Earth_history1- Dashawn Lawton.docx
pdf
keyboard_arrow_up
School
Essex County College *
*We aren’t endorsed by this school
Course
102
Subject
Geology
Date
Apr 3, 2024
Type
Pages
3
Uploaded by MajorIceTarsier35
SCI102
Name: Dashawn Lawton
Spring 2023
Activity 12
Geologic Age
Objectives of this lab:
●
Determine the relative ages and the sequence of geologic events as illustrated in a geologic cross
section.
●
Calculate, plot, and use daughter/parent ratios, together with the half-life, to determine absolute
ages for rocks and minerals.
13.1.
Figures 13.8 and 13.9 are geologic cross sections. Determine the sequence of events that led to
the present situation, and list them in order, from oldest to youngest, in the blanks provided. Use
the letters on the illustrations to specify rock units or events. Identify the rock types represented
by each letter from the symbols given in Figure 13.10; identify other events by name (for
example, “uplift and erosion”). The number of blanks is the number of events required.
Figure 13.8
Youngest
_______G___________
________D__________
________A_________
________B__________
________F__________
________C__________
________H_________
Oldest
________E__________
Figure 13.9
Youngest
________A__________
________C__________
_________E________
_________G_________
_________H_________
_________F_________
_________B_________
_________D_________
Oldest
_________I_________
13.2.
The purpose of this problem is to illustrate how numerical ages of rocks or minerals can be
determined using radioactive decay.
a.
Complete columns A and B in the table that follows. For example, after one half-life, the parent
fraction is 0.5 and the daughter fraction is 0.5; after two half-lives, the parent fraction is 0.25 and
the daughter fraction is 0.75. Remember, the sum of the two fractions must equal 1.0.
Half-lives
Elapsed
A.
Parent Fraction
B.
Daughter Fraction
C.
Daughter/Parent Ratio
0
1
0
1.0
1
0.5
0.5
1
2
0.25
0.75
3.0
3
0.125
0.875
7.0
4
0.0625
0.9375
15.0
5
0.03125
0.96875
31.0
b.
Next, complete column C in the table by dividing values in Column B by corresponding values
in Column A. For example, for one half-life elapsed, (Col. B)/(Col. A) = 0.5/0.5 = 1
c.
Using Figure 13.11 and the data in the preceding table, construct a graph in which the ordinate
(Y-axis) is “Daughter-Parent Ratio” and the abscissa (X-axis) is “Half-Lives Elapsed.” The point
representing one half-life is already plotted. Plot the rest, and draw a
smooth
curve connecting
the data points; that is, do not connect the points with straight-line segments, but estimate the
curvature between the points as best as you can so the entire curve bends smoothly.
d.
For samples 1-3 in the following table, first calculate and record the daughter-parent ratio,
N
D
/N
P
. Then, using your graph in Figure 13.11, determine the number of half-lives that have elapsed for
each sample and write your answer in the “Half-Lives Elapsed” column.
Sample
Number
Atoms of
Parent (N
P
)
Atoms of
Daughter (N
D
)
N
D
/N
P
Half-Lives
Elapsed
Age In Years
1
2135
3203
1.5
1.33
10,906
2
4326
10,815
2.5
1.8
14,760
3
731
14,620
20
4.36
36,490
e.
If the half-life of this isotope is 8200 years, calculate the age in years of the samples in the
preceding table and write your answers in the “Age In Years” column. Show your work.
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