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I apologise as this will be vague - but I am building a world set in the future (late 21st century) and looking at realistic ways for rapid desertification of huge land areas, say America, and civilisations reduced to small towns and roaming bandit packs, as well as one 'mega-city' controlled by AI and heavily governed.

Basically the world economy and governments have collapsed. I'm already planning a mass 'exodus' - a huge percentage of humanity leaving the Earth for a new planet - but I want a world where those 'left behind' are left to survive. I was envisioning a world like the one in Mad Max Fury Road, resources are scarce and much is desert-land.

I was thinking of a nuclear war, though I read this could lead to a Nuclear Winter.. Basically between the 'exodus' and where the story starts, I want it to be in the not-too-distant future so definitely under 100 years later. I don't want the land to be too irradiated - people should still be able to survive, even if struggling - but I was wondering if global warming could create such a post-apocalyptic world?

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  • $\begingroup$ Small economic problem: mega-city =/= no gov but heavy investment in security, bandit pack = heavily governed $\endgroup$
    – SparK
    Jul 18, 2017 at 18:52
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    $\begingroup$ If you removed Australians' technology, that might be enough in-and-of-itself. $\endgroup$
    – Nick T
    Jul 18, 2017 at 19:24
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    $\begingroup$ Do you want there to be sand all over the place? You can kill off all the plants pretty quickly, but that's not going to magically form sand. There will be a lot of dirt, rocks, and decaying buildings, roads, etc. $\endgroup$
    – JPhi1618
    Jul 18, 2017 at 20:38
  • $\begingroup$ A nuclear winter would kill vast tracts of agricultural land and wilderness too. Effectively, instant desert. Nuclear winters can be caused by small nuclear wars, say, India versus Pakistan. You need a global World War III to get one. $\endgroup$
    – a4android
    Jul 19, 2017 at 1:25
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    $\begingroup$ My understanding is that the last time Yellowstone erupted, it covered North American with dust to a depth of 2 metres. If the Canary Islands collapse (they are unstable and will collapse eventually), they will create a tsunami one mile high that will hit the east coast of North America covering it will salt water. There are no shortage of disasters that have occurred and will occur again and could occur in the next 80 years. $\endgroup$ Jul 19, 2017 at 8:46

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This did happen in the US. It was very bad. It was the Dustbowl.

enter image description here from http://www.npr.org/2013/09/10/220725737/dust-bowl-worries-swirl-up-as-shelterbelt-buckles

Thousands of square miles turned to blowing moonscapes. I have read that this was caused by a combination of poor farming practices and drought. I am still not clear on how it was undone.

But the question: could it happen again? The farmers who carried out the poor farming practices would never have done those things if they had known what would happen. They wanted to live on the land and farm it indefinitely. Could we make mistakes like that again - farming practices that exhaust and deplete the land, and then let it blow away?

We could if we did not care about tomorrow. In that context I was thinking about Bain Capital and the new way to make money. These financiers buy established companies and then run them into the ground, selling off all assets and the pension fund. The company goes bankrupt and the workers are left with no job and no pension. The rich get richer. They destroy a thing used for making in the interest of short term gain.

from http://www.rollingstone.com/politics/news/greed-and-debt-the-true-story-of-mitt-romney-and-bain-capital-20120829

Instead of building new companies from the ground up, we took out massive bank loans and used them to acquire existing firms, liquidating every asset in sight and leaving the target companies holding the note.

What if that happened to farmlands? You could invoke some new alien cash crop in this context as the catalyst for this. The government stops paying attention for one of many plausible reasons, and industrial farms are purchased by financiers. They run the land into the ground with farming practices that are in the short term profitable but in the long term devastating. The Dustbowl comes back, but this time to stay.

Upvote for this question for making me think of this terrifyingly plausible scenario.

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    $\begingroup$ It ended when the rains came back, but the land never really recovered. $\endgroup$
    – Separatrix
    Jul 19, 2017 at 8:55
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    $\begingroup$ @Separatrix - As a resident of Oklahoma, while I'm not a farmer myself, I do know we still produce a whole lot of grain and beef. So I'm curious what makes you say that. $\endgroup$
    – T.E.D.
    Jul 19, 2017 at 15:44
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    $\begingroup$ The overexploitation is already happening worldwide. Alot of it in South American and Asian tropical areas, where extensive cultivation of Soy and Palm oil for western consumers is a main driver causing extensive losses of rainforest. In these areas, a sustainable farming regime is not possible due to missing nutritious soil; It is only the material from burned-down jungle that allows for a few harvests. $\endgroup$ Jul 20, 2017 at 11:16
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    $\begingroup$ The situation could very easily occur if the great exodus happened BEFORE the new dust bowl. Mankind is gradually moving to the new planet, so the government cares less about earth and investors who already reside on the new planet exploit the farmland for short term gains. The dust bowl occurs, the moving rate rises exponentially and the poor are left behind. $\endgroup$
    – LAP
    Jul 20, 2017 at 11:17
  • $\begingroup$ It was undone by a reversal of poor farming practices, including planting trees around fields to shelter the fields from the winds, IIRC. $\endgroup$
    – jfa
    Jul 20, 2017 at 15:20
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For reference, I think the salt flats in Mad Max Fury Road was meant to be a dried up sea bed.


Realistic

Global warming: This will likely really happen. Yes, it is capable of creating the post apocalyptic environment you describe. And is, in my opinion, the most believable. This will shift plant-survivable habitats towards the poles, leaving what is currently tropical lands as desert.

Things about global warming that could kill plants:

  • Plants die directly from heat/dehydration
  • Plants die from fire caused by lack of water caused by heat
  • Global warming causes change in winds that mean rain no longer visits certain areas

Deforestation: If you cut down all the trees, they aren't coming back, because there's no naturally occurring seed for them. Particularly with plants, removing large portions of their neighbours will hugely reduce their reproduction rates and, after a certain point, could remove all traces of particular species within a few generations.


It is possible that these two could combine to cause sudden and rapid disintegration of plants over a wide area. If we look at the IPCC reports, we can find a predicted temperature rise of about 3°C degrees by the end of the century. This may not sound like much, but the last ice age was only 4.5 degrees different to what it is now. So congratulations, your post apocalyptic world is fairly likely in the next hundred years.

For the purposes of dramatisation, I would suggest a period of little noticeable change, and then a sudden period where lots of things change. This is ideal for your story as there will be a sudden societal shift (eg governments fall, wars etc) when this change happens. Yes, this is one of the plausible things that happens, though I haven't found a good source on it.

Although not mentioned in any of the parts of the IPCC report read that I, a typical thing spouted by global warming activists is the snowball/runaway effect. In short: decreased size of polar ice caps means less reflective area means higher temperature means decreased size of polar ice caps. Or: reduced number of trees has reduced number of seedlings has reduced number of trees for the next generation. This makes good story material.

There are supportive feedback loops as well though, trees are known to produce more oxygen in higher CO2 environments, so it isn't all doom and gloom. I trust the guys at IPCC to know what they're talking about, so if you want actual facts go read their extremely comprehensive reports.


Fictional:

Disease: A specialised bacteria wipes out everything with cell walls (aka all plants).

Move the Earth closer to the sun: Nukes, asteroid impact, villainous plans involving really big rockets....

Radioactive Fallout that decays rapidly: Humans live in bunkers for a few years, so they survive, but not much outside does.

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    $\begingroup$ Thanks! So with the global warming scenario, is there a timescale for say, most of America (or at least huge swathes of it) to become desertified? If wind is affected, would it stop winds? I.e. I was thinking perhaps there would be desert sandstorms which could arise. Nuclear war / fallout would fit with the collapse in governance, wars breaking out etc. My concerns with that are: would radiation decay rapidly? (i.e. water still (mostly) drinkable, able to walk outside)... couldn't it cause a Nuclear Winter? That can last several decades or more I thought... Some food for thought! $\endgroup$
    – Ionatia
    Jul 18, 2017 at 18:04
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    $\begingroup$ Also, just as an FYI take a look at what the bikini atolls look like theguardian.com/world/2017/jul/15/…, or for that matter hiroshima and nagasaki theguardian.com/artanddesign/gallery/2015/aug/06/… A nuclear war won't necessarily have the the long term effect you might think it would. At this point we just don't know what it would do on a large scale. So make it up if you want. $\endgroup$ Jul 18, 2017 at 18:49
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    $\begingroup$ Global warming does not mean desertification. Global warming means the planet warms - it does not mean all the water is gone. Yes, some areas will become more desert-like - longer droughts - but it also means other areas will become lush and fertile and still others could become swamps with too much water. To create a desert one needs to eliminate the clouds that could rain on it. A 'nuclear winter' could make it cold enough that very little water evaporates thus reducing rainfall and creating vast deserts around the world. Not to mention that with the lack of sunlight, plants will fail. $\endgroup$ Jul 18, 2017 at 20:10
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    $\begingroup$ For what it's worth; none of the things you mentioned as moving the Earth will do so. It's way too heavy for that, you'd blow off the entire upper layer (you know; the part we live on) long before you'd meaningfully change the orbit. $\endgroup$
    – Erik
    Jul 19, 2017 at 7:45
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    $\begingroup$ @Ionatia : The worst case scenario for global warming leads to the vast majority of America being desertified by the end of the 21st century. Wind will be affected, but it won't be stopped - tornadoes and hurricanes will become more common and stronger. Sea levels will rise substantially (between 1 and 10m), so the megacity will be Bos-wash minus the bits near the coast. $\endgroup$ Jul 19, 2017 at 8:56
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Radiation can have this effect, but the timelines might be a bit longer than you wanted.

The key thing that prevents the Earth from achieving this degree of desertification is ultimately life...life struggles to keep it's environment intact so it may continue to grow/live. Large plant life (trees in particular) resist erosion with their roots holding together soil and retaining water. Bushes and shrubs protect their earth from the sun and wind as well. Even grasses band together to hold the soil they need in place. You remove life, you remove the greatest resister of erosion.

This leaves the nuclear option valid, though a bit challenging as you have to nuke a huge segment of the earth. Nuclear winter is very much a possibility, but it'd reverse quickly...it's just an extension of the timelines (10-20 years) as much as anything.

Introduce another possibility...the earth gets fried from space. Currently, the Earth is protected by it's magnetic field from the majority of what we'd call "Space weather". Space is messy...there is radiation of all sorts flying in all directions, with the source of life on Earth (our sun) being a major source. If for any reason this magnetic field was overwhelmed or ceased to exist, then Earth would be fried pretty quickly...plant life on earth with shrivel quickly as it's bombarded with radiation originating from space.

So my answer - remove the Earths Magnetic field. There are a few potentials...

1) Age. A magnetic field requires a molten core to exist...if Earths core was to transition to solid, we would lose our magnetic protection. I'm not sure how this would onset (I think it's a slow drawn out process)

2) Magnetic reversal - It appears that Earths magnetic field is subject to a major reversal event where north and south switch sides on a multi-century scale. No clue how the reversal process would play out, but if this reversal saw the collapse of the magnetic field for a short period of time (a year?), Earth would heavily fry.

3) Space event. You get a CME (coronal mass ejection) of a certain size coming straight for earth or a supernova event nearby (by nearby I still mean several light years), you could have an event that completely overwhelms our magnetic field and fry the earth...this would be a much shorter event, but due to it coming at us at the speed of light, we wouldn't be able to easily detect it.

4) Evil Megalomaniac. Drill to the center of earth and drop nukes til something happens? Dunno.

A little theoretical, but "space weather or interference with Earths magnetic field" would be my favorite choice for what you are going for here. Knowing this event was happening would provide plenty of time and reason for your exodus to take place.

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    $\begingroup$ Based on the timescale of geomagnetic reversals, "a year" doesn't sound long at all. Life survives it just fine. If you were to remove the geomagnetic field totally, it would take millions of years for the atmosphere to erode to a significant degree. $\endgroup$
    – Nick T
    Jul 18, 2017 at 19:12
  • $\begingroup$ @Nick T - You are right...but the atmosphere 'eroding' wasn't part of the answer and I wasn't implying it would degrade in my answer here. It's vulnerability to 'space weather' or a CME from our own sun during this period thats the risk to life here $\endgroup$
    – Twelfth
    Jul 19, 2017 at 18:31
  • $\begingroup$ Day to day, so long as there is sufficient mass between you and the sun, you're fairly safe from high-energy ionizing radiation and the solar wind. In most places, there's usually about 10 tons of mass per square meter above you. Over geologic time periods, the magnetic field is important as it keeps that mass there. $\endgroup$
    – Nick T
    Jul 19, 2017 at 19:01
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We are already well on our way to desertifying much of the world. Over the past 70 years, the U.S. has lost 30% of its arable land due to erosion. Dust storms have hit major agricultural states in the U.S., such as this one that hit Denver in 2012: http://vogeltalksrving.com/wp-content/uploads/2012/06/dust-storm-over-denver-th-e-worldgeography.com_.jpg

Why is this happening? Our current industrial scale farming practices are destroying the biology in the soil. These microbes are essential to the dirt's ability to hold water, to aggregate (clump up so that it doesn't erode) and to solubilize nutrients so that plants can uptake them.

Because we are monocropping (growing only one crop at a time, like corn, or soybeans) and not rotating crops (because our government subsidizes bad farming practices), we are inviting huge infestations of pests. This, in turn, requires greater and greater toxic soups of pesticides to 'control' pest populations (shocker: these chemicals are only about 25% effective) as the pests become resistant to the latest batch of pesticides. The fallacy of this approach is that for every one target organism that is killed via this method, we are killing a thousand or more beneficial organisms, and accelerating this downward spiral.

We are introducing so many toxins into the environment, in such vast quantities, that we have not only destroyed the mycorrhizae in our soils but even entire functional groups of bacteria. If you were a soil scientist, you would understand how impossible and scary that is.

Without microbes, plants can't efficiently uptake nutrients, so we have to pour more and more fertilizers on to maintain the same level of fertility. The excess fertilizer gets washed into the watershed, causing eutrophication of our streams, rivers and lakes (the Great Lakes are dead/dying because of this) and creates a 7800 square mile (and growing) seasonal dead zone in the Gulf of Mexico, devastating shrimping and fishing grounds (That's bigger than Connecticut and Rhode Island combined).

This, combined with global warming/climate change, means that our soils are less and less resilient, and less and less able to sustain life of any kind, let alone feed the world, as it is the microbes in the soil that allow plants to offset abiotic stress like high and low temperatures, drought, and salinity.

To top it all off, we are running out of phosphorus, the key limiting nutrient for plant growth. Sometime between 2028 and 2040, the US will be out of its domestic deposits of rock phosphate and will be entirely dependant on foreign sources for its food security. 75% of the worlds phosphate deposits are controlled by one country: Morroco. The bulk of the rest is in China, which has already banned the export of this vital resource.

If you are interested in researching this scenario for your story, I highly recommend you read this book: https://www.amazon.com/dp/B0032JTFGQ/ref=dp-kindle-redirect?_encoding=UTF8&btkr=1

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    $\begingroup$ Great (and depressing) Answer! I was about to answer in a similar way using the information from this ted-talk video Welcome to Worldbuilders! +1 $\endgroup$ Jul 19, 2017 at 14:21
  • $\begingroup$ Source for the 30% of agricultural land lost to desertification please? $\endgroup$ Jul 19, 2017 at 15:17
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One from left-field: The new technology developed for the creation of the spaceship used in the planet exodus caused an accident resulting in a supermassive magnesium fire, that couldn't be put out until such time as it had sucked most of the moisture out of the air & seas to provide its oxygen.

Edit: The left-behinds would have suffocated, but for the solar-powered OxyGen™ machines that had been built (also for the exodus) that generate oxygen from hydrogen. These were put into use once the fire finally died down.

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  • $\begingroup$ But then the left-behinds would suffocate. $\endgroup$
    – Chris H
    Jul 19, 2017 at 13:32
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You have two options when it comes to fiction. (A) Try to explain why your world is the way it is. (B) Ignore why your world is the way it is. You'd be surprised how often (b) is chosen because (a), when you come to the nuts and bolts of the matter, usually leads to proving the context of the story is utter hogwash (did I say "hogwash?" I meant "fiction." "utter fiction.") So, assuming we really want (a)...

1) I'm going to start my stream-of-conciousness thought experiment with an axiom and hope to break it. "There is nothing Man can do in the short term to create a habitable long-term desert." Deserts require really just one thing: a lack of water. Heat certainly helps, but water is the key. Where there is water, there is life. Can Man remove the water from an reasonably large area (say, 10,000 square miles, 100-miles on a side). No. Heck no. That's because the next rain storm is less than a year away.

2) Planetary events can create a desert in a reasonably short period. The earth does this through geological events. Something shifts, which causes the weather to shift with it. Lake Bonnevile is an excellent example of desertification in this way. Check it out. Geological events can happen quickly --- but the consequences still take time. Lake Bonneville's first drop took a year and is estimated to have moved 1,000 cubic MILES of water. (Water, water, water...) Nevertheless, the desertification of Idaho and Utah still required centuries. (However, at least we have a plausible issue... how do you drain an aquifer? Probably can't. Rain.)

So, is there a way to combine these two that might be plausible? Let's look at the movie, The Core. Man creates a tool that causes artificial earthquakes that happens to stop the spin of the planet's core. Bummer! What if such a tool created an earthquake that caused a substantial portion of the U.S. ground to rise, say, half a mile? Short period of time, serious desert almost everywhere in the U.S. Has consequences, something has to balance out the shift in weight or the planet will wobble. But it's a possibility.

3) Astronomical events can easily desertify an area. One solar flare in the right place at the right time and... except for water. It may burn the ground to a crisp, but unless it takes a huge chunk of ocean with it, the rain comes and life returns fairly quickly.

Now, having said all this, there is one thing you can research: why are there resevoirs that have been around for decades that have no appreciable plant life around them? That has a lot to do with having the right mix of soil and bacteria (because seeds get blown in on the wind, dropped by birds, etc.). Kill the bacteria... hmmm... that might be a good premise and it's something Man could do relatively quickly. "We were just trying to remove a particularly pestiferous weed, you know, DNA-specific poison and all that. We didn't expect to kill all the bacteria. Sheesh! Give us a break!"

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Those same weapons that would likely bring a 'Nuclear Winter' would equally decimate our Ozone layer. Even once the skies cleared, what little remaining alive and above ground will rapidly roast in the extreme ultraviolet radiation in sunlight. When combined with a natural peak of our 11 year cycle of solar activity, the soil would be rendered sterile, most land based life would perish, and the result would make your 'Mad Max' scenario look pretty good by comparison. - Just my $0.02

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    $\begingroup$ I think you are heavily exaggerating the effects of UV radiation. Most plant life is readily resistant to it (newscientist.com/article/…) Forests and other green spaces wouldn't see UV hit the soil (plants absorb prior)...Unless there is something I'm missing, I don't think this will come close to a desertification trend. $\endgroup$
    – Twelfth
    Jul 18, 2017 at 18:14
  • $\begingroup$ @Twelfth: UV is commonly used for sterilizing all manner of things, and after a hefty nuclear winter (sub freezing darkness for a few decades) there won't be much forest or green space . We banned CFCs in products to protect the Ozone so that Earth doesn't end up looking a lot like Mars $\endgroup$
    – Joe
    Jul 18, 2017 at 18:18
  • $\begingroup$ @Joe: The critical factor in UV sterilization is intensity. As a parallel, lots of things are sterilized by heat, but most of us aren't much bothered by sitting in a 100F hot tub, or even a 180F sauna. Likewise, Earth wouldn't look like Mars even if the ozone layer disappeared completely, since solar UV is a very minor factor in what makes Mars Mars-like. A thin atmosphere and miniscule amounts of H2O and O2 have a lot more effect. $\endgroup$
    – jamesqf
    Jul 19, 2017 at 4:32
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I saw plenty of high-tech or catastrophic reasons, as well as the "show, don't tell" trope. If you are interested in a more depressive/dystopic/passive setting, and not so much in a action-apocalypse-catastrophe big bang event, then read on.

But you can do a simple thing: just extrapolate slightly from today, and let stuff fall out of kilter ever so slowly. Most of the things you want (deserted land areas, big concentrated megalopolis) are already well on their way right now, at least locally.

Let yourself be inspired from real ghost towns. Google for the reasons they actually existed. Nudge your reality just so it gets ever more attractive for people to run for the big city. Maybe automation gets so good that crops just don't need much human intervention anymore. And by the time we notice, all real farmers are naturally dead/very old, and something comes up which the machines cannot handle.

Or we get something like the Dustbowl mentioned above, some natural weather phenomenon which takes a few more years. We do have very visible (to the average human) climate change already in many parts of the world, just let that accelerate slightly and by the end of 20xx you can be pretty bad off.

At as many points as possible, make sure that it is clear that humankind could have stopped it if they just had stopped being selfish/greedy for once, but that there simply never was that single point in time where it was obvious what was happening. Just a long, slippery slope leading to nowhere.

All of this should lead to an excellent, depressing background to your story, and should be very believable.

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There's a book that describes an event like this. A virus attacks all grass like species. If all grasses died it would probably cause lots of desertification. In the books plot the primary effects of the virus explored was the lack of food. Rice, wheat and other grass food crops died. You might could explain the virus problem from the different angle of desertification. I enjoyed reading it by the way.

https://en.wikipedia.org/wiki/The_Death_of_Grass

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    $\begingroup$ Interesting idea... haven't read the link yet but I'm curious if the concept mentions anything about a rise of Ferns (which filled the same Niche of Grass before Grass evolved). Also, since the OP discusses possible planet evacuation, are there measures that could prevent the plague from being brought to other worlds (or mutating to other plants/living things)? A virus capable of wiping out what is quite possibly the most populous macro-organism on our planet is going to move pretty quick (and evolve quickly more infections will mean it reproduces more, which opens it up to more mutants). $\endgroup$
    – hszmv
    Jul 20, 2017 at 12:29
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A post "impact winter" landscape might suit your needs. If >20km diameter chunk of iron impacted in the Sahara desert, it would throw up enough debris to block out the suns radiation for long enough to kill pretty much all plant life on earth. Once the debris settled, you'd be left with a global desert-scape. I think that would fit with your timeframe.

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Yellowstone Super-Volcano

It could potentially be pretty devastating to the American Bread-Basket, as prevailing winds would carry ash and detritus west to east. Large ash clouds could potentially suffocate existing foliage and crops. Depending on how long the volcano is erupting (a single powerful eruption is likely to have smaller micro eruptions for a few years after the event. The New Krakatoa island (the old one was blown apart in that eruption) is still rising at a rate of meters per year, which suggests ongoing volcanic activity.

Even a partial eruption (more likely with Yellowstone) would still cause some devastating effects and global cooling. Krakatoa was followed by the three of the globally coldest winters for that time period. Keep in mind that said eruption was orders of magnitude smaller than the last Yellowstone eruption.

Most of America is small towns in the region closest to the disaster, and denser on the coastal regions. By late 21st century, a merger of the NYC and Baltimore-Washington Metro area is quite possible, assuming the installation of a rapid transit system such as proposed high speed rail lines already in concept stages (Maryland has been working with Japanese companies for a rapid transit that would reduce the commute between Baltimore and D.C. from 40 to 15 minutes).

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  • $\begingroup$ I felt compelled to downvote this answer as it seems to just focus on how things could happen to the US, instead of globally. $\endgroup$
    – Puppy
    Jul 19, 2017 at 20:32
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    $\begingroup$ @Puppy OP specifically mentions a large Land Mass "Like America" so yes, so Yellowstone is something to consider and possible megacities that could happen in the aftermath and am well aware of local transit politics in a specific region of the country that is a likely candidate. No doubt this would have probable similar affects in Canada and Mexico, though I'm less certain about that. I did make sure he was asking for some kind of American perspective, as I haven't read enough to know probable outcomes beyond the global cooling period. $\endgroup$
    – hszmv
    Jul 20, 2017 at 12:25
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If you want something that "just happens" (i.e., not something humans did to themselves), I'd suggest moving the Earth closer to the sun by some kind of celestial catastrophe. Perhaps a rogue planet flies through the system and passes close enough to pull Earth inward. Or maybe a mega-asteroid slams into the moon, moves the moon and somehow pulls Earth along.

Or perhaps the Sun itself enlarges by some unspecified process. Maybe a rogue gas giant crashes into the sun, enlarging it. Or the sun begins the long slow process of expanding into a red giant.

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