How is the wood Venice is built on not decomposing over time?

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(Not sure about the flair.. sorry)
Wooden beams in earth (like with fences) rot over the years and break.
I was under the impression that this was because of water.
Shouldn’t Venice “sink” because of rotten beams?

In: Earth Science

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Because if the wood is submerged it doesn’t rot, you need to add air to the equation in order for the bacteria to get to the wood to start the decomposition process.

Amsterdam is similarly build on a lot of wooden poles. Because the ground water has always been high enough, some of these beams easily last for centuries. I’m assuming the same principles are at work in Venice.

https://medium.com/big-questions/beautiful-amsterdam-built-on-poles-who-would-pay-if-it-all-fell-down-7ae7436a73de

as others said you need oxygen in order for it to attract organisms that can break down wood; There used to be a show called swamp loggers, where they would try to fish ancient (like 10000yr old) logs out of swamps. Then turn them into things like counter tops and different things.

The conditions of the surrounding soil actually protect the wood from rotting, the dense mud/sediment and lack of oxygen won’t allow any life forms to decompose the wood. The same phenomenon (over millions of years) is also what [turns wood into stone](https://en.wikipedia.org/wiki/Petrified_wood).

Follow Up Question: Is there a plan / method in place for changing the posts in place now? Have they changed out any already?

Wood doesn’t rot underwater. There is actually a lucrative business in pulling submerged trees from lakes as the wood is old and craftspeople use it for art/furniture

Not sure if it’s true, but in my childhood I have heard that they used a larch. This tree has a very dense and hard wood and absolute protection against fungus. Back in a days I helped my grandpa to build shelves in a cellar and he used larch wood for them. Many ears after ithose shelves were as good as new with no trace of decay.

I can easily believe that large poles would survive hundreds of years in the salt water with no integrity loose.

Water preserve wood. At least water in swamps. As an example, oak poles that was yout in a swamp to mark borders totally vanishes above ground in 100 years. The part that is still below the surface of the swamp are as good as new.

Medieval Copenhagen was also build on wooden beams.
The land Copenhagen is build on, is mostly wetlands, though almost all of it is now drained.
When old foundations are removed, you can get these ancient wooden beams out of the ground, that have these beautiful dark veins from being submerged for ages. They used to be sold to woodworkers for furniture material, but AFAIK since it happens so rarely, they are given to the archaeologists of the national museum.
Sunken logs do go for a rather high price, than normal timber, due to their special look.

It’s like when archeologist’s find an old wooden boat that’s been buried in a wet environment. They need to to keep it wet untill it’s treated to stop it from decaying .

I’ll add to other comments but… it depends on the water temp and what is in it. Old ships that are pulled up in some places have no wood left, others have a full hull. Most treasure wrecks in warmer water get wrecked by worms and parasites. Some in the same areas get covered deep in sandbars are just fine.

There have been wrecks pulled up in the Med that are in tact, other are gone except the fasteners. Unlike metal (air is the enemy) wood has many different issues. If the wood is in hypoxic areas that are cold they will last forever.

As others have mentioned, the wood rots because of the exposure to oxygen. The repeated wetting and drying of the material also causes the material to degrade at a much quicker rate. Here is a video from the channel “Battleship New Jersey” explaining the process and how it relates to warships.

https://youtu.be/aFcOm6dkuoc

Wood doesn’t rot when submerged, wet wood will but if it’s constantly underwater the rotting microbes can’t survive.