How can the terrain of a large area change abruptly in a short period of time?

Question

By "short period of time", I'm referring to the timeframe of weeks to months (not days or hours). For example: at the start of one day the land is flat, but after a few weeks or months there is a mountain there instead. Another example: the land is at first joined together, but after a few weeks or months it is now separate islands.

Ideally I'd like to avoid "A Wizard Did It" type explanations (which is what I currently have), instead having something plausible for how mass changing of terrain of landscapes could occur.

Answer 1

You could imagine a few things:

• water rising could separate a continent into islands; you'd explain it by

  • extreme tidal increase, possibly explained by a planet closing in
  • huge quantities of ice melting, possibly from increased heat

• intense tectonic activity (combined volcanism and earthquakes) has the ability to create mountains (volcans), strips of ground (solidified lava), rifts (between tectonic plates)...

• tsunami and other extreme natural events can cause massive changes in not so solid ground (swamps, dunes...)

• meteor showers (if for example the planet is going through an asteroid belt) can cause on impact sites major changes as well as trigger the other things described above.

I'm sure there are more explanations to be found ;-)

Answer 2

Some changes would be hard some would be easy. Many broad change categories could have many equally plausible reasons. To go over your specific examples (and a few others):

• Plain to Mountain: Is very easy: A prime real world example is the Mexican volcano of 1943 - Paricutin; it started as a crack in a farmer's corn field and within a year was almost 400 meters tall. So not quite a matter of weeks but speeding that up a bit would still be totally plausible. Mountain range is somewhat less likely but you could easily have multiple volcanoes erupting in close proximity (which is not actually implausible).
• Hilly area to Separate Islands: Permanent/long term is possible with an earthquake - or even a landslide - adjusting the path of a river to form a lake around them and thereby separating them. Short term options include a landslide as well or a favourite: the beaver damn that gives out upstream.
• Peninsula to Island(s): Earthquake is a great explanation, distant tsunami good, even a strong storm could take out a thin section of the peninsula thereby forming an island just off the coast.

As you can see from those examples, reasons are fairly easy to find for most changes. Fast plausible reasons may be slightly harder to find but still definitely can find them. Tectonic activity is generally good for high speed as are meteorite strikes and storms. The trick to maintaining believability is knowing what follows what. So you could have, for example: a rogue comet hits the planet, thereby melting polar icecaps and readjusting coast lines.

Answer 3

Your landscape is microscopic.

https://www.michaeloliveristudio.com/fullscreen-page/comp-iwmnzsof/ae780a63-dfd0-46b1-8be3-19dee9700a04/15/%3Fi%3D15%26p%3DmainPage%26s%3Dstyle-iwnyacvc

On this scale, things change fast. Windblown dust becomes a mountain. Fungal activity melts everything into a field of spores, which then desiccate into a cracked wasteland. Then rain washes it all away. Crystals form and push their way up into towering spires. The footprint of a passing squirrel opens deep gullies.

Answer 4

Breaking down:

Relativity easy, as gravity always drags things down. Erosion is a force without bounds and wind can really do a number on things.

Storms and tides: for a country next to the sea, the sea itself gives and takes. Storms with very high tides can change the landscape in days. Never mind if you give it weeks. What was a few hills next to the sea becomes a few island. Worse if you already start with a river delta. See the great flood of 1953.

Earth quakes: are a big changer of scenery in a lot of places. Almost every thing can be moved this way and building need a special way of building to be able to cope with it. See Lisbon Earthquake of 1755.

Glaciers: could be seen as a subset of water, and normally move to slow, but they do make a big impact on the country side. Maybe a runaway glacier?

Epic Floods: If a natural barrier brakes and a low land area get flooded you can change fast from a hilly country to islands. For a big one see: Zanclean flood.

Building up:

Building is harder then breaking down, and tends to lake longer. We humans can do a lot in little time.

Humans: On this planet we change things the way we think things are better. Sometimes correctly, sometimes wrongly.

Sand Stormes: If you live near a sand desert or dunes, with strong winds that sand will not stay in place. Not sure if is fast enough for your needs.

Answer 5

Another example (perhaps better for the OP) is the sudden draining of Lake Bonneville (http://en.wikipedia.org/wiki/Lake_Bonneville ), the remains of which are the present day Great Salt Lake & smaller lakes in the area. It lost the top 300 ft (100 m) or so in much less than a year. So one month you have lakefront property, then suddenly you have mud flats.

You could even design a reverse system if you play with geography a bit. On your continental divide is a Lake Missoula analog, which drains east because the westward drainage is blocked by ice. On the west is a closed, dry basin like the present-day Salt Lake basin. The ice tongue ruptures, and within weeks your dry plain is covered by hundreds of feet of water.

Answer 6

Pertinent questions are: do you want the changes to be a total surprise, and do you want the area to be relatively small (such as between two towns 20 miles apart)?

In either case, you're in trouble. There are means both to add and subtract altitude, but they both involve a lot of generalized energy which is hard to miss if applied over a short time.

Mountains can be created in two ways: volcanic eruption and thrust faulting. Volcanic eruptions can provide fairly rapid mountain building, but this is accompanied by earthquakes and major emissions of ash and/or nasty fumes. Thrust faulting (such as created the Rocky mountains) produces even worse earthquakes than volcanos do.

At the other end, floods can make major changes in landscapes, the most massive event known in the US being the creation of the Channeled Scablands. This produces quite distinctive landscape features, and the limited existence of such features is very strong evidence that the Biblical Deluge did not happen. But again, you're talking about really massive incidents, and such things would be noticed locally.

More in line with what I think you're after, rivers do change course spontaneously, and this can occur without too much fuss. Oxbows can short-circuit in a matter of days, producing new islands. At fairly large intervals (say, a thousand years) you can get a really major change in river course as a river "falls off" its delta. As a matter of fact, the Mississippi river is overdue, and only massive efforts by the Corps of Engineers have prevented the Atchafalaya River from leaving New Orleans cut off from the river.

Answer 7

meteors, coronal mass ejection at a planet with no atmoshpere, massive floods (for example look up channeled scablands, WA(created in moments by a flash flood)) massive landslides. overheating of the core causing softer crust and faster convection in the mantle accelerating tectonic movement incredibly. also hotspots create land somewhat quickly, like hawaii and the aleutian islands