GEOSCI 106 Lab 3_ Plate tectonics-March
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University of Wisconsin, Madison *
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Course
106
Subject
Geology
Date
Dec 6, 2023
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GEOSCI/ENVIR ST 106: Environmental Geology
Lab 3: Evidence for Plate Tectonics
Plate Tectonics: “A theory explaining the structure of the Earth as resulting from the interaction of rigid
lithospheric plates which move slowly over the underlying mantle.”
Assignment Overview:
The processes of plate
tectonics largely take place at depths of hundreds of
kilometers, making them largely invisible. (For
context, the deepest hole ever drilled reached just
over 10 km—we’ve never
seen
what is pictured in
the diagram to the left). Therefore, over the past 60+
years, geologists have amassed a wealth of data in an
effort to test and refine the theory of plate tectonics
that’s described in your textbook. The result is a set
of global scientific datasets that help us to understand
how the Earth is being continuously reshaped by
plate tectonic actions. In this lab, you will interpret
and verify how these global datasets—collected by geoscientists with different scientific
specialties—support the key ideas of plate tectonics.
Materials:
This lab will use several large maps, which are available as links in the lab module in Canvas.
In comparing and integrating data from different sources, you may find it useful to open all of the maps at
once and alternate between windows. Answering some questions may also require that you zoom and
scroll through sections of the map. On the Mac side, you may find this to be easiest in Preview.
Submission:
To submit the assignment on Canvas, use the following steps:
1.
In Google Docs, generate a PDF: File → Download as → PDF Document.
2.
In Google Docs, use Share → Get Shareable Link, and copy the link address.
3.
In Canvas, upload your PDF to the assignment.
4.
Paste the link address to your Google Doc in the assignment comments.
Instructions:
Fill out each red highlighted field (_________).
For the questions below, answer in complete thoughts of no more than 2-3 sentences. Where possible, use
geologic terminology about plate tectonics and plate boundaries in your descriptions.
Convergent plate boundary (oceanic-oceanic, oceanic-continental, continental-continental)
Divergent plate boundary
Passive continental margin
Active continental margin
Mid-ocean ridge
Hot spot
1
Geochronology
1. Examine the Geochronology map.
(a)
Where is the youngest ocean floor located? (0.5 points)
__Along the west side of the americas and closest to the plate lines_______
(b)
Where is the oldest ocean floor located? (0.5 points)
__The north side of the african plate_______
2. In the following figure, the distance between two points in South America and Africa that seem to “fit”
is close to 5,000 km. Using the ocean floor age data in the Geochronology map, what’s the average speed
at which these two continents have been moving apart since the Atlantic formed? Show how you
calculated this. (1 point)
_(Speed=Distance/ time)___s=5,01km/140,000,000years=0.000036km/yr_____
Seismology
3. Examine the Seismology map. Note the distribution of earthquakes on the map. In what geographic
regions is earthquake activity concentrated? (1 point)
2
__The loop around the Pacific Ocean called the ring of fire and the western coast of South
America_______
4. Compare the Seismology map to the Geologic Plate Boundaries map. What type of plate boundary (or
boundaries) are associated with the deeper earthquakes? (1 point)
__Subduction Zone _______
5. What type of plate boundary (or boundaries) only have shallow earthquakes? (1 point)
_____Spreading Ridge____
Volcanology
6. Examine the Volcanology map ( that most submarine volcanoes are not shown). Note the distribution
of volcanoes on this map. In what geographic regions is volcanic activity concentrated? (1 point)
The loop of the Pacific Ocean called the ring of fire_________
7. What type of plate boundary (or boundaries) is associated with volcanoes? (1 point)
_Subduction zone and spreading ridge________
Geography
8. Examine the Topography and Bathymetry map. Write down the location of two deep ocean trenches.
How deep are these trenches? (1 point)
Location of ocean trench
Depth (m)
_East Coast of Russia________
_10400 m________
_Just North of Puerto Rico________
____7600m<x<10400m_____
9. What types of plate boundaries are associated with deep ocean trenches? (1 point)
__Subduction Zone_______
3
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Synthesis
10. What piece(s) of evidence could be used to determine the rate and direction of plate motion? (1
point)
_If the same rock can be found on both sides of the plate boundary it can be used ________
11. Why do you think the oldest ocean floor is located only along passive continental margins? (1 point)
_Because the plate boundaries are not active so the are not separating exposing new
floor.________
12. Examine the 3D model for the following rock:
https://sketchfab.com/3d-models/basalt-ac9b5abe7c024180b23fddc4960374cb
.
(a)
What kind of rock is this: igneous extrusive, igneous intrusive, metamorphic, or sedimentary? (1
point)
_Igneous extrusive________
(b)
Which two minerals are likely to be the most abundant in this rock (1 point)?
_Pyroxene and Plagioclase________
(c)
Given your answer to part (a), write down a geographic location on Earth where you might expect
to find this rock. Why is that a plausible location for this rock? (1 point)
_On the seafloor because it is heavier than granite and it comes from the earth's mantle
through volcanos________
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