2014 (as of 2021 the last year for which data is publicly available), monthly mean temperatures at South Tarawa, the capital of Kiribati, ranged between , with maximum monthly temperatures ranging from and minimum temperatures ranging from . Caroline Island lies within a region of highly variable precipitation; between 1950 and 2010 the region received an average of of rain annually. Tides are on the order of , and trade winds, generally from the northeast, mean that corner of the island experiences the roughest seas. Caroline Island is among the most remote islands on Earth. It is from the closest land at Flint Island, and from the nearest continental land in North America. Geology Caroline Atoll is one of over 175 atolls and coral islands in the Pacific Ocean. The English naturalist and geologist Charles Darwin first suggested the theory, still accepted, that atolls originate from calcium carbonate platforms that grow around the cones of extinct, sinking volcanoes. Caroline Atoll's high volcanic island has subsided below sea level; the surrounding coral reef has developed upwards, built by corals, its typically annular shape caused by underwater weathering. The coral reef will continue to develop as long as it is not overtaken by rising sea levels, in which case the corals will perish and the atoll will stop growing. The Line Islands chain is made of seamounts and ridges from the Tuamotu Islands in the south to Johnston Atoll in the north; which rise from the ocean floor from a depth of . Caroline Island is one of 12 seamounts in the chain to rise above sea level. The igneous rocks of all the Line Islands consist of alkali basalts and hawaiites, and are similar to those found in the Hawaiian Islands. Several models have been proposed to explain the formation of the chain's complex geology. In 1972, the American geophysicist W. Jason Morgan postulated that the chain was formed 70 myr ago in parallel with the creation of the Hawaiian Islands, each by means of a single hotspot. Other experts argued against this model, pointing to geometric and paleomagnetic evidence, and the complex timing of the volcanic episodes that created the Line Island chain. In a 1976 paper, Winterer implied that chains of volcanoes were created by a series of individual hotspots. Over the next decade it was discovered that Late Cretaceous and Eocene volcanism had occurred close to Caroline Island,