Download the lesson`s assignment document

Science 12E: Lesson 1 Assignment
Part 1. Outline
Textbook Section 9.1
1. The first clue that the continents were joined together at one time was the fit of the continents
of __________ __________ and __________.
2. In 1915 a German scientist named Alfred Wegener developed the hypothesis of __________
__________.
3. He named his original continent __________.
4. In Wegner’s time, evidence of continental drift included:
a.
b.
c.
5. Evidence supporting continental drift came from similar fossils found on different continents.
An example of a fossil was an aquatic reptile called __________.
6. Wegener’s evidence was rejected until 1967, when a new theory called __________
__________ emerged.
Textbook Section 9.2
7. With more knowledge of the ocean floor, new evidence for sea-floor spreading became
available. Because many rocks are rich in iron, they can become magnetized. As magma
comes from the seafloor the iron in it “freezes” in the direction of the earth’s current
magnetic field. These newly formed rocks possess __________.
8. When rocks show the same magnetism as the present magnetic field, they are described as
having __________polarity. Rocks that show the opposite magnetism are said to have
__________ polarity.
9. More evidence for sea-floor spreading comes from earthquakes that occur along ocean
trenches. Shallow-focus earthquakes occur __________ and __________the trench, and
deep-focus earthquakes occur (choose one: nearer / farther away from) __________ the
trench.
1
10.
More knowledge of the ocean floor was gained by the drilling ship named the __________
__________. It confirmed that the ocean floor is __________along the central valley at the
mid-ocean ridge and __________in subduction zones or near the edges of continents far
from the ridge.
11.
None of the ocean floor is thought to be older than __________million years.
Textbook Section 9.3
12.
The uppermost mantle and crust make up the layer known as the __________ . (If you need
help with the layers of Earth, go to page 235.) The broken segments of the lithosphere are
known as __________.
13.
The plates continue to move over the earth’s surface in different directions forming
boundaries. The three main boundary types are:
a.
b.
c.
14.
Divergent plate boundaries are considered __________ because this is where new oceanic
lithosphere is being produced.
15.
When spreading occurs on a continent, __________ __________are formed. If a continent
completely splits apart, a new __________ is formed. (Hint: Study figure 16 on page 264.)
16.
Convergent plate boundaries are formed because lithosphere is generally destroyed as it is
forced into the mantle. The three types of convergent boundaries are:
a.
b.
c.
17.
Plates that slide or grind past each other create __________ __________boundaries.
Textbook Section 9.4
18.
__________ __________ in Earth’s mantle are the driving forces for plate movement.
2
19.
__________ is the downward area of convection flow in the mantle. The force of gravity
pulls old lithosphere, which is dense and cold, down into the deep mantle.
20.
__________ causes plates to slide down the sides of the oceanic ridge. The stiff ocean
lithosphere slides down the asthenosphere that is elevated near mid-ocean ridges.
21. There are places under the crust where magma swells upward. These places are known as
__________ __________.
Textbook Section 11.1
22.
__________ is a term that refers to all changes in the original shape and/or size of a rock
body, and __________ is the force per unit area acting on a solid.
23. The three types of stress that rocks commonly undergo are:
a.
b.
c.
24.
A floating crust in gravitational balance is called __________.
25.
Faulting occurs when movement occurs along a fracture. The four types of faults are:
a.
b.
c.
d.
Textbook Section 11.2
26.
Folds are formed by compression. The three types of folds are:
3
a.
b.
c.
Textbook Section 11.3
27.
Mountain building primarily occurs at these three types of convergent boundaries:
a.
b.
c.
28.
A __________ is any crustal fragment that has a geologic history different from connecting
terranes.
Part 2. Questions
1.
What four evidences did Alfred Wegener use to support his continental drift hypothesis?
2.
In Wegner’s time, what did scientists think was the reason for fossils of the same species
being distributed on different continents?
3.
What continents show evidence of glacial activity 220–330 million years ago? (Hint: Be
sure to study the maps in figure 4 on page 251.)
4.
Why did scientists in Wegener’s day reject his hypothesis?
5.
What name did the continental drift hypothesis change to when it became a theory in the
1960s?
6.
When rocks show the opposite magnetism of the earth, they exhibit __________ polarity.
7.
a. What property of some rocks allows us to use paleomagnetism as a proof of plate
tectonics?
b. What mineral (element) must the rock contain?
4
8.
The uppermost mantle and the crust make up the __________.
9.
Name and describe the three types of plate boundaries.
a.
b.
c.
10.
Africa is beginning to show signs of breaking up due to stretching. Where is this taking
place?
11.
There are three types of convergent boundaries. Describe what happens at each type.
a. ocean-continent:
b. ocean-ocean:
c. continent-continent:
12.
What is occurring along the famous San Andreas fault?
13.
What was found to be the oldest age of the seafloor?
14.
Briefly summarize the whole mantle convection model used to explain plate motion.
15.
What are the factors that influence the strength of a rock and how it will deform?
16.
Describe anticlines and synclines.
17.
Describe the difference between a normal fault and a reverse fault using the terms footwall
and hanging wall.
18.
Having read chapter 11 you should now know that there are different types of mountains.
Name three types and briefly describe how they are formed.
a.
b.
c.
19.
Identify the types of mountains formed at the three types of convergent boundaries.
5
a. ocean to ocean:
b. ocean to continent:
c. continent to continent:
20.
Having read the two paragraphs on page 324 that describe terranes, describe how different
terranes can be found in the same place.
Extra Credit
21.
Using the term isostasy, describe what would happen to Antarctica if its ice would melt.
Part 3. Lab Activity: Patterns of Magnetic Polarity Reversals
Introduction
While no one is quite sure why reversals in Earth’s magnetic field occur, the evidence for
reversals is permanently recorded in Earth’s crust. Oceanic crust has been likened to a tape
recorder moving on a giant seafloor conveyor belt. As magma along seafloor spreading
centers cools and solidifies, magnetic minerals align themselves with Earth’s magnetic field.
The magnetic minerals store a permanent record of the direction of Earth’s magnetic field
at the time. These recordings are not only helpful in understanding a part of Earth’s geologic
history, but they also provide the data necessary to make comparisons of spreading rates in
different ocean basins. Figure 13.1 shows the magnetic reversals that have occurred in three
different ocean basins over the last 80 million years. In this investigation, you will use the
patterns of magnetic polarity reversals to compare rates of seafloor spreading.
Lab Skills and Objectives


To measure the rate of seafloor spreading using patterns of magnetic reversals
To compare the rates of seafloor spreading in several different oceans
Required Materials: metric ruler, colored pencils, graphs (provided), and access to a scanner
Procedure
1. Print the figures 13.1 and 13.2 (the last page of the lab).
2. Along the time scale at the top of figure 13.1, locate 25, 50, and 75 million years. Lines are
drawn from those three dates straight down to the pattern for the South Atlantic, the North
6
Pacific and the Pacific Antarctic. Use the slanted lines already drawn as guides to determine the
ages of the three ocean basins.
3. The portions that represent 0 to 25 million years, 25 to 50 million years and 50 to 75 million
years, have been shaded to show the spreading rates for each of the three oceans.
4. Fill in the empty bar graphs in figure 13.2. For each ocean basin in figure 13.1, measure the
length of the shaded portion for each time period (0–25 million years, 25–50 million years, and
50–75 million years). Then use a matching colored pencil to color in the appropriate column of
the bar graph in figure 13.2.
5. When you have completed the graphs, answer the following questions.
6. Finally, scan your completed bar graphs, save the image as a PDF, .jpg, .jpeg, or .gif, and
submit the file as an attachment with the assignment for lesson 1.
Questions
1. Is Earth’s current polarity normal or reversed? What does normal polarity mean?
2. How does your bar graph in figure 13.2 for the South Atlantic show that the spreading rate has
been relatively uniform there over the last 75 million years?
3. For the North Pacific, in which time interval was the spreading rate
a. fastest?
b. slowest?
4. For the Pacific Antarctic, in which time interval was the spreading rate
a. fastest?
b. slowest?
5. In figure 13.1, use the distance scale for each of the three ocean basins to determine, to the
nearest 100 kilometers, the total distance from the spreading center to the seafloor that is 75
million years old (use the scale directly beneath the particular ocean as a guide).
a. South Atlantic:
b. North Pacific:
c. Pacific Antarctic:
7
6. According to your results in question 5, for which ocean basin has the overall spreading rate
been the slowest? the fastest?
7. Using your values from question 5, calculate the spreading rate, in centimeters per year, for:
a. the slowest ocean:
b. the most rapid ocean:
*In other words, 1 km = 105 cm (1 km = 100,000), and 1 million = 106 cm (1 m=1,000,000)
8. At a location in the Atlantic Ocean where the spreading rate is 1.5 cm/yr, the distance across
the ocean is 6,600 kilometers. How many million years has the Atlantic Ocean taken to open to
that distance at that location? (Remember that the spreading center is the middle of the ocean and
not at the edge.) To do this change 6,600 km to cm (see * above, then divide by 1.5. Take that
answer and divide by 2 to show the age from the center of the ocean where spreading begins!)
8
9