United World College (UWC) was embarking on a new Grade 4 academic unit about the Earth and changes to its geology. After spending weeks investigating the structure of the earth and types of rocks and visiting the Science Centre’s Earth: Our Untamed Planet exhibition, UWC wanted to offer its students a hands-on understanding of “the secrets that rocks reveal”, and invited Singapore Fossil Collectors to conduct a lecture and demonstration to its students.
We started our session with UWC’s 200-strong Grade 4 cohort at their Dover Campus in the morning of 6 February 2014, by cutting an aloe vera fruit to illustrate the structure of the earth, and peeling a Mandarin orange (Chinese New Year was just last week) to demonstrate the effects of plate tectonic movements on the geography.
With a four-billion year old zircon slab – the oldest rock in the world – we went through the geological time scale and radiometric dating. We then showed samples of Igneous, Metamorphic, and Sedimentary rock, to discuss the important permineralization process that offers palaeontologists fossil evidence.
The students were surprised by the range of fossil types beyond traditional fossilised skeletons, and handled samples of trace fossils such as coprolites and footprints, amber with inclusions, living fossils like Coelacanth and Ginko, casts, fake fossils, and even the mummified fossil of a Wooly Mammoth ear.
We then moved on to the main topic of how geological changes over deep time shaped the diversity of life. Firstly in the Pre-cambrian, students saw the earliest record of life as cyanobacteria, whose traces were left in three billion year old Stromatolite.
In the Cambrian, fossils preserved simple multicellular lifeforms such as Naraoia and Kimberella graduated into simple exoskeletons in Paradoxide trilobites. However, the first predators such as Anomalocaris ignited the Cambrian Explosion, an arms race which eventually led to advanced defence mechanisms such as the spines, bumps, antenna, feelers, compound eyes, and even eyes on long stalks that helped in camouflage.
The Silurian period was important as it saw the emergence of the Eurypterid, the first creature that could walk on land due to their exoskeleton and whose descendants include modern day arthropods such as insects and crabs.
Terrestrial life radiated freely in the Devonian, with plants spreading across the land and forming forests. Apart from the complex defence features of Devonian trilobites, this period of high sea levels also saw the spread of fish, from bony fish and sharks to armoured species.
As the super-continent Pangea came together in the Carboniferous, sea levels declined and this gave rise to extensive lowland swamps in North America and Europe. Trees with hard bark fibre lignin started to appear, which was too tough to be decomposed by the bacteria and fauna then. As a result, there was widespread burial of wood that became fossilised as the coal deposits extracted from the ground to power the earth today. This carbon burial led to very high oxygen content in the atmosphere; estimated at 35 percent compared to 21 percent today. The moist environment and heavy oxygen concentration reduced the respiratory effort of terrestrial creatures, and led to insect and amphibian gigantism. The Carboniferous is unique for its fossils of the two-foot long giant dragonfly Meganeura – the largest flying insect to ever roam the planet – as well as the 2.6-metre long millipede Arthropleura, the largest known land invertebrate of all time.
Subsequently, the Permian period that was not only infamous for featuring the largest extinction event of all time, but witnessed Pangea’s breaking apart. The students saw fossil specimens such as Mesosaurus and Glossopteris, whose appearance on once-united continents offer compelling evidence of continental drift.
The Permian period is known as the age of amphibians, but there were also marine reptiles such as Claudiosaurus germaini, whose descendants in the Triassic included the common marine reptile Keichousaurus. The Triassic also saw the appearance of dinosaurs, with the earliest dinosaurs such as Eoraptor and Coelophysis.
By the time of the Jurassic, dinosaurs became dominant. Fossils of the apex predator Allosaurus could be found all over Laurasia. (At that time, tyrannosaurid ancestors such as Dilong paradoxus and Guanlong wucaii only measured a couple of metres in length). By the Middle Jura
ssic, Pangaea’s separation into Laurasia and Gondwana which formed the Tethys Sea and Atlantic Ocean. Deeper seas led to the growth of marine reptiles such as the pliosaurs and plesiosaurs.
Finally, the Cretaceous period witnessed the widespread distribution of our favourite dinosaurs, ranging from the Triceratops and the T-Rex in North America, to the larger ‘African T-Rex’ the Carcharodontosaurus as well as the largest carnivorous dinosaur, the Spinosaurus, in Africa. Interestingly, students learnt that tyrannosaurids and spinosaurs have been found as close to Singapore as in Thailand, Malaysia, and Australia. Students also saw samples of the KT-boundary layer, evidencing the global asteroid impact that brought about the extinction of these dinosaurs.
Following that, the more modern periods of the Miocene and Pleistocene were marked by fossils of megafauna such as the Wooly Mammoth, Giant Kangaroo, Giant Sloth, and Sabre-tooth Tiger, as well as the first appearance of the earliest humans.
The UWC students had a wonderful time, and left the following comments:
“I really liked how you explained the whole history of the earth. It was so interesting to find out about the earth clock and that humans have only been around for three seconds. It was so cool!”
“This was really good information and an amazing presentation. I never knew we still lived in the Ice Age!”
“I think you answered all our questions that we couldn’t find the answer to.”
“Your presentation was awesome, loved it…I was inspired.”
The teachers of the Grade 4 Team at the United World College of South East Asia also were also generous with their feedback:
“Calvin, Han and Andy were a wonderful addition to our unit about The Changing Earth. Prior to the presentation, Calvin was in contact to ensure the talk was tailored to our needs with age appropriate content. The talk was well organised and interesting for the audience and both the students and teachers learnt a lot! The display of fossils was wonderful for our students to observe and they enjoyed being able to look so closely at such a wide selection. The students were so enthusiastic about the presentation!”
Thanks for this opportunity to share our passion. The Singapore Fossil Collectors look forward to meeting the students again next year!