I'm trying to figure out what sort of mechanism might...

[guyanonymous]

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]

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]

"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]

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/xrefme...p/T041365A.gif ). If the rest of the ice goes then that's roughly another 70 meters ( http://www.cejournal.net/wp-content/...k-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]

These ideas have got me moving in the right direction.

Thanks guys and gals!

[ottobot]

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.

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]

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]

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]

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]

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...