The rare earth elements reflect that these cherts formed in the deep-water basin far from continent where terrestrial material had no obvious effect to them.

To avoid contamination, Wells in the Bengal Basin can be drilled into deep layers that were oxidized during the last ice age, in which the water is free of arsenic, Berg says.

But as the tsunami propagates into the really deep water of the Pacific Basin, [the shallower origin] does decrease its amplitude somewhat.