The Alps and the major flanking ranges are largely the upturned edges of tilted blocks considerably modified by water and ice erosion by rivers and glaciers. The main divide culminates in the Mt. Cook area with 17 peaks above 10,000 ft, from Mt. Sefton (10,359 ft) in the south to Mt. Elie de Beaumont (10,200 ft) in the north. Mt. Cook (12,349 ft) is on a south-trending spur from Mt. Dampier (11,287 ft) near Mt. Tasman (11,475 ft) on the main divide. South from Mt. Sefton, the Southern Alps maintain a height of about 7,500 ft to Haast Pass (1,847 ft), the lowest alpine pass.

North of Mt. Elie de Beaumont the main divide decreases in height, with a few peaks above 8,000 ft (e.g., Mt. Tyndall, 8,282 ft; Mt. Whitcombe, 8,656 ft), descending to Mt. Rolleston (7,453 ft) just south of Arthur's Pass. Some subsidiary spurs and flanking ranges contain peaks higher than those on the adjacent main divide (e.g., D'Archiac, 9,279 ft, and the Arrowsmith Range (Mt. Arrowsmith, 9,171 ft)). Whitcombe Pass (4,025 ft) and Browning Pass (4,752 ft) are low passes free from snow in summer, but only Arthur's Pass (3,020 ft) in the north and Haast Pass in the south are used for transalpine roads.

Peaks and ranges above 5,000 ft show the effects of glaciation with cirques and glacial valleys dominating the landscape, and the major valleys show glacial features – moraines and ice-sheared walls – for many miles down stream from existing glaciers.