#mt. moran

[earthstory]

roam

Can you believe the late spring snow! Catching up with #ROAM Founding  Member @jimmychin and @dougworkamn in the Tetons.

[mouseandboo]

Postcrossing US-8190943 by Gail Anderson Via Flickr: Postcard with a photo of String Lake and Mt. Moran in the background. The picture was taken at Grand Teton National Park in Wyoming. Sent to a Postcrossing member in Germany.

[mountaineeringtheworld]

Hammock swinging under Mount Moran.

[earthstory]

Moran Diabase

If you’ve traveled national parks in the western United States, you might be able to go to your own photos and find this geologic feature. This photo captures the side of Mount Moran, one of the peaks in Grand Teton National Park.

The Teton Range in Wyoming is exposed by a series of faults that cut into some of the oldest parts of the North American Continent. The Wyoming Province is a sliver of ancient, Precambrian Aged crust that accreted to the edge of the growing Laurentian continent. The deepest rocks beneath Wyoming are therefore ancient, highly metamorphosed igneous rocks.

Much of the face of Mount Moran exposes interfingering lines of granite that crosscut older, metamorphosed gneisses. If you look closely at this image, many of the light streaks are these igneous rocks; they have been dated to be about 2.5 billion years old, meaning the rocks they intrude must be even older.

On the face of Mount Moran you also see a single black line that for a time vanishes beneath the Skillet Glacier. This line is a dike, an intrusion of a mafic igneous rock we call a diabase. The dike of diabase on Mount Moran can be tracked for about 15 kilometers to the west (the mountain range is bounded on its east side by a large fault, and so if the dike exists there it is deeply buried).

That dike cross cuts the gneiss and the granite, so it must be younger than either of those. Dating of those rocks indicates they are about 800 million years old, fitting that hypothesis. The diabase dike reflects a time of rifting; rocks elsewhere in the western U.S., including the Grand Canyon, suggest rifting at about that time. A sliver of continental crust, part of the western edge of North America, rifted away at that time, creating basins offshore where sediments could begin to be deposited. Those sediments can today be found in places like Death Valley, but the igneous rocks here show that the deformation penetrated all the way into the continent.

-JBB

Image Credit: http://bit.ly/1WTzNkp

References: http://1.usa.gov/1TxraXL http://bit.ly/1T5SnU0 https://www.nature.nps.gov/geology/parks/grte/

[connor-burrows]

Mt. Moran Reflection by danielbolandrocha

[photos-worth]

Oxbow predawn, by TravisLucas1

Taken September 20th 2015 just before sunrise on what promised to be a nasty rainy day. this was my day off trying to capture some of the remaining fall color

[outdoormagic]

Full Moon Sets on Mt. Moran by Barbara Hayton