Introduce/review weathering and erosion:
'Weathering' is wearing rock into small particles. 'Erosion' is the movement of those particles.
Weathering and Erosion wear away landforms and make new ones.
Wind, water and ice all cause weathering and erosion.
Wind, water and ice all cause rocks to collide with each other: the wind blows small grains into rocks, water on a beach crashes rocks together, ice in a glacier grinds rocks together underneath it as it moves.
Show students rocks that will be added to the tumbler, and draw around them, and write in rock types, to record their sizes and shapes.
Suggested rocks local to Vancouver: granite and basalt (intrusive and extrusive igneous respectively), sandstone and mudstone (sedimentary).
Optional: Add rocks to the rock tumbler as soon as possible, so that it can tumble for close to an hour.
We’ll see what happens as those rocks collide in the rock tumbler. We’ll only tumble it for an hour. Wind, water and ice in Earth's landscapes bang rocks together for much much longer than this.
Erosion of a mountainside by water demonstration.
Erosion by ice:
Using the same water erosion tray, find a part of the mountainside that has not been washed away.
Mould the white modeling clay into a long, wide glacier shape.
Push the 'glacier' through the mountainside, showing how it gouges out the landscape. As the ice of a glacier is slowly pulled down the valley by gravity, rocks are frozen into it and are plucked from the surface. The rocks and pebbles stuck in the ice scrape at the ground, eroding it.
Ice is the most powerful erosive force.
When a glacier retreats (melts), it leaves a U-shaped valley, with a flat bottom and steep sides. Image of a valley formed by a glacier: https://learning.royalbcmuseum.bc.ca/pathways/alpine-plants/image-5-u-s…
Wind erosion activity, with challenges and free play, to see how wind shapes a desert landscape.
Rock tumbler revisit:
Look at the rocks in the tumbler, to see what has happened in just an hour.
Pull rocks from tumbler, dip in water to rinse off, and lay on the same labelled paper for sizing again.
Even in an hour, the softer rocks should be starting to break apart into smaller pieces.
Any the mud in the tumbler is from small bits that have fallen off the rocks mixing with the water.
Discussion:
Wind, water and ice cause rocks to crash into each other, breaking them into smaller pieces.
Summary of lesson:
Weathering and Erosion by water, and ice and wind change the shape of our landscape.
