Tsunami in Tonga

Some thoughts regarding the recent tsunami near Tonga.

Picton Castle has a well loved former crewmember from Tonga, Vai. She has been back home for awhile. Since the news broke about the underwater volcano eruption near Tonga which caused a tsunami, we have had many inquiries as to her wellbeing. While we have not heard from her directly it is likely that she and her family are doing just fine. The Vava’U group of islands in the far north of Tonga where Vai lives is particularly well protected from the worst effects of a tsunami.

For the effects of tsunamis on land to occur a number of factors must be in alignment. Fortunately for Vava’U these things do not line up there.

Curiously in 1976 I was at sea in a ship in the South Pacific when it seemed that a tsunami passed under us. Quite interesting. In the middle of a very deep ocean. We were sailing along in the Danish built wooden Brigantine Romance in light and fair conditions, no swell, lovely sailing, far from land. A beautiful day at sea. We experienced a very strange shock for no evident reason. It felt like we went hard aground briefly or maybe hit an underground mountain that then suddenly disappeared. It felt like a giant hydraulic hammer smacked us in the keel. It seemed as if we rose about a foot in an instant, and straight down again. The seas surface shimmered for a moment. A coffee cup capsized and rolled around. A couple crew lost footing briefly on deck. Later Captain Kimberly told me that was a tsunami.

Deep sea tsunamis travel very fast but have no height. They are hydraulic shock waves. They gain height as the land slopes up approaching dry land and the energy changes from speed to slowing down and building up height and thus waves. Vava’U, in the northern group of Tonga is very steep too and is a fairly high island surrounded by high cliffs, not conducive to the wild hazardous effects we have seen ashore in other places more vulnerable to tsunamis.

We still are keen to hear from Vai.