As a reader of this blog, you might already know plenty about the amazing biodiversity in Singapore, ranging from pitcher plants to crocodiles. While these flora and fauna are certainly interesting, have you read about the amazing life of rocks in Singapore? If not, sit tight as I introduce to you one of the many types of rocks in Singapore!
Seemingly unimportant, yet found everywhere, Singapore has a surprisingly large variety of rocks despite our small size. I would even argue that they are the bedrock (pun intended) of every aspect of the Singapore we know and love today. Before we begin, allow me to give you a quick crash course about rocks.
There are 3 types of rocks: igneous, sedimentary and metamorphic.
Firstly, we have igneous rocks. Derived from the Latin word for fire, these rocks are formed from solidified lava or magma (Rocks Information, 2017). These rocks are generally hard and can be commonly found in Bukit Timah and Pulau Ubin (Friess & Oliver, 2015). Picture 1 depicts granite, an igneous rock.
Picture 1: Granite, an igneous rock. , Taken from: http://geologylearn.blogspot.com/2015/03/granite.html
Secondly, we have sedimentary rocks. As its name suggests, these rocks are formed by sediments. Transporting agents like rivers transport and deposit these sediments, causing them to pile up. With layers of sediments piling on top of one another, the bottommost layers eventually fuse together to form a new type of rock (Rocks Information, 2017). Such rocks can be found in Jurong and Sentosa (Friess & Oliver, 2015). Picture 2 depicts sandstone, a sedimentary rock.
Picture 2: Sandstone, a sedimentary rock., Taken from: https://www.minimegeology.com/home/mgeo/page_84/banded_sandstone_sedimentary_rock.html
Thirdly, we have metamorphic rocks. When igneous or sedimentary rocks experience high temperatures and pressures, they transform (or undergo metamorphosis) to form metamorphic rocks (Rocks Information, 2017). These rocks are the least common ones in Singapore due to the lack of high pressure and temperature we usually need to form them (Friess & Oliver, 2015). Picture 3 depicts gneiss, a metamorphic rock.
Picture 3: Gneiss, a metamorphic rock., Ttaken from: http://www.sciencekids.co.nz/sciencefacts/earth/metamorphicrocks.html
Armed with some basic background information about rocks, let us now go on a virtual field trip in Pulau Ubin through my phone lens.
For those who have never been there, Pulau Ubin is an Island located in northeastern Singapore. Despite experiencing no geologic activity today, Singapore saw frequent earthquakes and volcanic eruptions a mere 250 million years ago (Friess & Oliver, 2015). “Old” Singapore was comparable to today’s Indonesia. The upwelling of magma and the occasional volcanic eruptions translate to a large amount of igneous rocks being formed. Most of Singapore, Pulau Ubin included, sits on large igneous rocks.
Picture 1 above shows an igneous rock known as granite. It consists of visible grains of greyish-white feldspar, black mica and transparent quartz. These crystals are visible because the magma cooled slowly underground over a long period of time. Eventually, erosion of the land on top revealed these rocks. Since these rocks are more resistant to erosion (because of how hard they are), they result in the “hilly” appearance of Pulau Ubin (and Bukit Timah) (Friess & Oliver, 2015) as seen in the picture 4 below.
Picture 4: Ubin is the dark coloured, hilly part of the picture in the background! Photo: Lee Yang
In our hot and wet climate, feldspar in granite weather quickly. Surfaces of granite exposed to water (especially the corners) decompose, causing the parent rocks to become smaller and rounder (Friess & Oliver, 2015). Such rounded rocks are common in Singapore, Ubin included. Picture 5 shows one of such rocks in the process of rounding. As we can see, most of the rock is still “trapped” underground and perhaps a few thousand years later, more of the rock will be exposed!
Picture 5: One of the many granite rocks still stuck underground in Ubin. Photo: Lee Yang
Feldspar decomposes into clay, which is then transported by water and carried to the sea. In Chek Jawa, I saw a mini delta formed by a small river. In Picture 6 below, we can see the river as it heads into the sea and deposits the clay particles in the delta, forming the mud of the mangrove. Mangroves are very important habitats that provide many ecoservices such as being nurseries for fishes and coastal protection (Brander, et al., 2012), and one mightc say that without all this mud, the mangroves would not be present. On a side note, Picture 7 below shows a Black Spitting Cobra we encountered! Needless to say, the mangrove was teeming with life, and I argue that the geography (climate and geology included) of Singapore plays a fundamental role in sustaining Singapore’s high biodiversity. Hence, as we appreciate the diverse wildlife of Singapore, let us not forget the seemingly unchanging and boring rocks for breathing life into Singapore. I hope that this post has given a small preview of the complexity of the world and the beautiful web of relationships present, allowing you to better appreciate the Earth for everything it has and have made our planet just that bit more precious to you.
Picture 6: Can you see all the clay deposited by the stream? Photo: Lee Yang
Picture 7: A well camouflaged Black Spitting Cobra. Can you see it? Photo: Lee Yang
Written by: Lee Yang
Brander, L. M., Wagtendonk, A. J., Hussain, S. S., Mcvittie, A., Verburg, P. H., Groot, R. S., & Ploeg, S. V. (2012). Ecosystem service values for mangroves in Southeast Asia: A meta-analysis and value transfer application. Ecosystem Services,1(1), 62-69. doi:10.1016/j.ecoser.2012.06.003
Friess, D. A., & Oliver, G. J. (2015). Dynamic environments of Singapore. Singapore: McGraw Hill.
Rocks Information and Facts. (2017, January 18). Retrieved from https://www.nationalgeographic.com/science/earth/inside-the-earth/rocks/