Wyoming, being hard to access for a lot of scientists, doesn’t get a lot of attention when it comes to studying how Earth formed and what that might teach us about the future of our planet, or even from tourists, who think Yellowstone is in Montana (okay, like 4 minutes of it is).
But it should. Because there’s a LOT going on here. For starters, the Uinta mountain range is right at the border of Utah, Colorado, and Wyoming. And it’s amazing. One of the few mountain ranges originally from sedimentary rocks (rocks that have been weathered and transported to be redeposited, as opposed to rocks that form from volcanoes or in the mantel and then exposed to the surface), the range is also one of the few that runs East-West instead of North-South. The flanks of the east-west trending Uinta Mountains contain a sequence of Palozoic and Mezozoic strata (really-old and somewhat-old) ranging from the Cambrian (super-duper old) Lodore Formation to the Cretaceous (dinosaurs!) Mancos Shale, all of which have been spectacularly tilted during the uplift of the mountain range.
The Wind Rivers are another amazing natural feature in Wyoming. Typically considered part of the Rock Mountains, though that’s technically incorrect as they have different formation events regardless of their proximity to one another, the range has granitic plutons (large plugs of granitic rock welling up from the mantle), indicating an Archean subduction zone. That means the core of the Wind River Range is nearly 4 billion years old! Whoo!
The range runs roughly NW-SE for over 100 miles. The Continental Divide is parallel to the range, making this one of the most unique mountain ranges in the US. With the exception of the Grand Teton in the Teton Range, the next 19 highest peaks in Wyoming are also in the Wind Rivers.
Ice Ages beginning 500,000 years ago carved the granite into their present shapes (geomorphology). Lakes were formed by the glaciers and numerous cirques (circular valleys made by glacial ice) were carved out of the rocks, the most well known being the Cirque of the Towers (if you’ve ever seen a postcard of Wyoming with a glacier and a jagged peak, its probably of the Towers). Several of these are some of the largest glaciers in the U.S. Rocky Mountains. Gannett Glacier, which flows down the north slope of Gannett Peak, is the largest single glacier in the Rocky Mountains.
The Leucite Hills
Or more formally known as the Leucite Hills Volcanic Province, this unique geological setting encompasses a huge area in Southwest Wyoming, including Table Mountain, Pilot Butte, Cross Mesa, Matthews Hill, Boar’s Tusk, and more.
Geologically, it’s made of some weird stuff. And that’s saying something, for a geologist. Active around 3.4-1.4 million years ago, these rocks have been classified as Diopside-Leucite-Phlogopite Lamporites. The name is so long mostly because no one really understands how they formed, so geologists have kinda named it “The everything rock (or why is this stuff even here)”.
A lamporite is an rock rich in potassium and magnesium and other elements that shouldn’t naturally like to bond together. It forms from the melting of the mantle deeper than 100 miles down. It’s close cousins to kimberlites, which are magma pipes of mantle rock that can contain diamonds. But while kimberlites are much more common and therefore better studied, lamporites only sometimes have diamonds. And therefore don’t get much love from industry or science, because who wants to spend a bunch on money studying some old rocks that probably won’t turn up a profit? Right?
Boar’s Tusk is thought to be the remains of a magma chamber that includes lamporite. There are then a number of lava flows around this area that are from this ancient volcanic activity that brought up more of these unusual rocks.
I’ll save Yellowstone and Devils Tower for their own posts. We just got back from Devils Tower (the first National Monument), and we’re planning at trip back to Yellowstone soon (the first National Park). Pretty cool place, Wyoming.