Tag Archives: fun facts

Fun Fact Friday, August 5, 2022: Exfoliation

It’s #FunFactFriday

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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Filed under Fun Fact Friday, Geology, National Parks, Photography, Yosemite National Park

It’s Trivia Tuesday 3-29-2022!

Old Faithful erupting at Upper Geyser Basin, Yellowstone National Park
Heart Spring in the foreground and the Lion Group of geysers in the background at Upper Geyser Basin
The scalloped edges of Doublet Pool at Upper Geyser Basin
A bright bacterial mat leading toward a hot spring at Biscuit Basin.
Geyser Beads

It’s #TriviaTuesday Folks! So, how many of you have ever visited one of the geyser basins in Yellowstone National Park, marveling at the colorful hot springs and the energetic geysers? Do you know how to tell if what you are looking at is a geyser or hot spring (if there is no sign to identify it)? Especially if a geyser, when not erupting, looks like a hot spring?

According to a cool little video on the NPS site for Yellowstone, you should look at the edges of a thermal feature. “Hot springs often have ledges or walls of sinter (silica deposits) around them, because as the water level fluctuates, it leaves behind silica deposits. The edges may even be scalloped or lacy, such as what you see when looking at Doublet Pool in Upper Geyser Basin.

“Beadwork,” or pebbly-looking sinter indicates a geyser. “As the water splashes with each eruption, it deposits silica, creating a bumpy appearance.” At some geysers that look like hot springs, you’ll notice rounded, riverstone-like pebbles beneath the water. These rounded stones are called “geyser eggs” and are formed by silica deposition and water movement.

Colorful orange and yellow bacterial mats are also good indicators of hot springs, since that means the water is warm enough for thermophilic (heat-loving) bacteria to thrive, but not hot enough to be a geyser.

The thing is, the landscape beneath and above Yellowstone is always changing. Excelsior Crater Geyser used to be a geyser, and is now a hot spring – well, it’s a hot spring right now that hasn’t erupted in several decades, but it could become a geyser again if the conditions change.

And now, you are that much smarter for the day. 🙂

Copyright Rebecca L. Latson, all rights reserved.

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Filed under National Parks, Photography, Trivia Tuesday, Yellowstone National Park