Post #447916

Excavation at a development site in Lynnwood, WA shows stratigraphy from the recent past, geologically speaking. An over 3,000 foot thick ice sheet covered the area that melted away 12,000 years ago. The lower dark gray layer is till, a mix of clay, silt, sand, gravel, etc. that was smeared and packed under the ice sheet as it advanced. Very dense. Above that is some clay/silt sand/gravel, not as dense, may be weathered till or outwash. The contact is abrupt. #geology #Pleistocene #glacier