Early Earth atmosphere was about ~0.5 atms at sea level.

Originally posted by humy
But, given the very high error of measurement, I assume such a lake would be unlikely to have been so below sea level as to massively effect their measurement.

I wasn't thinking that the 'below sea level' would throw off the calculations, I just thought it was worth mentioning that many large salt lakes are actually below sea level or close to sea level, so although my argument demonstrated that salt lakes should not be ignored, one shouldn't assume salt lakes are all high altitude.

Originally posted by humy
How many very high altitude salt water lakes have lava flowing into them?
-Compare that with the number of places where lava flows into the sea.
What is the ratio of volume of lava flowing into vary high altitude salt water lake to volume of lava flowing into sea?
I think THAT is a more critical number than the length of coastlines.

It depends on the configuration of the continent. Large moving continents like the Americas have a string of mountains at very high altitude with salt flats (which can turn into salt lake or are former salt lakes) around them. Many of the volcanoes in the Americas are surrounded by high altitude salt. The other side of the pacific the 'ring of fire' is mostly island chains and thus not much room for salt lakes.
Africa's rift valley has a lot of volcanoes and salt lakes, but the lakes tend to be close to sea level as it is a split rather than a compression.

Originally posted by twhitehead
Then why did they take the trouble to search for lava that was supposedly 'at sea level'?

-just to do everything they can to minimize the risk of their estimate being too way-off the correct mark.