PART ZERO:
Extremely Brief Overview
of the
Geology of the Colorado Plateau--
A visit to Four National Parks
and a State Park
in Arizona and Utah
The Colorado Plateau is where we spent our few days of Summer vacation in 2008.
One of my favorite topics is the Basin and Range, where I live, which is land still being stretched toward the northwest. As it stretches there are breaks perpendicular to the force pulling on the land, and between these breaks land is tilted to make up the space created, forming over a hundred roughly north-south mountain ranges all over Nevada, especially, as can be seen on Ray Steiner's map:
But this is NOT about the Basin and Range, we drove eastward off that stretching land mass to the adjoining, more stable one called the Colorado Plateau. What the Basin and Range is being stretched away from is that plateau.
Here is a great map of the Colorado Plateau from the National Geographic website:
{On that map, Canyonlands would be the green area below "Horsethief Point" and Goblin Valley would be near "Facvtory Butte."
Want to see this earth-movement to the northwest, the growth of the Rockies, and the relatively stable Colorado Plateau in between for yourself? If you look at the stretching of the western US in this video by Tanya Atwater available on the website of the Nevada Seismological Laboratory, you see the land being pulled apart between the Wasatch Range of Utah and the Sierra Nevada of California.
Where it is pulled apart is the Basin and Range, to the right of the Basin and Range is an area that is not being pulled apart in Utah, Arizona and Colorado.
That stable area is the Colorado Plateau. {If you want to know more about this video and the science that underlies it, see Tanya Atwater's description of her work at this link.}
The Colorado Plateau has experienced a long series of depositional events when different layers of sedimentary rock were laid down. Then came a time of uplift of the whole region and the deposition stopped. The whole plateau has been lifted up many thousands of feet, a little at a time over a very long time. The whole time during that uplifting process and afterward, it has also been eroding down.
It is that eroding action, by water, that has carved the spectacular scenery we saw this July in the Grand Canyon-, Arches-, Canyonlands-, and Capitol Reef- National Parks.
The Grand Canyon being the deepest, it displays more of the geological history of the region than the other national parks. Two billion years of deposition are on display, thanks to the Colorado River (and others, of course) seeking the get back to sea level). The dates when these rock layers were deposited range from 200 million years to 2 billion years ago, and represented de[osits from within shallow salt-water seas, freshwater lakes, and the shorelines of both.
When that mysterious mountain-building event, the Laramide Orogeny, was busy creating the Rocky Mountains, it lifted this whole area up in the process, and the existing rivers cut down through the rock as it was lifted up. At some points the river is a mile below the rim, still removing sedimentary rock layers as evidenced by the sediment load that caused the river to be named Colorado!
The range of exposed sediments at Capitol Reef National Park is from 20 to 270 million years, and includes sediments from rivers, seas, deserts and swamps. The swamps added the shales that now add salt into the region’s drainage water. Some of the shales are rich in uranium and have been mined in the past and may be in the future.
Canyonlands National Park is geologically similar, with evaporating seas also adding salt layers into the mix. At some point in the past, there was a desert that stretched through this area and all the way to Las Vegas: the red sandstones at Red Rock Recreation Area is the same type of cemented sand drifts seen throughout the region.
Arches National Park is very close to Canyonlands, and is similarly the result of uplift and erosion, there are also arches in Canyonlands, in the sandstones at the surface. The durable sandstone that forms these arches is the Entrada Sandstone.
Goblin Valley State Park is also a case of the Entrada Sanstone being more resistant to weathering than its surrounding layers of other sandstones, siltstones and shales. There is a wall behind the goblins that is eroding back, leaving formations with more resistant sandstone caps behind: the goblins!
I always say that just because you can name something, doesn’t mean you understand it. Similarly, just because you can describe something in a paragraph doesn’t mean you understand it. But the point of this discussion is that no matter how much you read and write, when you see it, your sense of wonder will totally swamp your understanding. Enjoy the wonder!
These places are wonderful, they will cause you to be filled with wonder.
They present eye candy as well as muscle and lung candy, with their ups and downs they invite walking, climbing, biking and when you accept that invitation it is bound to raise your heartrate and there is no cleaner air to pump into your lungs.
Visit these places, look and move, and you will be more alive while there, and afterward.
Go to Grand Cayon National Park, Arizona
Go to Arches National Park, Utah
Go to Canyonlands National Park, Utah
Go to Goblin Valley State Park, Utah
