Читать книгу The Terrestrial Macroinvertebrates of the Sub-Antarctic Iles Kerguelen and Ile de la Possession - Maurice Hulle - Страница 15

The morphology of the Îles Kerguelen is mainly related to their magmatic origin and glacial erosion. Their geological history is long. The most ancient parts emerged about 35–40 million years ago and the last magmatic events date back to about 30,000 years ago. Mount Ross rises to the South at 1,830 m a.s.l. Part of the western and central regions is covered by an ice cap, the Cook cap, which rises to 1,000 m a.s.l. and covers about 550 km². The North (Péninsule Loranchet) and the South-West (Péninsule Rallier du Baty) are mountainous and rise to 1,260 m a.s.l. To the east, Péninsule Courbet constitutes a vast area of glacial erosion which is at a low altitude and is dotted with numerous lakes (Giret et al. 2003a) (Figure 1.4).

Figure 1.1. South Indian Ocean sub-Antarctic islands

Île de la Possession was formed between 8 million years ago and about 10,000 years ago for the most recent episodes (Delépine 1973; Giret et al. 2003b). The island culminates at 934 m a.s.l. at Pic du Mascarin. Large alluvial valleys (Vallée de la Hébé and Vallée des Branloires) open onto the north-east coast (Figure 1.5).

Figure 1.2. The Îles Kerguelen

Figure 1.3. The Îles Crozet

Figure 1.4. Topography of the Îles Kerguelen

Figure 1.5. Topography of Île de la Possession (Crozet)

A large part of the two islands, Kerguelen and Possession, is mountainous with an altitude of over 200 m a.s.l. Areas below 100 m in altitude represent 32% and 22% respectively on the Îles Kerguelen and Île de la Possession, and areas below 200 m represent 50% and 40%, respectively (Figures 1.4 and 1.5).