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I'm working on a fantasy/sci-fi story set on Earth but in the far future. Hundreds of millions of years from now, after the rise and fall of many civilisations, the world has gone back to a medieval-like society, but relics can be found from ages past that are capable of amazing things: hovercrafts, laser weapons etc.

I'd like to design the map for this world, but I am unaware of what would affect the continents other than continental drift. I would like some idea of what the future continents or super continents would look like.

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  • $\begingroup$ I changed your question title to focus it a bit more... your previous title was broad and seemed to duplicate existing, but the specific question you had in your text appeared to be a unique question, and a good one, IMHO, so I wanted to make sure it got more recognition. Please check my edits to make sure I didn't mess something up about your intent. $\endgroup$ – SRM Feb 5 '17 at 3:51
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    $\begingroup$ Rising sea level due to climate changes... $\endgroup$ – user6760 Feb 5 '17 at 5:56
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    $\begingroup$ @LeviHinton Forget that about hovercrafts, laser weapons etc. if you want to stick to realism. The simple fact is: The more complex a device, the shorter the lifespan because it needs constant supervision. Some devices may last centuries, but do not expect modern electronic to survive even 20 years of neglect. $\endgroup$ – Thorsten S. Feb 5 '17 at 11:07
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    $\begingroup$ Hundreds of millions of years? If there are humans over this time, do not forget their potential for destruction (atom bomb, for example). $\endgroup$ – Mijago Feb 5 '17 at 12:12
  • $\begingroup$ In regards to the technology much of it will be in ruin and what isn't is rare and will be used or maintained by the people living in the time the story is set. Which will be just under one billion years. Humans are still around to help create relatable characters but there will be sub-humans. People who evolved to live in subterranean environments and descendants from a civilization that used gene therapy, manipulation etc $\endgroup$ – Levi Hinton Feb 5 '17 at 14:05
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Forces of creation

  • Volcanism. Volcanoes and similar tectonic activity can produce surprisingly large landforms - take a look at Japan and Hawaii. This is most common in ocean subduction zones but it may be possible to build more land this way above the sea.
  • Convergent plate movement. You can get some pretty large mountain ranges by smushing together existing chunks of land - take, for example, the Tibetan Plateau, home to the world's tallest mountain. This is related to continental drift, as are many ideas presented here, but it is a complicated phenomenon that will produce many results.
  • Matter from space. This not likely, and it's really only happened on a large scale once, but a planetary-sized event could send a whole lotta stuff down. This also counts as destructive.
  • Living things. Life has completely changed the Earth's atmosphere (also building up massive piles of iron sediment in the process), created massive deposits underground, massive deposits aboveground, and changed the color of the planet as seen from space (hint: it's green now). It is reasonable to believe similar changes may occur in the future.

Forces of destruction

  • Weathering and erosion. Wind, water, plants, and other phenomena can break down the land, often in dramatic ways. This has given us the Grand Canyon, among other things.
  • Subduction. The continents don't just drift! Material can be re-absorbed over time, as it has been for billions of years.
  • Glaciers. Ice ages are unpredictable and poorly understood. If one were to occur, we could see glaciers carving up the terrain.

Neutral

  • Rising sea levels. If human emissions continue, the climate will continue to change. The poles will shrink, and the sea will slowly overcome the land. There are some pretty good simulators for this.
  • Sinking sea levels. If the Earth cools, water will be trapped in ice, lowering the sea level.
  • Transform plate movement. This can shift the locations of land masses greatly over time.
  • Divergent plate movement. Playing on the "continents are complicated" idea, it's entirely possible for continents to split apart, just as they can push together or move around. This is why the Atlantic Ocean is getting larger, and why the African continent will soon split in two.

Many of these forces are complex, and you don't have to consider them all. Consider one of the most commonly suggested supercontinents, and play with it:
| Pangaea Ultima | Amasia | Novopangaea |

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    $\begingroup$ Thank you both. As for the edit. This is my first question and made from a phone. Edits are welcome. $\endgroup$ – Levi Hinton Feb 5 '17 at 4:35
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    $\begingroup$ Not to mention all the lakes made deliberately or by accident by certain specie of two legged mammals. $\endgroup$ – Maciej Piechotka Feb 6 '17 at 4:43
  • $\begingroup$ @MaciejPiechotka We're not the only ones who do that, and we certainly weren't the first :) $\endgroup$ – Luaan Feb 22 '17 at 12:47
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Even hundreds of millions of years in the future the Earth might still be in the Quaternary Ice Age which only started 2.6 million years ago. Currently we are in an intergalacial period. Anthropogenic warming will delay the onset of the next glacial phase for, possibly, another one hundred thousand years. Most likely this will only be a brief hiatus for the Quaternary Ice Age.

It is useful to look at the history of the Ice Ages to understand what might happen hundreds of millions of years in the future with respect to glaciation.

The Earth is passing through an ice age known as the quaternary glaciation, and is presently in the Holocene interglacial period. This period would normally be expected to end in about 25,000 years.[34] However, the increased rate of carbon dioxide release into the atmosphere by humans may delay the onset of the next glacial period until at least 50,000–130,000 years from now. On the other hand, a global warming period of finite duration (based on the assumption that fossil fuel use will cease by the year 2200) will probably only impact the glacial period for about 5,000 years. Thus, a brief period of global warming induced through a few centuries worth of greenhouse gas emission would only have a limited impact in the long term.

Please note this source differs in its estimate of the impact of global warming from this answer. That estimate was based on Curt Stager's book Deep Future: The Next 100,00 Years of Life Earth (2011). Who said predicting the future was easy?

A considerable number of factors affecting the future of the Earth can be discovered here. This to summarize concisely, but here are some of the salient factors.

Human Influence

Humans play a key role in the biosphere, with the large human population dominating many of Earth's ecosystems.3 This has resulted in a widespread, ongoing mass extinction of other species during the present geological epoch, now known as the Holocene extinction. The large-scale loss of species caused by human influence since the 1950s has been called a biotic crisis, with an estimated 10% of the total species lost as of 2007.[6] At current rates, about 30% of species are at risk of extinction in the next hundred years.[15] The Holocene extinction event is the result of habitat destruction, the widespread distribution of invasive species, hunting, and climate change.[16][17] In the present day, human activity has had a significant impact on the surface of the planet. More than a third of the land surface has been modified by human actions, and humans use about 20% of global primary production.[4] The concentration of carbon dioxide in the atmosphere has increased by close to 30% since the start of the Industrial Revolution.

Random Events

These include asteroid or comet collisions, nearby supernovas, and a gamma-ray burster pointing at the solar system. It might include unforeseen technological events causing massive environmental degradation, the rearrangement of the Earth's surface, and the extinction of the human species All of which are unpredictable and, obviously, do not follow any long-term trends which is a useful for any reasonable futurological exercise.

Geodynamics

The following geological events will occur in the relative near fture compared to your hundreds of megayears timescale. But hey give an indication of what a dynamic geological system can produce over sufficiently long timescales.

Tectonics-based events will continue to occur well into the future and the surface will be steadily reshaped by tectonic uplift, extrusions, and erosion. Mount Vesuvius can be expected to erupt about 40 times over the next 1,000 years. During the same period, about five to seven earthquakes of magnitude 8 or greater should occur along the San Andreas Fault, while about 50 magnitude 9 events may be expected worldwide. Mauna Loa should experience about 200 eruptions over the next 1,000 years, and the Old Faithful Geyser will likely cease to operate. The Niagara Falls will continue to retreat upstream, reaching Buffalo in about 30,000–50,000 years.[9]

In 10,000 years, the post-glacial rebound of the Baltic Sea will have reduced the depth by about 90 m (300 ft). The Hudson Bay will decrease in depth by 100 m over the same period.[30] After 100,000 years, the island of Hawaii will have shifted about 9 km (5.6 mi) to the northwest. The planet may be entering another glacial period by this time.

Continental Drift

This is driven a combination of subduction and the presence of a hydrosphere (a fancy way of says Earth has seas and oceans on its surface). The arrangement of land masses progressively undergoes change. The longer the timescale the more massive this changes will be.

At present, the continents of North and South America are moving westward from Africa and Europe. Researchers have produced several scenarios about how this will continue in the future.[46] These geodynamic models can be distinguished by the subduction flux, whereby the oceanic crust moves under a continent. In the introversion model, the younger, interior, Atlantic ocean becomes preferentially subducted and the current migration of North and South America is reversed. In the extroversion model, the older, exterior, Pacific ocean remains preferentially subducted and North and South America migrate toward eastern Asia.[47][48]

As the understanding of geodynamics improves, these models will be subject to revision. In 2008, for example, a computer simulation was used to predict that a reorganization of the mantle convection will occur over the next 100 million years, causing a supercontinent composed of Africa, Eurasia, Australia, Antarctica and South America to form around Antarctica.

This is an image of Pangea Ultima the predicted future super-continent

The above image of Pangea Ultima a predicted future super-continent.

50 million years from now the Mediterranean sea may vanish and the collision between Europe and Africa will create a long mountain range extending to the current location of the Persian Gulf. Australia will merge with Indonesia, and Baja California will slide northward along the coast. New subduction zones may appear off the eastern coast of North and South America, and mountain chains will form along those coastlines. To the south, the migration of Antarctica to the north will cause all of its ice sheets to melt. This, along with the melting of the Greenland ice sheets, will raise the average ocean level by 90 m (300 ft). The inland flooding of the continents will result in climate changes.[46]

As this scenario continues, by 100 million years from the present the continental spreading will have reached its maximum extent and the continents will then begin to coalesce. In 250 million years, North America will collide with Africa while South America will wrap around the southern tip of Africa. The result will be the formation of a new supercontinent (sometimes called Pangaea Ultima), with the Pacific Ocean stretching across half the planet. The continent of Antarctica will reverse direction and return to the South Pole, building up a new ice cap.

This based on one of three models for the formation of a future super-continent (in this case the introversion model).

The subduction flux model led to this possible future supercontinent

a computer simulation was used to predict that a reorganization of the mantle convection will occur over the next 100 million years, causing a supercontinent composed of Africa, Eurasia, Australia, Antarctica and South America to form around Antarctica.

While the extroversion model of continental drift gave this future.

predicted that the continents of North and South America would continue to advance across the Pacific Ocean, pivoting about Siberia until they begin to merge with Asia. He dubbed the resulting supercontinent, Amasia.[52][53] Later, in the 1990s, Roy Livermore calculated a similar scenario. He predicted that Antarctica would start to migrate northward, and east Africa and Madagascar would move across the Indian Ocean to collide with Asia.[54]

In an extroversion model, the closure of the Pacific Ocean would be complete in about 350 million years.[55] This marks the completion of the current supercontinent cycle, wherein the continents split apart and then rejoin each other about every 400–500 million years.[56] Once the supercontinent is built, plate tectonics may enter a period of inactivity as the rate of subduction drops by an order of magnitude. This period of stability could cause an increase in the mantle temperature at the rate of 30–100 °C (54–180 °F) every 100 million years, which is the minimum lifetime of past supercontinents. As a consequence, volcanic activity may increase

The formation of a supercontinent will be main event that will sahpe the face of the Earth. Since there are three models of continental drift each predicting their own version of a future supercontinent the only recommendation that can be made to the OP is choose the one that suits your story best and go with it.

The general changes to planet Earth over next few hundreds of millions of years which impact on life on the planet and which will influence factors concerning its cartography. many of which need to be taken into account with respect to their impact on any human inhabitants.

Over time intervals of hundreds of millions of years, random celestial events pose a global risk to the biosphere, which can result in mass extinctions. These include impacts by comets or asteroids with diameters of 5–10 km (3.1–6.2 mi) or more, and the possibility of a massive stellar explosion, called a supernova, within a 100-light-year radius of the Sun, called a Near-Earth supernova. Other large-scale geological events are more predictable. If the long-term effects of global warming are disregarded, Milankovitch theory predicts that the planet will continue to undergo glacial periods at least until the Quaternary glaciation comes to an end. These periods are caused by eccentricity, axial tilt, and precession of the Earth's orbit.[10] As part of the ongoing supercontinent cycle, plate tectonics will probably result in a supercontinent in 250–350 million years.

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    $\begingroup$ Isn’t this basically a “link-only answer”? $\endgroup$ – JDługosz Feb 5 '17 at 8:37
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    $\begingroup$ @JDługosz Close enough. Caught with too little time, having other matters drag me away, and the link to the future of Earth is information heavy. I had decided, prior to be being nudged by yourself, to do an edit and flesh things out. $\endgroup$ – a4android Feb 5 '17 at 9:48
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The future of Earth is most likely to continue to be shaped by natural forces, especially if civilizations rise and fall over the course of time. Even far future predictions like "The Future is Wild" only go about 200 mega years into the future, after that there is enough randomness to cause predictions to simply fail.

Even a mere 5 million years into the future, if humanity survives at all it will probably have evolved into post-post-post humanity (our species can be reliably traced back to about 5 million years ago, and hominids have undergone a tremendous amount of change during that time). Depending on your views of the "Singularity" and post humanity, it is quite plausible in story terms to simply posit that super intelligent AI's or post humans reshaped the Earth to their liking, having the ability to discover principles in physics, chemistry and biology that allowed them to do this easily and (relatively) cheaply. Given the enormous amount of energy that even a small earthquake or volcano can release, clearly the post humans have access to the ability to control huge amounts of energy and apply it in a controlled and non destructive fashion.

What this would look like long afterwards is almost impossible to visualize. Any post human civilization would probably want to maximize the ability to use all the 195 Petawatts of solar energy that strikes the Earth, so plants and animals may have been replaced long ago with some sort of artificial biosphere (technosphere) dedicated to harvesting and processing solar energy. Spidery silicon "plants" might make up most of the ground coverage on Earth in this time, and of course after millions of years, the operating instructions would have randomized and "mutated" into things far different than their long ago creators imagined. Rather than travel, post humans may have become sessile, and developed a web of connections between each other and other "beings" in their technosphere, leaving a web of artificial nerve fibres joining nodes all across the landscape.

Post humans would recognize that the Earth might become uninhabitable in 500 million to one billion years in the future as the Sun gradually increases its output, so the sky might be filled with some sort of obscurant to reflect excess solar energy back into space, or there are billions of tiny mirrors in orbit, or the planet itself has been moved into a larger orbit to reduce the solar energy and keep the planet cool. If the system is still working to adjust the orbit of Earth, the night sky has a spectacular show as asteroids periodically make close passes by the Earth to exchange momentum and push the Earth farther out from the Sun. The Moon may or may not be affected by this, depending on the desires of the post humans who built the system.

If the post humans adjusted the orbit of the Earth, it is also quite possible they moved other planets around, so the night sky may well be unrecognizable. If they used Star Lifting to mine matter from the Sun rather than adjust the orbit of the Earth, there may be Uranus sized artificial gas giants in the sky, originally "built" to house the hydrogen "mined" from the now cooler Sun.

And of course the most spectacular object filling the night sky might well be the Matrioshka Brains surrounding the Sun and expanding outwards into deep space.....

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The answers so far have not included climate effects nor the effects of the rise and fall of civilizations, in that amount of time there is a decent chance that non-human species would rise to sentience.

By climate I refer to world circling effects like the wind carrying the Sahara over to South America to improve the soil of the Amazon basin. If something happens to change or stop the Gulf Stream all of Northern Europe will be much less habitable than it is now. The effects of El Niño on Central and South America .. etc.

The effects of civilisaton .. does anyone build a space elevator in that time? Do we import asteriods to replace resources used up by over mining/ extracting? Does an ocean get revamped to produce algea as a basis for food production, and then get reclaimed as “natural” ocean .. do the tree huggers ever establish a world side ban on logging .. so that trees overgrow the world? Then do they get logged off in reaction over the next few hundred centuries? Does genetic modification replace evolution as the driver to create new species?

There is no limit to the global effects that mankind can create over the time span of your question.

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