The Indian Ocean is the third-largest of the world’s five oceanic divisions, bounded by Asia to the north, Africa to the west, Australia to the east and the Southern Ocean to the south. Covering approximately 70,560,000 square kilometres, it accounts for roughly 20 per cent of the water area of Earth’s surface.
Geologically the youngest of the oceans, the Indian Ocean formed only 20 million years ago from the fragmentation of the ancient Tethys Ocean. With an average depth of 3,741 metres, it is also the warmest ocean, profoundly influencing global climate through its interaction with the atmosphere and the Indian Ocean Walker circulation. Its marginal seas include the Andaman Sea, the Arabian Sea, the Bay of Bengal and the Laccadive Sea. Ecologically diverse, the Indian Ocean supports coral reefs, mangroves, seagrass beds and a significant portion of the world’s tuna catch, though it faces mounting pressures from climate change, overfishing and pollution. Historically a hub of cultural and commercial exchange since ancient times, it remains crucial for global trade, particularly in oil and hydrocarbons.
The Indian Ocean features in our Field Notes coverage of rare deep-sea discoveries and marine biodiversity.
