Sri Lanka lies on the Indian Plate, a major tectonic plate that was formerly part of the Indo-Australian Plate. It is in the Indian Ocean southwest of the Bay of Bengal, between latitudes 5° and 10°N, and longitudes 79° and 82°E. Sri Lanka is separated from the Indian subcontinent by the Gulf of Mannar and Palk Strait. According to Hindu mythology, a land bridge existed between the Indian mainland and Sri Lanka. It now amounts to only a chain of limestone shoals remaining above sea level. Legends claim that it was passable on foot up to 1480 AD, until cyclones deepened the channel.
The island consists mostly of flat to rolling coastal plains, with mountains rising only in the south-central part. The highest point is Pidurutalagala, reaching 2,524 meters (8,281 ft) above sea level. The climate is tropical and warm, due to the moderating effects of ocean winds. Mean temperatures range from 17 °C (62.6 °F) in the central highlands, where frost may occur for several days in the winter, to a maximum of 33 °C (91.4 °F) in other low-altitude areas. Average yearly temperatures range from 28 °C (82.4 °F) to nearly 31 °C (87.8 °F). Day and night temperatures may vary by 14 °C (25.2 °F) to 18 °C (32.4 °F).
Rainfall pattern is influenced by monsoon winds from the Indian Ocean and Bay of Bengal. The “wet zone” and some of the windward slopes of the central highlands receive up to 2,500 millimeters (98.4 in) of rain each month, but the leeward slopes in the east and northeast receive little rain. Most of the east, southeast, and northern parts of the country comprise the “dry zone”, which receives between 1,200 and 1,900 mm (47 and 75 in) of rain annually. The arid northwest and southeast coasts receive the least amount of rain at 800 to 1,200 mm (31 to 47 in) per year. Periodic squalls occur and sometimes tropical cyclones bring overcast skies and rains to the southwest, northeast, and eastern parts of the island. Humidity is typically higher in the southwest and mountainous areas and depends on the seasonal patterns of rainfall.
An increase in average rainfall coupled with heavier rainfall events has resulted in recurrent flooding and related damages to infrastructure, utility supply and the urban economy.
The country has 103 rivers. The longest of these is the Mahaweli River, extending 335 kilometers (208 mi). These waterways give rise to 51 natural waterfalls of 10 meters or more. The highest is Bambarakanda Falls, with a height of 263 meters (863 ft). Sri Lanka’s coastline is 1,585 km long. It claims an Exclusive Economic Zone (EEZ) extending 200 nautical miles, which is approximately 6.7 times the country’s land area. The coastline and adjacent waters support highly productive marine ecosystems such as fringing coral reefs and shallow beds of coastal and estuarine seagrasses. Sri Lanka has 45 estuaries and 40 lagoons. The country’s mangrove ecosystem, which spans over 7,000 hectares, played a vital role in buffering the force of the waves in the 2004 Indian Ocean tsunami. The island is rich in minerals such as ilmenite, feldspar, graphite, silica, kaolin, mica and thorium. Existence of petroleum and gas in the Gulf of Mannar has also been confirmed and the extraction of recoverable quantities is underway.