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.
There are other agents of weathering: sun, plants and animals.
At the beach or in rivers, rocks collide with each other as they are tumbled together.
We can model this: add rocks to the rock tumbler (before other activities, 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. Beach and river rocks are banged together for much much longer than this.
Show students rocks that will be added to the tumbler, draw around them with a sharpie on paper, then write in rock types, to record their original sizes and shapes.
Suggested rocks local to Vancouver: granite and basalt (intrusive and extrusive igneous respectively), sandstone and mudstone (sedimentary).
Weathering rock with water activity, to compare how fast different rocks are weathered.
Show chemical weathering of a carbonate rock with acid.
Wind erosion activity, with challenges and free play, to see how wind shapes a desert landscape.
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…
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. The harder igneous rocks look basically the same.
Mud in the tumbler is from small bits that have fallen off the rocks mixing with the water.
Summary:
Wind, water and ice weather rocks (break them into small pieces) and move these fragments to new places (erosion).
Weathering also happens by the sun (heating and expanding rocks), plants and animals, and the wind.
Erosion also happens by the wind.
Weathering and Erosion change the shape of our landscape.
