The geography of a region determines to a large extent the history and life of its people. We shall hence attempt to present a broad picture of the environment of the Jaffna Peninsula.
The Jaffna Peninsula, longitude 700 54’-800 2 E and latitude 90 30'- 90 50 N, is situated close to the equator. It is approximately forty miles long and four to eighteen miles wide. On its western and northern sides it is bounded by the Palk Strait, on the east and south sides it i~ hemmed in by the Bay of Bengal and the Jaffna Lagoon respectively. While the Jaffna Lagoon separates the Peninsula from the mainland on the West, the Elephant Pass Lagoon separates it from the mainland on the East. The Thondamanaru and Upparu Lagoons are two internal lagoons within the Peninsula; these help drain the rainwater. There is also a small "stream" called Valukkaiyaru which is eight miles long and which helps to drain in the southwestern portion of the Peninsula.
There are many islands adjoining the Peninsula:
Karaitivu – Deriving its name perhaps from a shrup named karai
Nainativu – scared to both Hindus and Buddhists.
Eluvaitivu – literally the island of goats
Analaitivu – Known for its good fresh water.
Velanai - known also as Kayts, Uratturai and Tanaltivu
Mandaitivu - less than a mile from Jaffna town Neduntivu - meaning island at a long distance from Jaffna and renamed Delft by the Dutch.
There are two more islands named Palaitivu and Kachaitivu (the latter now belonging to India) which are not inhabited. Fishermen from the Peninsula go to these islands for fishing. There is another islet called Paruttiturai, which is a barren land close to Eluvaitivu.
The Jaffna Peninsula is a vast limestone block, the history of which dates back to the Miocene period, when the entire Island lay submerged.
The limestone of Jaffna "is a gray yellow and white organogenic, porous limestone (reef limestone), very karastic in its upper near surface part" and "is typically a compact, hard, partly crystalline rock". The limestone, said to be 270 feet deep thick, is underlain by a thick sandstone formation." It consists of calcium carbonate that is soluble in the rain water containing carbondioxide. The rainwater filters through the karastic openings and other weak points. As the soluble parts disappear, the remaining parts form caverns. Most of these caverns are at Urikkadu.
Limestone wastes are found scattered throughout the Peninsula. In the northern and western parts of the Peninsula, limestone appears on the surface in the form of hard coral rocks marked with tiny holes resulting from exposure to rain.
The string of islands lying off the West Coast of the Peninsula is said to represent a drowned portion of the Peninsula.
"Levelness" is a distinguishing feature of the Peninsula and its islands. Only at cliffy Keerimalai, limestone and sandstone hill rises to a height of thirty feet above the sea level, the highest point. The level of the land is so low that in various places the sea runs in and forms the large lagoons which cut through the Peninsula's center and eastern portions. These winding lagoons, which are not accessible to heavy ships, lend a particular beauty to the landscape of the Peninsula.
Along the lagoon area the soil is alkaline. When this land is irrigated, a thin coating of salt comes up to the surface. Vegetation consists of a leafless shrub called talai (koddanai and oleander).
In the northern and western parts of the Peninsula, where limestone is to be found on the surface, no vegetation other than cactus plants and tiny shrubs is possible as there is either very little or no soil covering at all. The scanty vegetation survives partly due to the moisture brought by the wind and partly due to night dews. Palmyrah trees, however, flourish even in this unproductive land, because their strong and long roots are capable of reaching the level of water under the surface.
In certain areas, limestone surface is removed and a thin layer of soil is placed to form garden soil.
Stretches of sand are to be found on the Peninsula's northeast and southeast. During the monsoon periods, sands are carried by the waves and currents from the coast of South India and are blown on shore by the wind, a process which results in the formation of sand dunes. Wooden fences are erected in many places to stop the sand dunes encroaching on the cultivated land. No vegetation is evidently possible on these areas of sand other than a few Palmyra plants.
Tracts of gray loam, whose lower layers are dark or bluish in colour and are flecked by brown hydrated oxides, are found extensively in the Peninsula. Derived from limestone, it is of clayish nature, but it gets hardened and is turned into a white powdery soil of good quality during the dry season.
There is rich red soil (similar to the Mediterranean terret rossa) of fine texture at the core of the western half of the Peninsula. It is claimed to be decomposed limestone, namely "lime from the comminuted coral" and contains iron oxides. The redness of the soil is attributed to the fact that either the soil is not leached or there is an admixture of iron. The red soil area is the garden land of the Peninsula.
The gray and red soil layers are generally so thin that they are unsuitable for the growth of trees. But vegetables could easily be grown because of the soil's fine texture, which is conducive to both root development and exposure to light. In fact, paddy is cultivated on the gray loam soil while tobacco is grown on the red soil.