Dikes from the Sea

view of dikes from sea

This photograph was taken from a fishing boat in the Gulf of Saint Lawrence from a distance of about 250 meters (300 yards) from the shoreline.  The dikes are the vertical slashes in the bedrock.  The bedrock is syenite, a rock similar to granite but with a lower proportion of  quartz.  The syenite bedrock is more resistant than the dike-forming rocks in the area, so the dikes have weathered to become the bold negative relief features which are easily seen on the treeless landscape.  The surface of the bedrock was probably at the same level as the surface of the dikes during the last glaciation of the region, only a few thousand years ago, but the dikes have weathered more rapidly than the syenite bedrock when exposed to the atmosphere, creating the vertical slashes seen here.  The streamlined appearance of the landscape is due to abrasion by the ice sheet, which was very thick at this location.  There is no soil on the bedrock in this area because the glacier had removed it and new soil has not yet had sufficient time to form.