are fairly consistent, with a difference between daily highs and lows averaging to . However, across the year, the difference is much less; the mean daily temperature in the warmest month is only warmer than that of the coolest. Rainfall is heavy and there is constant high humidity. The most common daily pattern follows an adiabatic process, with a calm, clear morning, followed by a breeze blowing in from higher pressures over the sea, culminating in a cloudy and drizzly afternoon. At night, the weather pattern reverses, and drizzle and heavy dew dissipate the cloud cover for the morning. Tropical cyclones are the only violent weather, but they can be destructive. Like the other islands in the archipelago, Malaita is near the Andesite line and thus forms part of the Pacific Ring of Fire. Earthquakes are common on the island, but there is little evidence of current volcanic activity. The main structural feature of Malaita is the central ridge which runs along the length of the island, with flanking ridges and a few outlying hills. There is a central hilly country, between Auki and the Kwai Harbour, which separates the central ridge into northern and southern halves, the latter being somewhat longer. The northern ridge reaches a height of about , while the southern goes up to . Geologically, Malaita has a basaltic intrusive core, covered in most places by strata of sedimentary rock, especially limestone and chert, and littered with fossils. The limestone provides numerous sinkholes and caverns. Malaitan hydrology includes thousands of small springs, rivulets, and streams, characteristic of a young drainage pattern. At higher altitudes waterfalls are common, and in some places canyons have been cut through the limestone. Nearer the coasts, rivers are slower and deeper, and form mangrove swamps of brackish water, along with alluvial deposits of gravel, sand, or mud. The coastal plain is very narrow. Inland soils are of three types, wet black, dry black, and red. The wet black soil, too poorly drained for most horticulture except taro, is found in valleys or at the foot of slopes. Dry black makes the best gardening sites. The red soil, probably laterite, does not absorb runoff and forms a hard crust, and is preferred for settlement sites. Environment There are several vegetation zones based on altitude. Along the coast is either a rocky or sandy beach, where pandanus, coconuts, and vines predominate, or a