Tuesday, April 12, 2016

On the road again … but where? (geo-challenge)

Where on Google Earth? (click on image to view)

Here’s a special deal to celebrate the start of 2016 geo-tripping: three geo-challenges for the price of one! I visited all in a period of five days, traveling by car. Where was I? [answers here]

Ordered by increasing age of strata:

#1 Darker brown is caused by seepage from the base of a super important aquifer.

#2 Thousands of immigrants passed by—did anybody notice the white ash layers and curious wavy contact?

#3 This rock is gray when fresh, weathering to pale yellow or almost white. This is its type area, and its geological period is eponymous as well.

Please answer, speculate, discuss in Comments below. I’ll add locations in a few days, and posts will follow. Happy geo-travels!


  1. Fascinating. I'll look forward to the big reveal! ;-)

  2. 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 think it shouid 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.

  3. Why is the contact on #2 wavy?

    1. That's the big question, Cindy! The geo-guide (2003) offers only speculation—inexplicable surface erosion or soft sediment deformation before deposition of next layer of sediments. I hope to find more discussion, for a post about it.

  4. Answers added here: http://plantsandrocks.blogspot.com/2016/04/on-road-in-nebraska-geo-challenge.html