Summary Show how water, as liquid and ice, weathers and erodes rocks and landscapes. Science content Earth/Space: Landforms, Erosion (3) Activities in this lesson Rock tumbler Weathering rocks by water Chemical weathering/Carbonate acid test Erosion by water and Landform formation Procedure Intro Weathering = wearing rock into small particles. Erosion = moving those particles. SLOW processes. Weathering from water, ice and wind, sun, collisions, plants/animals. Chemical reactions also weather. In their own ways they break up rock into small particles. Water, ice and wind can also cause erosion, moving the small bits of rock to a new place. We’ll focus on Weathering and Erosion by Water and Solid water [ice]. Rock tumbler At the beach or in rivers, rocks collide with each other as water bangs them together. We’ll see what happens as rocks collide by using a rock tumbler. Weathering rock with water Weathering of rocks by water happens in different states of matter. [Review solid, liquid, gas terms.} Liquid water, as rain and rivers, gradually wears away rocks by washing off little pieces. Cold weather freezes water into ice. Ice expands as it is made, so if it is in a tiny crack, it can push outwards with enough force to break a rock apart: ‘Weathering it’. (Also weathering, the Sun heats up rocks and breaks them, and Wind blows bits off rocks.) Test how liquid water weathers different kinds of rocks. Chemical weathering Water can also carry chemicals that interact with rocks, change their chemistry, and break them down. Oxygen in the air can chemically react with iron in rocks, making them turn red - basically rusting! Rainwater absorbs CO2 from the air to make a weak acid, which chemically reacts with rocks. Find out what happens when a weak acid interacts with chalk rock Erosion demo Once rocks have been weathered (broken up), the bits can move. The movement is called Erosion. This demonstration shows erosion by liquid water, and how it shapes the land. Erosion by ice can be demonstrated in the same tray with a modeling clay 'glacier'. Ice is the most powerful weathering and erosive force. When a glacier retreats it leaves a wide U-shaped valley. Rock tumbler revisit Even in an hour, the softer rocks are starting to break apart into smaller pieces. See the mud in the tumbler from those small bits that have fallen off mixing with the water. Grades taught Gr 2 Gr 3
