Where on Google Earth (click on image to view).
Lynn David met all three of the recent geo-challenges:
"Obviously Nebraska.... cannot mistake that bend in the Platte River.
#1 Looks like you're on the bluffs above the Niobrara River (one of my favorite rivers) just northeast of the sand hills area, which might make that the Ogallala. Though I keep thinking it shoud be something older in the Arikaree, Laramie or Chadron?
#2 Looks to be the Scotts Bluff area which would make it the Tertiary Arikaree and Gering formations sediments which are mostly fluvial or wind-blown in origin with quite a bit of volcano-clastic sediments, probably from Colorado.
#3 Never been there. But going to guess it's the Niobrara."Other readers sent correct answers by email, with more praise for the Niobrara River. They're right—it's great for both plants and rocks!
Locations are inserted in bold. Posts with more details will follow.
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Ordered by increasing age of strata:
#1 Darker brown is caused by seepage from the base of a super important aquifer. Niobrara National Wildlife Refuge; base of Ogallala Group, above Rosebud Formation (either Arikaree or White River group; geologists disagree).
#2 Thousands of immigrants passed by—did any notice the white ash layers and curious wavy contact? Scotts Bluff on the Oregon Trail; Brule (White River) and Gering (Arikaree) formations below and above the mysterious wavy contact (Cindy—currently investigating, more to follow, hopefully).
#3 This rock is gray when freshly exposed, weathering to pale yellow or almost white. This is its type area, and its geological period is eponymous as well. Cretaceous Niobrara Chalk at the confluence of the Missouri and Niobrara Rivers.
Actually, this photo is in South Dakota (the state line is in the lake).
Happy geo-travels!
