[7] The metamorphic rock surface was created by the transformation of ancient sediments under intense heat and pressure during mountain-building processes.

[6] Beginning about 200 million years ago, forces within the Earth's mantle began to separate the lands of the Southern Hemisphere, and a crustal plate supporting both India and Sri Lanka moved toward the northeast.

[6] About 45 million years ago, the Indian plate collided with the Asian landmass, raising the Himalayas in northern India, and it continues to advance slowly to the present time.

[6] On the east, the Uva Basin consists of rolling hills covered with grasses, traversed by some deep valleys and gorges.

[6] To the north, separated from the main body of mountains and plateaus by broad valleys, lies the Knuckles Massif: steep escarpments, deep gorges, and peaks rising to more than 1,800 meters.

[6] The land descends from the Central Highlands to a series of escarpments and ledges at 400 to 500 meters above sea level before sloping down toward the coastal plains.

[6] In the southeast, a red, lateritic soil covers relatively level ground that is studded with bare, monolithic hills.

[6] In the highlands, river courses are frequently broken by discontinuities in the terrain, and where they encounter escarpments, numerous waterfalls and rapids have eroded a passage.

[6] In the north, east, and southeast, the rivers feed numerous artificial lakes or reservoirs (tanks) that store water during the dry season.

[6] Several hundred kilometers of canals, most of which were built by the Dutch in the 18th century, link inland waterways in the southwestern part of Sri Lanka.

Its position between 5 and 10 north latitude endows the country with year-round warm weather, moderated by ocean winds and considerable moisture.

[6] During this season, periodic squalls occur and sometimes tropical cyclones bring overcast skies and rains to the southwest, northeast, and eastern parts of the island.

[6] Much of the rain in these areas falls from October to January; during the rest of the year there is very little precipitation, and all living creatures must conserve precious moisture.

[6] Also, the topmost branches of the tallest trees often interlace, forming a canopy against the hot sun and a barrier to the dry wind.

[6] When water becomes available, either during the wet season or through proximity to rivers and lakes, the vegetation explodes into shades of green with a wide variety of beautiful flowers.

[6] In the wet zone, the dominant vegetation of the lowlands is a tropical evergreen forest, with tall trees, broad foliage, and a dense undergrowth of vines and creepers.

[6] During the Mahaweli Ganga Program of the 1970s and 1980s in northern Sri Lanka, the government set aside four areas of land totalling 1,900 km2 as national parks.

[6] The typical settlement pattern in the rice-growing areas is a compact group of houses or neighborhood surrounding one or several religious centers that serve as the focus for communal activities.

[6] The nature of agricultural pursuits in Sri Lanka has changed over the centuries and has usually depended upon the availability of arable land and water resources.

[6] Until the 13th century, the village farming communities were mainly on the northern plains around Anuradhapura and then Polonnaruwa, but they later shifted to the southwest.

[6] In the Central Highlands around Kandy, villagers faced with limited flat land have developed intricately terraced hillsides where they grow rice.

[6] In the 1960s and 1970s, the wet cultivation area was expanding rapidly, as the government implemented large-scale irrigation projects to restore the dry zone to agricultural productivity.

[6] Plantation farming resulted in a drastic reduction in the natural forest cover and the substitution of domesticated crops, such as rubber, tea, or cinnamon.

[6] It also brought about a changed life-style, as the last hunting-and-gathering societies retreated into smaller areas and laborers moved into the highlands to work on plantations.

[6] Through the late 20th century, workers on large plantations lived in villages of small houses or in "line rooms" containing ten to twelve units.

The mobility of the coastal population during colonial times and after independence led to an increase in the size and number of villages, as well as to the development of growing urban centers with outside contacts.