Comet creating in the Upper School classroom

January 14 2025

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Class 9 witnessed Geography Teacher, Alistair Pugh, who delivers the Geology Main Lesson, simulate a comet or cosmic snowball on Friday, as he mixed the key ingredient of dry ice with soil (because comets contain bits of rocky material), water and soya sauce (imitating organic molecules such as carbon and potassium).

Comet creating in the classroom as part of Class 9’s Geology Main Lesson.

This practical process, alongside other simple yet surprisingly good analogue experiences – such as the ice cube glacier (below) – help the pupils experience the processes which shape and change the natural world in this non-exam morning lesson block.

Frozen CO2 at minus 78 degrees centigrade (dry ice) comes at the beginning of the Main lesson, dealing with the dynamic life of the solar system. The warmer water used the more fierce the reaction, because you are immediately forcing the carbon dioxide to melt and go back as a vapour.

These experiments complement the wider Class 9 curriculum, which is guided by the overarching theme of ‘contrasts’: rough and smooth; ice cold and room temperature, solid and liquid; form and chaos – and of course, creation and destruction, leading ultimately to equilibrium.

Gritty ice cubes: Most people think of a glacier as a river of ice – just solid water. But a glacier is more than that. All glaciers are combinations of water ice, plus all the rocks and pebbles and gravel which are trapped inside them. This is what allows glaciers to scrape away at the landscape as they move, carving out valleys, such as Glencoe—or the Grassmarket!

A highlight of this Main Lesson is a trip to the lead-mining museum at Wanlockhead, one of Europe’s most important mineralogical sites in Scotland’s highest village. Learn more about the Geology Main Lesson in Class 9 and see how it fits into the broad Upper School Curriculum here:

Geology Main Lesson