Wikipedia:Reference desk/Archives/Science/2019 January 26

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January 26

What was the last continent with a 360° rain shadow shield?

Mountainous on every perimeter. Sagittarian Milky Way (talk) 02:47, 26 January 2019 (UTC)

Has there ever been one? ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:21, 26 January 2019 (UTC)

If South America hits Africa and separates before the Andes erode enough then it could happen in the future at least. Sagittarian Milky Way (talk) 15:25, 26 January 2019 (UTC)

Aren't they moving away from each other? ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:13, 26 January 2019 (UTC)

Yes, for many millions of years more but after that the Atlantic might close. Sagittarian Milky Way (talk) 23:45, 26 January 2019 (UTC)

Or it might not. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:38, 27 January 2019 (UTC)

Then SMW should have started that sentence with if. —Tamfang (talk) 22:22, 31 January 2019 (UTC)

If memory serves, the (completely fictional) Maple-White Land was a plateau that was sort of isolated from weather on all sides:

"Surely...the rain must find its way down somehow. There are bound to be water-channels in the rocks. The rain must go somewhere.... The only drawback is that we have conclusively proved by ocular demonstration that there are no water channels down the rocks." From Chapter 9, available online at Project Gutenberg.

Naturally, such geographical and hydrological isolation would "invariably ... lead to some assertion as to extinct or prehistoric life," ergo, iguanodons, and such.

Nimur (talk) 05:19, 26 January 2019 (UTC)

Or at least Shangri-La. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:03, 26 January 2019 (UTC)

Vaalbara. Count Iblis (talk) 23:08, 26 January 2019 (UTC)

Vaalbara was a long time ago, but the Messinian salinity crisis was prior to 5.33 million years ago. The Mediterranean Sea was in this situation then. Graeme Bartlett (talk) 04:45, 27 January 2019 (UTC)

That's not exactly the same thing, the Messinian Mediterranean was a endorheic basin, which is just a drainage basin with no outlet to the sea. Invariably, these basins become saltier, as there's no way for incoming water to carry dissolved salts into the ocean, where they can be diluted. Endorheic basins can receive plenty of rain, but the salinity goes up regardless because of the lack of outlet. What the OP is asking about is if there has ever been a landmass which was entirely within a rain shadow. A rain shadow requires tall mountains; Endorheic basins can be surrounded by mountains but don't have to be. They can also be depressions that are simply lower than the surrounding land. --Jayron32 21:15, 28 January 2019 (UTC)

This question seems too vague to answer clearly -- how big a break counts, how big a continent is needed, how many mountains inside the feature or extra land outside the feature would be considered to spoil it. I mean, the Great Basin seems like it might qualify, or various parts of Asia that are not genuinely endorheic but certainly have a lot of mountains running every which way. Wnt (talk) 14:40, 29 January 2019 (UTC)

Indeed, the Tarim Basin isn't a continent (although it is very big), but it is surrounded by mountains and has a very low rainfall. Mikenorton (talk) 17:01, 29 January 2019 (UTC)