Chapter 8 Section 2 Review Page 196

Relative Age Dating Absolute Age Dating

2. Explain why calculations of absolute age based on rates of erosion and deposition can be inaccurate. The rate at which sediment is deposited or eroded away can vary from year to year due to many factors.

3. Describe varves, and describe how and where they form. Varves are layers of sediment made of one layer of sand covered by one layer of silt. They are deposited at the bottom of glacial lakes and represent one year of deposition.

Varves

4. Suppose you have a shark’s tooth that you suspect is about 15,000 years old. Would you use 238U or 14C to date the tooth? Explain your answer. You would use radiocarbon (14C) dating because the object is organic and because it is too young to be accurately dated by using 238U.

Radiocarbon Dating: Parent to Daughter

Section 2: Determining Absolute Age Chapter 8 Study Notes Section 2: Determining Absolute Age

1 The ______ age of an object is called _______ age. numeric absolute

2 _______ age is the ______ age of an object. Absolute numeric

3 _______ are banded _____ of sediment deposited _________ in glacial lakes. Varves layers annually

13 A ______ is most like a tree ____. varve ring

14 Radioactive ____ is used to compare the absolute age of rocks because radioactive decay happens at a relatively ______ rate. decay constant

15 ________ dating is determining age through _________ of isotopes. Radiometric comparison

16 In __________ decay, parent isotopes are compared to __________ isotopes. radioactive daughter

17 In ________ dating, scientists compare the proportion of a radioactive ______ isotope to a stable _________ isotope. radiometric parent daughter

18 A ________ is the time it takes for half of a sample of radioactive isotope to decay. half-life

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