Assignment 6_Deep Time
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School
Utah Valley University *
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Course
1010
Subject
Geology
Date
Apr 3, 2024
Type
docx
Pages
6
Uploaded by MinisterJellyfish19486
Name: Chandler Yen
Geology 1010
Assignment 6
Deep Time
Instructions:
1)
Answer the 13
questions below about deep time. 2)
Don’t be scared of numbers, I will provide any equations you will need to solve the problems. 3)
Hints will be provided in green italicized
text.
4)
Take your time and have fun!
Goals:
1)
Use the principles of relative dating to determine the sequence of geological events.
2)
Be able to determine the numerical ages of rocks using radiometric dating.
Background Information:
Before the theory of evolution was proposed by Charles Darwin in 1859, geologists had already noticed that fossil assemblages changed from one stratum to the next (i.e. through time). This concept is termed
faunal succession. For example, geologists noticed that the abundance of mammal fossils occurred higher stratigraphically (i.e. later in time) than the abundance of reptile fossils. Geologists were able to use the faunal succession of fossil assemblages to correlate distant rock beds to each other. These correlations led to the construction of the geologic time scale, a global record of rocks and their relative ages. However, before geologists can correlate the ages of rocks from different areas, they must first figure out the ages of rocks at a single location. Within a single locality, geologists are able to determine which rock units are the oldest and which are youngest. This type of analysis is called relative age dating.
With the discovery of radioactive decay in the early twentieth century, scientists have been able to accurately date minerals in igneous rocks. As technology and techniques have advanced, scientists have been able to expand the accuracy and variety of rocks that can be dated. In this assignment you will do both of these tasks in two parts.
Part 1: Relative Dating
B,A,D,E,C
A,D,C,B,E
B,A
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I,E,D,H,F,B,A,C,G
Part 2: Radiometric Dating
Using the table and graph provided, please answer the
following questions.
6)
Approximately what percentage of parent isotopes
remains after 2 half-lives have passed?
25%
7)
If a rock initially contained 10 milligrams of a radioactive
parent when it first crystallized, how much remains after 4
half-lives?
.625
8)
What % parent remains after 10 half-lives?
.01
9)
If a mineral contains 1.56% of its original parent isotopes,
how many half-lives have passed?
6 half-lives
10)
Approximately what percentage of parent isotopes remains after 0.5 half-lives have passed? 75%
11)
How many half-lives must pass before only 10 % of the original parent isotopes remain? 3.5-4 half lives
12)
Assume a parent isotope has a half-life of 100 million years, how old is a sample that contains 15 % of its original parent isotopes? 250 million years old
13)
Assuming a parent isotope with a half-life =
4.5 billion years, what percentage of the original
parents remains after 6.75 billion years have
passed?
75%
Number
of
half-lives
elapsed
Fraction
remaining
Percentage
remaining
0
1/1
100
1
1/2
50
2
1/4
25
3
1/8
12.5
4
1/16
6.25
5
1/32
3.125
6
1/64
1.563
7
1/128
0.781
...
...
...
n
1 / 2
n
100(1 / 2
n
)
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