Mid-Indian Ridge

in the narrow sense, a part of the median ridge of the Indian Ocean, between the Tropic of Capricorn and the islands of Amsterdam and St. Paul. It is approximately 2,000 km long and 800 to 900 km wide. It rises 1,000 to 1,500 m above the ocean floor, and the sea above the ridge is less than 3,000 m deep. The Mid-Indian Ridge consists of narrow ridges 300 to 500 m above the ocean floor (to a maximum of 1,000 m) and canyons extending from northwest to southeast. The deepest canyons (maximum depth, 4,245 m) form a rift valley in the axial part of the ridge. The Amsterdam Plateau near the southeastern end of the ridge is an uplifted region that reaches an elevation of approximately 1,500 m above the ocean floor. Underwater mountains rise from the plateau, and the peaks of two of these mountains form the volcanic islands of Amsterdam and St. Paul. Foraminiferal oozes are found in low areas, and basalt outcrops are found on the steep slopes.