Mt. Whitney Portal Store & Hostel Forums General Mt. Whitney Portal Store Message Board Cool Sinkhole North of Trail Camp

There is a remarkable sinkhole north of the trail camp. It's right on the pass/saddle at the top of the canyon which leads to Mirror lake, slightly NNW of Wotans Throne. The approximate GPS of the sinkhole: 36, 34.077'N; 118, 16.913W. It looks like the collapse happened recently, judging from the color of the dirt. This photo was taken Sept. 18, 2009, looking toward the north or northeast.

Very cool photo of the hole, and it does look new.
I can't get a sense of the size of the hole in the photo. What was the diameter?

The diameter of the crater is approximately 12 feet. It's approx. 6 feet deep. I didn't climb down into it, partly because I wanted to leave it untouched.

I saw this on Aug 29 when I was up there doing Wotan's Throne.

I wasn't in photo mode as I walked by it. Thanks for capturing it to prove that I wasn't imagining things.

I don't know what could have caused this. It sure looks like a sinkhole, but can you get a sinkhole in a glacieral moraine? I thought you only got sinkholes in limestone!

I noticed something similar to this when I was doing Langley on Thursday. It wasn't quite as wide or as deep, and am quite sure it wasn't there the last time I did Langley in October of last year.

Prolly caused by a broken water main. You know, the one that serves the Starbucks

It almost looks like a huge boulder was removed from the earth, and that is the hole it left.

2dtrail probably hit the nail on the head. It was likely created by a large boulder falling from above and that is the first dent it made before coming to rest somewhere further down the hill. Lucky you weren't standing there to witness the event.

As a geologist, my assesment is that it is not an impact crater. The top edges are too sharp, and where's the rock and cliff that it fell from. there would be debris shooting out from the middle of the hole (non visible. Looks like it is probaly from a sinkhole type phenomenae. Perhaps there was a large section of ice below it that finally has melted leaving a void. It does not appear to be an area underlain by solid rock. THis would be the best time of year for the underground melting to occur. wish I could go check it out myself.

This interesting hole was found at the notch on the East Ridge of Candlelight Peak. It appeared to be a fairly new also, and I was surprised that it turned out to be a tunnel.

No, you got it all wrong! It's one of them thar a "crop" circles.

Then again, that is one heckuva pit for a WAG bag. Anyone see Paul Bunyan in the area?

Fumarole? Then there would be cause for concern. But there ain't no steam rising from the crater.

Caused by: ground settling and rocks shifting from ice melt or tremors?

Gotta love the mysteries of the Sierra Nevada. Another excuse to go out there and see it for one's self!

Have fun.

This thread reminds me of Aron Ralston's quote from his book Between a Rock and a Hard Place: "Geologic time includes NOW".

Could they be a result of all the Seismic activity going on, kind of like a precursor the recent events around the world. All of those faults a kind of interconnected?

It's always the fault's "fault."

I'm sure it's just those Tremors worms from down in the valley. (Call Kevin Bacon, I'm sure he's a friend of somebody on the board...)

I don't know Kevin...but I have a friend who knows a guy whose brother.....

The picture shows that the soil near the surface there is comprised of a well consolidated blend of mostly fine grained sand & silt with some small rock. I would say this surface is more of an alluvial deposit than a glacial moraine. There could be an older glacial moraine deeper. This deeper layer of bigger, boulder sized rocks could have lots of voids or spaces between the rocks where the fine grained soil has not filled in. Ground water flow could cause the smaller, fine grained soil to wash down in to the voids and cause the sink hole to form on the surface. It's like sub-surface erosion. Its not likely that that a centuries old underground ice formation recently melted there. Water flows freely through voids between the rock in a moraine. The temperature below the surface increases with depth and ice would not form or be preserved at that depth.

Whatever had kept the surface layers bridged over the voids below has now been breached. So this area may likely see more subsidence in the future as more water will now be drawn to this localized depression.

Rick F,

Temperature does not increase with depth untill you get well below the ground surface. In the upper few hundred feet it is very uniform. However, each winter water freezes if it is trapped just below the ground surface and then will melt during the summer months if temperatures are hot enough. (just like perma frost).
The larger boulders are probably from the surface and mixed in with the rest of the exposure. Ground water flow would be heaviest in the late spring and summer months, not in the fall.
The water flows in the rivers and sprngs in the late summer and fall is from the few visible snow fields and from ice that frozen from the past winter and trapped just below the ground surface. This is very common throughout the sierra's.

From the coordinates and using google earth, plus looking at the deposits they do not appear to be alluvial. Alluvial deposits are usually layered. The mixed nature of the variious size of deposit is more like a debris flow or moraine type deposit.
I'm sticking to my first guess of being related to melting ice just below the ground surface, however it could just be a void below collapsed, like the cool picture of the natural tunnel.

Dont,

I respect your opinion and I concur with your conclusion, based on only the visual evaluation we have of the the picture, that the deposit on the surface is most likely the upper layer of a debri flow. However, this debris flow is not like the waves of terminal moraines we see in the broad gully between Pinnacle Ridge and the south facing slopes below the basin that impounds Iceberg Lake.

I also maintain that temperature does increase with depth even at shallow dimensions. The earth is very hot at its core. the upper layers of soil, even at shallow depths, insulate and help slow the loss of Earth's heat into the cooler atmosphere. This is why in areas with seasonal freezing temperatures, water lines are buried at depths of 6 feet to prevent freezing. If what you are saying is true waterlines would have to buried hundreds of feet to prevent freezing.

Another thing many of us notice as evidence of this is that when crossing moraines, even when its freezing and there is ice & snow on the surface, you can still hear water running down below. The water stops flowing only when the source on the surface is frozen, not because the flow itself is frozen below.

The sink-hole could not be caused by the sudden loss of volume due to recently thawing ice. Permeation of fine-grained debris into voids, very likely. Seismic shifting, possibly.

Rick, the prevention of freezing past the first couple of feet is more a function of the thermal mass of the soil/rock. Once you get a couple of feet down, the temperature of the ground approaches the climatic mean temperature for the area. Here in MO, that's in the mid to upper 50s and you find that caves down several hundred feet tend to stay about that temperature, varying only a few degrees from summer to winter. That's why foundations, footings, etc., have to be a certain depth depending on latitude and altitude, so the bottom of the footing is below the frost line and the structure isn't subject to frost heave from the freezing and thawing of the top couple of feet of earth.

I believe you have to go down many hundreds to a thousand feet before you start to get appreciable warming from the core temperature conducting upward. (Unless, of course, you're standing on top of a recently-active volcano like the Long Valley Caldera near Mammoth!)

(Disclaimer) I'm an engineer, not a geologist but I've spent a fair amount of time in various "tourist" caves all around the country and enough time in spring-fed water to have a very good idea of "climactic mean temperatures" in various places. (Usually, brrrrrrrrr!)