FRQ_ Plate Tectonics
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University of Kentucky *
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101
Subject
Geology
Date
Apr 3, 2024
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2
Uploaded by ProfessorSparrow3401
FRQ: Plate Tectonics
A) Japan, Indonesia, and the Philippines are examples of volcanic island chains that
have formed along subduction zones between plates in the western Pacific.
a)Explain how subduction leads to volcanic activity when two tectonic plates
collide along a subduction zone.
When two tectonic plates collide along a subduction zone, a denser oceanic plate
is forced underneath a continental plate. The subducting plate melts into magma
from high temperature and pressure. Due to the difference in density, magma rises
through fractures and reaches the earth’s surface. This results in volcanic activity
and the formation of volcanic island chains.
b) Describe what happens when, instead of two plates with different densities meet,
two continental plates converge and subduction does not occur.
When two continental plates converge, they resist subduction due to similar
density. Instead, they compress and buckle. This compression can lead to the
formation of mountain ranges such as the Himalayas. The collisions can also
result in earthquakes as plates push against each other. In contrast to subduction
zones, where magma from the subducting plate reaches the surface and causes
volcanic activity, two continental plates collide and compress, forming mountain
ranges and earthquakes.
B) Although the landscape following a volcanic eruption may appear unable to support
ecological communities, over time the area can be transformed through succession.
a) Explain the process of soil formation created from primary succession.
After a volcanic eruption, the surrounding site is barren, containing no organisms
or soil. The soil must re-form to support new life through primary succession.
Pioneer species, such as lichens and moss, will develop and begin to break down
the volcanic rock. These early colonizers die and contribute organic matter to the
developing soil. Eventually, the soil will become more fertile from the organic
matter and can support a broader variety of organisms.
b) Describe one characteristic of secondary succession that differs from primary
Succession. One characteristic that differs from primary succession is the existence of a
pre-existing soil. In primary succession, there is no pre-existing soil, and it must
start with a pioneer species. However, secondary succession involves an already existing soil
base. Oftentimes the soil will already have seeds, nutrients, and
necessities to support life. Secondary succession usually occurs due to
disturbances that leave some ecological remnants intact, such as forest fires,
floods, or harvesting. This is also why secondary succession occurs much faster
than primary succession.
C) In addition to volcanic activity, highly destructive tsunamis are generated along
Pacific Plate subduction zones.
a) Explain how a tsunami is generated along a subduction zone.
A tsunami occurs due to a sudden displacement of a large amount of water from
tectonic activity on the ocean floor. At a subduction zone, the subducting plate
can lock against the other tectonic plate, resulting in the accumulation of stress.
Suddenly, the stress results in a rupture that causes an upward or downward
movement of the seafloor, and this shift displaces a large volume of water
vertically. This creates massive waves known as tsunamis.
b) Identify one ecological impact that tsunamis have on coastal environments.
One ecological impact that tsunamis have on coastal environments is the
destruction of important habitats, such as wetlands and coral reefs. The damage
done to these critical ecosystems can disrupt biodiversity and the entire coastal
food web.
D) Southern California experiences periodic devastating earthquakes along the San
Andreas Fault, which is a transform boundary located along the eastern edge of the
Pacific Plate.
a) Describe what happens to the tectonic plates along a transform boundary at the
moment when an earthquake occurs. When plates along a transform boundary slide horizontally
past each other, they are held in place by frictional resistance that accumulates stress. The
stress eventually exceeds the frictional resistance, resulting in a fault rupture and the
release of seismic waves. The ground shakes as the seismic waves spread outwards, resulting
in an earthquake.
b) The plates along the San Andreas fault are moving about 35 mm per year relative
to each other. If a plate manages to move along a transform boundary an average
of 15 mm per year, assuming such continued gradual movement, calculate how
long it will take that plate to move six feet. Use this conversation factor: 1 inch =
2.54 cm. Show your work.
First, convert 6 feet to cm: (6 feet/1)*(12 inches / 1 foot)* (2.54 cm/ inch) =
182.88 cm
Next, we can set up an equation to determine the years to reach 182.88 cm:
15(mm/year) * x(years) = 182.88cm.
Third, convert millimeters to centimeters: 15mm=1.5cm. The equation is
1.5x=182.88.
Isolate x by dividing by 1.5: x=121.92 years.
c) Propose a solution that humans may use to mitigate the impact of earthquakes on
populated urban areas.
Humans should enforce strict building codes and regulations to ensure safety and
minimize earthquake impact. They should implement building designs that are
structurally reinforced and use materials that can absorb and dissipate seismic
waves. Many urban centers that are prone to earthquakes can consider utilizing
early warning systems to be able to prepare in advance.
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