakes. Consequently, pressure placed on the earth’s crust lead to volcanic explosions that
release the excess pressure.
ii.
Divergent boundaries
These are boundaries formed when plates are moving away from each other. A divergent
boundary creates deep trenches when it occurs on the ocean floor. Moreover, the earth
movements expose internal land forming process causing earthquakes and volcanicity.
Moreover, divergent boundaries create new landforms as the ocean water retreats to fill the gaps
formed leaving dry seabed. A good example is the mid-Atlantic ridge, a divergent boundary
between the American and Eurasian plates.
iii.
Transform-Fault Boundaries
These are boundaries formed when plates are sliding against each other. The movement is
horizontal. The boundaries are characterized by fault lines and are common on the sea floor. The
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boundaries are also characterized by mild earthquakes caused when the plates jam against each
other and force movement, creating excess pressure at the boundary. An example of a transform
or fault boundary is the San Andreas Fault zone in the United States.
Question 2: Natural event that occurs as a direct result of plate boundary interactions
Volcanic activities are common at the boundaries. Both divergent and convergent
boundaries cause molten magma to rise up from the mantle. Divergent plates expose a new crust
that succumbs to excess pressure if it is underwater. This leads to an eruption. Similarly,
convergent boundaries generate a lot off pressure that is stored in the crust. The pressure is
released through a volcanic eruption.
Question 3: Compare and contrast ideas behind plate tectonics and the theory of continental
drift
i.
Similarities
The similarities between the two theories are evident in logic and observable geological
manifestations. The explanations of the two theories lead to the same conclusion. The conclusion
made is that plates are in constant motion and move towards or against each other. Formation of
boundaries is a common characteristic of both theories.
Another similarity is that the plate movements in the two theories lead to natural events
such as earthquakes, folding and volcanicity. This happens at the boundaries when plates
converge, diverge or slide past each other.
ii.
Differences
The continental drift theory states that the earth was made up of single continent, Pangaea
and sea, Panthalassa. This continent broke off to form the various continents we have today. The
theory is supported by the relationship between the fossils found in continents that are believed
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to be fused a long time ago. Such fossils have been found in Africa and South America,
indicating that the continents may have been one.
The continental drift theory is supported by the jigsaw fit of continents, an idea that
argues that the continents can fit exactly into each other if they are brought together. This implies
that they were once single landmass.
Plate tectonics argue that the earth is made up of several plates that are in constant
movements towards or away from each other (Frisch, Meschede & Blakey 2011). The
movements of the plates define the types of boundaries formed by the tectonic plates. The theory
is supported by many land forming processes that are defined by plate movements and features.
Such features include; ocean trenches, ridges and fault lines. They are formed as result of
volcanicity, folding and earthquakes.
iii.
Why plate tectonics is more plausible than continental drift
Plate tectonics is more plausible than the continental drift theory. This is because the
assertions made by the continental drift lack geological evidence. The pioneer of continental drift
theory, Wegener, claimed that the plates were propelled on a solid ocean floor, an idea geologist
do not support. The theory relies only on the jigsaw fit and fossil similarities.
Plate tectonics was developed to shed more light on the nature of the plates and
boundaries. The theory is supported by ridges, fault lines and also volcanic features on the ocean
floors that show interactions between plates (Tomecek 2009). The theory is also supported by
observable land features such as the San Andreas fault line in California that was caused as a
transform boundary between the pacific and North American plates. The features show that
plates include the whole crust as portrayed in the plate tectonics theory.
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References
Frisch, W., Meschede, M., & Blakey, R. C. (2011). Plate Tectonics: Continental Drift and
Mountain Building. Berlin, Heidelberg: Springer-Verlag Berlin Heidelberg.
Tomecek, S. (2009). Plate tectonics. New York: Chelsea House.
Stille, D. R. (2007). Plate tectonics: Earth's moving crust. Minneapolis, Minn: Compass Point
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