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I am adding a new area to my game (a free-roam RPG): the ashlands. I put a small volcano (only about 15ft wide and long, and about 20ft tall. Really, more of a lava vent) on the western edge and have the wind coming in from the west (so that the ash is being blown all over the actual ashlands. Then I realized it: there was nothing stopping the ash from covering the rest of the island. So, toward the eastern edge, I put some tall hills (about 30ft high, the height of the ash cloud coming out of the volcano).

Question: realistically, would his be enough to catch at least most of the ash, or would higher hills be required?

(If an answer needs a man-made approach...)

Note that the society is on medieval tech, some magic, and is on an island that is a mix between cold, forest, and tagia. Caves, mines, and workers are plentiful, but wizards and of the sort are far and few between. Magic is cast from rare crystals found in the mines. Force fields and things can be used.

EDIT: the volcano is of a circular shape with a thin, flat edge on the tip rim, with a steep slope leading to it's. Deep inside (down about 50 ft) is a pool of magma (the volcano is not very active, maybe a small eruption every few hundred years).

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  • $\begingroup$ Maybe the people in this land are only a couple of millimeters tall. $\endgroup$ – Willk Jun 27 '18 at 20:45
  • $\begingroup$ @HDE226868 ok, I edited the question. Labeled the "mountains" as hills and gave a description to the volcano. $\endgroup$ – The Mattbat999 Jun 27 '18 at 20:46
  • $\begingroup$ @Willk that could possibly make matters worse. Trying to build a defense against a 15ft volcano (in which to them would be massive)plus anything that is normal sized to us would also be able to wipe out a town in seconds. A rat could come through and kill everyone!. $\endgroup$ – The Mattbat999 Jun 27 '18 at 20:53
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    $\begingroup$ You seem to be seeking a rain shadow effect, but ash is not water vapor - it enters the atmosphere differently, and falls out of the atmosphere differently. See volcanoes.usgs.gov/vhp/ash_info.html for great information on ash behavior and plume prediction. $\endgroup$ – user535733 Jun 27 '18 at 20:56
  • $\begingroup$ Do you mean thousands of feet? $\endgroup$ – Rafael Jun 27 '18 at 23:22
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You might take a look at pictures of the eruption going on on Hawaii right now. It's about as non-energetic as an eruption on land can be, and it's got 100' lava fountains and volcanic smoke of several different kinds climbing to thousands of feet. A 30 foot mountain (This is high? Am I missing something? Is this Lilliput?) won't stop much of anything.

You ought to start, actually, by deciding what kind of volcano you're talking about. Broadly, they come in two flavors: Stratovolcanoes and and Shield volcanoes (there's a third kind, but I don't think that kind makes a difference for you. See this article for some details.

A stratovolcano is the kind everyone thinks of: cone-shaped, erupts with a towering plume of ash and rock and steam, frequently goes BOOM! (Mt. St. Helens and all the Cascade volcanoes, Vesuvius, Fuji, Krakatoa, Yellowstone.) They tend to form when an ocean plate is being subducted. They get real big and are really bad neighbors.

A shield volcano is what you have on Hawaii (actually, it's what Hawaii is). They rarely go boom, don't form pointy mountains with craters at the top, and are more likely to ooze lava than to blow it out the top. They get even bigger and are really bad neighbors.

So: Your 10' volcano might be the very beginning of a new volcano forming, but it won't stay 10' high for very long if it's a stratovolcano. Paricutin started just that way -- but it didn't stay small for long.

If it's a new shield volcano, it might not grow tall quickly, since the lava from shield volcanoes tends to be very liquid and flow away, but it will mess up all the land it can get to. (See this map of the current Kilauea eruption.)

I think you're out of luck if you want your volcano to be realistic.

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  • $\begingroup$ Ouch. Drew up ash textures and actually put this in beofre reading. Oh well. It had slipped my mind what is going on in Hawaii. Thanks for the good information though! $\endgroup$ – The Mattbat999 Jun 27 '18 at 21:00
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You have a serious sizing problem. As one answer put it:

Is this Lilliput?

A 30 ft hill is unlikely to stop a cow from walking up it, forget a ash plume that reaches thousands of feet into the sky, that hill trying to stop the ash is like an ant trying to stop a truck. Your 20 ft volcano isn't very realistic either, Volcanoes grow (kinda), every time they erupt, the ash and lava coat its sides and become new stone and soil over time, making the volcano larger, how it does so varies with the type of volcano, I could go into a whole lot of detail about how this works but I'm lazy so you get the crappy "volcanoes kinda grow" explanation.

In the end if you want to stop those ash plumes, you need to have an absolutely gigantic mountain range, and even then, it will only limit the ash. A much more realistic solution is to simply have the wind blow it in a different direction. You said you still wanted the ash blown over the ashlands so reposition your volcano to suit, your volcano can be in the west with the wind blowing it over the ashlands and then the ocean.

An alternative to what you're proposing is to cut out the ash spewing volcano, swap it with a much more gentle one that may not even be erupting and then make the entire Ashlands a major geothermal zone. Still highly exotic, but not nearly so science defying.

On another note, a good reference for inspiration for what you're trying to do is the game Elder Scrolls 3: Morrowind. The game is set on an island the size of Sicily which is dominated by an active supervolcano, which has a massive effect on island life

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  • $\begingroup$ I played Morrowind. Drew some inspiration from the whole idea of part of the island is covered in ash. Didn't want half the game world to be dominated by a mountain. $\endgroup$ – The Mattbat999 Jun 28 '18 at 1:54
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Your ashlands are actually the caldara of a super volcano (eg Yellow Stone)

Yellow Stone is still active. Yours is not.

This is because your open magma pit allows the magma to not build up pressure. The bubbling magma is the source of your ash clouds.

If the ash plume is heavy, volcanic lightning should be expected.

Hills aren't going to keep the ash in, you are going to need mountains. These mountains are actually the edge of the caldera after its last eruption.

You might want the winds from the west to be extremely cold so that the ash is cooled down quickly and not rise as high as the mountains.

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Anything that wont stop a bird wont stop weather. You could have winds coming from the opposite direction.

If the mountains were a huge mountain range they could divert some of the plume. If this is an active volcano though these can put ash into the stratosphere and beyond.

An island though doesnt seem big enough though. High ocean winds from the opposite direction might be plausible.

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