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With global warming comes rising sea levels. This has been going on for at least fifty years.

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So haven't there been some islands that have been swallowed by now? An island could be nothing more than a rock jutting up a few centimeters out of the sea. There are many such "rock" islands that surround larger islands, and I'm wondering if any have been devoured by now.

I don't need a whole list of such islands, although a link to such a list would be probably the best answer one could hope for. What I'm really looking for is a few examples, or maybe the largest island known to have disappeared thanks to the rising sea.

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  • $\begingroup$ A really nice way to try answering this question would be an estimate from a DEM with good bathymetry and a map of global sea-level change for the last x years. It would be hard to take other factors into account without maps of subsidence, sedimentation, carbonate factory production, etc, but it would be a start. $\endgroup$ – kwinkunks Sep 21 '15 at 11:38
  • $\begingroup$ I have just rejected an edit asking for a more general case ('erosion'). This question specifically asks about sea level rise. $\endgroup$ – Jan Doggen Nov 9 '18 at 16:22
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Definitely, there are lots.

As you say, sea-level is rising in most (but not all) coastal areas. Indeed, at the end of the last ice age ca. 12,000 years ago, sea-levels rose about 120 m. Many islands and land bridges — such as Beringia across the Bering Strait, and Doggerland across the North Sea — drowned.

I can't find any lists of drowned islands, but here are some places you will find them today and in the geological past:

  • 'Banks' on the eastern seaboard of North America would have been emergent during the ice age — Georges Bank and the Grand Banks for example. As they drowned, they would have formed islands — lots, in the case of Grand Bank.
  • The Hawaiian archipelago is part of a famous chain of drowned islands, but the change in sea-level is not the only thing that's drowning them. As the plate moves over an upwelling in the mantle — the same thing that's causing the volcanism there — it subsides and cools. I'm sure there are many drowned islands in other extinct and active volcanic provinces and seamount chains: the Zubairs, Canaries, Azores, Iceland, the South Pacific, etc. Sometimes life keeps up for a bit as a coral reef grows around the sinking island, perhaps forming an atoll.
  • Near-sea-level islands like atolls abound in places like the Maldives. These atolls are volcanic and actively subsiding. Sea-level may or may not inundate them, depending on whether the coral growth can keep up. Another fragile island is Sable Island off Nova Scotia — clinging to the edge of the continental shelf.
  • Volcanos can explode as well as sink slowly into the sea. Krakatau Island is probably the best example. This one has nothing to do with sea-level.
  • Rift basins start as mountainous tears in the crust, then subside and flood. Global sea-level change will often act to accelerate this. An example might be the various island groups on the shores of the Red Sea. These will likely sink into the sea eventually.
  • Salt-domes in Louisiana (e.g. Avery Island) form hills, but the domes continue offshore for hundreds of kilometres. Many of them would have been exposed in the past, some even more recently than the last ice age.

Maybe others can chip in some other scenarios; I'm sure there are dozens.

The point is that sea-level is not the only factor — subsidence, sediment accumulation rate, and erosion also play their rôles. But sea-level always plays some part, and can change quickly relative to the other factors.

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  • $\begingroup$ I know there are other causes, such as subsiding tectonic plates. I wanted to restrict the islands to those that have drowned only due to rising sea in recent history. I'm no expert on global warming but I would have thought there would be at least one example of an island that has drowned by now. $\endgroup$ – DrZ214 Sep 21 '15 at 4:51
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    $\begingroup$ I'm a geologist — 10 ka BP is recent history :) Seriously though, you could take any tidal island anywhere sea-level is rising as your example. But I'm not sure you can ever really take everything else out of the equation. Compaction, isostatic rebound, sediment accumulation, reef growth — all these processes are capable of keeping up with, even surpassing, sea-level change. Westhaver Island in Mahone Bay, a drumlin near where I live, is in the process of drowning, but deforestation and consequent wave erosion are contributing factors. Natural systems are always complex. $\endgroup$ – kwinkunks Sep 21 '15 at 11:30
  • $\begingroup$ And don't forget that although rising sea level is the norm, there are areas where the land is rising faster. There are coastal areas of Greenland where uplift is caused by isostatic rebound after the ice has retreated. In these areas there are many new islands appearing. $\endgroup$ – Gordon Stanger Oct 2 '15 at 11:37
  • $\begingroup$ @GordonStanger Right, see the first link in my answer. $\endgroup$ – kwinkunks Oct 2 '15 at 14:29
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Three very recent examples are

I wonder if there are any predictions concerning the future rate of such happenings.

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    $\begingroup$ The question asks due to sea level rise. Do these meet that criterion? $\endgroup$ – Jan Doggen Nov 9 '18 at 16:23
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    $\begingroup$ @JanDoggen probably. Islands rarely just disappear because of static increase in sea level. They disappear because of wave action, or storm action. A higher sea level makes these effects more severe and more likely to eliminate the island. $\endgroup$ – Gimelist Nov 10 '18 at 6:01

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