Tuesday, 9 June 2015

The Amazing Geology of Digby Neck

This post is quite a challenge as I have to condense roughly 350 million years of "rock history" into a couple of paragraphs but here goes.
So 350 million years ago, Digby Neck was a really happening place. We were part of a supercontinent called Pangaea and attached to present day Africa. If that isn't enough, we were located on or near the equator! By this time, major fault lines had created steep sided basins called rift valleys. Sea levels were going up and down which is why we find, at the Seawall Cliffs near our house, areas where mud flats have dried out and the cracks have been filled with sand. So when it was subsequently buried and became rock, it looked like a mosaic tiled floor.
the spectacular red cliffs of the Seawall seen from our deck

Then as they say, all hell broke loose!. Lava started flowing out of big cracks on the valley floor. Sometimes it was slow but sometimes it was a volcanic eruption. Eventually, it formed the North Ridge out of a solid rock called Basalt.
Basalt is the most common rock on earth but it leads to some very interesting things. Depending on how fast it cools, large columns can form. You can see an amazing example at Balancing Rock farther out the Neck.
Balancing Rock - spectacular basalt column

If the basalt cools really fast, as it tends to do near the edge and bottom where it contacts other rock, cracks and fissures can form. Since nature abhors a vacuum, superheated water containing something called silicates starts to be forced into them and as it cools, the silicates are precipitated out of the rock and form quartz and, more rarely, agates. That's what happened here from 250-200 million years ago and my next post will discuss this spectacularly beautiful rock/gemstone- agate. In my next post, I'll show you some beautiful examples of this stone and how we are making use of it in the shop.

In some places, gas bubbles got trapped in the rock as it cooled and they too filled with silicates but they tend to be only quartz- not agate.
quartz-filled air bubbles in basalt

Eventually, via continental drift, we separated from Africa and moved from the equator to where beautiful Digby Neck exists today. Large faults caused the breaks in the Neck which add to its beauty. Come and see it for yourself.    

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