Ok, be honest. What comes to mind when I write the word “exfoliation?” To me, a picture of dry, flaky skin first comes to mind. However, exfoliation has a geological context to it, too. It’s a weathering process and one of the best places to see this process is along Tioga Road in Yosemite National Park.
As you drive that road, take a look at the granite hills and domes all around you. Notice that interesting sort of “onion peel” effect on the rock layers? That’s exfoliation! It’s a type of weathering and is common in granites.
You see, granite formed beneath the earth’s surface, under immense pressure. So, when the surface sediments and rocks – collectively termed as overburden – covering that granite are eroded or removed and that granite is exposed, the pressure beneath which the granite lay is gone and the granite begins to expand, forming all sorts of fractures (joints). Weathering (like frost heaving) causes plates, or flakes of rock to strip away the surface rock much like onion skin peels away from the onion.
And now you know.
Copyright Rebecca L. Latson, all rights reserved.
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It’s #TriviaTuesday folks! So, here’s another shot of Grizzly Giant sequoia tree in Mariposa Grove at Yosemite National Park. It’s estimated to be almost 3,000 years old and stands 209 feet (63.7 m) tall. You might notice that it has a decided lean to it, and that’s not just because of the ultra-wide-angle lens perspective. It really does lean, and in the early 1900s, they were so worried it might fall over that supporting cables were proposed to hold it up. Turns out, the cables were never installed and Grizzly Giant seems to be holding its own. Could be because of its root system. Sequoia trees have a very shallow root system, but those roots grow to great lengths and intertwine with the roots of other trees. Sort of like if you are leaning over to pick something up, and you’ve linked arms or clasped hands with a person standing next to you to keep you from falling. Those other trees might be helping Grizzly Giant to stay put.
According to the latest article in the National Parks Traveler, the Washburn Fire *seems* to be turning away from the Mariposa Grove, which would be a good thing. But, the fire continues to grow in size, which is not a good thing.
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