Here and there along the way to Alder Stream are found pockets of shale, poor grade slate, greenstone and pillow lava
Meandering stream in Eustis
Shale and poor grade slate are found in the first few miles from Stratton past the King Bartlett Rd.
Just south and north of Alder Stream along Rt. 27 are numerous rock cuts showing green, finegrained, angular rock commonly known as greenstone. This is a chlorine-rich rock which is also rich in iron and magnesium. It is a metamorphosed rock (probably from the basaltic pillow lava found nearby)--meaning that the basalt was recrystalized under moderate heat and pressure where it cooled and is now exposed as the result of erosion.
Pillow lava roadcut on route 27 northbound just past Alder Stream on the right side of the road. You can easily see the "pillows" that the oozing lava made. The pillows got tucked in and against each other in all kinds of shapes to fill voids. Basalt is a dark, and heavy rock containing a lot of iron and magnesium. This is the mechanism by which most of the earth surface is formed. This rock was probably made when the North American continent 'drifted' away from Africa and the new Atlantic Ocean was formed between them. The pillow lava is still forming new crust halfway between America and Africa at the Mid-Atlantic Ridge.
The pillows were flattened quite thinly in some places.
The top of the lava bed was flattened by glacial erosion. This is a view from the top, showing a cross-section of the pillows, which are further eroding through the action of ice.
another view showing the flattened top. It might be inferred here that the glacier was moving from left to right in a southbound direction from the appearance of the rock. There is greater breakup of the rock on the right with a carrying off of the debris.
That the lava cooled rapidly is evidenced by fine grain, lack of mineral separation and the small holes or vessicles which formed from expanding air bubbles. These were later filled by white calcite.
Veins of calcite between pillow surfaces
There is a tendency for all angular blocks of rock to be reduced by erosion to a round or spheroidal form. This is because block forms displays more surface area in sharp external angles.
Here is an example of the spheroidization of rock from erosion and, perhaps of exfoliation as well (process of shedding outside layers or surfaces of rock.).
Greenstone with patches of green (chlorite ?) minerals and of light-colored (calcite?) minerals found north of the Pillow Lava and near a soapstone quarry.
This is part of the bedrock along a roadcut north of the pillow lava at a site where a quarry was mined for soapstone, a massive talc. Asbestos is also found here in very small quantities.
In a small clearing in the woods, a deer is grazing as I am observing the rocks. |
