Friday, February 1, 2013

Glacial Striations on Lopez

I always enjoy seeing glacial striations. The San Juan Islands have lots of hard glacially striated bedrock. This particular bedrock exposure on the south end of Lopez Island provided some distraction from the specific issue of my site visit.

Striated bedrock and a some of my field gear.
Striations run from right (north) to left (south)

Fine striations scratched into the metamorphosed sandstone

Take 2,000 or 3,000 feet of ice pressing down on the glacial erratic in the picture and it is easy to visualize the bedrock being scratched, but all the small rocks within the overlying drift would have made an effective "sand paper".

Broad swale like erosion into bedrock

At this location near the southwest corner of Lopez Island the striations were oriented almost exactly north-south. The striations provide a data point regarding ice movement over the area.  

No comments: