Monday, May 26, 2008

Exloring the deep past

I noticed the other day that the college has put up bollards around "Raymo's rock" in Parking Lot 17. This is an outcrop that was saved some years ago when a few acres of the campus were paved over for parking. It occurs to me that it might be nice to have a sign there explaining this island in a sea of asphalt. How about this?
The north-south polish and grooves you see on this granite outcrop are the work of ice, not so long ago -- 15,000 years -- when all of New England was covered with a moving glacier.

The granite itself was implanted at the base of a long-vanished mountain range that was pushed up here 300 million years ago when drifting continents collided to form the supercontinent of Pangaea ("all-earth").

The reason this outcrop has been saved is the band of black volcanic rock that fills the crack running transverse to the glacial grooves. This is the only known place on campus where we have evidence of that time 200 million years ago when Pangaea was being stretched asunder and the present Atlantic Ocean was being born. The crust was rent, and molten rock welled up through cracks from below, here forming a rather modest dike. Elsewhere -- Connecticut and New Jersey, for example -- vast sheets of lava poured out across the land, incinerating forests, sizzling into lakes and marshes, and sending dinosaurs scampering before the fiery flood.
There. I'll send this on to Facilities Management and see what they come up with.