ESC1000Lab10NewWorksheet

ESC1000Lab 10: G EOLOGIC T IME Name:___________________ Section:______ Activity 10.3: Principles of Cross-Cutting and Inclusions 1. Is the igneous intrusion, dike E, older or younger than rock layers A – D? E is ________ 2. Is fault H older or younger than rock layers A – D? H is _________ 3. Is fault H older or younger than sedimentary layers F and G? H is __________ 4. Did fault H occur before or after dike E? Explain how you arrived at your answer. I know H occurred ________ dike E, because __________________________________ ________________________________________________________________________ ________________________________________________________________________ 5. What evidence supports the conclusion that the igneous intrusion labeled sill B is more recent than the rock layers on either side (A and C)? _____________________________ ________________________________________________________________________ ________________________________________________________________________

Activity 10.5: Applying Relative Dating Principles 1. Identify and label the unconformities in Figure 10.12 . 2. Is rock layer I older or younger than layer H? What relative dating principle did you apply to determine your answer? Rock layer I is ________________ than layer H. Relative dating principle: _____________________________________ 3. Is fault L older or younger than rock layer D? What principle did you apply to determine your answer? Fault L is _____________ than rock layer D. Relative dating principle: _____________________________________ 4. Is igneous intrusion J older or younger than layers A and B? What two relative dating principles apply to your answer? Intrusion J is ______________ than layers A and B. Relative dating principles: _______________ and ____________________ 5. Is the igneous intrusion labeled dike K older or younger than layers C – F? Intrusion K is __________________ than layers C – F. 6. List the entire sequence of events, in order from oldest to youngest, by writing the appropriate letters in the spaces provided next to Figure 10.12 .

5. What is the geologic range of the fossil in box Y? From the _________________ period through the __________________ period. 6. Imagine that you have discovered a rock outcrop that contains the fossils identified in Questions 4 and 5 . What is the geologic range of this rock? From the _________________ period through the __________________ period. 7. Figure 10.17 illustrates two different sequences of sedimentary rock strata located some distance apart. a) Determine the geologic range/age of each rock layer by its fossil content and write your answer on the figure . b) Draw lines connecting the rock layers of the same age in outcrop 1 to those in outcrop 2. c) What term is used for the process of matching one rock unit with another of the same age? ______________________________________________________ d) Based on the ages of the rock layers in outcrop 1, identify an unconformity. Remember that an unconformity is a break in the rock record. Draw a wavy line on the figure to represent the unconformity.

Activity 10.8: Numerical Dating with Radioactivity 3. What percentage of the original parent isotope remains after each of the following half-lives have elapsed? # of Half-lives Percentage of Parent Isotope Remaining One Half-life: Two Half-lives: Three Half-lives: Four Half-lives: 4. Geologists know that potassium-40 decays to argon-40, with a half-life of 1.3 billion years. If an analysis of a feldspar crystal in a sample of granite shows that 75 percent of the potassium-40 atoms have decayed to form argon-40, what is the age of the granite? The granite sample is _____________ years old. 5. Determine the numerical ages of rock samples that contain a parent isotope with a half-life of 100 million years and have the following percentages of original parent isotope: 50%: Age = 25%: Age = 6%: Age = Activity 10.9: Applying Multiple Dating Techniques In Activity 10.5 , you determined the geologic history of a hypothetical region, shown in Figure 10.12 , using relative dating techniques. Use Figure 10.12 to answer the following. 1. An analysis of a mineral sample from dike K indicates that 25 percent of the parent isotope is present in the sample. a) How many half-lives have elapsed since dike K formed? ___________________ b) If the half-life of the parent isotope is 50 million years, what is the numerical age of dike K? Write your answer below and next to dike K on Figure 10.12 . Dike K is ______________ million years old. 2. An analysis of a mineral sample of intrusion J indicates its age to be 400 million years. Write the numerical age of rock J on Figure 10.12 . 3. Are rock layers H and I younger or older than 100 million years? Explain. Layers H and I are _______________ than 100 million years, because _______________ ______________________________________________________________________________ __________________________________________________________________ 4. Determine the possible age range of rock layer E. Layer E is between ______________ and ______________ million years old. 5. Determine the age of rock layer A. Rock layer A is greater than _______________ million years.