Scales Creek Flow



The Portage Lake Lavas number about 400.  They were erupted from fissures along the great Keweenaw rift, and then flowed out and filled the basin which was then located along the western half of Lake Superior.  These flows were enormous compared to flows that are erupted typically in Hawaii, Italy, Guatemala and other volcanically active areas. Most Keweenaw flows were 10-40 feet thick, but several flows were larger.  The Greenstone flow, which underlies the Cliff near Phoenix is up to 1200 ft thick.  In Houghton, a thick flow crosses through town near Franklin Square.  This flow, called the Scales Creek Flow, is about 200 feet thick for a distance of at least 20 miles.  It represents a very dramatic outpouring of lava which probably formed an extensive lava lake and took centuries to solidify.  The flow makes a resistant layer which makes a ridge within the city.  Where it crosses Houghton Ave, the road bends and there is a large road cut.  Many roads do not cross the barrier.  Below the Scales Creek flow is a mineralized horizon, probably influenced by the relatively impermeable flow which channeled hot water solutions along the permeable flow tops just underneath the Scales Creek.


Scales Creek Lava Flow



Why do the city roads bend or terminate when they cross large lava flows?

Why do thick flows make ridges?

Basalt can be a plain, gray rock with no observable crystals.