GEL111 Topic #3B Review
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Geology
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Dec 6, 2023
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Physical Geology 111
Review Exam #1
Topic 3 (Chapter #3)
Key Terms and Concepts:
1.
How do the differences between continental and oceanic crust affect the ways plates interact? Why
does lithosphere with continental crust ride above lithosphere with oceanic crust?
Why is the area
around a divergent boundary higher than the surrounding seafloor?
2.
Before the theory of plate tectonics the concept of continental drift was proposed in the early 20
th
century. Many lines of evidence were cited to support continental drift.
(a) What are 3 lines of
evidence used to support the drifting of the continent? Explain how each of these lines of evidence
was used to support continental drift
.
(b) Why was this concept almost universally rejected despite
many lines of evidence supporting it? (c) What concept resurrected continental drift some 30 years
later in the 1950s?
3.
What are 3 lines of evidence that verify sea-floor spreading? Explain how each verifies seafloor
spreading.
What is the main mechanism causing the spreading of the seafloor? How does it work?
4.
Why does the ocean crust show a sequence of magnetic polarity changes symmetric across the mid-
ocean ridge?
Explain fully. What is the average rate of seafloor spreading in cm/yr (100,000 cm = 1
km), if the age of the magnetic anomaly shown below is 4 million years old at point A?
Show your
work.
5.
(a) Oceans have been on Earth for billions of years, but the oldest seafloor is only 200 million years
old.
How is this possible? (b) The graph below displays age of the ocean crust in millions of years
with respect to water depth. According to the graph on the next page, describe how depth of the
seafloor changes with the age of the ocean crust.
What is responsible for this pattern? Explain.
A
6.
(a) What are the 3 types of plate boundaries?
(b) Discuss each type specifically, detailing the
processes going on at each boundary and give a map view diagram showing direction of plate
movement. (c) Give a real-world example of each.
7.
List the 3 subtypes of convergent plate boundaries. At which convergent plate boundary would you
find i) subduction, ii) volcanic island, iii) continental volcano, iv) trench, v) collision. Identify what
features (earthquakes, volcanoes, age of seafloor and topography) are found at what type of plate
boundary.
Draw a cross-sectional (side) view of each type of plate boundary.
8.
For each geologic setting below, name the specific type of plate boundary (transform, divergent,
continent-continent convergent, ocean-ocean convergent, ocean-continent convergent) that
describes the site, characterize the volcanic activity (volcanoes or no volcanoes), and characterizer
the
seismic activity (only shallow earthquakes, both shallow and deep earthquakes,
only deep
earthquakes, and no earthquakes) that we expect and provide an explanation why.
a)
Japan
b) Himalayas
c) Cascade Range
d) San Andreas
e)
Mid-Atlantic Ridge
9.
For each site below, draw a geologic both cross-sectional profile (i.e. side view) of the plate
boundary. Include in your sketch (1) the name of the type of boundary, (2) show the direction of
relative plate movement with arrows, (3) label the location and generic name for any topographic
features of importance (i.e., mountains, volcanoes, trenches), and label the type of crust on each
plate. Be sure to show sea level in all diagrams where it is relevant.
Next to each drawing, tell me
which location(s) have
deep earthquakes
,
volcanism
and
young symmetric seafloor
.
Cascade Mountain Range in Pacific Northwest U.S.
Mariana Islands/Trench
Mid-Atlantic Ridge
Himalayas
San Andreas
The Appalachian Mountains are seemingly a plate tectonic anomaly, as they reside in the middle of
the North American Plate. Try to explain their presence geologically.
a)
How are the alignments and age distribution patterns of the Emperor Seamounts and Hawaiian
Islands explained? (Map View of Emperor Seamounts and Hawaiian Islands Shown Below)
What
direction is this plate moving? In addition, be sure to explain how these volcanoes were formed and
why their ages differ.
(The Big Island of Hawaii is the Easternmost Island in Hawaiian Island Chain).
Also, explain what caused the bend between the Hawaiian Ridge and Emperor Seamounts.
Finally,
identify which of these volcanoes is still volcanically active and explain why?
b.
What is the average rate of movement in cm/yr for Northhampton Bank since its formation? You
must show work to receive credit. (Ma means millions of years) (100,000 cm in 1km)
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