Snarky_Kong’s misconception, and yours, is that the snowball earth theory means that all the water on Earth froze. It does not state this, only the top few meters of the sea are thought to have frozen. Even if the sun was switched off, the Earth’s internal heat would prevent the seas from totally freezing for hundred of millions of years. The overall sea level can only rise by 4.5 meters if only 50 meters of it freeze. That’s the volume you have to play building blocks with, not the total volume of the oceans. There is not enough water because most of it is still in liquid form.
It’s a dynamic system. To expand on my points about glaciation and precipitation, glaciation occurs when snowfall exceeds ablation (melting and sublimation). In a completely ice-locked world, precipitation would be very low. The sun’s energy cannot sublimate as much ice as it can evaporate warm water. It’s ability to clear snow from terrain features that rise above the level of the glaciers would be undiminished. The low lying land might be completely glaciated, but it’s not possible to transport enough ice to bury all the mountains. As I said above, the Earth might look a bit like a dirty snowball, with mountain ridges peeking clear of the ice.
Try putting some numbers to your argument. From this document (PDF), Deep sea, the portion of the ocean deeper than 200 meters, covers 85 percent of seawater. That, in turn, is 71% of the surface of the Earth. So dropping Sea level by 200 meters only increases the percentage of land from 29% to 40%. The water you’ve removed gives you somewhere between 61 million and 72 million cubic kilometers of water, or 66 to 78 million cubic kilometers of ice. That’s enough to bury the increased amount of land by between 320 and 380 meters of ice, or 1000 to 1200 feet.
The Snowball Earth theory also is based on the fact that glacial striations from the right time frame (~700 MYA) were observed on rocks presumed to be at low altitude and at low latitudes. I.e., there were glaciers in subtropical areas. But that is based on accurate readings of plate tectonics and of orogenic elevations – not the easiest thing to confirm that far back.
In any case, we’re quite well aware that large portions of Siberia and Beringia were unglaciated even at the height of the Pleistocene Ice Ages, Cold enough that you got LOx on your bagels, yeah, but not iced over.
Also remember that at that time (the Varangian glaciation is the traditional term, though I see Wikipedia is reporting a renaming binge), 95% of the world’s land mass was united in a Pangaea-like supercontinent called Rodinia that stretched from pole to pole. We have no idea what conditions were like in the water hemisphere.
There are terrain features much higher than 380 metres. Glaciation does not occur on steep slopes, the weight of snow builds up and eventually much of it is removed in an avalanche. Here is a picture of a glacier in Antarctica. Notice how it covers the valley between the mountains. If you want to cover a mountain in ice, you have to do it from the bottom up. In that picture, notice that there is a lot of bare rock in view. That’s because precipitation is very low in Antarctica, which gives the sun more time to sublimate exposed snow. That’s what I’d expect to see on a snowball Earth.
You are correct that exposure of land isn’t the primary reason it’s not possible to cover all the land in ice, but in the post you quoted I also talk about glaciation and precipitation. It’s a dynamic weather system, and lego-brick arguments aren’t very useful. As more water freezes the water cycle is reduced.
There is no misconception. I just answered a different question. The answer to “is there enough water on Earth to cover the planet in ice” is yes. That is what I answered. The answer to “if the Earth cooled, would ice cover the planet?” is a different question that I did not address.
Snowball Earth would presumably be like Snowball Antarctica - some areas glaciated, some areas snowbound, some areas ice on liquid water, and some areas of somewhat exposed rock. (Like the tops of mountains - scatterings of snow and exposed rock.) Eventually, the seas freeze over everywhere and the process pretty much “freezes in place”. After a long time, theory says, volcanic activity creates greenhouse gas levels that tip the heat balance back to temperate, since there is no life actively turning that CO2 to O2.
Is there enough water to do this? Heck yeah… read the numbers posted.
I suspect instead of the typical recent ice ages, where the climate settled at heavy snowfall and mile-thick glaciers down to Wyoming and the Alps, as snowball earth cooled the snow line would keep moving south, creating more distributed, less thick snow buildup - but still deep enough to turn to ice in any flat locale.
As mentioned earlier, since the plates move around and geology has done a lot of work since then, it’s hard to be precise. However, one other piece of evidence is glacier-relocated boulders at very tropical latitudes. Also, any active volcanoes probably at least temporarily create clear spots. Since the only humidity would come from sublimation or volcanic activity evaporation, the precipitation levels probably dropped drastically once the oceans completely froze (if they did) so the snow/ice distribution at that point, less glacial movement, is what the planet ended up like.
Fair enough. Unfortunately, some of the posters in this thread, including the OP, don’t understand that. You answered a different question to the one originally asked, which is specifically about the snowball earth theory. Yes, technically there is enough water, but there is no natural mechanism for distributing it in such a way to cover all the landmasses. In much the same way, it would be possible to cover the landmasses in paint if you applied a thin enough coating.
I can’t find any good elevation data to give an answer of how much land the ice would cover if it just swelled from the ocean, so I gave the lazy answer. If the Earth was cooled enough you wouldn’t have 800’ of ice over the whole planet, it’d be more like 1,000’ of ice (about MSL) over 90% of the planet, or something like that.
But it’s not neccesary to cover all land masses in a uniform sheet of ice to get a “snowball earth”. As has been said, at this point there were no land plants, and no animals at all. To choke off most life on Earth, you don’t need to glaciate the land, you just need sea ice at the equator.
Of course in our modern world most of the water in the atmosphere comes from evaporation from the oceans. Freeze over the oceans and no more evaporation, only sublimation. Although there’s no saying that you couldn’t get summer ice melts–it’s not that glaciers and permanent sea ice never melt, it’s that they never melt completely.
But even so, your point stands–if almost all of the oceans are covered with ice almost all the time, you’re going to have very dry air, which means very little snowfall on the continents, which means you could have places which are below freezing all year round, yet are ice free because the ice sublimates faster than it is deposited.
And of course, there’s no saying that the planet was below freezing all year. Plenty of glaciated areas are well above freezing for long periods in the summer, it’s just that whatever ice melts during the summer is replaced by an equal or greater amount of snow in the winter, if it doesn’t then that area isn’t glaciated.
So the “snowball earth” scenario doesn’t require that every square kilometer of land was covered by ice. Just that there were continental glaciers in the tropics, which would have meant tropical sea ice. If vast areas of land were cold dry deserts that’s not incompatible with the snowball earth theory.
