A varve is a deposit of sediments laid down in a glacial lake.
During the warm season when the lake is ice-free, a thicker layer of heavier material is deposited, while duriing the cold season the finer material already in the water slowly settles. Another feature found in varves are ice-rafted erratics, which are rocks that fell out onto the ice and then fall to the bottom with the Spring thaw.

I'll have some photos up of this particular location, and in the meantime here is a video of its exploration. The exposed cut is ~33 feet from crest to roadbed, and the layers range from a mm or less, to just over a cm. The lake itself disappeared at the end of the last ice age when the glacier trapping it against the mountains retreated.

http://www.youtube.com/watch?v=yjvSt9d-Das

I haven't mastered the intricacies of Folders yet for close grouped features, so in the mean time here is another varve location and short video showing the formation.


45� 55' 34" N 122� 13' 32" W: Elevation: 1122 Feet

http://www.youtube.com/watch?v=Bhevdu1ZsbY