Île Kerguelen, covering an area of 1,318 mi2 (3,414 km2), has a highly irregular coastline with a number of large peninsulas linked to the island by low, narrow isthmuses. These large features are further sub-divided by fjords into smaller peninsulas. Remarkably, despite its total area, no point on the main island is more than 12 mi. (20 km) from the sea.
Inland, the main features are the numerous valleys and ridges with the highest point, the glaciated Mount Ross, reaching a height of 6,068 ft. (1,850 m). Mount Ross is the youngest volcanic edifice recognized in the Kerguelen Archipelago. The Kerguelen Islands lie in the Northern part of the Kerguelen-Gaussberg ridge, having been built up by a series of thick lava flows over millions of years.
Cook Glacier covers nearly one third of the island, and the abundant rainfall combined with glacial meltwater keeps numerous streams and lakes full of water. Peat marshes, lignite, and guano deposits are found on the island.