subtlebulk t1_ixi3wge wrote
Related, in the U.S. there was a place called Sharps Island off the coast of Maryland that had a historic colonial era community. In 1848 it was said to measure 449 acres, by 1942 just 17 acres, and by the 1960’s it was gone. There were a number of islands in the Chesapeake Bay that suffered the same fate (https://www.chesapeakequarterly.net/sealevel/main8/ ). Apparently the culprit was land subsidence after the end of the last glacial maximum. That’s just my understanding though, so take it with a grain of salt.
It’s kind of sad to think that we lost the archeological record on these Welsh islands, but that’s how it goes I guess.
codefyre t1_ixin69r wrote
Land drying tends to be a major cause as well. Many low-lying islands are made up of boggy sedimentary soils slowly deposited over thousands of years. Boggy soils contain a lot of water. When humans drain that soil for farming, the removal of the water allows the remaining soil to compact and settle. If the land is low enough, it can fall below the surrounding water level and the island will vanish.
The Delta in California has this issue today. When Europeans first mapped it in the 1700's, they found around 60 islands with fertile soil. The islands were surrounded by levees and farmed starting in the mid-1800's. Today, all of the islands are at least 10 feet below sea level, with some of them approaching 30 feet below sea level. Only the large modern levees and constant pumping keep them dry. Some have failed over the years, converting those islands into open water. This will likely happen to all of them over the next 100 years, allowing the San Francisco Bay to extend itself all the way into the Central Valley.
matinthebox t1_ixjlag3 wrote
> When humans drain that soil for farming, the removal of the water allows the remaining soil to compact and settle. If the land is low enough, it can fall below the surrounding water level and the island will vanish.
or, alternatively, you dam off half of your country and continue to live below sea level. Damn those Dutch are stubborn.
burnbabyburn11 t1_ixm2it6 wrote
The Netherlands are 41,543 square km, compared with California’s 423,971 square km. To dam off half of California is 10x more land than to dam off half of the Netherlands.
foospork t1_ixiu2rz wrote
I’ve been watching Tangier Island, VA (near Crisfield, MD) fade away over the past 10 years.
IIRC, it’s been inhabited by European settlers since the 1600s. It was used as a base by the British during their attack on Washington during the War of 1812.
Tangier Island looks like another place that will soon succumb to this fate.
elriggo44 t1_ixlmb4j wrote
Smith island as well.
nathhad t1_ixly4wa wrote
Unfortunately, islands in the Bay are inherently impermanent. They move, they leave. Barrier islands on the surrounding coast are the same way. Historically this has been the case long before we started doing things that often accelerate the process. Building "permanent" structures on them is really a fool's game, but unfortunately that's something we seem to have forgotten culturally. Some places are suitable for long term occupation, some really just aren't.
TheGrandExquisitor t1_ixiqiwz wrote
This is very common along the US Atlantic coast. The Outer Banks of S. Carolina are a good example of this. Islands come and go out there over relatively short periods. One decent storm can drastically alter the geography of the area.
Penitent_Exile t1_ixi7acs wrote
Heavy agriculture tends to do that with bodies of water. Look up history of Missouri. Poor river.
vorschact t1_ixkexxh wrote
The possibilities of what could have been found in the archeological record of Doggerland always saddens me. Tracking migration to the British isles would be amazing.
stefan41 t1_ixl1s6y wrote
My grandparents were members of the sharps island yacht club before I was born. They lived on Leeds Creek nearby. The “yacht club” consisted of people rafting up their boats on the sandbar that used to be the island and drinking.
sadpanda597 t1_iya9i04 wrote
Your quotes seem to imply that this isn’t an awesome club to be a part of.
stefan41 t1_iye2fop wrote
I mean, it’s awesome in terms of it being fun, but it wasn’t a yacht club in any real sense of the world. The name of the club was intended as a joke.
worotan t1_ixi85sy wrote
> They suggest that the islands could be the remnants of a low-lying landscape underlain by soft glacial deposits laid down during the last ice age. Since then, forces of erosion have worn away the land, reducing it to islands, before these too were worn away and disappearing by the sixteenth century.
im_a_goat_factory t1_ixkqbjc wrote
A place in NJ is underwater, town bank is the name. It’s been underwater for over 150 years
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