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Stop 3
The third stop was beside the lube area of the Wal*Mart. There are some black rocks cropping out on the grassy patch beside the road leading to Lowe's.
Across the street are the same metamorphic rocks you just saw behind Tokyo Express.
This black rock at the feet of those students is the … wait for it… Rich Acres Gabbro. Yes, the same dark rock you saw at the first stop!
At stop 2 you were asked what could have caused the higher temperature metamorphism at the base of the gneiss. Well, here it is; the proverbial smoking gun.
The intrusion of this gabbro metamorphosed the gneiss. This lets you get a relative age of the two rocks. Since you already have the relative age of the light and dark rocks from stop 1 you can now give a relative age sequence to all three rocks. Not bad for a first outing in geology!
