A volcanic eruption melts a large area of rock, and all gases are expelled. After
Chapter 24, Problem 24.48(choose chapter or problem)
A volcanic eruption melts a large area of rock, and all gases are expelled. After cooling, 40 18Ar accumulates from the ongoing decay of 40 19K in the rock (t1/2 _ 1.25109 yr). When a piece of rock is analyzed, it is found to contain 1.38 mmol of 40K and 1.14 mmol of 40Ar. How long ago did the rock cool?
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