Tsunami redraws maps

This is amazing. Especially the part about the Straits of Malacca, although I suspect the earthquake might be more responsible than the tsunami.

Water depths in parts of the Straits of Malacca, one of the world's busiest shipping channels off the coast of Sumatra, reached about 4,000 feet before last month's tsunami. Now, reports are coming in of just 100 feet - too dangerous for shipping, if proved true.

I read somewhere — it might have been on the USGS web site — that the 9.0 earthquake on 26 December involved the ocean floor lifting something like 15 meters along 100 km of the subducting plate. But 3,900 feet is more like 1,200 meters! Maybe a lot of it was the tsunami rather than the earthquake. The same source said the aftershocks resulted in — or were a result of, I'm not sure which is the more accurate terminology — movement along a total length of 1,200 km of the subduction zone.

The first thing I noticed about this earthquake is that it was not so far from Krakatoa, which I had thought was the biggest such event in recorded history (in 1883). Maybe not, it turns out. Tambora (1915) was probably bigger. Santorini (or Thira, c. 1650 BC) likely was also, though no written accounts survive. Prior to recorded history there was Toba (73,000 ± 4000 years ago) and Yellowstone (600,000 and 2,000,000 years ago), which has covered half of North America in up to two meters of debris. These last two are examples of supervolcanoes, a vague and non-technical term, eruptions of about a dozen of which have been deduced.

I have been citing some interesting facts about Krakatoa to my friends (sometime erroneously mixing them up). The tsunami it generated was nearly 40 meters high. This wave was measured around the world. It did not, as I recently asserted in meat-space, travel around the world several times. That was the barometric pressure blast [sound wave]; the sound of the explosion was heard over one third of the globe. It was measured in numerous places all over the world for the following five days and was determined to have traveled around the world seven times! I also asserted that it was responsible for the Year Without a Summer, but that was Tambora. Temperatures did drop measurably after Krakatoa, but only 1.2° C.

To think that one these or any other really BIG disasters could happen anytime. Anywhere.