[00:00.504]Across the South Pacific,
[00:02.037]time continues to work its magic on rock.
[00:05.740]Millions of years of erosion and sinking have reduced the volcanic mount of Maupiti
[00:11.828]to little more than a hill.
[00:13.858]Eventually, this hill will disappear too.
[00:16.729]And when it does,
[00:17.836]it will look like this - Mataiva,
[00:20.830]a coral atoll.
[00:22.610]Rising above the waves,
[00:24.103]a coral atoll's reef surrounds a shallow lagoon.
[00:27.806]Where there was once a mighty peak,
[00:30.560]now there is only water.
[00:33.162]There are thousands of atolls like Mataiva dotted around the South Pacific,
[00:38.091]their size and shape determined by the original volcano.
[00:42.762]Some atolls are round, their rings unbroken,
[00:46.570]while others have been bent out of shape by ocean currents and earthquakes.
[00:51.142]And a few span huge distances,
[00:54.233]a testament to volcanoes whose size and power were once truly colossal.
[01:00.109]Rangiroa in French Polynesia.
[01:02.771]Over 30 miles wide,
[01:04.607]its lagoon is so large that if you were floating in its centre,
[01:07.942]you wouldn't see land in any direction.