This map shows today’s land areas as well as parts of the seas which were once land ( Sunda Land ) .
Malaysia’s lands and seas form the northern part of Sundaland an amazing geographical region stretching down to Java and across to Sumatra and Borneo. The region was once entirely land, but much of the lower lying central portion was drowned during a major rise in sea level which occurred after the last Ice Age. Thus, the islands and land masses we see today were formed. Malaysia’s seas the Strait of Melaka and the South China Sea lie on the Sunda Shelf. The depth of water over the Sunda Shelf is very shallow, less than 200 metres. This feature has given rise to unique ecosystems, and has also allowed the geology of the sea bed to be explored. Drowned valleys on the Sunda Shelf reveal that the area was once land, drained by rivers. The valleys often have paired terraces indicating that over time the sea level did not simply rise but fluctuated rising and falling over the period before the last major inundation. In Malaysia, there is much evidence of these fluctuations, especially from the most recent rise, 5,000 years ago, known as the Holocene transgression . Geological data and coastal formations in Malaysia, such as marine notches, show that the mid – Holocene reached its maximum height around 5,000 years ago when the sea level was 5 metres above its present level.
Apart from physical features, such as drowned river valleys and beach ridges, core samples of rocks and sediments from the west coast of the Peninsula have been analysed. The findings reveal fossilized plant remains, such as pollen of different types of vegetation, from 10 metres under the current sea level to some kilometres inland of today’s coastline where mangrove remains have been identified.