# Geography help (for world building) **URL:** \ **Category:** Factual Questions\ **Created:** [September 11, 2008, 9:00pm UTC](https://boards.straightdope.com/t/geography-help-for-world-building/463157 "2008-09-11T21:00:27Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Silver\_Tyger](https://avatars.discourse-cdn.com/v4/letter/s/fbc32d/32.png) [@Silver\_Tyger](https://boards.straightdope.com/u/Silver_Tyger)\ **Post date:** [September 11, 2008, 9:00pm UTC](https://boards.straightdope.com/t/geography-help-for-world-building/463157/1 "2008-09-11T21:00:27Z")
Hobby work, not homework. I’m world building, how ever I am not a geography guru (so please forgive me for any blatant errors or stupidities). I’m trying to severely isolate this tribe. I want them to have moved (back in pre-history) from a plain to a valley between two mountain ranges and then been closed in by something. I was thinking a canyon, but I have no idea how long it takes for canyons to form or if that’s even feasible (aren’t canyons a desert thing?). Maybe a cliff formed instead? Help me out. It’s a relatively lush area, full of forests. I had the idea that in spring time there’s a lot of temporary streams. For that matter, how small of an area can I make this? They’re hunters and occasionally farmers (no domesticated animals). I figured they can clamber up the mountains or down the canyon / cliff to hunt and fish or otherwise take long trips to gather food. ---
**Author:** ![bordelond](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bordelond/32/150_2.png) [@bordelond](https://boards.straightdope.com/u/bordelond)\ **Post date:** [September 11, 2008, 9:22pm UTC](https://boards.straightdope.com/t/geography-help-for-world-building/463157/2 "2008-09-11T21:22:33Z")
Without a lot of time to flesh out an answer, and as a guide to further discussion in this thread, I suggest having a look at the gegography of Papua New Guinea. Many tribes there were historically isolated in mountain valleys. Even tribes separated by a dozen miles (as the crow flies) spoke in languages unintelligible to one another. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [September 11, 2008, 10:13pm UTC](https://boards.straightdope.com/t/geography-help-for-world-building/463157/3 "2008-09-11T22:13:33Z")
Earthquakes and volcanoes can reshape terrain quite dramatically. ---
**Author:** ![Silver\_Tyger](https://avatars.discourse-cdn.com/v4/letter/s/fbc32d/32.png) [@Silver\_Tyger](https://boards.straightdope.com/u/Silver_Tyger)\ **Post date:** [September 11, 2008, 10:35pm UTC](https://boards.straightdope.com/t/geography-help-for-world-building/463157/4 "2008-09-11T22:35:10Z")
I forgot about Papau New Guinea. Now, can I find some maps of it… **Quartz** , do you have some specific examples? I can’t visualize how to make that work. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [September 13, 2008, 12:39pm UTC](https://boards.straightdope.com/t/geography-help-for-world-building/463157/5 "2008-09-13T12:39:07Z")
> [@Silver Tyger Girl](#): > > **Quartz** , do you have some specific examples? I can’t visualize how to make that work. For volcanoes, there are the Mexican ones - field one day, great honking volcano a year later - and then there’s the Deccan Traps. Nothing seals in a valley like having to cross a sea of lava. An earthquake might shatter a mountain, causing a huge pile of rubble to seal the valley. Or it might cause land to shift upwards or downwards. Or it might open a gap through which the sea can flow (q.v. the Mediterranean). The sea can then evaporate leaving a vast and impassable salt flat. Or you can reverse it: think of the Great Rift Valley. Huge rift walls on either side, with the habitable area in the middle, the rift stretched every so often by earthquakes. ---
**Author:** ![mack](https://avatars.discourse-cdn.com/v4/letter/m/b19c9b/32.png) [@mack](https://boards.straightdope.com/u/mack)\ **Post date:** [September 13, 2008, 1:41pm UTC](https://boards.straightdope.com/t/geography-help-for-world-building/463157/6 "2008-09-13T13:41:57Z")
What you describe sounds like a hanging valley. [http://piru.alexandria.ucsb.edu/~geog3/concept\_illus/941\_ex.jpg](http://piru.alexandria.ucsb.edu/~geog3/concept_illus/941_ex.jpg) > **[What Are the Characteristics of Erosional Landforms?](https://www.thoughtco.com/erosional-landforms-4122800)** > > View this gallery of erosional landforms, and learn more about what forms an erosional landform as well as their characteristics. You’d need a year-round supply of fresh water, a big enough area for game to be harvested and have it replenish itself, a spot to grow some tubers, perhaps. You could have a scenario where the tribe lives in the valley and the route they use to make their way up and down the cliff was suddenly destroyed by a landslide. ---
**Author:** ![Meurglys](https://avatars.discourse-cdn.com/v4/letter/m/258eb7/32.png) [@Meurglys](https://boards.straightdope.com/u/Meurglys)\ **Post date:** [September 13, 2008, 2:11pm UTC](https://boards.straightdope.com/t/geography-help-for-world-building/463157/7 "2008-09-13T14:11:25Z")
I suppose a glacier could seal off the entrance to a valley - in extreme conditions they can form reasonably quickly, but you’re still talking decades, probably, for anything substantial. If an earthquake lowered the valley entrance by several feet, it could easily become a swamp if rivers backed up and couldn’t flow as before. Depending on all sorts od other factors, I could see it becoming a bit impassable at least! Especially if man-eating crocodiles just happened to move in! 😉 ---
**Author:** ![Silver\_Tyger](https://avatars.discourse-cdn.com/v4/letter/s/fbc32d/32.png) [@Silver\_Tyger](https://boards.straightdope.com/u/Silver_Tyger)\ **Post date:** [September 13, 2008, 4:18pm UTC](https://boards.straightdope.com/t/geography-help-for-world-building/463157/8 "2008-09-13T16:18:58Z")
> [@mack](#): > > What you describe sounds like a hanging valley. > > [http://piru.alexandria.ucsb.edu/~geog3/concept\_illus/941\_ex.jpg](http://piru.alexandria.ucsb.edu/~geog3/concept_illus/941_ex.jpg) > > [http://geology.about.com/library/bl/images/blhangingvalley.htm](http://geology.about.com/library/bl/images/blhangingvalley.htm) > > You’d need a year-round supply of fresh water, a big enough area for game to be harvested and have it replenish itself, a spot to grow some tubers, perhaps. Whoa. Those look COOL. Tubers are actually against their religion (seriously - they won’t eat any plant that they have to kill to harvest), but that’s the basic concept. Thanks everybody! ---
**Author:** ![Darryl\_Lict](https://avatars.discourse-cdn.com/v4/letter/d/7cd45c/32.png) [@Darryl\_Lict](https://boards.straightdope.com/u/Darryl_Lict)\ **Post date:** [September 13, 2008, 5:02pm UTC](https://boards.straightdope.com/t/geography-help-for-world-building/463157/9 "2008-09-13T17:02:41Z")
[Ngorongoro Crater](http://en.wikipedia.org/wiki/Ngorongoro_Crater) is a volcano caldera with pretty tall and steep walls that is a self-contained ecosystem. It’s damn spectacular, although probably not what you are looking for.