Examine the Wind Gap in Haystack Mountain.

1. What is the elevation of the floor of the wind gap? Answer

2. What is the elevation of Braddock Run at the westward base of Haystack Mountain? Answer

3. What is the difference in elevation between the floor of the gap and the bottom of the valley of Braddock Run? Answer

4. Assuming that every century, the stream has managed to erode the valley one inch, how long has it been since Braddock Run flowed through Haystack Mountain? Answer

5. Using the geologic time scale, when would this change have taken place? Answer

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