Each group should plot on graph paper the ½ life of the radioisotopes using the special graph paper supplied by the teacher. The y-axis has a log scale and begins at 100% of the parent radioisotope present; the next point is 100/ 2, or 50% parent radioisotope present; the next point is 50/2, or 25%; and so on.). For example, if the ratio of C-14 to C-13 is 1:3 than the fossil is how old? 5600 +5600. Correct? For each of the radioisotopes listed above, make a radiometric graph going to 3 half-lives. Be sure to make one graph using uranium-lead and potassium-argon dating to one half life. This will become useful later. Why? Uranium-Lead dating method Very careful measurements in laboratories, made on VERY LARGE numbers of U-235 atoms, have shown that each of the atoms has a 50:50 chance of decaying during about 704,000,000 years. In other words, during 704 million years, half the U-235 atoms that existed at the beginning of that time will decay to Pb-207. This is known as the half life of U- 235. Many elements have some isotopes that are unstable, essentially because they have too many neutrons to be balanced by the number of protons in the nucleus. Each of these unstable isotopes has its own characteristic half life. Some half lives are several billion years long, and others are as short as a ten-thousandth of a second. The uranium-lead radiometric dating scheme has been refined to the point that the error margin in dates of rocks can be as low as less than two million years in two-and-a-half billion years. An error margin of 2–5% has been achieved on younger Mesozoic rocks. One of its great advantages is that any sample provides two clocks, one based on uranium-235\'s decay to lead-207 with a half-life of about 700 million years, and one based on uranium-238\'s decay to lead-206 with a half-life of about 4.5 billion years, providing a built-in crosscheck that allows accurate determination of the age of the sample even if some of the lead has been lost. Potassium-argon dating method This involves electron capture or positron decay of potassium-40 to argon-40. Potassium-40 has a half-life of 1.3 billion years, and so this method is applicable to the oldest rocks. Radioactive potassium-40 is common in micas, feldspars, and hornblendes, though the closure temperature is fairly low in these materials, about 125°C (mica) to 450°C (hornblende). #1-23 meters deep from top of hill (limestone) #2-18 meters deep from top of hill (limestone/volcanic ash) #3-34 meters deep from base of hill (sandstone) #4-39 meters deep from top of hill (sandstone) #5- 50 meters deep from bottom of hill (slate) #6-26 meters deep (limestone) #7-10 meters into hill (basalt) #8-50 meters deep from base of hill (pegmatite) #9- 3 meters deep into hill (erosion surface of limestone) #10-52 meters deep from top of hill (pegmatite) #11- on bank of stream (in shale) #12- from base of hill 63 meters deep (in granite) #13-47 meters deep from base of hill (pegmatite) #14- 2 meters de.

1. Each group should plot on graph paper the ½ life of the radioisotopes using the special graph
paper supplied by the teacher. The y-axis has a log scale and begins at 100% of the parent
radioisotope present; the next point is 100/ 2, or 50% parent radioisotope present; the next point
is 50/2, or 25%; and so on.). For example, if the ratio of C-14 to C-13 is 1:3 than the fossil is
how old? 5600 +5600. Correct? For each of the radioisotopes listed above, make a radiometric
graph going to 3 half-lives. Be sure to make one graph using uranium-lead and potassium-argon
dating to one half life. This will become useful later. Why?
Uranium-Lead dating method
Very careful measurements in laboratories, made on VERY LARGE numbers of U-235 atoms,
have shown that each of the atoms has a 50:50 chance of decaying during about 704,000,000
years. In other words, during 704 million years, half the U-235 atoms that existed at the
beginning of that time will decay to Pb-207. This is known as the half life of U- 235. Many
elements have some isotopes that are unstable, essentially because they have too many neutrons
to be balanced by the number of protons in the nucleus. Each of these unstable isotopes has its
own characteristic half life. Some half lives are several billion years long, and others are as short
as a ten-thousandth of a second.
The uranium-lead radiometric dating scheme has been refined to the point that the error margin
in dates of rocks can be as low as less than two million years in two-and-a-half billion years. An
error margin of 2–5% has been achieved on younger Mesozoic rocks.
One of its great advantages is that any sample provides two clocks, one based on uranium-235's
decay to lead-207 with a half-life of about 700 million years, and one based on uranium-238's
decay to lead-206 with a half-life of about 4.5 billion years, providing a built-in crosscheck that
allows accurate determination of the age of the sample even if some of the lead has been lost.
Potassium-argon dating method
This involves electron capture or positron decay of potassium-40 to argon-40. Potassium-40 has
a half-life of 1.3 billion years, and so this method is applicable to the oldest rocks. Radioactive
potassium-40 is common in micas, feldspars, and hornblendes, though the closure temperature is
fairly low in these materials, about 125°C (mica) to 450°C (hornblende).
#1-23 meters deep from top of hill (limestone)
#2-18 meters deep from top of hill (limestone/volcanic ash)
#3-34 meters deep from base of hill (sandstone)
#4-39 meters deep from top of hill (sandstone)
#5- 50 meters deep from bottom of hill (slate)
#6-26 meters deep (limestone)
#7-10 meters into hill (basalt)

2. #8-50 meters deep from base of hill (pegmatite)
#9- 3 meters deep into hill (erosion surface of limestone)
#10-52 meters deep from top of hill (pegmatite)
#11- on bank of stream (in shale)
#12- from base of hill 63 meters deep (in granite)
#13-47 meters deep from base of hill (pegmatite)
#14- 2 meters deep from base of hill (shale)
#15-12 meters into ground from hill (basalt)
#16- 5 meters deep from base of hill (limestone)
I don't understand how to use dating methods, I need help, thank you! Figure 1. Block diagram
shale and siltstone volcanic ash surface erosion imestane sandstone surface erosion ate granite
Highly magn fied Trilobites found Triceratops dinosaur view of single-celled in the limestone
fossils found in the fossils found in the shale and siltstone slate (ac tarchs and bacteria)
Radiometric age Most recent rock formed: List the rocks frorn oldest to most recently formed
Oldest rock
Solution
Radiometric dating method uses radioactive elements degernation property. Radioactive
elements decay half to their original amount in a distinct time. The timing of all decays counts
for the time length for a moment.
In the question slate is the most old form and shale and siltstone is the most new form. In their
zone the higher depth of rock has older form.
So the list of the rocks from oldest to most recently:
on bank of stream (in shale)
14- 2 meters deep from base of hill (shale)
9- 3 meters deep into hill (erosion surface of limestone)
2-18 meters deep from top of hill (limestone/volcanic ash)
7-10 meters into hill (basalt)
15-12 meters into ground from hill (basalt)
1-23 meters deep from top of hill (limestone)
6-26 meters deep (limestone)
16- 5 meters deep from base of hill (limestone)
4-39 meters deep from top of hill (sandstone)
3-34 meters deep from base of hill (sandstone)
12- from base of hill 63 meters deep (in granite)

3. 10-52 meters deep from top of hill (pegmatite)
13-47 meters deep from base of hill (pegmatite)
5- 50 meters deep from bottom of hill (slate)
14- 2 meters deep from base of hill (shale)