Science Questions: Fire and Ice

[seawasp]

A couple of idle questions which involve science I don't know much about... at least not at this level.

1) In many a disaster scenario (most recently seen in Sluggy Freelance), some super-technology device, such as a mega-drill, frickin' superlaser, etc., bores a hole from the surface down to some ridiculous depth in very short time, and this usually is shown as causing some sort of catastrophe like a sudden volcano. I'm wondering if there would, in fact, actually BE any significant consequences from such an event, assuming it didn't occur right on top of a volcano that already exists and is about to blow. Say, here, in the heart of New York State, if I were to just magically bore a hole straight to the earth's core in a matter of a second, would there be a catastrophe, a small eruption, or nothing at all except a big hole that closed itself up to (some depth)?

2) Another common scenario in some SF has been either a base on a world like Pluto, or an earthlike world cast out into the void, where something happens and the whole base/planet cools to interstellar void temperatures. My question is if -- assuming you DON'T have any macroscopic reasons to be able to tell (if there were any biologicals present, they were already long dead, maybe mummified so there's hardly any water left in them, etc. -- you could tell that they had been, in fact, in a -200 deep freeze before they thawed out. That is, you step out into, say, a bunch of dirt and examine it. Can you tell that it was once subjected to -200 degree temperatures for a long period of time -- and could you tell this a year after it thawed, a hundred years, a thousand? Assume no biological activity to mess up your analysis (i.e., if it's been thawed for ten thousand years, there still haven't been any bacteria, etc., to start decay or other stuff going.)

Comments

[howardtayler.livejournal.com]

Re #2: Depending on how cold it got, some sorts of only-seen-in-extreme-cold crystals might form. When it warms up, those crystals melt or sublime. Perhaps the structure in which they were embedded remains intact, and this provides a molecular "signature" indicating that extreme low-temp crystals formed.

But I'm guessing. You need a materials guy.

[argonel.livejournal.com]

Not only is a materials guy necessary, but a specialist within the material field is necessary. I can tell you all sorts of things that happen to iron and steel when the temperature changes, but not much about biologicals or other organics.

[keithmm.livejournal.com]

Going to the core would be excessive: once you get down to the mantle, everything after that is needless because of what I'm about to say:

It really, really depends on the size of the hole and the geological setting, not just a volcano. In certain circumstances, a small weakness in a zone of structural weakness can have a large effect. Ignoring that, you're looking at the size of the hole. Make it too small and lateral pressure from the crust on down is likely to squeeze it into nothing almost instantaneously, so the effect is likely minimal. Make it larger and you could possibly get something like a brief volcano, but I doubt it would be a long lasting one, and how destructive it would be would depend on what the upper mantle was like in the area it penetrated. If the mantle happened to be fairly dry(1), and you weren't near a hotspot, I suspect the effect would be pretty negligible.

1. Volcanoes form in two places, as everyone knows: hotspots and subduction zones. In the subduction zones, the water that gets dragged down is a critical component in the vulcanism that results.

[kengr]

Regarding the hole, a lot will depend on the diameter. A few centimeters, and odds are it'll close up at depth.

A few decimeters, and odds are that you'll get an eruption of sorts.

Remember, at the very least, the *mantle* is liquid. So once you hit that depth you have a liquid, under a *lot* of pressure and the hole provides a means of escape.

Diameter affects rate of flow. If it's slow enough, the rock on the sides will cool the fluid enough to solidify before it reaches the surface.

Going deeper than the mantle doesn't really matter because once whatever made the hole goes away, the hole will close up as the surrounding materials flow into it.

If the diameter is large enough the stuff flowing in to close it will cause significant seismic events. Otherwise, the only thing to worry about is the magma flowing up thru the hole.

Don't forget that a lot of magma tends to have dissolved gases or water. That can be significant when the pressure gets released.

Instant Vocano

[tamahori]

I have no idea on (2). As far as (1) goes, it's important to remember that the shift from 'crust' to 'mantel' isn't a clear line ... the rock just gets hotter and softer on the way down.

So I'm guessing the hole would have to be quite wide indeed for it not to collapse from having the very hot and soft rock lower down just squeezing in on it before much actual magma has much of a chance to get up.

My guess is, assuming you're not drilling down into a already very easy to trigger point (near active volcano, fault-line, etc) that you'd need to have a very wide hole to get anything 'useful' coming up to the surface, and it's going to self-seal itself fairly quickly even in that case.

Or to put it another way, anything capable of _making_ the hole is going to be more dangerous than the resulting hole. :) I am of course not even remotely a scientist, so I could be talking totally out of my arse here.

This is also assuming you're just going down though rock. If you run into a high pressure gas field or oil field or hot water, you could get quite a messy result up at the surface, but it wouldn't be magma causing the issue.

If you're just trying to cause a problem, and you're in an already 'fragile' location, you probably want to drill the hole, and then drop something down it to cause problems ... quite what you'd use would vary depending on conditions, but in some cases even just a lot of cold water could cause problems.

-- Brett

[rdmasters.livejournal.com]

Okay, only Howard has had a serious go at this one, and he's largely stumped.

Cosmic deep-freeze and vacuum exposure.

From the deep freeze you may get some crystallographic evidence as Howard suspected, but it's going to be hard to come by.

You will get: regolith-like structures from cosmic-ray bombardment and meteroites (not to mention high-velocity impactor traces), vacuum welding in metallic objects, and core temperature. Despite the radioactives in the mantle and core regions, you are still going to get substantial core cooling. This will result in the planet having an unusually weak magnetic field, and being very hard to warm up again. In fact, now that I think of it, you are going to have significant atmosphere loss from bake-off during any sort of rapid thaw process, and if you slow down the thaw, you are going to have other problems.

The big one is going to be atmosphere and post-thaw duration. The moment you get any sort of atmosphere post thaw, evidence will start to disappear. Vacuum welding evidence will start to vanish beneath corrosion, regoliths will erode.

Sorry, but biologicals will be an issue - I cannot come up with a scenario where they will not. Virii and bacteria are extremely hard to kill off - as are fungal spores. I'll put that aside for now, though, and talk post-thaw duration and atmosphere effects.

This is where your biggest issues and (potentially) your biggest signs will be. If you have a rapid thaw, that will require a near pass to a stellar object. This will result in significant boil-off, and a significantly thinner atmosphere, with a very different composition, as the lighter elements will have departed first. This will include water, so you will have a much more arid landscape, but with historical evidence of bodies of water. (If this is sounding creepily like Mars at this point, there is good reason for that - it's the best model we have to work with.) This will be A CLUE to a traumatic past. With the atmosphere restored, it will still take millions of years for the surface temperature to return to 'normal' levels for the resulting orbit. (Another aside - for the sake of simplicity and plot, I am going to ignore the effects of tidal vulcanism and crust distortion from the close pass!)

So, to the post-thaw period. You will get erosion and corrosion happening at once. Over the first 10 years, not much to see. Over 100, your regoliths in non-desertified areas will degrade rapidly, but you will still get lots of microscopic evidence. 1000 years - corrosion will be a big issue for any exposed metallic objects, and in ferrous items any sign of vacuum welding will likely have vanished in corrosion layers - especially in dissimilar metal welds. The regoliths in most areas will be starting to degrade. 10,000 years - metallic evidence will be mostly gone. Regoliths in non-desert regions will be subject to significant erosion and polishing. Desert regions subject to winds will see the regoliths also degrading back to basic sands. 100,000 - Only dry caves will contain significant regolith evidence. Past 1,000,000 years - deep microscopic analysis will still show signs of past regolithic structures, but these will be mostly subsumed within the normal background of erosion and recompacting. You will still have unusually low levels of vulcanism, though, and that will persist for the life of the planet, due to core cooling.

Yes, biologicals will make things harder, but not by much, especially if there has been significant boil-off of the lighter elements. The resulting mostly arid environment will be one of the biggest clues to what has happened. Actually, they could make it a bit easier, as you will have a thriving microscopic environment, and a lot of mummified remains (these will decompose, but with an arid environment it will take 1000s of years).

Caveat: I am not a -gist of any sort, but I do read around a lot, and have paid a lot of attention to the martian and lunar surface analyses.

[seawasp]

Hmm. I thought that even bacteria would die off eventually.

Figure that it's somewhere you're NOT going to get regolith -- say in a cave deep underground that once had gardens and grow-lights (so you have dirt and not just rock). Possibly hard vacuum exposure, yes, but maybe a think atmosphere of stuff that doesn't freeze at liquid nitrogen temps.

And it was warmed up nice and evenly.

[rdmasters.livejournal.com]

Bacteria, virii, and fungii all sporify in sudden extreme conditions, and are very hard to kill after that point. A good hard roasting will do it, but hard radiation just mutates them so the following generations are different.

So posit a survival bunker whose heaters give out? Because you are going to need a sealed environment to not get vacuum. Complex biologicals will have a distinct structure, because they will end up effectively freeze-dried.

The rest of it will be more complex... so, yeah, you're going to need a cyronics specialist to answer that. I'll ask around.

[rdmasters.livejournal.com]

A co-worker just pointed out that there would be an unusual dust layer in the geological record. Polar ice cores would show it up, as would areas underneath thaw-prompted collapse. Think something similar to the K-T layer.

[mrmeval.livejournal.com]

#1 I don't know for sure. There is a dam they built in China is causing minor earthquakes so we can do some damage with more mundane tech.
http://en.wikipedia.org/wiki/Three_Gorges_Dam

As a guess an instantaneous hole would be almost instantly filled. The surrounding material would just flow into it at various speeds. If we're talking 100 miles wide and 100 miles deep, that might be a tad different. When you have the geophagy ray perfected let me know so I can get off this rock. ;)

#2 Nickel iron bodies such as meteorites display a unique pattern.
http://www.meteorlab.com/METEORLAB2001dev/labphoto/cube.htm

You would find some indication of freeze and thaw but I am unsure of degree. Freezing would not be uniform at first and probably not of millions of years in a hot planetary body. .... I think this has been asked before on the bar.

Formation of seasonal ice bodies and associated carbonates.
http://www.caves.org/pub/journal/PDF/v71/cave-71-01-48.pdf

Astrobiological implications of hydrosphere, cryosphere, biosphere interactions at Icelandic hot springs
http://alan-channing.co.uk/cryobio.aspx

Formation of cryogenic aggregates and others from a book on google books.
http://tinyurl.com/y8d6h8d

Ah Cryolithology may be the discipline you need. It seems to be a very small niche discipline though.

[baronger.livejournal.com]

I think everyone has it for number one. At least from all the MOHO drilling projects that are being attempted. They can't get past a certain depth (varies depending on location and local conditions), and the hole seals up. At depth the rock flows like liquid silly putty.

As for the 2nd scenario. You might be able to tell from the mummified remains that they had died to freezing. Ice crystals tend to destroy cell walls. Though the exact temperature below freezing might be more difficult to tell.

[baronger.livejournal.com]

Had an idea.

Think thermal mass, or better yet a baked Alaska.

If the planet had only recently been back to a normal temperature. The deep rocks should still be icy cold. Also if it was only a quick trip (relatively) you should have a strange phenomenon of warm icy cool, as the deep rocks wouldn't have chilled down toward absolute zero yet.

[keithmm.livejournal.com]

I'm an idiot. I live in a part of the world that's an example.

If the place had only recently been dethawed, you're going to have massive permafrost. The devil is in the details regarding the dethawing, but if you assume a planet was (captured? placed into?) in an Earthlike orbit, you are going to have permafrost way south of where you'd expect climatologically, and the permafrost in polar regions would be much deeper than what it should be.

And the thawing of permafrost is going to have geologically observable effects, especially where it contains a lot of water ice.