It is not unusual to find groups of rocky islands close to a
coastline, but stuck out in the middle of an ocean? That is where you will find
the St Peter and St Paul Rocks – in the Atlantic Ocean about 590 miles from
northeast Brazil and 1,100 miles from west Africa.
They are 15 small islands that rise to no more than 60 feet
above the sea. The total land area is about 160,000 square feet. They are
uninhabited, although the Brazilian Navy has established a scientific station
and lighthouse on the largest island.
The name comes from the event that led to their discovery in
1511. A Portuguese nobleman, Garcia de Noronha, was in charge of a fleet of six
caravels on a voyage to India. One of the caravels, “St Peter”, crashed against
a rock at night in the middle of the ocean, and the crew had to be rescued by the
crew of another caravel, “St Paul”.
The St Peter and St Paul Rocks, despite their apparent lack
of importance, are extremely interesting from a geological point of view. They
are the very top of an undersea mountain that only just breaks the surface. The
technical term for the sort of feature they represent is “megamullion”, this
being a ridge that runs at right-angles to a mid-ocean ridge, which in turn
marks the point where two tectonic plates are moving apart and allowing new
ocean crust to form. The Rocks are the world’s highest megamullion (at 12,000
feet), being composed of mantle rock, and are not an undersea volcano that has
reached the surface.
The Rocks were visited by Charles Darwin when on board HMS
Beagle in 1832. He noted that they had very little to offer in the way of
wildlife, and that he not been able to find a single plant anywhere on the
islands. He did find two birds, a moth, a crab and some spiders, but that was
about it.
Had Darwin stayed longer, he might have noted the relative
richness of the tidal pools, which support sea slugs, shrimps and lobsters. The
islands are visited by many migrating seabirds, and the seas surrounding them
are populated by some 75 species of fish, including deep-water eels, sharks,
and five – including the St Paul’s Gregory – that are found nowhere else.
This is a place that very few people visit, or are ever
likely to.
© John Welford
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