Islands: How They Form & Where to See Them

Islands are the closest thing to a controlled experiment in evolution: the same colonising species arrive, and then diverge according to what the island offers. The effect scales with isolation, which is why the most interesting islands — biologically and culturally — are almost always the hardest to reach. The same logic applies to tourism: the islands with the most distinctive character are usually the ones without an airport capable of taking a jet.

How islands form

The mechanism, without the jargon.

1. 01Continental islands were once attached to a mainland and separated by rising sea levels or tectonic drift.
2. 02Volcanic islands build up from the seafloor, usually at hot spots or plate boundaries, and erode back down once the volcanism stops.
3. 03Coral islands form on the subsiding flanks of extinct volcanoes — the classic tropical atoll sequence.
4. 04Tidal and barrier islands are built by sediment deposited by waves and currents, and they move over time.

Best time to see them

Depends entirely on which monsoon or storm belt you are in. The general rule in Southeast Asia is to follow the dry coast: east side from May to September, west side from November to April. In the Atlantic and Caribbean, avoid September and October for hurricane risk.

How to get there

Ferries, fast boats and small aircraft are the usual options, and all three get cancelled by weather. Schedules on remote islands are often weekly rather than daily, which means a missed boat costs several days rather than a few hours.

Tickets, permits & fees

Marine park and island conservation fees are common and usually modest, though some of the more protected places charge substantial permits and limit daily visitor numbers. Liveaboard diving is priced per berth and includes almost everything.

Notable islands

Five worth building a trip around.

• Socotra

  Yemen

  Around a third of its plant species are found nowhere else, including the dragon's blood tree. The most alien-looking island in the Indian Ocean.

  October–April Guide

• Raja Ampat

  Indonesia

  The most biodiverse marine environment measured on earth, with over 1,500 fish species and 75% of all known coral species.

  October–April Guide

• Svalbard

  Norway

  A high Arctic archipelago where polar bears outnumber people in most areas and the sun does not set for months.

  June–August

• Île Amsterdam

  Southern Indian Ocean

  One of the most remote inhabited islands anywhere, staffed by a handful of researchers and reachable only by supply ship.

  November–March

• Sri Lanka's Knuckles

  Sri Lanka

  Not an island, but a mist-covered range of near-vertical peaks where cloud forest survives in a rain shadow that makes no sense on paper.

  January–April

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