Recently upheaved from the sea were spread at low levels with alternate inundations of salt and fresh water.
To the south-east of the lake is the Monte Nuovo, a volcanic hill upheaved in 1538, with a deep extinct crater in the centre.
From this point a zone of upheaved coral rocks skirts the shore for some distance.
The entire island is an old coral reef upheaved 200 ft., honeycombed with caves and seamed with fissures.
They are peculiar in having their altitude dependent on the depth of revived erosion, instead of the amount of faulting, and they are sometimes topographically reversed, in that the revived scarp overlooks a lowland worn on a weak formation in the upheaved fault-block.