Giant rock spikes sticking out of the ground

Question

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:

_{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?

Answer 1

Gigantic Crystals from an evaporating ancient ocean

The formations you picture are reminiscent of crystals.

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.

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

Answer 2

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)

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

Answer 3

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.

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.

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.