Relative Dating Answer Key

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Locally, physical characteristics of rocks can be compared and correlated. Once you find your worksheet, click on pop-out icon or print icon to worksheet to print or download. Use this information to sequence the cards in a vertical stack of fossils in rock strata.

By matching partial sequences, the truly oldest layers with fossils can be worked out. The brachiopod, crinoid, eurypterid, foraminifera, gastropod, horn coral, pelecypod, and trilobite could probably not be used as index fossils since they overlap more than one stratum. This relative time scale divides the vast amount of earth history into various sections based on geological events sea encroachments, mountain-building, and depositional events , and notable biological events appearance, relative abundance, or extinction of certain life forms.

Relative Dating Answer Key

A RELATIVE DATING ACTIVITY and INTRODUCTION PALEONTOLOGY, AND in particular the study of dinosaurs, is an exciting topic to people of all ages. Although most attention in today's world focuses on dinosaurs and why they became extinct, the world of paleontology includes many other interesting organisms which tell us about Earth's past history. The study of fossils and the exploration of what they tell scientists about past climates and environments on Earth can be an interesting study for students of all ages. Teaching about Earth's history is a challenge for all teachers. Time factors of millions and billions of years is difficult even for adults to comprehend. In this activity, students begin a sequencing activity with familiar items — letters written on cards. Sequencing the rock layers will show students how paleontologists use fossils to give relative dates to rock strata. Extinction of species is common; most of the species that have lived on the earth no longer exist. RELATIVE DATING Student Activity INTRODUCTION Scientists have good evidence that the earth is very old, approximately four and one-half billion years old. Scientific measurements such as radiometric dating use the natural radioactivity of certain elements found in rocks to help determine their age. Scientists also use direct evidence from observations of the rock layers themselves to help determine the relative age of rock layers. Specific rock formations are indicative of a particular type of environment existing when the rock was being formed. For example, most limestones represent marine environments, whereas, sandstones with ripple marks might indicate a shoreline habitat or a riverbed. The study and comparison of exposed rock layers or strata in various parts of the earth led scientists in the early 19th century to propose that the rock layers could be correlated from place to place. Locally, physical characteristics of rocks can be compared and correlated. On a larger scale, even between continents, fossil evidence can help in correlating rock layers. The Law of Superposition, which states that in an undisturbed horizontal sequence of rocks, the oldest rock layers will be on the bottom, with successively younger rocks on top of these, helps geologists correlate rock layers around the world. This also means that fossils found in the lowest levels in a sequence of layered rocks represent the oldest record of life there. By matching partial sequences, the truly oldest layers with fossils can be worked out. By correlating fossils from various parts of the world, scientists are able to give relative ages to particular strata. This is called relative dating. This would also mean that fossils found in the deepest layer of rocks in an area would represent the oldest forms of life in that particular rock formation. If certain fossils are typically found only in a particular rock unit and are found in many places worldwide, they may be useful as index or guide fossils in determining the age of undated strata. By using this information from rock formations in various parts of the world and correlating the studies, scientists have been able to establish the. This relative time scale divides the vast amount of earth history into various sections based on geological events sea encroachments, mountain-building, and depositional events , and notable biological events appearance, relative abundance, or extinction of certain life forms. Objectives: When you complete this activity, you will be able to: 1 sequence information using items which overlap specific sets; 2 relate sequencing to the Law of Superposition; and 3 show how fossils can be used to give relative dates to rock layers. Materials: two sets of sequence cards in random order : nonsense syllables; : sketches of fossils , pencil, paper Procedure Set A: 1 Spread the cards with the nonsense syllables on the table and determine the correct sequence of the eight cards by comparing letters that are common to individual cards and, therefore, overlap. Sequence the remaining cards by using the same process. Interpretation Questions: 1 After you have arranged the cards in order, write your sequence of letters using each letter only once on a separate piece of paper. Starting with the top card, the letters should be in order from youngest to oldest. Procedure Set B: 1 Carefully examine the second set of cards which have sketches of fossils on them. Each card represents a particular rock layer with a collection of fossils that are found in that particular rock stratum. All of the fossils represented would be found in sedimentary rocks of marine origin. The letters on the other cards have no significance to the sequencing procedure and should be ignored at this time. Find a rock layer that has at least one of the fossils you found in the oldest rock layer. This rock layer would be younger as indicated by the appearance of new fossils in the rock stratum. Keep in mind that extinction is forever. Once an organism disappears from the sequence it cannot reappear later. Use this information to sequence the cards in a vertical stack of fossils in rock strata. Arrange them from oldest to youngest with the oldest layer on the bottom and the youngest on top. Interpretation Questions: 1 Using the letters printed in the lower left-hand corner of each card, write the sequence of letters from the youngest layer to the oldest layer i. This will enable your teacher to quickly check whether you have the correct sequence. RELATIVE DATING Teacher Version INTRODUCTION Scientists have good evidence that the earth is very old, approximately four and one-half billion years old. Scientific measurements such as radiometric dating use the natural radioactivity of certain elements found in rocks to help determine their age. Scientists also use direct evidence from observations of the rock layers themselves to help determine the relative age of rock layers. Specific rock formations are indicative of a particular type of environment existing when the rock was being formed. For example, most limestones represent marine environments, whereas, sandstones with ripple marks might indicate a shoreline habitat or a riverbed. The study and comparison of exposed rock layers or strata in various parts of the earth led scientists in the early 19th century to propose that the rock layers could be correlated from place to place. Locally, physical characteristics of rocks can be compared and correlated. On a larger scale, even between continents, fossil evidence can help in correlating rock layers. The Law of Superposition, which states that in an undisturbed horizontal sequence of rocks, the oldest rock layers will be on the bottom, with successively younger rocks on top of these, helps geologists correlate rock layers around the world. This also means that fossils found in the lowest levels in a sequence of layered rocks represent the oldest record of life there. By matching partial sequences, the truly oldest layers with fossils can be worked out. By correlating fossils from various parts of the world, scientists are able to give relative ages to particular strata. This is called relative dating. This would also mean that fossils found in the deepest layer of rocks in an area would represent the oldest forms of life in that particular rock formation. If certain fossils are typically found only in a particular rock unit and are found in many places worldwide, they may be useful as index or guide fossils in determining the age of undated strata. By using this information from rock formations in various parts of the world and correlating the studies, scientists have been able to establish the. This relative time scale divides the vast amount of earth history into various sections based on geological events sea encroachments, mountain-building, and depositional events , and notable biological events appearance, relative abundance, or extinction of certain life forms. Objectives: When you complete this activity, you will be able to: 1 sequence information using items which overlap specific sets; 2 relate sequencing to the Law of Superposition; and 3 show how fossils can be used to give relative dates to rock layers. The nonsense syllables or letters sometimes overlap other cards and are being used to introduce the students to the concept of sequencing. The cards should be duplicated, laminated, and cut into sets and randomly mixed when given to the students. It is recommended that students complete Procedure and answer the associated Interpretation Questions correctly before proceeding to. The cards in represent rock layers containing various fossils. For , you may want to color code each organism type i. Sequencing the rock layers will show the students how paleontologists use fossils to give relative dates to rock strata. To enhance this activity, have students match the fossil sketches to real fossils. You may use fossils from the John Hanley Fossil Teaching Set. To request a Fossil Teaching Set, call the Geology Museum at the Colorado School of Mines 303 273-3815. The following is a list of fossils in the John Hanley Fossil Teaching Set that may be useful in this activity. Brachiopod VGastropod VI-2 Trilobite VIIIPelecypod VI-1 Graptolite XAmmonite VI-3b Corals IIIa, IIIbShark's Tooth XI-1a Crinoids IXa, IxbForaminifera I illustrates a hypothetical stratigraphic section of rocks which include fossil assemblages represented in. It may be useful to share with students after they have completed and answered the Interpretation Questions. Procedure : 1 Spread the cards with the nonsense syllables on the table and determine the correct sequence of the eight cards by comparing letters that are common to individual cards and, therefore, overlap. Sequence the remaining cards by using the same process. Interpretation Questions: 1 After you have arranged the cards in order, write your sequence of letters using each letter only once on a separate piece of paper. Starting with the top card, the letters should be in order from youngest to oldest. The correct sequence of letters for the cards in from youngest to oldest rock strata is MDXONBUAGCT. Please note that none of the letters in this sequence may be reversed and still be correct. The sequence must be exactly in the order as written. It is not uncommon to have students reverse the M and D for example and begin the sequence with DM because that is the way they are printed on the card. It is good at this time to remind them that these letters represent fossils in a rock layer and that one fossil next to another within a rock layer implies no particular sequencing; they both are approximately the same age as that particular rock layer. The following question may help clarify this point. Using the Law of Superposition, the rock layer OXD is beneath rock layer DM and, therefore, is older. The fossils within rock layer OXD i. Therefore, D in the rock layer OXD is older than D in the rock layer DM. Procedure : 1 Carefully examine the second set of cards which have sketches of fossils on them. Each card represents a particular rock layer with a collection of fossils that are found in that particular rock stratum. All of the fossils represented would be found in sedimentary rocks of marine origin. The letters on the other cards have no significance to the sequencing procedure and should be ignored at this time. Find a rock layer that has at least one of the fossils you found in the oldest rock layer. This rock layer would be younger as indicated by the appearance of new fossils in the rock stratum. Keep in mind that extinction is forever. Once an organism disappears from the sequence it cannot reappear later. Use this information to sequence the cards in a vertical stack of fossils in rock strata. Arrange them from oldest to youngest with the oldest layer on the bottom and the youngest on top. Interpretation Questions: 1 Using the letters printed in the lower left-hand corner of each card, write the sequence of letters from the youngest layer to the oldest layer i. This will enable your teacher to quickly check whether you have the correct sequence. The graptolite, placoderm, ammonite, ichthyosaur, and shark's tooth could possibly be used as index fossils since they are found in only one layer. Technically, however, given only this set of strata, one cannot say that the shark's tooth and ichthyosaur could be used as index fossils because we do not know if they continue in younger rock layers above this set of strata. The brachiopod, crinoid, eurypterid, foraminifera, gastropod, horn coral, pelecypod, and trilobite could probably not be used as index fossils since they overlap more than one stratum. Marine sedimentary rocks such as limestone, shale, and sandstone might contain fossils similar to those depicted in this activity. This activity illustrates this law because when the cards are placed in the correct order, the vertical stack shows the oldest fossils in a rock layer in the bottom of the stack and the youngest fossils in rock stratum on the top. Stratigraphic Section for Set B Set B.

By matching partial sequences, the truly oldest layers with fossils can be worked out. This is called relative dating. This rock con would be younger as indicated by the appearance of new fossils in the rock stratum. The following question may help clarify this point. Foryou may want to color code each organism type i. Extinction of species is common; most of the species that have met on the earth no longer exist.