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How do I create an absolutely isolated series of mountain alpine valleys cutoff from the world in a geologically realistic way?

I am trying to create an absolutely isolated series of alpine mountain valleys in a fantasy world with forests home to tribes that cannot travel and have been cutoff from the world. My problem is that the most isolated valleys in Bhutan that I have found appear to be rocky. Alpine valleys require a river or stream to pass through them generally or be in rainfall range. Thus the gorge of those rivers or river valley will allow passage out. Most passes through Bhutan appear to follow gorges, rivers, or the lay of the land.

I am presently researching Tibet and Bhutan for inspiration yet not sure I quiet understand how to place this realistically in my world yet. Even Tibet was populated by humans and passable.

The idea I am coming upon is that a river and streams pass through successive alpine valleys forming small gorges between the valleys before going subterranean once again. Thus travel within this small 'land' of valleys is possible. The valley is blocked north by massive 7,000 to 20,0000ft mountains with a pass that is also impassable. The only high elevation pass south beyond the lower range of mountains is blocked by a colder global climate age thus cutting the valleys off from the world. The area is still biodiverse as it has not always been cutoff from the world.

My other option is that an earthquake creates a pass out of the valley but that would seem more supernatural and perhaps less geologically realistic.

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    $\begingroup$ a pass that is also impassable That's a contradiction. A pass is, by definition, passable. You can make a pass tricky to navigate, long and winding, through difficult terrain, but if no one can get through it, it's not a pass and it ought to traversable regularly e.g. by traders, not just by near-suicidal explorers. $\endgroup$ – StephenG Oct 25 '17 at 1:06
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    $\begingroup$ There are passes in history that were not passable 6 months out of a year I suppose "former pass" would have been more accurate that clears into a pass with climate change. $\endgroup$ – Seanchaí Oct 25 '17 at 1:07
  • $\begingroup$ Granted, but you need to be clear about the fact that if it's impassable completely now (even if it was in the past) then it's not a pass. So if e.g. it's now permanently blocked by a landslide or something, it's not a pass even if it was before. If it's just weather blocked for long periods that's fine. $\endgroup$ – StephenG Oct 25 '17 at 1:16
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    $\begingroup$ You might consider that you don't have to have the mountains be the only barrier. You could also have the area around the mountains be dangerous (insufficient water, hostile isolationist tribes, angry fauna, ghost legends) to increase the isolation of your highland types. $\endgroup$ – akaioi Oct 25 '17 at 15:24
  • $\begingroup$ please clarify: are the valleys isolated against each other or is it possible to travel from one to the next, just not anywhere else? $\endgroup$ – Henning M. Oct 25 '17 at 20:56
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As always, New Guinea to the Rescue!

Turns out there are some isolated tribes on that island who have been isolated for a long, long time, 10-20 thousand years, in fact! Here's a reference: http://www.sciencemag.org/news/2017/09/islanders-new-guinea-are-some-most-diverse-people-world-here-s-why (Note the link between isolation and diversity; makes sense, right?)

Update: I'm emphasizing this genetic diversity point because the different highland types have been isolated from each other as well as the lowland guys on the same island, to hint that such a highland region could work out even if attached to a continent.

Their climate looks kind of like what you want, as the elevation mitigates the tropical nature of it. Check it out...

enter image description here

More details here: https://en.wikipedia.org/wiki/New_Guinea_Highlands#Central_Range_sub-alpine_grasslands but the money quote is:

Above 3,000 metres elevation, the high mountain forest yields to remote sub-alpine habitats including alpine meadows, conifer forest, tree-fern (Cyathea) grasslands, bogs, and shrubby heaths of Rhododendron, Vaccinium, Coprosma, Rapanea, and Saurauia all quite different from the tropical rain forest that covers most of New Guinea.

The alpine habitat above 4,000 metres consists of compact rosette and cushion herbs, such as Ranunculus, Potentilla, Gentiana, and Epilobium, grasses (Poa and Deschampsia), bryophytes, and lichens.[ 2 ]

It even has the word "alpine" in it! ;D I can't promise you edelweiss, but work with me here.

Okay I know PNG is an island, but it's a really big island. Does that count?

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Use a very large mesa that has a concave profile, that is, the surrounding steep slopes are the highest points and the inside is like a bowl.

A mesa is usually made of sedimentary rocks, so it can have Karst characteristics, that is large cave systems underneath as well as internal valleys that have been formed by water. This would mean that you could have valleys with rivers that get drained through impassable subterranean cave rivers that appear as waterfalls at the sides of the mesa.

Climate-wise check out akaioi answer.

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  • $\begingroup$ So like the Grand Mesa in Colorado though possibly a bit larger which rises 6000 feet but concave with the walls of the mesa rising like mountains? Could massive mountains be placed around this massive mesa which would make it further isolated? en.wikipedia.org/wiki/Grand_Mesa $\endgroup$ – Seanchaí Oct 25 '17 at 6:56
  • $\begingroup$ I doubt that. Massive mountains mean that continental plates are colliding which makes sedimentary layers stick out at all kinds of steep angles and generally be waved and broken. A mesa on the other hand would need flat and undisturbed sedimentary layers. Volcanos might help though, or a general volcanic active area like the Danakil Depression, though those usually need active plate boundaries as well. $\endgroup$ – Khris Oct 25 '17 at 7:04
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Put them on an island.

Iceland is pretty isolated because it is in the middle of the North Atlantic.

iceland map

Iceland has the alpine terrain you are looking for.

icelandic alpine meadow http://www.onegeology.org/extra/kids/earthprocesses/alpineglaciers.html

icelandic meadow https://www.123rf.com/photo_33927927_warm-summer-days-in-iceland-green-meadows-and-streams-of-meltwater.html

Could people on Iceland make boats and leave? Yes. It is a bit of a haul - 1200 km to Scotland. It is closer to Greenland. Here is what the east coast of Greenland looks like on Google maps.

greenland coast

So: your people are on a remote island, with the closest mainland presenting only forbidding glaciers. Bonus for using alpine Iceland clone: Iceland has volcanoes and geysers! Nothing better for a cold winter than a natural hot tub.


One more thing to keep your people on their island: sea monsters galore.

iceland and sea monsters https://upload.wikimedia.org/wikipedia/commons/e/ea/Carta_Marina.jpeg

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  • $\begingroup$ It spoils my story to put them on an island. $\endgroup$ – Seanchaí Oct 25 '17 at 1:06
  • $\begingroup$ A peninsula then. $\endgroup$ – Willk Oct 25 '17 at 1:52
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    $\begingroup$ @Will ... you. I like you. $\endgroup$ – akaioi Oct 25 '17 at 2:09
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Your people would have to have arrived at their location somehow.

Perhaps, in ages past, a pass existed which lead to or over the top of one of the mountains. Some intrepid explorers discovered a way into these isolated valleys, but returning was impossible or very difficult (I would say that they would have had to be able to leave in order to tell others about their wondrous find, and to bring them back).

Once the area became settled, a natural change of some sort blocked the already difficult passage, or perhaps the settlers wanted to isolate themselves from a tumultuous world and blocked the access themselves.

The river going subterranean is a good idea. If the descendants of the original settlers are unaware of the existence of life outside their valleys, they might consign the bodies of the dead, or those considered cursed to this path into the underworld.

Mountains are created when tectonic plates squish together and lift the land up. Mountains are also created due to volcanic activity. Either of these geologic events would work to isolate your society, or in combination.

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  • $\begingroup$ The Kingdom of Guge in Western Tibet was extremely isolated, but is not the environment I want. It is across a cold desert on the Tibetan plateau. Despite the very creative answers here, I wonder if I am overthinking it. Surely in a mostly medieval world access to a place nestled in mountains like the Tibetan Plateau and by geographic random 'luck' isolated from the world by high mountains would be virtually unreachable. Perhaps a random explorer or party could get to them, but in a colder age it could be completely cutoff especially in the colder months. $\endgroup$ – Seanchaí Oct 25 '17 at 8:47
  • $\begingroup$ In some of these areas like Tibet we are talking hundreds of miles with not a living soul. Those are huge distances. Areas of Alaska were untouched for hundreds of years. I think having a completely isolated people in a cold age is possible, and once the cold age warms the possible passes are 'passable' once again. $\endgroup$ – Seanchaí Oct 25 '17 at 8:53

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