W 72 degrees 32' 34"
Our fearless leaders (Jim Sirch and Dr. Jay) unfurl a large CT Geology map as we visit the site of terminal moraines left by the last glacial maximum (about 12,000 years ago).
At this site, granitic and gneissic boulders remain atop glacial till and sand. The boulders have a rounded appearance due to glacial transport and wind/wave erosion.
A perfect day for the beach!
Erosion of the beach and boulders increases as people stray off of the walkways and trample protective vegetation. (No plants were harmed as a result of our excursion!)
The smallish red spots are garnets that have formed in granitic gneiss.
Gneissic rock.
Granitic gneiss. Granite contains feldspar (usually pink or white), quartz and biotite mica (black). When granite is subjected to intense heat and pressure it is metamorphosed into granitic gneiss.
The foliation ("lines" in the rock not too apparent in this picture) indicate that the rock was previously subjected to tectonic squeezing and shearing. This probably occurred when ancient continents collided together during the creation of Pangaea (the "supercontinent") 600 million years ago.
This photo shows gneiss with magnetite crystals in it. (The magnetite crystals are the small black circles). The area around the magnetite crystal is "bleached" white since the magnetite pulls the iron out of the rock immediately surrounding it.
Very cool photo of grains of granite that have intruded into the surrounding gneiss.
In this photo, I am pointing to a large pegmatite crystal. Pegmatite usually occurs as a large (over 3 cm), chunky crystal of granite containing feldspar, mica and quartz.
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