Originally posted by humyI would assume it would have to be independently verified, vetted and such. The question then would become how did Earth double that pressure in the last couple billion years.
I find it just a bit surprising that they could actually estimate that from the rocks.
Originally posted by twhiteheadFrom a probability standpoint it is overwhelmingly more likely that if lava flows into salty
It is based on evidence that the lava entered sea water. There are salty lakes at high altitudes, so I think it needs to be confirmed with more locations before considering it proven.
The atmosphere has changed considerably with the great oxygenation with the arrival of plants being one of the best known. It is not surprising that the pressure would change. A more interesting question is what keeps it in balance today?
Originally posted by googlefudgeI disagree. Most major mountain ranges in the world have salt lakes or former salt lakes (salt flats). They are considerably more common than you appear to realise.
From a probability standpoint it is overwhelmingly more likely that if lava flows into salty
water it will be into the sea at or near sea level.
Originally posted by twhiteheadWe are doing a differential here between shorelines of salt lakes and shorelines of the
I disagree. Most major mountain ranges in the world have salt lakes or former salt lakes (salt flats). They are considerably more common than you appear to realise.
What the continents were like at the time being discussed, I do not know. Do you?
Originally posted by googlefudgeI disagree. And certainly not on such a scale that the possibility that it was a salt lake can be ignored.
We are doing a differential here between shorelines of salt lakes and shorelines of the
I don't care how many salt lakes there are... Sea front is going to massively dominate.
Originally posted by humyhttps://en.wikipedia.org/wiki/List_of_countries_by_length_of_coastline
I would imagine more like ~10,000 to one or more judging from the map of modern Earth and extrapolating a very rough bold-figure estimate from that.
Originally posted by twhiteheadI was wrong, looking over the data I could find, papers on the topic, the figures for
I disagree. And certainly not on such a scale that the possibility that it was a salt lake can be ignored.
[b]it's still going to dominate over salt lakes.
Ten to one? Hundred to one?
Particularly as a lot of rainfall over land is caused by plant life [specifically trees] which pump large amounts of water into the air... and there was no lan ...[text shortened]... t rain.
This all might favour salt lakes. Most salt lakes seem to be in low rainfall areas.[/b]
Originally posted by twhiteheadI did not know that.
Ignoring for now the coastline length paradox, the whole world has something like 1.1 to 1.6 million kilometres of coastline. Great Salt Lake, Utah, is over 100 kilometres long with a very irregular coast, but lets assume it was dead straight, that is already 200 kilometres of coastline. That's already better than 10,000 to one with just one lake.
Originally posted by twhiteheadIf the rock they tested was cooled in a lake below sea level then their estimate of atmospheric pressure at sea level may be slightly too low and it may have been actually slightly below 0.5 atm at sea level. 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.
If the earth were a single continent then it would have considerably less coast line.
The Caspian sea is over 1000 km long and below sea level.
Originally posted by humyThen why did they take the trouble to search for lava that was supposedly 'at sea level'? If you are right about Mt Everest, then they could simply test all lava finds and if most of them are below 1 atms they can be pretty sure the atmospheric pressure was lower than it is today.
They estimated that the atmospheric pressure when the lava cooled was ~0.5 atm thus, if it cooled in a salt water lake and if, say, the pressure at sea level was actually ~2 atm back then, the salt water lake would presumably had to be at an unrealistic high altitude and higher than mount Everest.
Thinking this way makes me think even if it was a salt water la ...[text shortened]... ffect their estimate of atmospheric pressure if the rock was cooled in a lake of equal altitude?