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I've tried researching this question myself, but the only data I can find is over huge timescales, like situations where the continents have reformed back into a Neo-Pangea.

I'm not looking for any real drastic changes in positioning, just relatively minor things like seas disappearing or continents slightly shrinking or pushing into each other.

Would there be any noteworthy changes at all, or would it be pretty much the same as today aside from some minor changes that wouldn't affect anything?

Let's just assume humanity suddenly stopped existing today for the purposes of the question, so they don't make any more changes to the world than they already have.

As always, I'm very grateful for any answers, and if you need anything clarified feel free to leave a comment and I'll do my best to clear things up.

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    $\begingroup$ Barring massive flooding from ice caps melting, the map would look identical. Continents move as fast as fingernails grow. A thousand years is nothing in geologic time scales. $\endgroup$ – Samuel Mar 23 '18 at 6:04
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    $\begingroup$ @Samuel Not quite true. On a continental scale, yes. On a local scale? Things can change a lot. Take a look at how the coast has changed around the area of Thermopylae. I think it may be possible for some bodies of water to change drastically, but I don't have any data on that. $\endgroup$ – Andon Mar 23 '18 at 6:33
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    $\begingroup$ I'd object to your statement on "minor things". Closing Gibraltar and drying out the entire Mediterranean sea will have a large impact on the climate of entire Europe. $\endgroup$ – L.Dutch - Reinstate Monica Mar 23 '18 at 6:37
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    $\begingroup$ @Samuel sea levels and continental drift aren't the only actors. Coastal erosion is a thing. $\endgroup$ – David Richerby Mar 23 '18 at 11:50
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    $\begingroup$ You ruling out huge glassy radioactive plains? $\endgroup$ – Carl Witthoft Mar 23 '18 at 13:56
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A millennium is a blink of an eye on a geological scale. But interesting things can happen in a blink of an eye. Even disegarding the changes which may happen as a result of the present climatological instability, small but important modification can occur here and there.

I have no idea of the geographical changes between today and 3000 CE; but I do know of some geographical changes between 1 CE and today, either because they happened in places in which I have a local interest, or because they are somehow important to various historical events, or because I found out about them by accident and found them interesting enough to remember.

Geographical changes during the last 1000 or 2000 years

  • While sea level is today not very different from what it was in the first century, in some places the sea advanced or retreated considerably:

    • Some cities which used to be seaports in the first century are now several miles inland. For example:

      • In the Antiquity Ephesus and Miletus were major ports on the Ionian coast; they are now several kilometers inland.

        Silting of the gulf of Miletus

        The silting evolution of Miletus Bay due to the alluvium brought by the Maeander River during Antiquity. Map by Eric Gaba, available on Wikimedia under the CC-BY-SA-3.0 license.

      • Closer to me, in the Antiquity the city of Histria was a seaport on the western coast of the Black Sea. Now its ruins lay on the shore of a shallow lagoon, and the sea is kilometers away.

        Greek colonies in Dobruja

        Ancient towns and colonies in Dobruja; modern coastline shown as a dotted line. Map by Bogdan, available on Wikimedia under the CC-BY-SA-3.0 license.

    • On the other hand, in some places the sea advanced. For example, what is now the IJselmeer in the Netherlands used to be a low-lying plain in the first century, with a large lake known by the Romans as Lake Flevo. In 1287, Saint Lucia's flood broke through and submerged the former river Vlie, creating a large shallow gulf which was called the Zuiderzee.

      The region of the Netherlands in the 1st century CE

      The region of the Netherlands in the 1st century CE. Map by the Dutch Nationale Onderzoeksagenda Archeologie (www.noaa.nl), available on Wikimedia under the CC-BY-SA-3.0 license.

      Then in 1932 the long effort of the Dutch to build the Afsluitdijk was brough to completion, and the gulf was separated from the sea and became a lake, which the Dutch then proceeded to drain in order to increase the territory of their country; and now the Netherlands has a new 1500 square kilometer province, called Flevoland.

  • Rivers sometimes change course dramatically. For me, the most spectacular example is the Oxus, which is today known as the Amu Darya. Until the 16th century it used to flow into the Caspian Sea, through what is now the dry Uzboy valley; it then changed its mind, abandoned the Caspian and went to empty into the Aral Sea.

    The old course of the Oxus (Amu Darya), when it flew into the Caspian

    The old course of the Oxus (Amu Darya), when it flew into the Caspian Sea, marked as "Old Bed of the Oxus". Map from 1903, available on Wikimedia. Public domain.

    At the beginning of the 18th century, Peter the Great, emperor of Russia, sent prince Alexander Bekovich-Cherkassky to find the mouth of the Oxus, with the intention of establishing a trade route from the Caspian to Transoxiana. The prince dutifully mapped the coast and returned with the sad news that the river no longer flowed into the Caspian...

  • Speaking of the Aral Sea, the Soviet Union killed it in the 20th century. The former immense lake of 68,000 square kilometers is now a desert, the Aralkum.

  • Speaking of the Soviet Union and Transoxiana: in the 1930s the Soviet Union conceived a titanic project to "divert the flow of the Northern rivers in the Soviet Union, which "uselessly" drain into the Arctic Ocean, southwards towards the populated agricultural areas of Central Asia, which lack water" (Wikipedia). The Northern River Reversal eventually grew and grew, design and planning progressed through the 1960s and 1970s, so that by 1980 the Soviets were talking of diverting 12 major Siberian rivers into the Central Asian desert. They even envisaged using atomic bombs to move massive amounts of dirt speedily. Then the Soviet Union fell; but who knows?

  • Speaking of using atomic bombs to dig canals, Egypt is considering a plan to dig a canal from the Mediterranean to the Qattara Depression, flooding it and creating a solar-powered 2000 megawatt hydropower plant.

    Map of the flooded Qattara Depression, with several proposal waterway routes

    All proposed routes for a tunnel and/or canal route from the Mediterranean Sea towards the Qattara Depression. Map by AlwaysUnite, available on Wikimedia under the CC-BY-SA-3.0 license.

    And yes, in the 1950s the international Board of Advisers led by Prof. Friedrich Bassler proposed to dig the canal using atomic blasts, part of President Eisenhower's Atoms for Peace program.

  • The Frisian Islands on the eastern edge of the North Sea are notoriously shifty, so that the approaches to the Dutch ports have changed considerably from the Middle Ages to the present. For example, the northern part of what is now the island of Texel was until the 13th century the southern part of the island of Vlieland; it then left Vlieland and became a separate island, the Eierland; in the 17th century the Dutch reclaimed the land between the Texel and Eierland, and the two islands became one.

    Eierland when it was a separate island

    Eierland when it was a separate island. Map from 1702, available on Wikimedia. Public domain.

Geography is not static

The list could be very much expanded. The Panama Canal. The proposed Nicaragua Canal. The lockless Suez Canal, which has brought the marine life of the Red Sea into the Mediterranean. The Hot Gates of Greece. The shifting barrier islands off the coast of Texas. The absent-minded Yellow River of China. The wandering lake Lop Nor. The unstable coastline of England -- how many of the medieval Cinque Ports are still ports, that is, if they exist at all?

Geography changes wherever you look closely.

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  • $\begingroup$ Civil projects claiming large pieces of land like these are still happening. For example, Maasvlakte 2 near the Netherlands and Palm Islands near Dubai. Who knows how many of such projects will have been completed and/or destroyed by the year 3000. $\endgroup$ – Mast Mar 23 '18 at 10:39
  • $\begingroup$ That's fascinating, thanks! Similar to the theory that around 7000 years ago there was a big flood (Evidence Noah's Biblical Flood Happened, Says Robert Ballard) $\endgroup$ – Xen2050 Mar 23 '18 at 10:52
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    $\begingroup$ @Xen2050: The Black Sea was definitely a much smaller freshwater closed lake at the end of the last glacial maximum, known in Russian geological works as Lake Novoevksinsky. It then filled up and connected to the Mediterranean through the Bosphorus. The only debate is whether happened slowly or, as Ballard proposes, very quickly. $\endgroup$ – AlexP Mar 23 '18 at 10:57
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    $\begingroup$ It's worth noting that while the Oxus was a particularly dramatic example, it's not an isolated phenomena. eg the Mississippi's delta relocates every thousand years or so as its old route gets too long/too shallowly sloped and it finds faster way to sea. It's most recent mouths have all been somewhere in Louisiana but I've read that the geological record indicates that it's been across the state line in both directions if you look farther back. If not for major intervention in the 60's its main exit would've changed in the last decades en.wikipedia.org/wiki/Old_River_Control_Structure $\endgroup$ – Dan Neely Mar 23 '18 at 14:17
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    $\begingroup$ @Gnudiff: Added a final paragraph mentioning the Panama Canal and more. $\endgroup$ – AlexP Mar 23 '18 at 16:42
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Would there be any noteworthy changes at all,

just assume humanity suddenly stopped existing today for the purposes of the question

Global Warming would continue for a while, if for no other reason than approximately 2.5% of CO2 is sequestered per annum.

http://euanmearns.com/the-half-life-of-co2-in-earths-atmosphere-part-1/

Sequestration of CO2 from the atmosphere can be modelled using a single exponential decay constant of 2.5% per annum.

At that rate, it would take 14 years to return to a CO2 value of 280ppm.

But in the meantime,

  1. much polar ice has disappeared, and blue ocean absorbs more energy than white ice, and
  2. the permafrosts are thawing, releasing lots of methane, which an even stronger greenhouse gas. This northern warming is causing even more methane to be released, in a vicious cycle.

Thus, it's very possible that most of the Greenland icecap will be melted, and also Antarctica, raising the ocean levels by 70 meters.

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    $\begingroup$ @Separatrix one of the question's stipulations is that humanity instantly disappears. Thus, my answer is predicated upon humans not pumping any more GHGs into the atmosphere. $\endgroup$ – RonJohn Mar 23 '18 at 10:11
  • $\begingroup$ Ah yes, I wasn't planning to answer so stopped reading it halfway down. $\endgroup$ – Separatrix Mar 23 '18 at 10:15
  • $\begingroup$ @Separatrix been there, done that... :) $\endgroup$ – RonJohn Mar 23 '18 at 10:17
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    $\begingroup$ @Depends what you mean by humanity disappears. If you mean that us and all our constructions, artefacts, etc. disappear, then you've just got a few decades of AGW followed by return to pre-industrial climate over a century or so. However, if you mean only the people disappear, the rapture would be followed by numerous accidental fires from lightning and unattended machinery failing. That would create a significant pulse of CO2 and other pollutants that could twist climate change in an unpredictable way. $\endgroup$ – Oscar Bravo Mar 23 '18 at 12:03
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    $\begingroup$ You can't model CO2 removal like that - the implication, among other things, is that CO2 would drop below pre-industrial and keep dropping. That would contradict the pre-industrial record somewhat. $\endgroup$ – Andrew Dodds Mar 23 '18 at 15:24
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You mention plate tectonics as a cause of change; there are others

  • Rising sea levels. Wikipedia has a map from NASA about how a 6-meter sea level rise would change the world map. Current predictions seem to be something between 0.3m and 2.5m in the next hundred years, so 6m doesn't seem crazy over 1000 years.

  • Coastal erosion can cause significant changes: for example, the seashore at Hemsby in eastern England is receding at the rate of about 35 metres (115 ft) per year.

  • Post-glacial rebound. During the ice age, ice-covered land was weighted down; it's slowly springing back. For example, much of Finland was underwater a few thousand years ago, even though sea levels were much lower. Southern England is pivoting downwards as Scotland rises, which will lower southern England by about 0.5m in the next thousand years.

  • Vulcanism can and does create new islands.

  • Deposition from rivers causes estuaries to grow out into the sea.

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In addition to the previously noted changes due to climate and normal geology, the sudden removal of humans a la Discovery Channel's Life After People would quickly lead to the breakdown of electrical and mechanical infrastructure, including pumping stations (e.g., the California Aqueduct, New Orleans' pumping stations, and the Netherlands' pumping stations in Flevoland), with the obvious results. In the longer term (a few centuries at most, according to Discovery), the majority of earthen and concrete structures are likely to fail, which includes essentially all of the world's dams, dikes, and levees. Their collapses will cause significant flooding, erosion, and scouring of low-lying areas downstream, and some river channels will be changed significantly enough to still show the effects a millennium hence.

Earth's cities and highways are also likely to be largely buried in vegetation (again, per Discovery), with the result that urban and linear features that are prominent from the air or even space will become much harder to see.

The disappearance of humans will also eliminate agriculture and logging, which is likely to reduce silt and fertilizer runoff in most places, with at least some visible changes in watersheds. (For example, mangroves can be expected to make a larger comeback in some rivers; clear-cut areas of the Amazon and other forests will recover to some extent; and a number of river deltas like the Ebro's will stop growing so quickly and may actually erode.) The Aral Sea may make a comeback as well.

Astronomy might also play a small part; according to Wikipedia, there's about a 20% chance of an asteroid strike large enough to create a crater actually hitting land and doing so.

By the way, spacecraft, even the ISS, are too small to make much of a mark, and what little damage they do cause would be hidden by vegetation and weathering very quickly (years, or decades at most).

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"Is removing people sufficient to stop global warming?" Good question. Answer is not clear. If we have passed the tipping point for arctic permafrost collapse, arctic ocean being ice free in summer, then we may release huge amounts of methane clathrates.

On top of this while oil has to be pumped, natural gas is often under pressure. As distribuiton systems break down, more methane is released.

Net result: ALL of antarctica and Greenland melt over the space of that thousand years.

So we have an new continent free from ice in the south, we have a new archipelago of islands where Greenland was. We have new ecologies in the arctic regions, and the ocean shoreline moves in a bunch.

Details here: https://www.nationalgeographic.com/magazine/2013/09/rising-seas-ice-melt-new-shoreline-maps/#/07-ice-melt-antarctica.jpg

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