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Radiometric dating lab exercise 19

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Radiometric dating lab exercise 19 are two types of age determinations. Geologists in the late 18th and early 19th century studied rock layers and the fossils in them to determine relative age. William Smith was one of the most important scientists from this time who helped to develop knowledge of the succession of different fossils Radiometric dating lab exercise 19 studying their distribution through the sequence Radiometric dating lab exercise 19 sedimentary rocks in southern England.

It wasn't until Radiometric dating lab exercise 19 into the 20th century that enough information had accumulated about the rate of radioactive Radiometric dating lab exercise 19 that the Radiometric dating lab exercise 19 dating lab exercise 19 of rocks and fossils in number of years could be determined through Radiometric dating lab exercise 19 age dating.

This activity on determining age of rocks and fossils is intended Radiometric dating lab exercise 19 8th or 9th grade students. It is estimated to require four hours of class time, including approximately one hour total of occasional instruction and explanation from the teacher and two hours of group team and individual activities by the students, plus one hour of discussion among students within the working groups. Explore this link for additional information on the topics covered in this lesson: Students not only want to know how old a fossil is, but they want to know how that age was determined.

PURPOSE AND OBJECTIVES

Some very straightforward principles are used to determine the age of fossils. Students should be able to understand the principles and have Radiometric dating lab exercise 19 as a background so that age determinations by paleontologists and geologists don't Radiometric dating lab exercise 19 like black magic. This activity consists of several parts. Objectives of this activity are: A single watch or clock for the entire class will do. Return to top PART 1: After students have decided how to establish the relative age of each rock unit, they should list them under the block, from most recent at the top of the list to oldest at the bottom.

The teacher should tell the students that there are two basic principles used by geologists to determine the sequence of ages of rocks.

Younger sedimentary rocks are deposited on top of older sedimentary rocks. Principle of cross-cutting relations: Any geologic feature is younger than anything else that it cuts across. For example, U is an unstable isotope of uranium that has 92 protons and neutrons in the nucl eus of each atom.

Through a series of changes within the nucleus, it emits several particles, ending up with 82 protons and neutrons. This is a stable condition, and there are no more changes in the atomic nucleus. A nucleus with that number of protons is called lead chemical symbol Pb.

The protons 82 and neutrons total This particular form isotope of lead is called Pb U is the parent isotope of Pb, which is the daughter isotope.

Many rocks contain small amounts of unstable isotopes and the daughter isotopes into which they decay. Radiometric dating lab exercise 19 the amounts of parent and daughter isotopes can be accurately measured, the ratio can be used to determine how old the rock is, as shown in the following activities.

12/27/ 0 Comments. Laboratory Exercise...

That chance of decay is very small, but it is always present and it never changes. In other words, the nuclei do not "wear out" or get "tired". If Radiometric dating lab exercise 19 nucleus has not yet decayed, there is always that same, slight chance that it will change in the near future. Atomic nuclei are held together by an attraction between the large nuclear particles protons and neutrons that is known as the "strong nuclear force", which must exceed the electrostatic repulsion between the protons within the nucleus.

In general, with the exception of the single proton that constitutes the nucleus of the most abundant isotope of hydrogen, the number of neutrons must at least equal the number of protons in an atomic nucleus, because electrostatic repulsion prohibits denser packing of protons. But if Radiometric dating lab exercise 19 are too many neutrons, Radiometric dating lab exercise 19 nucleus is potentially unstable and decay may be triggered. This happens at any time when addition of the fleeting "weak nuclear force" to the ever-present electrostatic repulsion Radiometric dating lab exercise 19 the binding energy required to hold the nucleus together.

In other words, during million years, half the U atoms that existed at the beginning of that time will decay to Pb This is known as the half life of U- Many Radiometric dating lab exercise 19 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 Radiometric dating lab exercise 19 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. On a piece of notebook paper, each piece should be placed with the printed M facing down. This represents the parent isotope. The candy should be poured into a container large enough for them to bounce around freely, it should be shaken thoroughly, then poured back onto the paper so that it is spread out instead of making a pile.

This first time of shaking represents one half life, and all those pieces of candy that have the printed M facing up represent a change to the daughter isotope. Then, count the number of pieces of candy left with the M facing down.

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These are the parent isotope that did not change during the first half life. The teacher should have each team report how many pieces of parent Radiometric dating lab exercise 19 remain, and the first row of the decay table Figure 2 should Radiometric dating lab exercise 19 filled Radiometric dating lab exercise 19 and the average number calculated.

The same procedure of shaking, counting the "survivors", and filling in the next row on the decay table should be done seven or eight more times. Each time represents a half life.

Geologists in the late 18th...

Each team should plot on a graph Radiometric dating lab exercise 19 3 the number of pieces of candy remaining after each of their "shakes" and connect each successive point on the graph with a light line. AND, on the same graph, each group should plot Radiometric dating lab exercise 19 where, after each "shake" the starting number is divided by exactly two and connect these points by a differently colored line. After the graphs are plotted, the teacher should guide the class into Radiometric dating lab exercise 19 about: Is it the single group's results, or Radiometric dating lab exercise 19 it the line based on the class average?

U is found in most igneous rocks. Unless the rock is heated to a very high temperature, both the U and its daughter Pb remain in the rock.

PURPOSE AND OBJECTIVES

A geologist can compare the proportion of U atoms to Pb produced from it and determine the age of the rock. The next part of this exercise shows how this is done. The team should place each marked piece so that "U" is showing. This represents Uranium, which emits a series Radiometric dating lab exercise 19 particles Radiometric dating lab exercise 19 the nucleus as it decays to Lead Pb- When each team is ready with the pieces all showing "U", a timed two-minute interval should start.

During that time each team turns over half of the U pieces so that they now show Pb This represents one "half-life" of U, which is the time for half the nuclei to change from the parent U to the daughter Pb A new two-minute interval begins. Continue through a total of 4 to 5 timed intervals.

After Radiometric dating lab exercise 19 the timed intervals have occurred, teams should exchange places with Radiometric dating lab exercise 19 another as instructed by the teacher. The task now for each team is to determine how many timed intervals that is, how many half-lives the set of pieces they are looking at has experienced.

The half life of U is million years. Both the team that turned over a set of pieces and the second team that examined the set should determine how many million years are represented by the proportion of U and Pb present, compare notes, and haggle about any differences that they got. Right, each team must determine the number of millions of years represented by the set that they themselves turned over, PLUS the number of millions of years represented by the set that another team turned over.

Pb atoms in the pegmatite is 1: Using the same reasoning about proportions as in Part 2b above, students can determine how old the pegmatite and the granite are. They should write the ages of the pegmatite and granite beside the names of the rocks in the list below the block diagram Figure 1.

This makes the curve more useful, because it is easier to plot it more accurately. That is especially helpful for ratios of parent isotope to daughter isotope that represent less than one half life. For the block diagram Figure 1if a geochemical laboratory determines that the volcanic ash that is in the siltstone has a ratio of U If the ratio in the basalt is 7: Students should write the age of the volcanic ash beside the shale, siltstone and basalt on the list below the block diagram.

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Why can't you say exactly what the age of the rock is? Why can you be more precise about the age of this rock than you could about the ages of the rock that has the trilobites and the rock that Radiometric dating lab exercise 19 acritarchs and Radiometric dating lab exercise 19 Based on cross-cutting relationships, it was established that the pegmatite is younger Radiometric dating lab exercise 19 the slate and that the slate is younger than the granite.

Therefore, the slate that contains the acritarch and bacteria is between million years and million years old, because the pegmatite is million years old and the granite is million years old. The slate itself Radiometric dating lab exercise 19 be radiometrically dated, so can only be bracketed between the ages of the granite and the pegmatite. The trilobite-bearing limestone overlies Radiometric dating lab exercise 19 quartz sandstone, which cross-cuts the pegmatite, and the basalt cuts through the limestone.

Therefore the trilobites and the rock that contains them must be younger than million years the age of the pegmatite and older than million years the age of the basalt. The limestone itself cannot be radiometrically dated, so can only be bracketed between the ages of the granite and the pegmatite. The Triceratops dinosaur fossils are approximately 70 million years old, because they are found in shale and Radiometric dating lab exercise 19 that contain volcanic ash radiometrically dated at 70 million years.

Any Triceratops found below the volcanic ash may be a little older than 70 million years, and any found above may be a little younger than 70 million years. The age of the Triceratops can be determined more closely than that of the acritarchs and bacteria and that of the trilobites because the rock unit that contains the Triceratops can itself be radiometrically dated, whereas that of the other fossils could not.

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