About Mulu > Unique Geology
Unique Geology and Landscapes
The geology of the Mulu region of Sarawak consists of sandstone and limestone rocks. These sedimentary rocks were laid down in the sea between 90 and 20 million years ago. Since then, they have been uplifted and tilted and subjected to the forces of erosion. A rare combination of factors has lead to the unique landscapes visitors can admire in Mulu today.
The sandstones were the most resistant to erosion. They form the highest mountains in the region, located in the southeast of the Park. They culminate in Gunung Mulu with its characteristic pyramid-shaped summit, at an altitude of 2376m. Weather permitting, the summit of Gunung Mulu can be seen from The Matumau Lodge. Visitors to Mulu can climb to the summit of this sandstone mountain, but it is a very sporty trek of several days.
The limestones are over 1500m thick. This thickness is quite unusual. In addition the rocks are very pure, homogeneous and massive. For millions of years, they have been eroded by the extremely high rainfall of this tropical region. The highest peaks that remain are Gunung Api (1710m) and Gunung Benerat (1615m). Other characteristic cone-shaped hills with whitish cliff faces are also the remnants of the massive limestone.
The limestones are so important to what Mulu is that we have highlighted them (in green) on our map of the region.
The geological and climatic conditions were very favorable to dissolution of large volumes of rock both above and below ground. Over millions of years this has led to the development of an extensive network of huge caves and caverns, in this tropical karst region. Some of the largest caves in the world are in Mulu.
In place the roofs of caves collapsed into the underlying voids. This is what happened att the Garden of Eden - one of the world's largest collapse structures - and a scenic tour destination.
As caves were "growing" underground, rivers on the surface were eroding the rock down, creating deeply incised valleys and beautiful gorges, the most spectacular of which is the Melinau Gorge. Rain eroding the massive soluble limestone rocks sculpted the Pinnacles, forests of huge needle-like limestone towers, for which Mulu is famous.
Alluvial deposits were laid down in the main valleys. Today the streams have eroded down into the alluvium leaving visible terraces of mainly sandstone gravels and cobbles. The Matumau Lodge is located on alluvium in the scenic Melinau valley.