St. Peter and St. Paul’s Rock’s Islets
The St. Peter and St. Paul Rock’s (SPPR) constitute rocky outcrops of three small
islets, with a surface less than 0.01 km
2 , precisely located at 0°56
0 N–29°22
0 W in
the middle of the Atlantic Ocean. These islets belong to Brazil. The largest islet
covers an area about 130 m long and 50 m wide and it rises 18–20 m above sea
level. There is no vegetation, and the only tree seen during our journey in 1997
was a small palm, probably imported by the Brazilians.
These islets are in the middle of the Equatorial Atlantic Ocean and they are
among the few islands in the World that are not volcanic in origin. Most of the
world’s islands are volcanic and were formed by the repeated extrusion and piling
up of volcanic rocks. The SPPR islets are of particular interest because they are the
only emerged land mass in the Atlantic that exposes a tectonically emplaced,
metamorphosed, mantle peridotite. The St. Peter and St. Paul’s Rocks islets in the
Atlantic and the Zabargad Island in the middle of the Red Sea are the only known
islands in the World that consist entirely of ultramafic rocks. Geologists like to
study these islets because they represent a displaced sample of our planet’s upper
mantle that is within their reach.
The first visit to the islets was during the scientific expedition of the HMS
BEAGLE in 1843. Darwin in 1891 was the first to state that the islets were unlike
any other island seen, and he reported that the rocks were olivine enriched, so he
categorically denied their volcanic origin (Linklater 1972). Another scientific party
landed on the St. Paul’s Rock’s during the HMS CHALLENGER expedition on
August 19, 1873, and was reported by John Murray in 1882. Also in 1882, Renard
wrote a detailed mineralogical description of the peridotites from the islets in the
volume dedicated to the CHALLENGER’s expedition (Linklater 1972).
HMS (His Majesty’s Ship) CHALLENGER was a 200 foot long, three mast,
square-rigged, wooden ship, with a weight displacement of 2300 tons. It was the
first ship to explore the sea floor. In the 1870s, the sea floor was basically
unknown, so Challenger sounded and sampled all the oceans except the Arctic,
thereby laying the foundation for modern oceanography. The captain of the ship
was George Nares, born in Aberdeen. The director of the scientific team was
Charles Wyville Thomson, a biologist and a professor of natural philosophy at
Edinburgh. The ship left Portsmouth on December 21, 1872. John Murray, to
whom we are indebted for publishing the first comprehensive results of the
CHALLENGER’s ocean explorations, was born in Ontario of Scottish parents and
pursued his studies in Scotland at the University of Edinburgh. He was 31 years
old when the expedition started and he had an extensive background studying
literature, chemistry and natural history. John Murray, using his family’s funds,
published the observations made during the HMS CHALLENGER’s voyage in fifty
volumes. When the ship arrived at the St Peter’s and St. Paul’s Rocks, all the crew
landed on the islets and the report indicated that the only inhabitants of the islets,
made-up of black looking rocks, were ‘‘noddies and boobies’’. Later on, in 1921,
the QUEST Expedition also collected rocks from the SPPR Islets.
282
8 Fracture Zones and Transform Faults
The St. Peter and St. Paul Rock’s (SPPR) constitute rocky outcrops of three small
islets, with a surface less than 0.01 km
2 , precisely located at 0°56
0 N–29°22
0 W in
the middle of the Atlantic Ocean. These islets belong to Brazil. The largest islet
covers an area about 130 m long and 50 m wide and it rises 18–20 m above sea
level. There is no vegetation, and the only tree seen during our journey in 1997
was a small palm, probably imported by the Brazilians.
These islets are in the middle of the Equatorial Atlantic Ocean and they are
among the few islands in the World that are not volcanic in origin. Most of the
world’s islands are volcanic and were formed by the repeated extrusion and piling
up of volcanic rocks. The SPPR islets are of particular interest because they are the
only emerged land mass in the Atlantic that exposes a tectonically emplaced,
metamorphosed, mantle peridotite. The St. Peter and St. Paul’s Rocks islets in the
Atlantic and the Zabargad Island in the middle of the Red Sea are the only known
islands in the World that consist entirely of ultramafic rocks. Geologists like to
study these islets because they represent a displaced sample of our planet’s upper
mantle that is within their reach.
The first visit to the islets was during the scientific expedition of the HMS
BEAGLE in 1843. Darwin in 1891 was the first to state that the islets were unlike
any other island seen, and he reported that the rocks were olivine enriched, so he
categorically denied their volcanic origin (Linklater 1972). Another scientific party
landed on the St. Paul’s Rock’s during the HMS CHALLENGER expedition on
August 19, 1873, and was reported by John Murray in 1882. Also in 1882, Renard
wrote a detailed mineralogical description of the peridotites from the islets in the
volume dedicated to the CHALLENGER’s expedition (Linklater 1972).
HMS (His Majesty’s Ship) CHALLENGER was a 200 foot long, three mast,
square-rigged, wooden ship, with a weight displacement of 2300 tons. It was the
first ship to explore the sea floor. In the 1870s, the sea floor was basically
unknown, so Challenger sounded and sampled all the oceans except the Arctic,
thereby laying the foundation for modern oceanography. The captain of the ship
was George Nares, born in Aberdeen. The director of the scientific team was
Charles Wyville Thomson, a biologist and a professor of natural philosophy at
Edinburgh. The ship left Portsmouth on December 21, 1872. John Murray, to
whom we are indebted for publishing the first comprehensive results of the
CHALLENGER’s ocean explorations, was born in Ontario of Scottish parents and
pursued his studies in Scotland at the University of Edinburgh. He was 31 years
old when the expedition started and he had an extensive background studying
literature, chemistry and natural history. John Murray, using his family’s funds,
published the observations made during the HMS CHALLENGER’s voyage in fifty
volumes. When the ship arrived at the St Peter’s and St. Paul’s Rocks, all the crew
landed on the islets and the report indicated that the only inhabitants of the islets,
made-up of black looking rocks, were ‘‘noddies and boobies’’. Later on, in 1921,
the QUEST Expedition also collected rocks from the SPPR Islets.
282
8 Fracture Zones and Transform Faults