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| Each tunnel is coated with a layer of white calcareous material. The big hole is man-made. |
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| Angular cut, showing the tunnel walls. |
I measured the holes in a piece of tunnelled wood that sits on my desk (approx. 10 x 5 x 5 cm.). The holes are circular, and most measure 1 cm. across. Of 24 tunnels in this piece, 20 go straight through; two are slightly curved. On the log above, a few of the tunnels look curved.
When the wood dries completely, the white coating usually crumbles and falls off. It is only a couple of millimetres or less thick.
The tunnel of one teredo can be up to 2 feet long. In the log below there are thousands of tunnels.
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| The log. It looks like someone has cut a slab off, realized that the wood is unusable, and discarded the log. The outside looks normal. |
*Teredos are usually called shipworms, but they are a species of clam, not a worm at all. The tiny bivalve shell is used as a file or scraper to burrow through the wood, which is their diet. Underwater termites!
Teredo navalis is a very destructive pest of submerged timber. In the Baltic Sea, pine trees can become riddled with tunnels within 16 weeks of being in the water and oaks within 32 weeks, with whole trees 30 centimetres (12 in) in diameter being completely warped within a year. (Wikipedia)
Our cedar log cabin float wouldn't last long in the ocean. Here on the lake the major concern is getting waterlogged. We use plastic barrels underneath to counter that sinking feeling. They can be topped off periodically to increase our flotation factor. The deck wood is wet now so we are sinking about four inches lower, but in summer when everything dries out we rise back up. The cabin deck is about six feet above the water level so a few inches seasonally isn't a problem,. - Margy
ReplyDeleteDo the waves reach your deck when it's stormy? Or are you high enough to stay dry even then?
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