Île Amsterdam & Île St. Paul
Located midway between Madagascar and the southwestern
coast of Australia, the two remote islands of Île Amsterdam and Île St. Paul lie at the southern extremities of
the Indian Ocean just ouside of the Roaring Forties region; the coast of Antarctica lies some 3,030 km to the south, Australia
3,500 km to the west-northwest and Madagascar 3,200 km to the northeast. Their closest island neighbours are the islands of the
Îles Kerguelen group, located around 1,280 km to the southwest.
Île Amsterdam and Île St. Paul — separated from one another by 88 km — form part of the Terres Australes et Antarctiques Françaises (French Southern and Antarctic Territories), which also includes Terre Adélie (French claims in Antarctica), the Crozet Islands and the islands of the Îles Kerguelen group.
Île Amsterdam, the larger of the two islands at 55 km² in area, is the remnant of an extinct shield volcano. It lies upon a transform fault that crosses the southeastern branch of the Indian Ocean Rise - the fault that divides the Indian Ocean from the Southern Ocean proper. The island is approximately oval in shape with maximum dimensions of 10 km by 7.5 km.
From its eastern coast the island rises via low cliffs and slopes to a gently sloping interior. climbing to a height of 881 m above sea level at the Mont de la Dives. The western side of the island, in spectacular contrast to the eastern coast, drops sharply to the sea in tall basalt cliffs of up to 700 m in height — a feature formed by the collapse of the western side of the volcano.
The island is of relatively recent origins, estimated to be in the region of 400,000 years old, formed by successive episodes of activity from several distinct craters — primarily the Mont de la Diveis and La Grande Marmite formations. The island is now thought to be volcanically extinct with no known historical eruptions, although there are possible indications of activity within the last 100 years at the Dumas Crater.
The smaller Île Saint-Paul (8.4 km²) comprises an impressive sea-flooded caldera formation lined by steep-sloped cliffs (reachng 272 m above sea level). From the caldera rim the interior descends gently to meet the sea on the opposite coast in low cliffs.
The islands have a relatively mild, oceanic climate with a mean annual temperature of 13.5° C — monthly means vary from 11.2° C during January to 17° C in February. Cloud cover is generally present and of low elevation. Annual precipitation averages 1,100 mm, with most of this falling as rain, with 239 rain days. Near-persistent winds blow in from the northwest and northwest — with wind speeds greater than 55 km/h on 150 days of the year.
The extreme isolation of these islands — more than 3000 km from any continental landmasses — has led to a high level of endemism amongst the native flora and fauna prior to human contact, although the islands have since been highly disturbed.
