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As one of the feature in my world, I want to create a very deep chasm, as deep as possible. If it can touch the core, it will be perfect.

Size does not actually matters, although I think the consequence of having a very deep chasm would be a big size. Note that to qualify as chasm, it must be relatively narrow.

Without being artificially created (although I think it's impossible to do it artificially), what are possible ways to create such chasm?

There is abundance of magic in this world, but please no "earth bending" the ground. Causing an earthquake seems to be able to do that, however please briefly explain how the earthquake create the chasm and the feature of the chasm created (I believe the one created from tectonic movement will be different from volcanic one?)

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    $\begingroup$ If we want to stay science-based, deep chasms can not exist. The force of gravity shapes any planet into a smooth ball. Even the hardest rocks will flow to fill in the chasm, if one is created. There is a limit on how tall the mountains and how deep the canyons can be. $\endgroup$ – Alexander Oct 25 '17 at 18:15
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    $\begingroup$ Another practical concern is water. Here on Earth, any chasm gets filled with water. If water has a place to flow, we have something like Grand Canyon with Colorado river at the bottom. If no, we have a deep lake like Baikal or Tanganyika. $\endgroup$ – Alexander Oct 25 '17 at 18:26
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    $\begingroup$ @Alexander hard rocks fracture, not flow, but at truly ridiculous heights the base of crushed gravel probably would start spreading outward. A very deep vertical chasm could be maintained up to that limit though; the exact height would depend on the properties of the rock. $\endgroup$ – brichins Oct 25 '17 at 23:20
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    $\begingroup$ Your gouge can't go too deep, lest it pierce down to the magma, which is basically a liquid under pressure. So if you "delved too greedily and too deep" your chasm would fill up with lava, which would eventually harden into a giant basalt plug. $\endgroup$ – akaioi Oct 26 '17 at 4:53
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    $\begingroup$ Is there room in your world for a giant worm God that ate a tunnel to the world's heart and now lives in the warmth of the core? $\endgroup$ – Muuski Oct 26 '17 at 17:27
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The best way to make a chasm on land is the way nature does it- slowly, and with water. As AndreiROM points out, the rapid appearance of a chasm is going to displace a huge amount of rock, proportional to the size, and that's going to have even larger effects on the planet, and even magic won't change that. Additionally, as David Lago points out, there are fundamental limits on the height of structures in a gravitational environment. Check out this site for the math about how tall a mountain could be, and essentially reverse the logic to get maximum depth on Earth- about 10km. If you decrease the size of your planet, you can go even deeper and get something more like the Valles Marineris on Mars, which isn't as narrow but is definitely huge.

However, even canyons that have been carved by water are extraordinary- I'll let the picture speak for itself. The Grand Canyon

The Grand Canyon is still tectonically active, but I believe it's stopped getting deeper because it's getting filled in more rapidly than it erodes, mostly due to humans removing the erosive water for use elsewhere. If this is chasm-like enough, you could argue that your planet simply allows for it to grow deeper. First, change the geology to be mostly limestone or sandstone, both of which have a high angle of repose, allowing them to form even steeper sides. Second, have the river drain from high mountain areas with consistent snowfall to ensure semi-constant erosion. With those qualifications, you could probably justify a chasm ~8km deep.

If you're especially eager to have it happen overnight, you'd have to handwave a little bit. Maybe there's a massive internal lake blocked off by some kind of dam that collapses, allowing the water to flow out very rapidly. These are called outburst floods and they were relatively common during ice ages. This still wouldn't happen overnight and wouldn't produce something as steep as the Grand Canyon, but it'd be faster if that's what your plot requires.

Honorable mentions

The other thing I want to mention here are the chasms in the ocean. The smaller of the two are the submarine canyons, which could be exposed by a reduction in sea level as water is stored as ice in the poles during an ice age. Congo Canyon starts at a depth of just 26 meters, and could be further exposed from there.

If you evaporate all the water off your planet, like what scientists currently believe happened on Mars, you'd be left with the subduction trenches. These are seen in the Heezen-Tharp map below at the northwest portion of the Pacific, along the Ring of Fire. enter image description here

I believe these are the largest chasm-like structures in the solar system, so they might be what you're looking for.

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    $\begingroup$ Grand Canyon isn't what I'm looking for, though it's nice to know that water erosion won't help me getting a narrow chasm. I'll see what I can do with limestone instead. $\endgroup$ – Vylix Oct 26 '17 at 15:04
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    $\begingroup$ It should be noted that the Grand Canyon is not the limit of this effect: Canyons can get much deeper, with the deepest on Earth being the Tsangpo Gorge in Tibet at 2,270 -- 6,000m. That's really, really deep, man. $\endgroup$ – errantlinguist Oct 26 '17 at 15:51
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    $\begingroup$ Just fyi outburst floods tend to cut horizontally not vertically. $\endgroup$ – John Oct 26 '17 at 18:15
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A cataclysm that creates a chasm that reaches the core of the planet would be a world-ending event.

However, deep chasms can form in somewhat milder ways as well.

If it's only the end result that matters, and time is not really of the essence, this might be caused by shifting tectonic plates. The Mariana Trench, for example, exists partially due to tectonic plate movements (as well as other geological processes).

If you want this thing to appear overnight, however, you're looking at an extinction level event such as a very sudden tectonic shift, caused perhaps by having the mantle rotate around the core of the planet.

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  • $\begingroup$ Even though this doesn't address how ridiculous a chasm to the core is. Even though its fairly simple and doesnt elaborate on very detailed and complex processes at all. Given the amount of subjects needing addressing here, I think this is the best possible answer. $\endgroup$ – anon Oct 25 '17 at 19:47
  • $\begingroup$ What do you mean by "having the mantle rotate around the core"? I don't see how that could create a chasm $\endgroup$ – Dubukay Oct 25 '17 at 20:31
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    $\begingroup$ Do you mean...... a chasm-taclysm ?? $\endgroup$ – Cedric Oct 26 '17 at 15:13
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    $\begingroup$ @cedric - get out. :-P $\endgroup$ – AndreiROM Oct 26 '17 at 15:29
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In response to one of your comments: Rock begins to flow with aobut 7000 feet of overburden. Not fast.

I witnessed this on a tour of the Bunker Hill Sullivan lead mine near Kellog Idaho. Throughout the lower levels, corridors were lined with chain link fence pinned with 1 foot bolts every couple of feet. The tunnels would gradually shrink from pressure, and chunks of rock would spall off, often traveling at high speed.

In other tunnels, they would rebore the tunnel on a regular interval to keep it from shrinking to nothing.


You can get bigger chasms with a lighter gravity. Less pressure. But lighter gravity means lower atmospheric pressure, and less ability to hold an atmosphere. So make the planet larger in diameter. This lowers the rate that gravity decreases with altitude.

You can also get deeper chasms with tougher rocks. Granite, gneiss and basalt generally do better than sedimentary rocks.

So your magic could be the remnant of a 'Make these lands stand until the sun grows cold and the stars grow dim' spell, so that they are harder than normal. This would have the side effect of slowing erosion.


In Larry Niven's "Known Space" stories, Canyon was the result of the Kzin testing a Slaver weapon that suppressed the charge on the electron. Nuclear repulsion gouged a canyon a couple hundred miles long and several miles deep. Niven does not address rock flow.

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    $\begingroup$ Came here for the Treatymaker, am not disappoint. For clarity, the Treatymaker projected a beam which suppresses the charge on the electron, and another which suppresses the charge on the proton. The beams hit the surface 30 miles apart "and a solid bar of lightning flowed between the two points. The weapon chewed twelve miles deep into the planet, exposing magma throughout a region the size and shape of Baja California on Earth". Oh, and the weapon/mining tool was developed or at least perfected by the human Wunderlanders. $\endgroup$ – akaioi Oct 26 '17 at 4:50
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It would need to be an unexplicable event since a hole deep to the core would never be possible,

"Today, the Kola Superdeep Borehole is the deepest hole in the world. Only a few inches in diameter, it goes down 12km and took Russian scientists more than 20 years to drill. They stopped drilling when the temperatures and plasticity of the rock became too great to make further drilling viable."

12Km. Only that. From the surface at sea level to the earth core it lengths aprox 6300km, and within the 12km mark the temperature and pressure turned the job impossible to carry on. We didn't even scratch the surface.

Let's say that the chasm was completely solidified already. It wouldn't work because the pressure of gravity would force the surroundings of the hole to the center, and the effect would be similar to what would happen if the surrounding areas were made of liquid. It would close in no time, and cause a HUGE earthquake that would kill every living thing on earth.

Maybe a 12km chasm would make more sense. And yes, some earthquakes (million years ago) could have possibly done the job.

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  • $\begingroup$ Interesting. Will such chasm eventually close, or at least "shallowing"? $\endgroup$ – Vylix Oct 25 '17 at 18:19
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    $\begingroup$ I don't know exactly what are the thresholds of a chasm/mountain, but I don't think it would stand more than 15km. The temperature index at this level is estimated to be around 400°C. It would close up almost instantly if build from nothing. Gravity tends to shape the planet as a sphere, and the amount of mass that would have to stand by the "walls" would be too much compressed and hot at the bottom of the chasm. Basically lava-like stuff. $\endgroup$ – David Lago Oct 25 '17 at 18:28
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    $\begingroup$ A worldwide settling of stone would be far from "kill every living thing on earth". Wipe out civilization, yes; kill every individual human, no. Pretty good leadup to a post-apocalyptic novel, come to think of it. $\endgroup$ – Brilliand Oct 25 '17 at 21:19
  • $\begingroup$ Nonsense. They stopped drilling for other reasons. snopes.com/religion/wellhell.asp $\endgroup$ – kaine Oct 26 '17 at 20:41
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Rock isn't solid enough to form anything like that.

If a chasm a mere 12 km across, 12 km deep and 100 km long formed, it would rapidly collapse as the near-liquid rock near the bottom (caused by immense heat and pressure that deep) would flow inward.

Rock required to fill such a chasm would weigh on the order of 3E16 kg. That much rock moving 6 km vertically (on average) would generate 2E21 J, roughly the power of 10000 dinosaur killing asteroids hitting the planet all at once.

I'm uncertain if life could survive that energetic an event.

A chasm all the way to the core is right out.

You may think rock is solid, but at planetary scales it is liquid, and we live on a thin layer of wet crust.

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The African Great Rift valley and the Red Sea are modern day examples of plate tectonics creating chasms in the earth as plates separate from each other.

enter image description here

pictoral description of the process

As noted, there is a maximum depth which can be reached before the rock essentially flows like a liquid, but rift valleys would be the largest and most spectacular examples of chasms which could naturally occur on a planet.

The other possible way to create a chasm would be a trench in a subduction zone, where plates are being forced together and one is riding over another. On Earth, these generally form under the oceans, but there is no real reason for this not to happen on land, assuming geological conditions are right.

enter image description here

Subduction zone, with a good view of the trench

So large and deep natural chasms are formed by the actions of plate tectonics, and will obviously occur at or near where the edges of the plates meet.

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  • $\begingroup$ Makes me wonder if OP is okay with the chasm being filled with water. A rift valley can form on land and stay dry if climate and geography are favorable, a subduction zone can not. $\endgroup$ – Khris Oct 26 '17 at 6:31
  • $\begingroup$ @Khris nah, I don't want it to be filled with water. However these illustration helped me understand how to make one. $\endgroup$ – Vylix Oct 26 '17 at 12:56
  • $\begingroup$ @Khris why a subduction zone cannot exist on land? $\endgroup$ – Vylix Oct 26 '17 at 15:06
  • $\begingroup$ Subduction zones exist along the edges of plates, but there is not particular reason to assume every plate edge will be under an ocean on every planet just because it occurs here on Earth. $\endgroup$ – Thucydides Oct 27 '17 at 3:58
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    $\begingroup$ The reason a plate goes under another one is that it is denser and lies deeper which is true for oceanic crust. If both plates were continental plates you'd get a collision with orogenesis instead of subduction. The wiki article also mentions that oceanic crust is like that because of the seawater. No ocean means no dense oceanic crust meaning that subduction is impossible ("the subducted lithosphere is always oceanic"). $\endgroup$ – Khris Oct 27 '17 at 5:53
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Rapidly (geologically speaking at least) reverse the convection currents in your mantle, with opposing currents on each side of the future rift. The super-high plateau of granite that has built up over millennia will begin to be pulled apart, and due to its weakness in tension and a fault up the middle (internal plane of the crystal structure or some other discontinuity) will suddenly split in half. It might even crack all the way down to the mantle, though the very bottom would fill in quickly.

No other world info to speculate on what causes the mantle reversal (aliens? near-miss with a sister planet? solar flares?) or the weakness through the center of the mountains (perhaps something religious, like an eons-old pilgrimage maintaining a line of offerings that weakened each new layer of rock). Whatever the cause, I would expect the change to have major cultural implications for several generations.

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If you want a magical answer, I love the idea of a magical natural disaster for something like this. This is the only way to have a "believable" core reaching massive chasm. Of course, this will stray from a science based answer.

For such a chasm to remain standing, there must be some property at the walls or in the interior of the chasm to allow it to remain. I am assuming you want this to have formed suddenly and people must be able to enter the chasm. This could be:

  • There are natural forcefields keeping the walls steady. Whatever formed the forcefields also blasted the matter into space. Magic would be needed to cross the field.
  • The chasm is full of an invisible form of matter and, while people far from the disaster sense that matter as intangible, the walls of the chasm interact with both types of matter. You would have to have a disaster which moves the chasm material out of "dimensional phase" (which is nonsense) with most of the planet. The walls are stretched between both dimensions (again nonsense handwavium) so interact strangely with both.
  • The walls of the chasm are frozen in time and, therefore, cannot be moved by natural forces. As you move towards the chasm, everything already there moves more slowly until you reach an event horizon where everything is frozen. Everything beyond that is just...gone. I like this as the result of a magical time travel paradox but those usually aren't natural.
  • There is a magical gravitational anomaly in the chasm. For some reason, matter near the central point acts much much heavier than normal but acts lighter as it moves away from that point. Such a point would, however, change the shape of the entire plant to something non-spherical. I don't have the math to visualize this properly at the moment.

These would immediately kill all of the planet if large enough. If the material in the chasm disappears, atmosphere will fill it suffocating us. If the matter is moved, that matter has to go somewhere.

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    $\begingroup$ the material is converted to energy to fuel the magical process or the force field. Remindes me of The Scar. $\endgroup$ – Henning M. Oct 26 '17 at 19:36
  • $\begingroup$ @HenningM. Fair point. I wish I'd thought of that. Especially if that could provide replacement atmosphere to fill the hole (Si converted to energy while O2 is the waste gas?). I need to think on how this would not be man made.... Could magical dirt eating termite-like animals do this? The shear amount of energy would astronomical though. $\endgroup$ – kaine Oct 26 '17 at 20:35
  • $\begingroup$ termites are too slow and would not make a chasm. Rather a complex buildup of magical energy and release of this energy through a magical flash or an ernergy short circuit between two magical thingie places, ley lines and all such. $\endgroup$ – Henning M. Oct 29 '17 at 23:29
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There's a lot of good science explanations already regarding what is or is not possible and to what extent. However, as stated in the original question:

There is abundance of magic in this world...

In general, if it can be explained with science, it isn't magic (even if it appears to be magic to those who don't fully understand it). Magic really only includes those things that defy scientific explanations and/or disobey the laws of science. (Otherwise, it would just be science.)

Therefore, it is worth asking what (if any) are the limits of magic in your world? Is it only capable of simple effects and parlor tricks? Can it ease manual labors (much like science can)? Can it influence things on a larger scale? Can it reshape worlds (like creating this chasm)? And so on.

If magic is capable of producing the effect desired, then no scientific explanation is needed. However, understanding the science that the magic is defying allows you to make clear just how magical and/or powerful the effect is.

If magic is responsible, then other questions arise, such as what caused the magic to happen? Was it a living being of some kind? Was it the result of "magical natural" causes (as opposed to "scientific natural" causes, usually just called "natural" causes in worlds without magic)? Was it deliberate, accidental, the "natural" result of other events, or something else? Over time, will the magic that caused it weaken/disappear, grow stronger, or stay the same? Was it a one-time occurrence or could/will it happen again? And so on.

There doesn't even need to be a rational explanation if no one knows the answers to these kinds of questions. "It's magic." or "No one knows why/how." may seem like hand waving, but that's exactly what magic is. Most people in a world with abundant magic would likely accept explanations along those lines (though not necessarily in those exact words). However, many might have adverse reactions (e.g., fear, superstition, etc.) to large-scale, unexplained phenomenon. Others would likely prey on such reactions in a bid for dominance/power (by trying to blame certain individuals or groups for it, etc.). Still others might want to learn how to replicate it (as a weapon, for example) or prevent it from happening again.

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  • $\begingroup$ Thanks for the concern. I'd certainly take your input. However, your answer seems to fit better as comment, not answer. Please stay around and post quality question and answer, and you'll get 50 rep points needed to have comment anywhere privilege. $\endgroup$ – Vylix Oct 26 '17 at 12:13

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