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Would it be possible for huge, hundreds-of-metres-long spikes of rock, ideally slanting at an angle, to arise under natural processes?

For clarity, I mean like this:

enter image description here

enter image description here

Copyright Joe Jesus

There are so-called "stone forests" of sharp rocky spires in places like Madagascar, but these spikes are vertical, not slanting like I'd prefer. Are such structures in any way plausible without artificial interference?

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    $\begingroup$ You can have slanted slopes, but not too much of overhang - that kind of formation will fall in geologically short time. $\endgroup$ – Alexander Mar 27 at 19:14
  • $\begingroup$ @Alexander Too short for one of any great size to form, and exist even for a few hundred/thousand years? $\endgroup$ – SealBoi Mar 27 at 19:33
  • $\begingroup$ @SealBoi Yeah, the greater the overhang, the shorter the lifespan of the formation. $\endgroup$ – Arkenstein XII Mar 27 at 19:47
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    $\begingroup$ @ArkensteinXII And I assume that the rock formations would have to be pushed out slowly such that the visible spike "grew larger"? $\endgroup$ – SealBoi Mar 27 at 19:51
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    $\begingroup$ @SealBoi Actually, something like that would be more likely to be an erosionary feature. It could be a remnant of a sedimentary sequence that is mostly gone now. $\endgroup$ – Arkenstein XII Mar 27 at 19:56
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Gigantic Crystals from an evaporating ancient ocean

The formations you picture are reminiscent of crystals.

enter image description here

Over millions or billions of years the ocean (or a huge lake) which was a concentrated solution of suitable minerals, has been evaporating. The near-perfect but absolutely huge crystals formed underwater and were supported by the waters as they formed. Now the ocean has evaporated sufficiently for these crystals to start to appear above the surface. Because of their crystallised structure they are immensely strong. They continue to grow laterally below the surface thus increasing the strength of the structure.


The following photograph shows actual salt crystals from the Dead Sea. Of course I am envisaging a much stronger form of crystal than salt.

enter image description here

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  • $\begingroup$ The problem is that these crystals are going to redissolve as soon as it rains on them. Their lifetime is extremely short. $\endgroup$ – Gimelist Mar 27 at 20:36
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    $\begingroup$ @Gimelist - The fact that the ocean is evaporating, suggests this is an arid area. There simply may not be much rain. Additionally it is possible that a land-bridge was suddenly breached, thus exposing them. By then they were so huge that it will take as long to dissolve them as it did to form them. $\endgroup$ – chasly from UK Mar 27 at 21:03
  • $\begingroup$ aridity is a time dependent thing. Climate changes. $\endgroup$ – Gimelist Mar 28 at 2:03
  • $\begingroup$ @Glimelist The Namib has been parched for 80 million years. That seems about enough time to evaporate a small sea. $\endgroup$ – SealBoi Mar 28 at 20:22
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Giant rock spikes = Needles.

The rocks in your photo are pretty huge. I think the sideways aspect of such big pieces of rock would be problematic.

Here are The Needles, in beautiful South Dakota. They are near Mount Rushmore. I suspect the big ones survive the eons because they are nearly vertical and so stresses are all compressive.

https://en.wikipedia.org/wiki/Needles_(Black_Hills)

Needles enter image description here

They range from 30-150 meters. They are made of eroded granite.

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the only real problem is the angle or the overhang, you can't have both on a large scale. your second picture is actually fine, real formations like that exist. Although the placement of the river makes no sense, a river is not going to stay on top of the hardest rock around, which it has to be to erode into that shape, it will be on one side or the other.

Entire forests of ridiculously sharp vertical stone spikes already exist, it is called Grand Tsingy, another is the common hoodoo type formation, both shown. The only problem that stone is not terribly stable at an unsupported angle. Basically if the stone is soft enough to erode in to a spike it is not strong enough to hold itself up under tension. Rocks are much stronger under compression than tension and overhangs are under tension. But really the nature of erosion means overhanging rock protects the softer rock belows so even when hard rock forms an angled spike, it really forms a cone with softer rock forming the rest of the shape.
enter image description here

enter image description here

The exception is when wind erodes the lower portion faster than a higher portion, but because of how wind works this happens in all directions, leading to top heavy outcrops or balancing rocks. The weakness of the rock limits this in size and to roughly balanced shapes. enter image description here

You can get overhangs like you want BUT they only occur in very strong rocks with angled bedding planes, usually with a huge mass of rock to counterbalance the overhang, meaning they are are very rare and limited in size. the closest you will get is in the below image, the Troll's Tongue. Which is impressive but still rather small on the scale of your images. basic rule is the bigger the piece of rock the closer to vertical the angle has to be.

enter image description here

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