Monday, 3 September 2007

Why I Care About Tsunamis

Our lagoon here at General Luna, Siargao Island, is roughly the same size as the one at Sissano, in North Papua New Guinea, and the geological and tectonic conditions are very similar, so if I wake up at night worriedly thinking 'What was that noise?' I'm not being paranoid.
General Luna, Siargao Island satelliteThe town of General Luna is just to the right of top centre. I live a couple of hundred yards along on the coastal road that leads East, and then North to Cloud 9, the famous surfing wave. Daku is the big island on the South side of the lagoon, Guyam is the little dot, about halfway between Daku and the town, and Pisangan, the main reef, extends north from the entrance to the lagoon just north of Daku.

About 50km over to the right is the Philippine Trench, 10,000 metres deep (you could dump Mt Everest out there, but you would still need a kilometre of rope to drop anchor on the summit). Our 'continental shelf' extends just to the seaward side of the reef; from there the seabed drops away sharply.

A seabed slump or landslide, like that at Sissano, is all it would need to wipe us all way, especially if, as in the case of Sissano, it involved what seems to have been a catastrophic release of sub-seabed clathrates, a reservoir of water-bound methane ice that can suddenly be released as an explosive gas. Hence the bubbles, the haze, and the strange glow at Sissano.

But not to worry. Our valiant government is doing what it can to advise us of what to do if it ever happens. They've put these two signs up in town, promininently near the public market and the seashore Boulevard.
Siargao Island Tsunami notice
Siargao Island Tsunami notice So, not to worry; and while you're running in a state of sheer blind panic past the evacuation route sign, do please take note that the . has fallen off, and it's only 1.4km, not 14, to the nearest high ground.

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