OceanOceanography
A layer about a kilometre down traps sound instead of letting it escape.
A low call entering it can travel thousands of kilometres, and navies used the effect to listen across oceans.
Source
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More ocean facts
Ocean facts from a place we have mapped less thoroughly than Mars. A male anglerfish merges with his mate for good, there are lakes at the bottom of the ocean, and below about 8,400 metres there are no fish at all. Each fact links to its source.
- The Mediterranean dried to salt flats around five million years ago.
- The most abundant photosynthetic organism on Earth was not discovered until 1986.
- There is a waterfall in the ocean bigger than any on land.
- We have better maps of Mars than of our own seafloor.
- Mars is better mapped than Earth's own seafloor.
- Sea level is not level.