Erosion during the last few tens of thousands of years has exposed the shale to oxygen-rich rainwater and snowmelt, causing gradual change of the pyrite to goethite in a process on-going to this day.
(Erosion during the last few tens of thousands of years; has exposed; the shale; to oxygen-rich rainwater and snowmelt) Context(Erosion during the last few tens of thousands of years has exposed,List([0, 66))):(Erosion during the last few tens of thousands of years; has exposed the shale causing; gradual change of the pyrite)
Erosion during the last few tens of thousands of years has exposed,List([0, 66))
Erosion during the last few tens of thousands of years Erosion during the last few tens of thousands of years
has exposed has exposed the shale causing
the shale to oxygen-rich rainwater and snowmelt
gradual change of the pyrite