Replicating the biblical flood

Question

The Biblical story of the Flood describes how over a period of 40 days the earth is flooded so that the peak of the highest mountain is 15 cubits/22.5ft/6.858m below the new mean sea level. The flood waters remain stable over for 150 days before being removed over the period of the following 220 days.

We could achieve such a flood by locating ice asteroids and depositing them on earth. We can assume that this is being done by beings with hard-science based spaceships which may exceed our current capabilities even given an unlimited budget, but must still obey the laws of physics as we know them. For example, if a required ship or ship type has a very large and powerful engine capable of lowering the requisite ice/water at a safe rate, the effects of the drive on the environment must be accounted for.

1. How much water would be required to flood Earth to this level?
2. How could the water be deposited to do the least damage or alteration possible (including heating or cooling or altering Earth's rotation or axial tilt) to Earth - aside from flooding it, of course? We could simply drop the ice as a single bolide, but there would be a great deal of cratering and other damage, the avoidance of which is highly desirable.
3. Given that the water must be deposited over a period of 40 days, and assuming an effectively equal rate of deposition over the entire surface of the globe during the majority of this period (at least 99% of the 40 days, with at most the initial and terminal 0.5% of this time ramping up and tailing off the rate of deposition respectively), at what rate must the water be deposited, and how would that compare to natural rainfall?
4. How could that amount of water be removed over a period of 220 days, again causing minimal damage or alteration to submerged land features. The maximum preparation time for this removal of the excess water is the aforementioned 150 days, though it may be less.
5. What would the world look like after 150 to 370 days entirely under water? What species (animal, plant or otherwise) could survive?

Answer 1

Although I have my reserves about the Biblical Flood (I believe it was limited to Noah's region and did not drown the whole earth) but for the sake of answering the question, I would put my two cents about flooding the whole earth.

Flooding The Planet

As stated by user6760 in the comments, you would require a water volume of astoundingly astounding, brain-reeling amounts to bring about a flood of this extent. Here is how you can do that, provided you have endless funds and countless spaceships (not to mention a truly limitless volume of water).

Step-1. You will need to silently land (and then sink) 50 mega-submarines, running on nuclear fuel, to the depths of the oceans. Each submarine is capable of producing a temperature of 4000°C, but they are not active right now. Lets call these Dec Subs.

Step-2. You will need to station some 36000 spaceships at a distance of nearly 10000 km from earth, in a spherical shape. These ships are all "sitting" on the colossal ball of ice you are going to fire on the poor earth inhabitants.

Step-3. Start shooting ice-balls on earth from spaceships' cannons at medium velocities (~2km/s). Each ice-ball should be ~27 cubic ft in size (3 x 3 x 3 ft) and each cannon should be machine-gunning 10 such ice-balls per second. Keep shooting until all the block of ice is shot at the hapless earth.

Effects (phase 1). The ice-balls enter the earth's atmosphere like asteroids. Due to earth's gravity, their velocity would have further increased and reached an extent of ~5 km/s. Friction with air would trigger immense heat generation and the ice-ball would simply melt, then quickly boil and vaporize before ever hitting the surface. The inhabitants on the night-side of the planet will see a confounding series of flash streaks in the night sky. Notice that all this shooting will have very little to no effect on the overall temperature of the earth's atmosphere. The heat generated by friction would be compensated for, by the heat absorbed by the ice during melting and vaporizing. For extra precision, you can go on calculate the precise amount of heat generated and then initially place the ice-balls at a temperature low enough to compensate for all the friction heat.

Effects (phase 2). You are bombarding earth's atmosphere day and night, relentlessly with water vapor. What is going to happen now? What could happen in the water cycle of our planet? Excessive increase in humidity would lead to excessive amounts of clouds, leading to excessive amounts of rainfall ... What else did you expect? Thanks to you and your ice-firing, earth has become a water-planet now :(

Removing the water.

1- You will need to safely land some 1000 submarines on earth. Each of them is capable of generating a temperature of 4000°C in a closed space (they are running on nuclear fission fuel). Also, now activate the Dec Subs (remember we installed them deep in ocean depths before we flooded the planet?) All these submarines would be splitting water into hydrogen and oxygen by means of Thermal Decomposition. There would be another set of 1000 submarines which would be actively carrying out electrolysis of water. Together these systems would be decomposing some 14000 cubic meters of water per second, releasing the resulting oxygen and hydrogen into the ocean which would bubble out of the surface.

Hydrogen, being the lightermost of all gases would float to the top layer of the atmosphere where several spaceships would be ready to filter it out of the atmosphere.

2- Several spaceships would be floating on the surface of the giant ocean (disguised as giant floating chunks of polar ice), filtering out excess oxygen from the atmosphere so as to keep the 21% ratio. These spaceships would also be boiling and vaporizing a lot of the ocean surface water.

3- There is yet another set of spaceships which would be filtering out water vapor from the atmosphere and transporting it regularly out of the earth's atmosphere into the mother-ship.

The water surface would be falling down slowly, but gradually. You are going to have to run your water decomposition and vaporization ships' engines at really high levels to be able to transport back all the water vapor and water gases (hydrogen and oxygen) back into the space where it came from.

Congratulations (not)! You have flooded and killed 95% of all terrestrial species with only a "temporary" increase in ocean levels of the earth.

NOTE: Don't forget to remove your oxygen and hydrogen filtering spaceships after their job is done.

P.S. Also remove your ugly Dec Subs. The benthic creatures don't like them. Thank you!

Answer 2

1. How much water would be required to flood Earth to this level?

 1.1. $V=\frac{4}{3}\pi r^3$

 1.2. The radius of Earth at the equator is $6378.1$ kilometers.  The radius of Earth plus the height of Mt. Everest + flood coverage is $6378.1+8.849=6386.949$ meters.

 1.3. To make this easier, I'm going to assume that Earth is a perfectly flat ball.  The volume of Earth, plus flood is $1091361395266.3 km^3$ or  $1.0913x10^{12} km^3$.  The normal Earth's volume is  $1086831493929.56 km^3$ or $1.0868x10^12$. The volume of water to be deposited is $4.5x10^9 km^3$. For comparison, the largest body of water on earth is the Caspian Sea is $69,400 km^3$. All water on Earth is only $1.386x10^9$ cubic kilometers km3. We are adding 3.247x the amount of water on earth.  Dang.

 2. How could the water be deposited to do the least damage or alteration possible (including heating or cooling or altering Earth's rotation or axial tilt) to Earth - aside from flooding it, of course? We could simply drop the ice as a single bolide, but there would be a great deal of cratering and other damage, the avoidance of which is highly desirable.

 2.1. Applying that much mass to the atmosphere in such a short period of time will surely alter Earth's rate of spin if applied to same side of Earth.  To counteract this, we will need to send in the water asteroids in pairs, one to each side of the planet so that the impact of one asteroid is counteracted by the impact of the other.

2.2. (I don't have the math/science to figure out how much energy all these asteroids will add to the atmosphere on reentry or how much of that energy will be absorbed by the water in the asteroid itself. I definitely don't have the science/math to figure out how all that water will change Earth's albedo. Sorry.)

2.3. Delivery Alternatives

2.3.1. If the asteroids break up in the upper atmosphere and handwave turn into water droplets then they could come down as rain. However, this much water over land will cause significant flooding and erosion and thus fails the "minimal changes to landscape" requirement.

2.3.2. If the asteroids break up over the ocean and come down as rain on the ocean then there's not much immediate erosion. The oceans will just rapidly rise.

2.3.3. Aliens are "kindly" depositing water directly to the oceans without the heat of reentry.

 3. Given that the water must be deposited over a period of 40 days, and assuming an effectively equal rate of deposition over the entire surface of the globe during the majority of this period (at least 99% of the 40 days, with at most the initial and terminal 0.5% of this time ramping up and tailing off the rate of deposition respectively), at what rate must the water be deposited, and how would that compare to natural rainfall?

 3.1. To keep to the flood time line, we need to deposit $4.5x10^9 km^3$ over 40 days so that's $\frac{1.125x10^8 km^3}{day}$. Annual global rainfall is about $\frac{5.23x10^5 km^3}{year}$ or $\frac{1433km^3}{day}$. Five orders of magnitude more rain will fall per day than usual. If average daily rainfall for the planet is $\frac{.27cm}{day}$ then a five orders increase would be $\frac{~270 meters}{day}$ or $\frac{11.25 meters}{hour}$. Done. Humanity doesn't last two days since half the world's population lives in coastal zones. There's no way to move that many people. Whether killed by weight of the waterfall rain or washed away with by the tsunamis, everybody dies.

 4. How could that amount of water be removed over a period of 220 days, again causing minimal damage or alteration to submerged land features. The maximum preparation time for this removal of the excess water is the aforementioned 150 days, though it may be less.

 4.1.  Lots and lots and lots of energy. Getting water into Earth's gravity well is easy.  Getting it out again under a hard-science requirement is incredibly difficult.  According to this What If question about getting just all the humans off earth,

 > would tax our resources to the limit and possibly destroy the planet.

Lifting 3.247x Earth's original water supply just isn't going to happen without considerable external power sources. Thankfully, the Magratheans know how to do this kind of thing.

 4.2. Extraction Alternatives

4.2.1. What if Earth absorbed that much water like a giant sponge? Huge earth quakes while the crust and mantle open up "pores" to make way for all that water to come in.  Huge steam explosions when hot magma hits cold water.  Making pockets to hold all that steam is going to make for greater instability later on....thus disqualifying this approach from the "change as little as possible".

4.2.2. The aliens who "loaned" us all that water now want it back. Using their "Infinite Energy Drives (TM)" they shuttle the water off the planet in their Big Gulp mega-barges.

 5. What would the world look like after 150 to 370 days entirely under water? What species (animal, plant or otherwise) could survive?

 5.1.  All the land animals that can't grasp onto floating debris are dead. Drowned. Amphibious or aquatic species may survive if they can make it past the initial flooding though non-carrion food and shelter will be difficult or impossible to come by. Crocodilians may survive just fine as they are accustomed to long periods in the water and can eat carrion.

5.1.1. Quick thinking humans may survive by making small rafts or piling into existing ships. Food and water are going to be a really difficult problem as untreated fresh water doesn't last longer than 2 or 3 months. Not many ships carry sufficient food for a year for max crew and passenger loads. Starvation is the likely end for those humans who make it onto ships.

 5.2. Most sea life would die too.  Corral reefs host an incredible amount and variety of life, all of which depends on being in relatively shallow, sunny waters. With the addition of 8 km of water overhead, the increase in pressure plus the lack of sunlight would kill practically all coral reef life. Ocean vent life may survive the increase in pressure though I have no way to prove that.

5.3 Vast majority of plant life is dead too. Few planet species can survive long term immersion in salt or fresh water. And those that can, how well do they do under 6 to 8km of water and absolute darkness? Probably not well enough to survive a year down there. For comparison, the Marianas Trench is 10,994 meters deep and hosts some really strange life.

5.4 I don't know the chemistry but based on the Marianas Trench article in 5.3,

At the bottom of Challenger Deep, calcium carbonate shells are not an option because the intense pressure -- over 1,000 times sea-level -- dissolves the mineral.

coral reefs as we knew them will disappear. Extending this dissolving behavior to other minerals, it may not be possible to avoid significant changes to the topographic features of Earth.

5.5 Depending on how the aliens remove the water and where they suck it up from, there may be significant erosion as the water drains away. Erosion characteristics of megafloods will show up everywhere. To compound the problem, all the plants that used to prevent massive erosion are dead or simply disintegrated by water pressure.

(I'd like to thank Wolfram Alpha for making some parts of the calculations far easier.)

Answer 3

Nice planet, we will take it.

Self-reproducing sonde >unintelligible sound< detected a planet with a rich source of deuterium on the surface. Prepare landing and exploitation.

We did not know from where they came. Some people recorded a great fireball appeared before the level rise but noone was sure.

The sonde landed perfectly in the ocean and sank to the bottom. A self-replicating Neumann machine it extracted deuterium and tritium from ocean water for its nuclear fusion reactor. It started to build copies of itself from the resources on the ocean bottom. The numbers of sondes began to grow exponentially. Each sonde has a balloon which stored the hydrogen and oxygen removed from the precious deuterium and tritium. This balloons had liquid hydrogen and oxygen due to the enormous pressure on the ocean bottoms.

The water rised, slowly but steadily. First it was seen as an unusual flood but the water did not recede.

First one, then ten. Then hundred, thousand, then millions of machines. While deuterium was only a part of 15 in 100 000, it amounts to 25 billion tons. The land part of earth was flooded and the water pressure sank. Finally the pressure was not enough to hold hydrogen and oxygen fluid, it began to boil and violently expand. The steady increase was now replaced by explosive growth, causing megatsunamis.

The water came and it took everything. Only people on boats survived, everything else died.

The sondes were finally complete. For ecological balance it was programmed to reconvert the stored hydrogen and oxgen in the balloons back to water. Because deuterium was rare, the water decrease was in the vicinity of meters. Finally all sondes started and left the Earth to bring the precious deuterium and tritium back to their civilization. It was really very unusual to find such a rich resource of water, it was an opportunity to be not missed. Alas, earthlings, but you had no use for the deuterium, we are very sorry.

Answer 4

This is not a complete answer but you may not need spaceships or asteroids since there is a lot of water locked up in the earth's crust

"Deep within the Earth's rocky mantle lies oceans' worth of water locked up in a type of mineral called ringwoodite, new research shows.

The results of the study will help scientists understand Earth's water cycle, and how plate tectonics moves water between the surface of the planet and interior reservoirs, researchers say."

Another link:

"After decades of searching scientists have discovered that a vast reservoir of water, enough to fill the Earth’s oceans three times over, may be trapped hundreds of miles beneath the surface, potentially transforming our understanding of how the planet was formed.

The water is locked up in a mineral called ringwoodite about 660km (400 miles) beneath the crust of the Earth, researchers say."

No idea how you could release this water (or put it back), but it is there...

Answer 5

Ignoring the logistical problems with causing a biblical flood for a moment, lets answer some of your questions from some one who did a lot of the math and look at some consequences most people don't consider because their intuition completely fails them at these scales. All numbers and calculations pulled from this analysis: http://www.holysmoke.org/cretins/fludmath.htm

1.) How much water would be required to flood Earth to this level?

~ 4.252x10^9 km^3 or more than 4 billion cubic kilometers

Note that we currently only have 1.37 x 10^9 km^3 of water on the planet.

2.) How could the water be deposited to do the least damage or alteration possible (including heating or cooling or altering Earth's rotation or axial tilt) to Earth - aside from flooding it, of course? We could simply drop the ice as a single bolide, but there would be a great deal of cratering and other damage, the avoidance of which is highly desirable.

Even if you could drop it from just 10 miles above the surface of the planet in an already liquid state, the act of dropping that much water over the course of 40 days would heat the surface of the planet to ~ 1800K or ~ 2,780F. That's just hot enough to melt steel which melts at around 2500F (since when is water hot enough to melt steel beams?). All the multi-cellular life on the planet doesn't need to worry about drowning, it will all cook and then melt. And remember, this is all from just dropping it from a relatively low height of 10 miles. I haven't the faintest idea how that much thermal energy could be safely dissipated and removed. You'd pretty much have to deposit all the water not as rain but just directly onto the surface using portals, but this is hard science and any real wormhole would likely just tear the planet apart.

3.) Given that the water must be deposited over a period of 40 days, and assuming an effectively equal rate of deposition over the entire surface of the globe during the majority of this period (at least 99% of the 40 days, with at most the initial and terminal 0.5% of this time ramping up and tailing off the rate of deposition respectively), at what rate must the water be deposited, and how would that compare to natural rainfall?

From 1 for the amount per day, dividing by the surface area of the earth with wolfram alpha, the amount of rain falling would be about 2.5 kg/m^2 per SECOND. Doing some more conversion with wolfram alpha, it looks like the highest recorded rainfall rate is ~ 0.6 kg/m^2 per second. So, the rain will be about 4 times as heavy as the heaviest anyone's ever measured.

4.) How could that amount of water be removed over a period of 220 days, again causing minimal damage or alteration to submerged land features. The maximum preparation time for this removal of the excess water is the aforementioned 150 days, though it may be less.

I have no idea how either the adding or removal could possibly be accomplished. The previous calculation assumed dropping the water from a height of 10 miles. But to remove it, you'll have to spend the energy necessary to push all of that water to escape velocity which will be many orders of magnitude greater, and because of the law about each action requiring an equal an opposite reaction, shooting all the water back into space would probably end up depositing even more thermal energy back on the planet; baking it again.

5.) What would the world look like after 150 to 370 days entirely under water? What species (animal, plant or otherwise) could survive?

Forget the time spent underwater, probably only microscopic life and perhaps some critters in the deepest part of the ocean could survive the heat.

Answer 6

Terraforming would accomplish this. Assume first that the highest mountain is really very short, and that most of the earth is within 800 feet of the ocean's surface.

A few tectonic plate movements and the water level of the whole planet is now above the highest point of land. A few more, and the land appears again. The rain is merely a consequence of increasing the water surface of the planet by 50% suddenly.

Probably the easiest way to manage this is to start off with an Earth that has only one above-water continent. We'll call in Pangaea for simplicity. We don't want the inhabitants of Pangaea to know what's really going on, though, so we're going to arrange things on the other side of the planet. The easiest method is to simply start freezing the ocean. This will expand the volume of water, and eventually you'll find that you've frozen enough to submerge Pangaea on the other side - it's only 800 feet tall at the tallest.

While your earnest crew is awaiting relief from your wrath, you might as well spend the next 150 days rearranging Pangaea into a set of continents more to your liking. Take your time, you don't want any tsunamis capsizing humanity. Carefully placed massive underground explosions along the tectonic plate lines forming Pangaea should encourage them to move. Now, while it might be tempting to move everything all at once to its final spot, for now you only need to move them enough so they can't be seen over the horizon from each other, and to start the process of movement. Let the next few thousand years of occasional earthquakes finish the job for you.

Moving them will result in some mountains forming, and new geological features, just make sure your crew is out of sight of them and that all they see is water.

Then melt the ice you created on the other side, and direct their boat (ocean currents, maybe) to the mountain you plan on landing them on.

Keeping the continents far enough they can't be seen, but close enough to travel to means that the small band and their animals can repopulate all the contents over the next few thousand years through a variety of means. If you want to speed this up, form temporary bridges, like the one between Russia and Alaska, when a few tribes are on the move. As they separate, this will become more difficult and you'll end up with a great deal of variety in species.

While tectonic actions can be quite violent, doing them carefully, slowly, underwater should have much less impact on the passengers than shooting meteorites of ice at the earth and then trying to get rid of the additional water.

Pretty sure this would come in under budget, too.