Only a few degrees south of the Tropic of Capricorn, oceanic Rapa Nui is one of a handful of islands to emerge from a submarine volcanic chain that stretches west from the Chilean mainland; the others, with no permanent inhabitants, are San Félix, San Ambrosio, and Sala y Gómez. The closest populated land is Pitcairn Island, 1,900 kilometers west, beyond which are the Polynesian outposts of the Mangarevas or Gambier Islands (2,500 kilometers west) and the Marquesas Islands (3,200 kilometers northwest).

Even farther from the Chilean coast—about 3,700 kilometers west of the mainland port of Caldera—Rapa Nui consists of lava flows from three distinct cones that fused to form a triangular landmass of just 171 square kilometers, resting on a subterranean platform that plunges abruptly into the depths of the Pacific. It is nowhere longer than 24 kilometers and nowhere wider than 12 kilometers.

All these volcanoes are dormant; the most recent eruption, at the northerly 507-meter Maunga Tereveka, occurred 10,000 years ago. The water-filled, 410-meter crater of Rano Kau, to the southwest, and the 400-meter Pu A Katiki are both nearly three million years old, with their last eruptions more than 180,000 years ago.

In addition to these major craters, there are several smaller but significant craters and other volcanic landforms, including sprawling surface lava fields and subterranean tubes that extend for considerable distances. Much of the island’s perimeter consists of rugged headlands, with no truly sheltered anchorages and only a few sandy beaches. There are no surface streams, as rainfall percolates quickly into the porous terrain, but a few areas have sufficient soil for horticulture.

As a subtropical oceanic island, Rapa Nui experiences relatively minor seasonal variations—the mean summer maximum temperature is 27.3°C, the mean winter minimum 15.5°C, and the annual average 20.7°C. The average annual precipitation is 1,126 millimeters; most rain falls between late autumn and early spring, but cloudbursts can occur at any time of year.