Alfred
Wegenera
German
Meteorologist and geophysicist who
advanced the theory of continental
drift, which is the basis for the model
plate tectonics.
Plate Tectonics- is a theory that explains
the structure of the Earth’s crust
associated with many phenomena
resulting from the movement of rigid
lithospheric plates that interact slowly
over the underlying mantle.
Lithospheric plates- are large sections of
the solid crust of the earth. These giant
pieces of the Earth’s crust that fit
together and move around on the
earth’s surface are also called tectonic
plates.
Types of Plate Boundaries. Studying
plate boundaries is important because
along these boundaries deformation of
the lithosphere is happening. These
geologic events have a great impact
not only on the environment but also on
us. There are three distinct types of
plate boundaries, which are
differentiated by the type of movement
they exhibit.
The first type of plate boundary is
termed divergent boundary wherein
plates move apart, creating a zone of
tension. Can you identify adjacent
plates depicting divergent boundary on
Figure 8?
Let’s take the case of the
Philippine plate and the Eurasian plate.
You will notice that the two plates are
moving toward each other. This is an
example of a zone where plates collide,
and this second type of plate boundary
is called convergent plate boundary.
The third type is the transform
fault boundary where plates slide or
grind past each other without
diverging or converging. The best
example of this plate boundary is the
San Andreas fault which is bounded
by the North American plate and the
Pacific plate.
Convergence of Oceanic Plates
Like the first type of convergent
boundaries discussed earlier, converging
oceanic plates will cause formation of
trenches, and these trenches will become
sources of earthquakes. Underwater
earthquakes, especially the stronger
ones, can generate tsunamis. The
Japanese term for “harbor wave,”
tsunami is a series of ocean waves with
very
long
wavelengths
(typically
hundreds of kilometers) caused by largescale disturbances of the ocean.
The leading edge of the
subducted plate will eventually reach the
mantle causing it to melt and turn into
magma. The molten material will rise to
the surface creating a volcanic island arc
parallel to the trench. Volcanic island arc
is a chain of volcanoes position in an arc
shape as seen in figure below.