Planet Spanning Hole?

[Prannon]

Alright, if a mod feels that this thread belongs in a different forum, or if it's just a dumb topic, please feel free to move it. It's a one off idea I had and I wanted to know what people thought might happen.

Here is the scenario. You have an earthlike planet with all the geological and biological characteristics of earth. It has the same general proportions, mass distribution, and such as that. Put aside any sort of sentient civilization for the moment, because my scenario concerns the planet, itself, more. This planet is orbiting rather peacefully about its star when all the sudden, a hole appears. Nothing "causes" it, so there aren't any meteor impacts or magic Nero core-boring-red-matter-bearing-death-needles to be concerned about. It might as well be an act of Q or God or whatever.

This hole is circular, has a kilometer radius and traverses the entire diameter of the planet, straight from one end to the other end, through all the layers of the sphere from crust to mantle to core and back out again.

Keep in mind again that this hole literally just appears in a blink of an eye. The mass that was there is now gone for no discernable reason at all. What I want to know is, what would happen next? How would the planet deal with this hole? What effects would gravity have on it? What would the local surface effects be? What would the planet look like afterward? Would the tectonic plates be changed all that much? Would volcanic activity increase globe-wide?

[Sarevok]

What kind of mechanism is keeping this hole from collapsing on itself ? Its hard to imagine a vacuum existing within the liquid like composition of the Earths mantle.

[madd0ct0r]

presumably a collapse at the sides of the hole, with nearly the entire shaft moving smaller simultaneously.

Slight end effects and a moderately more rigid crust means it holds out for half a second more, giving a a crater several kilometer in diameter and maybe a few dozen meters deep at each end.

Probably a lava spray at the center of crater throwing dust and stuff into the upper atmosphere with obvious consequences. Probable volcano due to the thinning (removal) of the crust at this point.

The crunch of the collapse would echo back and forth within the earth (like ripples inside a paddling pool)
Distortion of the surface (earthquakes, heaving and fractures) as this energy is absorbed by the crust. Same energy and shifting likely to trigger other volcanoes.

nuclear winter.

this is a total guess.

[Prannon]

What kind of mechanism is keeping this hole from collapsing on itself ? Its hard to imagine a vacuum existing within the liquid like composition of the Earths mantle.

There is no mechanism holding it open. Nor is it supposed to make sense where this hole comes from. That's not the point. It's more of a thought exercise of how a planet would react if this hole magically appeared. What do physics and planetary geology say would happen? If they say that the hole collapses in on itself along with other various side effects, then that's what I'm interested in. I'm hoping some folks a little more knowledgeable on planetary geology will weigh in on this, because I'm genuinely curious to know what would happen.

[Sarevok]

Lets hope captainchewbecca finds this thread. He is a geologist iirc.

[PaperJack]

There is a huge shock due to:
1. the air rushing in
2. the air being pushed out by the lava or whatever the mantle's contents are called
3. the lava rushing in slamming with more lava from the opposite side (a concentrical wave getting smaller)

[Gil Hamilton]

You just vanished around 10000 cubic kilometers of material out of the planet, so I imagine that is going to be rapidly filled down in the core and mantle (the amount of material removed is not THAT significant compared to the total volume of the planet) and that mantle material is going to be at high pressure and escape to the surface. You've breached the crust of the planet (not by much, the hole isn't that big), but it's enough to seriously disturb the local surface.

Meanwhile, air is going to rush to fill that void. Again, the volume you removed isn't a significant volume as compared to the volume of air in the troposphere, but the hole will create the MOTHER of all low pressure systems on either side of the planet until the pressure is equalized (shouldn't be that long, since those areas are about to become calderas). Plus, heat is being injected into it from exposure to the planetary core. This should generate a motherfucker of a pair of cyclones above the whole, particularly if the holes occur near oceans.

This shapes up to be a pretty nasty natural disaster. Life will go on, but it's going to be a shitty year for the inhabitants of the planet.

[Admiral Valdemar]

On the plus side, you can traverse to the other side of the planet by just jumping and taking a packed lunch. Remember to have someone catch you as you slow and reach the other end.

[Darmalus]

On the plus side, you can traverse to the other side of the planet by just jumping and taking a packed lunch. Remember to have someone catch you as you slow and reach the other end.

Assuming the hole was stable and didn't fill with magma, how far would this actually get you? You would eventually reach terminal velocity, and I doubt you would make it all the way to the other surface. Still, that would be a wild trip.

[Gil Hamilton]

Assuming the hole was stable and didn't fill with magma, how far would this actually get you? You would eventually reach terminal velocity, and I doubt you would make it all the way to the other surface. Still, that would be a wild trip.

If the hole filled with vacuum, you'd reach a height on the other side equal to the height you started at. If it filled with air, it would be somewhat less due to friction, at which point, you will fall back toward the center again. The trick would be not to hit one of the walls of the hole on the way down. Also, if you are in a frictionless environment, it's OK if you aren't caught the first time. You'll be back as you fall back through the center, bob back to where you started, and fall back again.

[Junghalli]

Don't forget that the sides of the hole are effectively a very tall cliff. Even leaving aside material rushing in under pressure, the sides will instantly start collapsing under gravity.

[Rossum]

My understanding is that planets are basically big balls of magma with a comparativly incredibly tiny thin film of solidified rock on top which we mere mortals deem to call the surface.

I think that one millisecond after the hole appears, the center of the planet would close back up due to literally the entire weight of the planet working to push down on the core of the planet. There might be a little air rushing into the holes on the sides, but there would be a lot of magma rushing into the hole all along its length through the planet. The hole through the molten mantle would be filled back up in less than a second.

After that, air or water would rush into the hole from the two holes on the surface. If one hole was underwater then the ocean would fall through and cool down the magma as it tries bubbling out... not sure how many gasses would rush out, there might be some sulfer-rich gasses and ash bubbling out but the ocean would filter out most of the gunk and keep the atmosphere clean.

If the hole is on dry land, any air that rushes into the hole would be quickly met with the bubbling magma. The magma would start bubbling out along with some gasses. I'm not exactly sure how a volcano would act if it was created by a hole directly to the center of the Earth. Most volcanoes have reservoirs and various shaped chambers that affect how they operate. I'm guessing that a direct hole to the center of the Earth would mostly result in gooey lava bubbling out and then hardening, after which the pressures would roughly equalize. There would still be a volcano but hopefully it would be one that erupts frequently and results in the gooey lava instead of siting silent for years and then spewing out large amounts of ash.

[Gil Hamilton]

My understanding is that planets are basically big balls of magma with a comparativly incredibly tiny thin film of solidified rock on top which we mere mortals deem to call the surface.

I think that one millisecond after the hole appears, the center of the planet would close back up due to literally the entire weight of the planet working to push down on the core of the planet. There might be a little air rushing into the holes on the sides, but there would be a lot of magma rushing into the hole all along its length through the planet. The hole through the molten mantle would be filled back up in less than a second.

Probably not. That would mean the rock is moving many hundreds of kilometers an hour. Rock isn't going to move that quickly. It will probably fill pretty rapidly though.

[Steel]

On the plus side, you can traverse to the other side of the planet by just jumping and taking a packed lunch. Remember to have someone catch you as you slow and reach the other end.

The time to pop out on the other side would be approx 45 minutes, so no packed lunch necessary.

(The strength of gravity decreases linearly with radius as you go deeper into the sphere, which gives SHM with frequency sqrt(R/g) R=radius of earth, g=surface gravity, and so plugging in the numbers gives about 42 minutes)

[Prannon]

These are some pretty interesting replies. It tickles the brain. I'm curious though, wouldn't a hole like this cause some rather nasty earthquakes across the globe as energy is released from all the collapsing material? And would anyone have any guesses about what shockwaves as far down as the core and mantle would do for volcanic and tectonic activity?

[CaptainChewbacca]

Radical, instantaneous collapse. Fortunately, 1 kilometer is pretty small so while you'd have some tremors I think the area of 'noticable' impact would be limited to a few thousand miles. There wouldn't be a massive global quake, and 'shockwaves' don't penetrate past the moho so don't worry about them.

It really depends WHERE this happens. If its in the middle of central asia or northern canada, it'll be a lot better than if it happens in northern Turkey or the Java sea. Mostly, it would collapse. I'm pretty sure it would collapse INWARD, but part of me fears the massive pressure would give you a brief, violent outward burst of mantle material.

[Prannon]

Alright, some questions CaptChewie. MOHO = what? Also, about shockwaves...since this hole is spanning through all layers of the planet, including the core, wouldn't that have some sort of global impact? Wouldn't shockwaves from the core make their way through the mantle, or do the layers have no interaction with each other aside from heat exchange?

I'm also curious as to why the location would have that much of an impact. What's the difference between Central Asia/Northern Canada and Turkey/Java Sea? I have a pretty good hunch that it has to do with the fact that Central Asia/Northern Canada are very geologically inactive areas in the middle of large plates.

Let's suppose, for a moment, that it did happen where a large number of plates converge on each other. What then?

[Ilya Muromets]

MOHO = what?

Ooh, I know that one!

Its short for Mohorovicic discontinuity, the boundary where crust meets mantle. For some reason, I can never ever forget that term ever since I heard it in high school.

[Jeremy]

It's kind of a weird area of semisolid/liquid material IIRC.

Is the Core radioactive? I heard that it might be a natural fission reactor.

[Admiral Valdemar]

Ooh, I know that one!

Its short for Mohorovicic discontinuity, the boundary where crust meets mantle. For some reason, I can never ever forget that term ever since I heard it in high school.

Also the name of a mine machine in Total Annihilation.

The 45 minute travel time through the hole was also a question on Q.I., which this thread reminded me of.

[starslayer]

Is the Core radioactive? I heard that it might be a natural fission reactor.

Yes, it is radioactive, but it's not a fission reactor. The core is hot because of the decay of radioisotopes; the residual heat from Earth's formation dissipated a long time ago.

Alright, some questions CaptChewie. MOHO = what? Also, about shockwaves...since this hole is spanning through all layers of the planet, including the core, wouldn't that have some sort of global impact? Wouldn't shockwaves from the core make their way through the mantle, or do the layers have no interaction with each other aside from heat exchange?

The problem is much of the interior of the planet is liquid (although the inner core is not), and the types of seismic waves that do the most damage to surface life and structures do not travel well through liquid.

[Rossum]

Hmm, would the hole running through the Earths magnetic core have any effect on the magnetic field?

[Gil Hamilton]

Hmm, would the hole running through the Earths magnetic core have any effect on the magnetic field?

It's not big enough, I would think. The Earth has a magnetic field because it's got a gooey nickel-iron core that is spinning and thermally/electrically conductive. You aren't removing that much material or changing any of those things.

[CaptainChewbacca]

Alright, some questions CaptChewie. MOHO = what? Also, about shockwaves...since this hole is spanning through all layers of the planet, including the core, wouldn't that have some sort of global impact? Wouldn't shockwaves from the core make their way through the mantle, or do the layers have no interaction with each other aside from heat exchange?

The layers have SOME interaction, but the fact is that a one-mile hole suddenly appearing is a very SMALL change in the earth. Keep in mind you've only removed one millionth of one percent of the earth's volume, its like taking a strand of spaghetti out of a bowling ball.

I'm also curious as to why the location would have that much of an impact. What's the difference between Central Asia/Northern Canada and Turkey/Java Sea? I have a pretty good hunch that it has to do with the fact that Central Asia/Northern Canada are very geologically inactive areas in the middle of large plates.

Let's suppose, for a moment, that it did happen where a large number of plates converge on each other. What then?

First off, its not possible to have more than 3 plates meet at a single point on earth at a time, that's a function of geometry. Secondly, a sudden stress in the middle of a plate is much more significant than a stress along a fault line. There's a greater chance of shifting and earthquakes.

Is the Core radioactive? I heard that it might be a natural fission reactor.

Just... no. Some 'fringe' geologists contend this to be the case, but its not.

The problem is much of the interior of the planet is liquid (although the inner core is not), and the types of seismic waves that do the most damage to surface life and structures do not travel well through liquid.

The Moho is the depth at which crust material goes from brittle rock to ductile mantle material. The mantle is not a liquid, but it is a fluid and as such transmits waves and energy differently, and does not transmit certain types of waves

Hmm, would the hole running through the Earths magnetic core have any effect on the magnetic field?

No. The change is too small to be significant, but you might speed up or slow down the earth's rotation by a second or two.

[Gil Hamilton]

To expand on a point that Chewie made, there is a difference between a liquid and a fluid. A fluid is a heavily general term refering to any substance that continually deformed when you apply a force to it and has the ability to flow. This includes everything from any gas, to liquid water, to glass (yes, many glasses are by definition fluids, you can see it with really old stained glass), to mantle material. A liquid is a specific subtype of fluid. Mantle material doesn't meet all the definitions of a liquid (I believe it's more like silly putty), so it's not a liquid, but meets the basic requirements of a fluid.