geol1020hw3

geol1020hw3 - HOMEWORK#3 GEOLOGY 1020 Spring 2008 Use the...

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HOMEWORK #3, GEOLOGY 1020, Spring 2008 Use the graph of 40 K - 40 Ar decay shown below to answer questions 12-14. ( 40 K is the parent, 40 Ar is the daughter) The half-life of the 40 K - 40 Ar decay is 1,250 million years. 0 10 20 30 40 50 60 70 80 90 100 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 Number of Half Lives Elapsed # P a r e n t s R m i g % 1. If 25% of the original number of atoms of 40 K in a feldspar crystal have decayed to 40 Ar, what is the age of the sample? A. 312.5 million years B. 500 million years C. 1,250 million years D. 2,500 million years 2. Based on that age, in what geologic period was the sample formed? A. Pennsylvanian B. Ordovician C. Cambrian D. Precambrian 3. What is the age and period of formation of a crystal which contains only 10% of the original 40 K atoms? A. ~125 million years, Cretaceous B. ~250 million years, Permian C. ~4250 million years, Precambrian (Archean eon) D. 12,500 million years, Precambrian (Hadean eon)
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Use the following figure to answer the next three questions. dashes = shale, block pattern = limestone, dots = sandstone, black is basalt 4. The extrusive lava flow dates at 6 million years.
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geol1020hw3 - HOMEWORK#3 GEOLOGY 1020 Spring 2008 Use the...

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