- Robert Montgomery
The Algoma district,containing such a large expanse of unexplored and undisturbed land is a treasure trove of geological phenomena. A few of my favorites are listed below.
An erratic is a piece of rock that has been eroded and transported by a glacier to a different area; it is left behind when the ice melts. Glacial erratics give us information about the direction of ice movement and distances of transport. Glacial erratics can be any size from small pebbles to large boulders the size of a house.
Puddingstone is a conglomerate rock consisting of individual stones within a finer matrix usually formed from quartz. This particular example is from St. Josephs island . It contains red and brown pieces of jasper. It can be highly polished and is used for jewellry.
Some of the work done by Northshore craftsmen using local puddingstone.
A GLACIAL "DROPSTONE." A granite stone is embedded within a layered sedimentary rock. The cobble may have been transported by an ice sheet and then released. The cobble embedded itself in the sediment on the ocean floor.
The ripple marks on this rock face were made some two billion years ago by waves of an ancient ocean that once covered this area. Buried by layers of silt and subjected to great pressure, the rippled sand became sandstone. blasting during road contruction uncovered this ancient phenomena.
