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Untitled edit
Why is there this "step" that forms the falls. Is it a harder rock type than that below ?Ruskin (talk) 05:22, 31 December 2014 (UTC)
This link https://books.google.co.uk/books?id=4n1IAgAAQBAJ&pg=PA170&lpg=PA170&dq=Gibbon+falls+geology&source=bl&ots=FZ8cAbz4UR&sig=HTbC3nhJLdDqLR8yBZZq-T9gTUI&hl=en&sa=X&ei=p4-jVOSvBNPpaLb-gbAL&ved=0CEAQ6AEwBDgK#v=onepage&q=Gibbon%20falls%20geology&f=false States "Eastward beyond Tuff Cliff, the road continues for 3 miles along the front of the slumped caldera block, nearly to Gibbons Falls, then turns abruptly Northward to cross the block. The falls held up by densely welded, vertically jointed Lava Creek Tuff, have retreated from the scarp of the slumped block."
Can anyone who knows elaborate a little.Ruskin (talk) 06:10, 31 December 2014 (UTC)
- In the simplest terms, yes, Gibbon Falls was formed when the river encountered a much harder seam of Basalt lava flow as it crossed the Yellowstone Caldera perimeter. It is actually the same reason for the existence of Virginia Cascades farther up river. Generally the tuff formation is which is responsible for the caldera rim is interspersed with much harder basalt and ryolite lava flows. See image below. Because the river formed and flowed pretty much along the caldera boundary, these falls formed when the Basalt lava flows were encountered.--Mike Cline (talk) 14:50, 31 December 2014 (UTC)