I've always been curious about this one.

The summit block of is massive rock tower has actually cracked and shifted.



Zoom in:



Some have said they thought the result above was caused by erosion, but I've always speculated that only a earthquake could have done this (maybe not the crack, but the shifting). I guess it would be hard to tell from the photo (or maybe even with the photo), but what do you think?

On another thread, I was informed that erosion on our planet, is of such significance, we don't have the cratering that Mars and the Moon have. So erosion is a pretty powerful force. That said, seems too uniform a shift on that spire. I'm going to shoot out a non expert guess that only some sort of strong force like an earthquake would crack and then shift that much rock.

Erosion is a pretty general term that I personaly think encompasses any type of break down of larger sized particles and there movement away from the source rock. That being said I would say that earthquakes can contribute to erosion.

To the OP I say that the apparent movement between the summit block and the rest of the pillar is NOT due to an earthquake simply because of the direction of the fracture of the rock. An earthquake is caused by oposing forces in the earth that eventually cause a slip along a fault. What force was pushing on that upper block to make it break?

The break between the block and the pillar is parrallel with the other bedding planes in the column(if you look both a couple feet below and above the break in the lower image you can see bedding planes running almost horizontal dipping slightly to the right.)

My GUESS on the formation of this formation based simply off the photos here is that for some reason you had a block resting at ground level. Then through erosion of the pillar(it erodes faster due to the fact that it is less resistant to erosion) the block is left hanging in the air.

The first photo you posted (the wider one) shows another smaller column to the right. If you line up the crack between that block and column and the bigger block and column that you are looking at you will notice that they line up. The two upper blocks may have been connected at one time and have eroded apart.

Global warming.

MoapaPk wrote:Global warming.

I like the way you think.

I am assuming the mystery is really only about the shift, since the horizontal crack itself is not particularly rare. With certainty, I would say that the crack and shift are not both results of one single dramatic incident like an earthquake. But it seems possible that large earthquakes could give the thing a small nudge once in a while.

But what about thousands (or millions) of cycles of ice and thaw? It's not in a particularly wet climate, but they do get rain, snow, freezing, and thawing there.

Damnit. 4 minutes. Dingus posted while I was typing.

While freeze thaw is a decent notion, it's interesting that it appears such a unique example given the other similar structures in the Arches NP. Perhaps the inclined fissure is important in this case as it allows water to trickle in easily. Given the location there would be negligible motion (prolly <1 cm) from seismic waves even from something unusually large (Mw 9.0) along the Cascadia Subduction Zone, and likely even less so from something along the San Andreas all things considered.

If the power of erosion (on a more massive scale) created the Grand Canyon, then we can theorize that erosion is powerful enough to
cause some sandstone fins to erode away, while others are simply cracked
and left standing.

In this case, "shifting" can happen over thousands of years , while a single
earthquake would have completely knocked the column's block off.

Because Arches NP rests atop a salt dome, some settling may have occured
at a small enough degree for the block to move ever so slightly without
tumbling completely to the ground and turning into sand particles.

I think we can rule out that the dude's Brother-in-law had anything to do
with this massive freak of Nature.

Also possible that there is no 'shift' but just the appearance of one given the fresh surface around where the Bro-in-law is standing indicates a recently detached section.

Science often proves that a 10-ton floor jack purchased at Costco
will completely malfunction under the weight of the "B.F.R." pictured here.

FortMental wrote:


These are caused by bored adults with hydraulic equipment.

Ha ha aaaaaaaaaaaa


Please, Name the first one, please

MoapaPk wrote:Mass Wasting

Bioturbation! (does that cover the brother-in-law with the jack?

FortMental wrote:[img]


These are caused by bored adults with hydraulic equipment.

Bored adults with photoshop, more like...

Christian