Building a Better World: Ice Caves

Welcome to the first installment in what promises to be a very nearly endless series.  I'll be bringing you the fruits of my research as I build Xtalea from the core up.  We'll be exploring everything from geology to biology to all sorts of interesting tidbits that come up.

Before we get to ice caves, I suppose we should break some ice.  Those of you who've become Wise Readers and follow my writing blog already have a general idea of what I'm up to, but the rest of you all are probably a bit lost.  For two decades now (no, that is not an exaggeration or typo), I've been working on a series of SF novels that span many worlds and thousands of years of time.  We begin sixteen thousand years ago, on Xtalea, which is the world I'm building now.  And since the world itself will end up being a major theme throughout the series, it's got to be done right.  The world itself is something of a character.

It will be an Earth-like planet, so I can take several cues from our very own world.  This is fortunate.  It makes the research a lot easier.  PZ's going to hate it, because it's essential to the ultimate plot-line for it to be quite similar to Earth.  But aside from tetchy biologists who want their aliens more alien, everyone else should be relatively satisfied, and that's all that ultimately matters.

Right, then.  We should all be on the same page, or at least in the same book.  So let's start building a world, shall we?  Get your spelunking gear on and descend.  There will be much science and lovely photos!




Before I ever really knew anything about Xtalea, I knew there would be ice caves.  They came up in a short story I wrote by way of figuring out some of my main characters.  One is remembering the ice caves where young soraani slept.  (As to why young soraani slept in extremely cold caves, you'll just have to sign up to be a Wise Reader to find out.  Email me at dhunterauthor at yahoo dot com if you haven't already.)

This was approaching a decade ago, and they've stuck in my mind since, in a vague sort of way.  As more pieces came together, I got more of a sense of them: they were somewhere beneath the main Academy buildings at Aa'radaan.  Aa'radaan was set in a valley strongly reminiscent of something you'd find in the Alps.  But they were always just a gleam in the darkness, although I knew they'd become an essential piece.

I knew nothing about ice caves.  I just knew these were caves with ice in.  Sum total of experience I'd ever had with ice caves in my life: a lava tube in Flagstaff, Arizona, which was nothing like what I was envisioning for Aa'raadan.  Lava tubes these weren't, but what were they?

A few weeks ago, I decided it was time to find out.  I engaged in a bit of Google-fu, and found out that it's bloody damned hard to find anything useful on ice caves written for the layperson.  It's mostly tacky tourist stuff.  One Wikipedia article that didn't take me far enough.  Plenty of images that meshed with what I'd been envisioning, though, which told me that what I needed for my world had analogues on Earth, and that meant there had to be information out there somewhere.  I picked a cave to focus on: the Eisriesenwelt.

Perfect!  And, miracle of miracles, one of the sites I found wasn't strictly tacky tourist.  In fact, it's one of the only sites for a popular tourist destination I've ever found that actually has a link to really solid scientific information, in-depth stuff that wasn't afraid to use large words.  It's just unfortunate those words were all  German when I clicked for the .pdf.  And that inspired me to dip my toes into actual scientific papers on Google Scholar.

Did you know there's lots that are freely available?  I didn't, until I realized if there's a link to the .pdf to the side of the search results, ordinary folk like me can read the original science without having to cough up substantial cash to a journal. This. Is.  Wonderful.

I spent an instructive few nights poring over the scientific literature, and came out with a treasure trove of information that will be essential for building a better Xtalea.

I had a few specific questions to answer starting out: were the kind of caves I envisioned plausible for the kind of terrain and climate Aa'radaan is in?  How are they formed?  Why do they have ice in them?  What sort of rock do they tend to form in?  And can they be as large as what I'd need them to be?  (Some of you might be thinking: Dana, you're writing speculative fiction.  You can have things any way you want.  But that's not strictly true, and besides, reality is one hell of a springboard for imagination.  So yes, these sorts of questions have to be asked, and yes, I'm willing to spend several nights reading peer-reviewed papers to answer them.)

We'd answered the first question when we stumbled upon Eisriesenwelt.  Absolutely, these kinds of caves can be found in that sort of valley.  Excellent.  Ice caves are real.  That will add some reality to the fantasy.

It helps to define what we're talking about when we discuss "ice caves."  I don't mean the kinds of caves that form in glaciers and are formed completely of ice.  Those are more properly termed "glacier caves."  Here's a great definition: "'Ice caves' are rock-hosted caves containing perennial ice or snow, or both"  (Luetscher and Jeannin 2004 .pdf).  In other words, they're like the caves we're all used to, only they've got constant ice in.

Why have they got ice in?

This is where it gets interesting.  There's different sorts, you see.  And you don't even need them to be in a super-cold region: they can form just fine in temperate regions where the mean annual temperature isn't even below freezing.  We'll see why in a moment.

From Luetscher and Jeannin 2004

Let's talk about types.  First, there's the static ice cave, where warm summer air doesn't get much of a look-in.  Remember the basics about how air moves: warm air rises, cold air sinks.  So if you've got a cave that slopes downward, and its opening is at the top, all that lovely cold winter air sinks right down into the cave and stays put.  In the winter time, when the outside temperatures are colder and the outside air thus denser, you get yourself a fresh infusion of freezing cold air.  In the summertime, the less dense warm air hasn't got a chance to oust all the cold air that's sunk down to the bottom.  And since the bedrock makes good insulation, there's not much chance all that cold air lurking down below is going to heat up.  Voila, icy cold cave, in which you can enjoy freezing temperatures at the height of summer.  In fact, there's a delightful description of this in Ice-caves of France and Switzerland by George Forrest Browne

We placed one of Casella's thermometers on a piece of wood on one of the wet stones, clear of the ice, and it soon fell to 34°. Probably the temperature had been somewhat raised by the continued presence of three human beings and two lighted candles in the small cavern; and, at any rate, the cold of two degrees above freezing was something very real on a hot summer's day, and told considerably upon my sisters, so that we were compelled to beat a retreat,- not quite in time, for one of our party could not effect a thaw, even by stamping about violently in the full afternoon sun.

Quite cold!

From Luetscher and Jeannin 2004

Our second sort of ice cave is a dynamic one.  It's got more than one entrance.  The key is relative elevation: one entrance has got to be higher than the other.  This allows all that nice air with its different densities and pressures to get a move on.  Air flow follows the seasons.  In the winter, cold air is drawn in through the lower entrance; water there finds itself frozen, and the warm air that swoops down in summer isn't strong enough to melt it again.  These caves have not one, but two, thermal anomalies: one at the lower bit where it's colder than you'd expect, and one at the upper bit where it's warmer.

From Luetscher and Jeannin 2004

The third type of cave is called a "statodynamic" ice cave, and if you've been paying attention to terms, you can probably figure out it's got features of both static and dynamic caves.  You get a bit of the "chimney-effect" seen in dynamic caves, where air can get a move-on, but it's also got a static area where air stagnates. 

The ice in ice caves comes mostly from snow that, like snow on a glacier, recrystallizes into ice, or from water that dripped, flowed or otherwise found a way inside and froze.  Hoar frost is also a contributor.  If the cave is near a glacier, you might also see the glacier ice coming in for a visit.

Hoar Frost in an ice cave

Now, here's a little detail that will blow your mind: one place you're not likely to find an ice cave is in a place with permanent permafrost.  That's right.  If the ground's always frozen and has been for some time, there's just not enough free water wandering around to form a decent ice cave.  Oh, it's cold in there, and you might get yourself some nice hoar frost, but as far as those lovely sheets and columns and streams of ice, you can fuggedaboutit.  Is that, or is that not, an awesome little factoid?  Dazzle your friends and win bets in bars with it.


There are several conditions other than the elevation of entrances and chimney effects that influence ice in caves: mean annual temperature is one (you're not likely to find ice caves in areas with no winter), which slope the cave entrance is on (south-facing is, after all, warmer), even tree cover (Citterio et al 2004).  So there's a lot that goes in to forming an ice cave, and that puts constraints on where I can site the buggers on Xtalea.  You're not likely to find one in the Siaan, for instance, which is closer to the tropics and is one of those regions that believes snow happens to other people.  Might be able to sneak one into the highest mountains there, but if I put one close to the coast, geologically-savvy readers will know I'm completely full of shit, and that will rather kill the semblance of reality, so we shall just avoid that.

Right.  So there we are: we have an idea of what ice caves are.  Not a lot of info on the type of rocks yet, although most of what I've seen is limestone.  As I dig deeper into the geology of Aa'radaan, I can determine what we're dealing with.  Limestone?  Possibly marble?  I've got a whole new big book on caves I'm about to read that will help me determine what the bedrock shall be.  And now I know roughly where those caves will be located, and where their entrances must be, which means they may not be beneath the Academy proper after all.  I also have new decisions to make: static, dynamic, or statodynamic?  Only more treks through Google images will answer that, but so far, it seems the caves that most closely match my mind's eye are the dynamic ones.  We have Eisriesenwelt, of course.  There are also a few more that provide great inspiration.  There's Demanovska in Slovakia:

Demanovska Cave of Liberty

In various parts of the cave, you can see enormous ice formations, pools of water, and typical cave formations - absolutely exquisite.

Glacière de Monlési in Switzerland:

Glacière de Monlési

"Glacière" is actually the proper term for an ice cave, but it hasn't caught on all that well in English, probably because everybody thinks it means "glacier," which it doesn't...  Regardless, it's an absolutely gorgeous cave.

We'll continue this discussion later, as I delve further into the world of ice caves.  We haven't even gotten to the cryogenic carbonates yet.  Caves have ice formations just as they have stone formations.  And there's doubtless much more to explore.

References: 

Marc Luetscher and Pierre-Yves Jeannin, "A process-based classification of alpine caves."  Theoretical and Applied Karstology, 17 (2004), pp. 5-10

Luetscher, M., B. Lismonde, and P.-Y. Jeannin (2008), "Heat exchanges in the heterothermic zone of a karst system: Monlesi cave, Swiss Jura Mountains." J. Geophys. Res., 113, F02025, doi:10.1029/2007JF000892