View Full Version : Fiery Gizzard: Question for geologists and rock hounds
illabelle
12-30-2019, 10:38
Saw this incredible rock formation along the Fiery Gizzard Trail in South Cumberland State Park / Grundy Forest about an hour NW of Chattanooga this weekend. Obviously it's erosion from the stream, but it's so strange! What kind of rock is it? Why does it have these distinct "teeth"?
For those who are interested, we hiked approximately 10 miles from the primitive hike-in campground (0.6m from the parking lot) CCW on the Fiery Gizzard Trail, then out-and-back to Raven's Point, then the Dog Hole Trail back to Fiery Gizzard. According to wikipedia, the trail and creek got its name from a story about Davey Crockett burning his tongue on a turkey gizzard while camped out there. Anyway, the trail is rugged and beautiful, with several small waterfalls, and a lovely system of creeks. After the ascent to Raven's Point, there are several nice overlooks. It took us just over 5 hours to hike the loop, but we didn't account for the fact that the trail is in the Central Time Zone, which our phones automatically adjusted to without telling us. We couldn't understand why it was getting so dark so quick! :) We used our headlamps to complete the last 3 miles.
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Slo-go'en
12-30-2019, 10:52
It's probably limestone, which errodes easily. Hard to say why it has the "teeth". Maybe those areas are a little softer then the area next to the open parts.
Time Zone
12-30-2019, 11:44
Very cool - thanks for sharing! I've not been back there in awhile, but it feels like home because I'm pretty sure deadfall is our official state tree.
Yes, looks like typical limestone weathering, dissolving away the softer parts first
When googling a bit I found that the area is a wild mix of various kinds of rock, many of it being sandstone, conclomerate, shale and clastic.
http://www.virginiaplaces.org/geology/cumberlandgapgeology.html
Your pic doesn't really look like limestone to me (at least not like the kind of we have here in the Alps), I'd rather guess it could be fine-grained conclomerate.
The specific erosion sure comes from some ingredients being more robust and others getting dissolved or chemically and/or mechanically eroded more easily.
The presence of water (the creek in your case) usually accelerates most kinds of erosion.
But then, what do I know? A closeup in good resolution might be worth something.
"gasious inclusions" when the earth was forming. During a later date when there was a period of 3 days of total darkness, the earth shook and trembled(earthquakes etc.) the layers of earth shifted causing the inclusions to be severed as you see in the photo. My best guess ;)
Zelph, we're all just guessing inasmuch as none of us were there when it happened
Did you see anything, new map or whatever, with the name of the waterfall you go behind? I keep meaning to ask online or in person, and keep forgetting:rolleyes:
How'd you like that one? I'm pretty fond of the reroute!
illabelle
12-31-2019, 07:01
Very cool - thanks for sharing! I've not been back there in awhile, but it feels like home because I'm pretty sure deadfall is our official state tree.
I know what you mean! :)
The trail was clear of deadfall. Plenty of rough rocks to climb over though.
There's so much vegetation that it can be hard to see the terrain except in winter with the leaves down. I remember taking a hike in the burn area near Gatlinburg, and we were shocked to see all the rocks - normally hidden under vegetation, leaves, and deadfall - but now exposed by the flames that moved through. I prefer the vege-blanket.
Illabelle,
Any chance you could pin down the exact location on one of the above linked maps?
illabelle
12-31-2019, 07:15
Limestone is the consensus both here and in a Facebook hiking group where I posted the pictures. I suppose the regularly spaced channels in the rock are just coincidence. But it's a good example of one of the many rewards of hiking in the woods. We get to see things that are quite marvelous and unexpected. It's a wondrous world we live in.
Sometimes I wish I had an "Live Expert" app on my phone. See an interesting rock/tree/animal? Tap the Live Expert (RockDoc perhaps?) and let him explain it as if he was there beside you.
illabelle
12-31-2019, 07:23
Illabelle,
Any chance you could pin down the exact location on one of the above linked maps?
Leo, this trail is in southeast Tennessee, about an hour northwest of Chattanooga. The two websites below have interactive map links.
https://rootsrated.com/chattanooga-tn/hiking/foster-falls-and-fiery-gizzard
https://www.alltrails.com/trail/us/tennessee/fiery-gizzard-trail-to-ravens-point
It was an interesting and energizing hike, but it's a 3-hour drive from home, so we probably won't do it again unless we have other reasons to be in the area.
illabelle
12-31-2019, 07:25
Did you see anything, new map or whatever, with the name of the waterfall you go behind? I keep meaning to ask online or in person, and keep forgetting:rolleyes:
How'd you like that one? I'm pretty fond of the reroute!
Owen, I'm not sure what waterfall you're referring to. There was nothing on the Fiery Gizzard Trail that resembles your description.
And I don't know anything about a reroute. Maybe you're on a different trail? Hope it's a good one! :)
I see what happened.
For those who are interested, we hiked approximately 10 miles from the primitive hike-in campground (0.6m from the parking lot) CCW on the Fiery Gizzard Trail, then out-and-back to Raven's Point, then the Dog Hole Trail back to Fiery Gizzard.
You hiked approximately *5* miles on the Fiery Gizzard Trail, then Raven Point and Dog Hole, etc(~10 total).
If you get a chance to go there again, and aren't racing the sun, stay on the Fiery Gizzard Trail for a couple more miles;)
That's the second part of the reroute, and features climbs and descents(and maybe a few other things!), rather than hiking up on the plateau above. And it's fantastic.
Where the trail followed the creekbed for awhile before that very steep climb up to where you went to Raven Point is the first part of the reroute.
Time Zone
12-31-2019, 13:01
Limestone is the consensus both here and in a Facebook hiking group where I posted the pictures. I suppose the regularly spaced channels in the rock are just coincidence.
And maybe not such a rare coincidence if it turned out that, upon taking precise measurements, they weren't quite equally spaced.
Your pic did make me look up pictures I took of some signage at Twin Arches in Big South Fork and at Window Cliffs. The former only mentioned sandstone (of varying degrees of erosion resistance), while the latter mentioned the great fragility of the limestone. So it appears we have both in the area.
Sometimes I wish I had an "Live Expert" app on my phone. See an interesting rock/tree/animal? Tap the Live Expert (RockDoc perhaps?) and let him explain it as if he was there beside you.
If you're lucky enough to be part of a larger hiking community (e.g. one of the meetup groups), maybe someone who is a rockdoc/arborist/botanist can join you! One of my hiking buddies knows her wildflowers well, and often when we're out I get free lessons in botany. If only I could remember them better. :rolleyes:
madfarmer
12-31-2019, 14:24
I live 10 minutes from here. It is limestone as others have said, and water dissolves it in interesting patterns.
The really interesting part of the geology is Fiery Gizzard, though, is that some of the sandstone shows evidence of minor folding. Everything on the plateau is sedimentary, but there must've been just a smidge of metaphormic activity. The 2,000 ft. plateau used to be 10,000 feet, so that much overburden compressed the layers that we now see exposed causing them to act just a wee bit "platic-like" and fold in ways that sandstone normally doesn't. You can see this phenomenon near the giant stacks just before Sycamore Falls.
Speaking of.... the waterfall someone was asking about is probably Sycamore Falls, though the reroute of the trail also goes behind a small seasonal waterfall. Feels nice in the summer to get sprayed.
You should check out Savage Gulf too for some other day hikes or longer backpack trips!
illabelle
12-31-2019, 18:05
I see what happened.
You hiked approximately *5* miles on the Fiery Gizzard Trail, then Raven Point and Dog Hole, etc(~10 total).
If you get a chance to go there again, and aren't racing the sun, stay on the Fiery Gizzard Trail for a couple more miles;)
That's the second part of the reroute, and features climbs and descents(and maybe a few other things!), rather than hiking up on the plateau above. And it's fantastic.
Where the trail followed the creekbed for awhile before that very steep climb up to where you went to Raven Point is the first part of the reroute.
Well, that explains it! :)
illabelle
12-31-2019, 18:07
I live 10 minutes from here. It is limestone as others have said, and water dissolves it in interesting patterns.
The really interesting part of the geology is Fiery Gizzard, though, is that some of the sandstone shows evidence of minor folding. Everything on the plateau is sedimentary, but there must've been just a smidge of metaphormic activity. The 2,000 ft. plateau used to be 10,000 feet, so that much overburden compressed the layers that we now see exposed causing them to act just a wee bit "platic-like" and fold in ways that sandstone normally doesn't. You can see this phenomenon near the giant stacks just before Sycamore Falls.
Speaking of.... the waterfall someone was asking about is probably Sycamore Falls, though the reroute of the trail also goes behind a small seasonal waterfall. Feels nice in the summer to get sprayed.
You should check out Savage Gulf too for some other day hikes or longer backpack trips!
You make me want to go back for another look. Kinda wish you'd been walking with us to point this stuff out.
illabelle
12-31-2019, 18:08
And maybe not such a rare coincidence if it turned out that, upon taking precise measurements, they weren't quite equally spaced.
Your pic did make me look up pictures I took of some signage at Twin Arches in Big South Fork and at Window Cliffs. The former only mentioned sandstone (of varying degrees of erosion resistance), while the latter mentioned the great fragility of the limestone. So it appears we have both in the area.
If you're lucky enough to be part of a larger hiking community (e.g. one of the meetup groups), maybe someone who is a rockdoc/arborist/botanist can join you! One of my hiking buddies knows her wildflowers well, and often when we're out I get free lessons in botany. If only I could remember them better. :rolleyes:
Used to have a wildflower friend like that, but sadly she has passed on. :(
TexasBob
01-01-2020, 13:39
It's probably limestone, which errodes easily. Hard to say why it has the "teeth". Maybe those areas are a little softer then the area next to the open parts.
Could be. The curious thing to me is that some of the eroded areas are wider at the top and narrower at the bottom close to the water level. You would think the rock close to the water level would erode faster than the part further from the water. They almost look like a side view of an upside down pothole like you sometimes see in a stream bottom or river bottom. Thanks for the picture illabelle.
4eyedbuzzard
01-01-2020, 14:38
It is possible that the holes or at least sections of them were formed prior to the slab winding up in its current position and orientation. The bottom of the slab appears to have sheared off from another layer. The holes and/or sections of them may have actually been formed when the slab was in a more vertical orientation at some point in the past. How many times it may have shifted and to what angles/orientation over the ages, eroding away all the while into different shapes as water eroded it at different angles before winding up in its current somewhat horizontal orientation and position is anyone's guess, but looking at the surrounding terrain, it looks like it likely may have been at an inclined angle on the hillside prior to shearing off.