Module 2 Questions
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Eastern Kentucky University *
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Course
108
Subject
Geology
Date
Dec 6, 2023
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docx
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4
Uploaded by aye.adams
Alyssa Adams
GLY108
10/17/2023
Answer the following
Questions for Review
(Chapter 2, page 33)
1.)
Describe the differences between Earth’s crust, lithosphere, asthenosphere, and
mantle. (1)
The lithospheric crust is characterized by gneiss (continental crust) and gabbro (oceanic crust).
Below the Moho, the mantle is characterized by peridotite, a rock mostly made up of the mineral
olivine and pyroxene. The asthenosphere is the denser, weaker layer beneath the lithospheric
mantle.
2.)
What does oceanic lithosphere consist of and how thick is it? (2)
Oceanic crust, the outermost layer of Earth's lithosphere is found under the oceans and formed at
spreading centers on oceanic ridges, which occur at divergent plate boundaries. The oceanic crust
is about 6 km (4 miles) thick. It is composed of several layers, not including the overlying
sediment.
3.)
What are the main types of lithospheric plate boundaries described in terms of
relative motions? Provide a real example of each. (3)
Divergent boundaries -- where new crust is generated as the plates pull away from each other.
Convergent boundaries -- where the crust is destroyed as one plate dives under another.
Transform boundaries -- where the crust is neither produced nor destroyed as the plates slide
horizontally past each other.
4.)
Why does oceanic lithosphere almost always sink beneath continental lithosphere at
convergent zones? (4)
Oceanic plates are formed from mantle material at midocean ridges. Young oceanic lithosphere is
hot and buoyant (low density) when it forms at a midocean ridge. But as it spreads away from
the ridge and cools and contracts (becoming denser) it can sink into the hotter underlying mantle.
5.)
Along which type(s) of lithospheric plate boundary are large earthquakes common?
Why? (5)
A divergent boundary occurs when two tectonic plates move away from each other. Along these
boundaries, earthquakes are common, and magma (molten rock) rises from the Earth's mantle to
the surface, solidifying to create a new oceanic crust.
6.)
Along which type(s) of lithospheric plate boundary are large volcanoes most common?
Provide an example.
(6)
Deep ocean trenches, volcanoes, island arcs, submarine mountain ranges, and fault lines are
examples of features that can form along plate tectonic boundaries. Volcanoes are one kind of
feature that forms along convergent plate boundaries, where two tectonic plates collide, and one
moves beneath the other.
7.)
Before people understood plate tectonics, what evidence led some scientists to
believe in continental drift? (8)
Before people understood plate tectonics, what evidence led some scientists to believe in
continental drift? -mountain ranges, fossils, and ancient rocks match as well, and it seemed to fit
like a puzzle.
8.)
What evidence confirmed seafloor spreading? (10)
Scientists have discovered that the magnetic poles of the Earth have reversed many times
throughout its history. Magnetic reversals are also recorded in the rock making up the oceanic
crust, and the pattern they create is evidence of seafloor spreading.
9.)
Explain how the modern theory of plate tectonics developed in the contest of the
scientific method. (12)
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In particular, four major scientific developments spurred the formulation of the plate-tectonics
theory: (1) demonstration of the ruggedness and youth of the ocean floor; (2) confirmation of
repeated reversals of the Earth magnetic field in the geologic past; (3) emergence of the seafloor-
spreading hypothesis and associated recycling of oceanic crust; and (4) precise documentation
that the world's earthquake and volcanic activity is concentrated along oceanic trenches and
submarine mountain ranges.