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guyanonymous
11-03-2009, 05:08 PM
I'm trying to figure out what sort of mechanism might <within reason> increase water sea levels on a fictional planet by 800m around the globe. In the end, the planet ends up a typical mishmash of climate zones. Most of humanity is destroyed.

That works out to 2.8E+19L of water for my planet. (I'm not worried about salinity levels - though it's something I should think about)

I'm ok with the water slowly,over thousands of years, receding back to "normal" levels, but it's not necessary.

Ideas?

I've thought about meteors (I think those are the ones made out of ice) hitting, etc, but the size involved would destroy the planet. Even if thousands smaller did so, they're still too large.

I'd like the solution to at least be in the realm of plausibility...not something "magical", if that makes any sense.

töff
11-03-2009, 05:16 PM
Melted polar caps comes to mind.

So do comets, which can contain a lot of water (ice). You might have one or many comets get disturbed out of stable orbit and crash into your planet.

You might also be more gentle about it, and postulate a big ring of ice particles (such as Saturn's rings) that your planet passes through. Imagine the Asteroid Belt, but smaller and wetter (icier). Again, you'd need an astronomical event to bring your rocky planet into proximity with such a mass of ice particles.

Then there's always artificial hydration. Maybe fish aliens are trying to terraform the planet. Let the alien engineers haul in some water!

Ascension
11-03-2009, 05:22 PM
At the extreme edge of plausibility you could have a giant earthquake swallow a whole continent, thereby pushing water levels up. Or you could have some volcano spew out some enormous amount of lava. Neither is all that realistic but it avoids giant craters and fires left over from impacts. My first thought was as Toff says...icy comets.

guyanonymous
11-03-2009, 05:23 PM
I'd thought about passing through some sort of ice-asteroid belt, but if most things are burnt up in orbit, does that remaining matter (i.e., H2O and H and O) end up inside or outside of the atmosphere?

If the particles are the size of a loaf of bread vs. the size of a VW bug vs. the size of a movie theatre, does that make a difference to where the matter ends up?

töff
11-03-2009, 05:26 PM
Water that "burns up" in the atmosphere recondenses and enters the planet's water cycle.

It's the dinosaur-killer effect you're wanting to avoid ... the transmission of a huge amount of energy into the planet's crust, kicking up dust that obscures the sun, and also causing earthquakes & tsunamis.

If you just say all the ice meteors were no larger than the hippie vans, you'd be fine, and you can dump as much water as you like into the system from space.

guyanonymous
11-03-2009, 05:35 PM
At the extreme edge of plausibility you could have a giant earthquake swallow a whole continent, thereby pushing water levels up. Or you could have some volcano spew out some enormous amount of lava. Neither is all that realistic but it avoids giant craters and fires left over from impacts. My first thought was as Toff says...icy comets.

That's why I'm wondering about size of particle and where the residual matter ends up....if everything can burn up in the atmosphere, but the water end up within the atmosphere, I don't have to worry about craters - which, really, I don't want to do, as I've got the planet already designed.

I, obviously, should have mentioned that earlier. :D

Initially the planet will be fairly cold, with most of the residents located close to the ocean using it's energies to generate heat, food, etc.

There are several billion residents of a fairly old civilization.

Then the "incident" happens.

90% of population killed....water levels risen (covering up most cities)...in subsequent years, starvation, disease, nature's turmoil at massive climate change, kills of most of the rest.

1000 years later, scattered small groups survive, though almost all under 5 people (mostly family groups). They are hunters/gatherers/ and exist at an animalistic level in terms of survival of the strongest.

There's the nutshell of my prehistory - but I want to figure out this event before I move forward.

guyanonymous
11-03-2009, 05:36 PM
Water that "burns up" in the atmosphere recondenses and enters the planet's water cycle.

It's the dinosaur-killer effect you're wanting to avoid ... the transmission of a huge amount of energy into the planet's crust, kicking up dust that obscures the sun, and also causing earthquakes & tsunamis.

If you just say all the ice meteors were no larger than the hippie vans, you'd be fine, and you can dump as much water as you like into the system from space.

This would be great!

Would the increase in matter result in an increase in atmospheric pressure?

Juggernaut1981
11-03-2009, 05:44 PM
Okay, long list of wierd things that could happen...

Comets come into atmosphere and melt leaving water and tiny dust landing.
Additional water will increase the oceans.
Water takes lots of energy to heat (in chemistry terms) so more water = more energy to maintain temperature = planet cools.
Enough water (e.g. comets landing to cause 800m sea level rise) would eventually accumulate into an ice age if the planet wasn't heated well enough.


So I'm guessing your society will probably still be stuck in the leftovers of an ice age. Atmospheric pressure is more regulated by temperature than things falling from space, but water from space will drop worldwide temperature if there is enough of it... and then change atmospheric pressure...

It's all rediculously interconnected. You want great answers, ask UN Climate Change what they know...

töff
11-03-2009, 06:01 PM
Would the increase in matter result in an increase in atmospheric pressure?If the matter becomes gas in the atmosphere, then yes. Our atmosphere is mostly free nitrogen, about 1/5 free diatomic oxygen, plus tiny little trace gases like argon.

But you can have anything you want in your comets ... just plain water and dirt would be fine, and if they don't bring in any atmospheric gases, then there's no increase in air pressure ... okay, maybe a little, due to the increased water volume ... I'm not really sure, to be honest. I kinda doubt it. Google for "vapor pressure" though. I once tried to figure the vapor pressure for neon on Pluto ~ omg I'm such a geek.

töff
11-03-2009, 06:04 PM
Water takes lots of energy to heat (in chemistry terms) so more water = more energy to maintain temperature = planet cools.
Enough water (e.g. comets landing to cause 800m sea level rise) would eventually accumulate into an ice age I dunno about that. Sure, keep dumping ice on a planet, it'll cool ... but solar energy plus core-produced radioactive heat, I would think, would soon bring back equilibrium.

Plus, the energy of the ice meteors themselves, as they brake into the planet, would ADD to the total energy of the system.

This is not an effect I would worry about unless I thought it was a fun thing to include.

guyanonymous
11-03-2009, 06:05 PM
Thanks for the suggestions!

I just want to figure it out enough that it can be there, the event most distant in the past that is dealt with on this planet. It's what happens after it sets the stage that is most important.

I'll likely work on the idea of a massive belt of ice intersecting the planet's orbit long enough for this volume of water to accumulate in the atmosphere, but brief enough to overwhelm the people, killing them all. Muahhaha. Or right, inside voice.

töff
11-03-2009, 06:05 PM
It's all rediculously interconnectedI'll sing that hymn with ya, brother!


You want great answers, ask UN Climate Change what they know...... but not that one :?

su_liam
11-03-2009, 08:38 PM
... but not that one :?

They probably know as well as anyone.

Juggernaut1981
11-03-2009, 08:42 PM
I dunno about that. Sure, keep dumping ice on a planet, it'll cool ... but solar energy plus core-produced radioactive heat, I would think, would soon bring back equilibrium.

Plus, the energy of the ice meteors themselves, as they brake into the planet, would ADD to the total energy of the system.

This is not an effect I would worry about unless I thought it was a fun thing to include.

I'm just thinking of the specific heat capacity of water, compared to most other things, and its stupidly large. Water's specific heat is about 4kJ/kg... Iron is 0.4kJK/kg

It just takes a lot more energy to warm up water. So depending on how much you dump in there, how fast, etc, etc, etc you could cause a nice dip in the temperature. I doubt the energy of the asteroids would compensate for the heat capacity of the water.

Nexis
11-03-2009, 09:06 PM
That's why I'm wondering about size of particle and where the residual matter ends up....if everything can burn up in the atmosphere, but the water end up within the atmosphere, I don't have to worry about craters - which, really, I don't want to do, as I've got the planet already designed.

I, obviously, should have mentioned that earlier. :D

Initially the planet will be fairly cold, with most of the residents located close to the ocean using it's energies to generate heat, food, etc.

There are several billion residents of a fairly old civilization.

Then the "incident" happens.

90% of population killed....water levels risen (covering up most cities)...in subsequent years, starvation, disease, nature's turmoil at massive climate change, kills of most of the rest.

1000 years later, scattered small groups survive, though almost all under 5 people (mostly family groups). They are hunters/gatherers/ and exist at an animalistic level in terms of survival of the strongest.

There's the nutshell of my prehistory - but I want to figure out this event before I move forward.

Ok how about this.

You say the world is a cold world. This could be the apex of a long growing ice age of the world. Most of the north and South hemispheres are under massive ice sheets, This will bring the sea level down a lot. Our last ice age reduced the sea level well over 300 m. Now the population are gathered mainly along the equatorial belt which has a cold temperate climate at best. This will explain the use of the sea for heat and power. Now you need some thing to happen that is quick but not so sudden, like an impact, that will destroy all things. I propose that the ice is crushing the continental plates together and now one of the mid sea faults fails and splits wide open causing a massive earthquake, tsunamis and volcanic action that cascades along all the major faults spewing forth magma, hot gases and a lot of other nastiness. This quickly heats up the seas and air melting the glaciers very quickly raising the sea level at an alarming rate. As the pressures dissipate the volcanic activity subsides over time but the big melt is unstoppable as the air and sea are warmer and greenhouse gasses are heating up the air. This disaster will take a few years to complete and devastate crops technology and displace and kill lots of people. All the water that was trapped in the ice is now flooding all the lowlands that were once coastline and if the land was low to begin with... Man that was long but fun.

guyanonymous
11-03-2009, 09:08 PM
More to think about - I like it, keep the suggestions coming!

And thanks!

töff
11-03-2009, 09:18 PM
specific heat capacity of water, compared to most other things, and its stupidly large. Water's specific heat is about 4kJ/kg...takes a lot more energy to warm up water. So depending on how much you dump in there, how fast, etc, etc, etc you could cause a nice dip in the temperature. I doubt the energy of the asteroids would compensate for the heat capacity of the water.If the ice meteors are "burning up on reentry" to steam in the upper atmosphere, there ain't no reason to worry about this at all.

I smell a stratometeorological thesis here: the caloric limit of net energy gain per the mass of an ice asteroid.

guyanonymous
11-03-2009, 09:24 PM
ha....

OK...so even if they average r. was 20m across, I'd still need over a trillion of these things to connect.

BUT...I revisited my spreadsheet where I worked this stuff out....there's actually only a difference of 10% between the volume of ice in Antarctica. etc, and the amount I need. So an event that causes my more substantial ice caps (fitting in with my living-near-the-ocean plan) to form would work.

The trick is to have it happen in a catastrophic (i.e., number of hours) manner. But that much ice, no matter what, isn't going to melt that quickly.

Hmm....

Coyotemax
11-03-2009, 10:43 PM
Solar flare-up?

Then again any flare of a magnitude that would melt the polar caps in a matter of hours is likely to incinerate the rest of the surface to a depth of several dozen miles, I imagine :)

waldronate
11-04-2009, 12:24 AM
Assuming an impact speed of roughly 25 miles/sec (roughly 40 000 meters/sec) then the kinetic energy of that beastie will be about 800 000 000 joules / kg (KE = MVV). Assuming the ice starts out at -270C then it takes 1 130 000 joules to heat the ice to 0C, ballpark 330 000 joules of energy to melt it, 418 000 to raise it to boiling, and another 330 000 to turn the ice into steam. That's a grand total of 2 208 000 joules to take a kg of ice from interstellar temperatures to just over boiling. That only leaves about 798 million joules of energy to heat that kg of ice.

It's why ice meteors make an incredibly bright light and a huge shock wave as they are decelerated rapidly. No real worry about cooling things off by dropping rocks from orbit. The big problem is to keep from frying the planet.

A 10cmx10cm column of water weighs 1kg per 10cm. An 800 meter column over that area weighs 8000kg. 8000 * 800MJ (ballpark) gives a delightful stellar-grade plasma if you drop it all at once.

guyanonymous
11-04-2009, 01:38 PM
OK. Would it be feasible for a large, fast traveling interstellar body to pull a planet into an orbit closer to it's star? And in doing so, exert such forces that might cause an entire continent to collapse/sink? Thus raising the water 800+ meters in the process, and changing the balance of nature all over the planet (currents/tides/winds, etc all affected...and this continent would be in my currently blank portion of the map which is in the north of the planet.

Would a sudden shift in such a large piece of land (larger than antarctica) toward the planet's core be enough to cause a significant shift in a planet's orbit on its own?

guyanonymous
11-04-2009, 01:39 PM
And remind me which physics formulas would apply to figure out what size mass, what distance, and what length of time it would take to cause my planet to move the distance needed...(hey, I like to obsess about tidbits).

töff
11-04-2009, 02:04 PM
"Sinking" a continent is simply a change in the flatness or roughness of your planet's surface. If you make the planet smoother, water spreads out. If you make it rougher, water collects in the low spots.

All you want to do is add water, right? What's wrong with a trillion ice meteors from an ice ring?

It's scifi, right? In the end, you pick the scenario you like, and it's explainable somehow.

waldronate
11-04-2009, 04:55 PM
As töff pointed out, the simplest solution is to melt polar ice. Civilization starts during an ice age when global sea levels are a few hundred meters below "norm". The world heats up for whatever reason and the ice melts over the course of a few hundred years. It happened here over the course of a few thousand years.

If your continents are lower-profile than ours here at home then a smaller increase in sea level will dump more land. Even here the 120 meter change from the height of the ice age to today cost us the huge peninsula in SE Asia ( http://images.encarta.msn.com/xrefmedia/zencmed/targets/maps/map/T041365A.gif ). If the rest of the ice goes then that's roughly another 70 meters ( http://www.cejournal.net/wp-content/uploads/2009/03/earthicefreemask-1024x512.gif ).

If you need the rate of change to be high (all of this happens in a matter of weeks or a few years) then you'll need some mechanism to compensate for the huge energy flux that just melts the ice but doesn't roast the land. I don't know what that would be, sorry.

There are also the Noah-type activities. The Noah myth is probably derived from a Babylonian one that is itself derived from myths that may likely relate to the flooding of the Black Sea basin 9 000 years ago. If your primary civilization areas developed in a landlocked basin (Med Sea basin or similar) then a catastrophic flood is much easier to implement because then it's just dropping a barrier to allow water to enter.

guyanonymous
11-04-2009, 05:16 PM
These ideas have got me moving in the right direction.

Thanks guys and gals!

ottobot
11-04-2009, 08:11 PM
That's why I'm wondering about size of particle and where the residual matter ends up....if everything can burn up in the atmosphere, but the water end up within the atmosphere, I don't have to worry about craters - which, really, I don't want to do, as I've got the planet already designed.

I, obviously, should have mentioned that earlier. :D

Initially the planet will be fairly cold, with most of the residents located close to the ocean using it's energies to generate heat, food, etc.

There are several billion residents of a fairly old civilization.

Then the "incident" happens.

90% of population killed....water levels risen (covering up most cities)...in subsequent years, starvation, disease, nature's turmoil at massive climate change, kills of most of the rest.

1000 years later, scattered small groups survive, though almost all under 5 people (mostly family groups). They are hunters/gatherers/ and exist at an animalistic level in terms of survival of the strongest.

There's the nutshell of my prehistory - but I want to figure out this event before I move forward.
well your planet was cold at the time of the event, so it would have lots of its water locked in ice caps. simply have global warming melt the ice caps, raising the water level quite a lot.

guyanonymous
11-04-2009, 08:50 PM
It's the time factor - an advanced civilization, in my mind, would be able to deal with melting icecaps over the period of years, and even months. But not likely in hours. But I don't envision them melting in hours.

Gidde
11-04-2009, 09:00 PM
A few well placed nukes would melt the caps pretty quick. Another (fictional) way to do it would be the way they did it in Green Mars (think it was Green) ... they stuck some mirrors and lenses in orbit and focused sunlight on them the way kids kill ants with magnifying glasses.

Ghostman
11-05-2009, 08:24 AM
Would placing a gigantic flat volcano (caldera) right under a glacier and have it erupt be a feasible explanation for such a fast melting?

guyanonymous
11-05-2009, 10:56 AM
An experiment/terrorist action by some scientist on the planet is also possible - but for nukes, at least of current yield, a lot would be required...

Notsonoble
11-06-2009, 12:09 AM
So make it bad luck combined with malicious intent... smack the planet with a comet the size of oh say new york city... it can break up before it hits, but because it broke up and was going for an ocean impact already... no body cared... what they didn't know is someone was getting ready to nuke the snot of an ice cap somewhere, probably intent on wiping out some major power but not much else, but the two events happened too close together...