[OokieWonderslug (OP)]

I read on geology sites that during the cretaceous period sea levels were as much as 800ft higher than today.

But other sites say that if both ice caps melted, Greenland and all the glaciers melted, the sea level would only rise about 250ft.

So where did the water go? Why can't we get another 800ft rise? That would be so cool. Where can we find enough water to deepen the oceans the other 550ft?

[Geezer]

Ookie,

I think this will get a better response in the Geology section. I'll move it there now.

[imatfaal]

Why can't we get another 800ft rise? That would be so cool. Where can we find enough water to deepen the oceans the other 550ft?

Wiping out the vast majority of human lives and habitation - cool?  Mad Trivia question that I have no idea of the answer to: which is the largest capital city that would be unaffected?

[Joe L. Ogan]

Is it possible that the original calculation was wrong?  Thanks for comments. Joe L. Ogan

[Evie]

This mainly has to do with the shape of the ocean basins then versus now. There were more mid-ocean ridges and shallower sea beds over the whole planet than now.

Also, there are a lot of different projections for what sea level was in the past. I've seen numbers that say sea level was more like 550 feet higher in the Cretaceous than now.

Along these same lines, we are currently in a trend of deepening ocean basins. This will somewhat counteract the water gained from melting glaciers, etc., though not as quickly if the earth continues to warm at the current rate.

Evie

[LeeE]

Why can't we get another 800ft rise? That would be so cool.

It would also be very wet.

[frethack]

The estimates that Ive seen are around 150-200m, but this number is subject to variation of course.  There were no land masses at the poles, and therefore no icecaps.  This could contribute more than 100m of sea level rise (dont remember the exact figure), and since the earth was up to 7C warmer than today on average, thermal expansion of the surface ocean would have been pretty extreme.  My guess would be somewhere in the tens of meters. 

Ill see if I can find more.