Fun Geological trip at Santubong 23 may 2010

Do you know the difference between sandstone and ignee rock? On 23 may 2010 MNS organized a  Geological trip  to the foothills of Mt Santubong.

At 9.30 we had first a briefing by Hans, a retired Geologist, and he explained how Mt Santubong was formed and if you look at the mountain you can see that there is a saddle or valley in the between the highest summit (810 m above sea level) and the next ridgetop. Here Sugai Mandi, the small river that we were following, has it’s source and it forms the waterfall where we had or lunch and our dip into the pool.

When you pick up a piece of granite or other type of rock, then for most people it’s just a piece of rock and to most there is nothing to see and it may look boring. Until a geologist looks at the same piece of rock and whauw he suddenly sees al sorts of things, and then this rock becomes interesting. If you got the chance to see a piece under a microscope you will be impressed with how many details you can see! In his sample he explained that there are different minerals (grains) that make up the rock. The most important mineral in the sandstone is quartz, which is silicium oxide.

Before we reached the stream he explained rock outcrops and you suddenly realized that actually you are walking on rocks that are some seventy million years old! These were formed from sand in big rivers. At the bottom of those ancient rivers there where big ripples, some perhaps as big as dunes but under water.

After a short walk we came at the river and we had a chance to look for stones and after a while a number of people had found interesting pieces, which after his explanation then suddenly became valuable pieces. People seemed to enjoy learning more about the rocks, which now began to tell us some stories.

Lay, a young 10-year-old boy, had found a very interesting piece of sandstone with a regular pattern of joints or cracks, where iron-rich solutions had caused red and orange colours. Since we were coming back the same way and were quite sure that nobody would take his piece of rock away, we set it apart to pick it up on the way back.

Also seen were lots of large boulders of sandstone scattered in the forest, that apparently came from the very steep slopes higher up on the mountain. As a result of very heavy rains, landslides may have caused rock avalanches long ago.

While walking towards the waterfall were still more interesting pieces to see and finally we came to the scenic waterfall where we stopped to have our lunch and dip into the water to cool down. Also the waterfall had some interesting geological details: here you could see that the sandstone forms thick layers, which are dipping towards the west.

Most of our group decided to continue walking along this beautiful and pleasant looptrail that ends at the Sarawak Cultural Village and this trail is also popular among tourists and locals alike that come here to relax or to exercise in the cool forest.

On the way back we stopped at the river to pick up our rock samples (these were not ordinary stones anymore!) and Lay took his piece and carried it as if it was the most precious treasure, after Hans had told him that it was a very unusual piece and he was really proud he had found this.

Now when you are walking somewhere and you see stones don’t just see them as just stones but as a very piece of information that can take us millions of years back into geological time.