Lab%208%20Plate%20Tectonics-2
pdf
keyboard_arrow_up
School
Binghamton University *
*We aren’t endorsed by this school
Course
116
Subject
Geology
Date
Dec 6, 2023
Type
Pages
5
Uploaded by ChefGorilla14415
“Geoworld” Plate Tectonics
Lab 8 Geol 116 Fall 2023
Simplified from exercise © 2003 Ann Bykerk-Kauffman, Dept. of Geol. and Envi. Sci., California State Univ. Chico
1
Purpose:
To better understand the principles of the plate tectonics theory by
applying them to the past, present and future analysis of a theoretical
planet.
Introduction
During this lab exercise, we will analyze the plate tectonics of part of a
mythical planet called Geoworld; a tectonic map of the area is shown on p. 5
.
Geoworld has a plate tectonics system just like ours on Earth, only Geoworld
is flat instead of spherical.
All questions are in bold face.
Please put your
answers in any blanks provided.
A.
Sea Floor Magnetic Anomalies
Geoworld has a magnetic field aligned in a north-south direction.
The
polarity of this field reverses at random intervals through time, just as the
one on Earth does.
The history of polarity of the magnetic field is well
known for the past 150 million years and is shown by the adjacent
magnetic
polarity time scale. Shading represents normal polarity (the magnetic field
points north) while white represents reverse polarity (the magnetic field
points south).
Detailed aerial and ship-board magnetic surveys have been conducted
over the oceans of Geoworld.
Parts of the sea floor have an extra strong
magnetic field while other parts have an extra weak magnetic field.
Just as
on Earth, the areas with anomalously strong magnetic fields are composed
of rocks that are magnetized with the same polarity as the current field while
areas with anomalously weak magnetic fields are composed of rocks that
are magnetized with the opposite polarity as the current field.
Portions of
the sea floor with an anomalously strong magnetic field are shaded; portions
of the sea floor with an anomalously weak magnetic field are unshaded.
Note that the magnetic anomalies form a striped pattern on the map of
Geoworld.
Note also that the pattern in the Elrond Sea is symmetrical while
that in the Aragorn Ocean is asymmetrical.
This is because there is an active
spreading ridge in the Elrond Sea but not in the Aragorn Ocean.
The center
of symmetry in the Elrond Sea is right along the spreading ridge.
Analysis of the Present State of Geoworld
2
“Geoworld” Plate Tectonics Lab
1. On the map on page 5, highlight the mid-ocean ridge in the Elrond Sea and label it the
Hobbit Ridge.
2.
Draw a diagram and explain the origin of the striped magnetic anomaly pattern visible in
the Elrond Sea.
3. The pattern of positive and negative magnetic anomalies in the Elrond Sea can be
correlated with the pattern of normal and reversed magnetism on the magnetic polarity
time scale.
Based on this correlation, how many million years (m.y.) ago did sea floor
spreading begin in the Elrond Sea?
Spreading Began
____
m.y. ago
4.
Using the magnetic anomaly pattern in the Elrond sea, determine the 1/2-spreading rate on
the Hobbit Ridge (i.e., determine how fast the Frodo continent is moving away from the
Hobbit ridge).
Give your answer in mm/y (millimeters per year).
Show your equations
and explain where each number came from.
Useful Information:
1 cm (10 mm) on the map = 400 km on Geoworld
1 mm/y = 1 km/m.y. (kilometers per million years)
distance = rate x time,
rate =
distance
time
,
time =
distance
rate
1/2 spreading rate =
___
mm/y
5.
What is the full spreading rate (in mm/y) of the Hobbit Ridge? (i.e., how fast are the Bilbo
and Frodo continents moving away from each other)?
Show your equations and explain
where each number came from.
Full spreading rate =
__
mm/y
“Geoworld” Plate Tectonics Lab
3
6.
Using the magnetic anomaly patterns in the Aragorn Ocean, determine when sea floor
spreading started to form the Aragorn Ocean crust (remember, spreading is not actively
going on now but it was at one time).
Spreading Started
__
m.y. ago
7.
At the time that active sea-floor spreading was occuring in the Aragorn Ocean, at what
rate was new sea-floor being created? (Think:
is this related to the full spreading rate or
the half spreading rate)? Show your equations and explain where each number came from.
Rate of formation of Aragorn Ocean crust
=
__
mm/y
B.
Plate Boundaries
1.
There are two major plate boundaries on the map.
You already highlighted one of them
in Part 1, A. 1.
above.
Highlight the other boundary also.
2.
Give one example of each of the following types of plate boundaries on Geoworld (Note:
the boundary between two plates can vary in type from place to place).
Divergent boundaries
Convergent boundaries
Transform boundaries
3.
How many lithospheric plates are there in all?
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
4
“Geoworld” Plate Tectonics Lab
C.
Transform Faults
There are several transform faults in the Elrond Sea.
The only parts of these faults that are
presently active are the parts between the segments of the Hobbit Ridge.
1.
Using arrows, show the sense of motion on each of the active transform faults on the map.
2.
In the space below, draw a diagram and explain why the sense of motion on a transform
fault is the way it is.
A.
When will the Bilbo Continent and the Sauron Trench first collide? Show your equations and
explain where each number came from. Note that, although you computed relative motion
across the Hobbit Ridge in Part 1, here you need to know the current rate of movement of the
Bilbo Continent toward the Sauron Trench; it turns out this is 50 mm/yr (computed in a part
of the exercise that you’re not doing).
Time of Collision =
___
m.y. from now
B.
How wide will the Elrond Sea be at that time?
Show your equations and explain where each
number came from.
Width of Elrond Sea =
___
km
Part 2:
Analysis of the Future State of Geoworld
“Geoworld” Plate Tectonics Lab
5
Plate Tectonic Map of Geoworld