Ch. 9 Lesson 3

What is weathering?

Sugar cubes-Weathering activity1. Describe the appearance of the sugar cubes.2. Place the sugar cubes in the jar & shake 5 times.3. Pour the contents of the jar onto a piece of

paper separating the sugar cubes and the crumbs. (don't eat any of it !!!)  

4. Describe any changes you notice in the sugar cubes. 

5. Return the sugar cubes to the jar and shake another 5 times.

6. Again pour the contents onto a piece of paper separating the crumbs and the cubes.

7. Did the second shaking cause the cubes to look more worn?    

8. Is the amount of crumbs greater than, the same as or less than the first shaking?

2 types of2 types ofweatheringweathering

mechanical chemical

mechanical weathering

• breaking of rock smaller pieces by forces:

•gravity

• water

• ice

ice wedging•water freezes in cracks of rock &

expands & forces rock to split

Rocks Change [01:13]

• plant roots

rate of mechanical weathering on rocks depends on:

1. type of materials in rock

2. conditions around it

sandstone granite

chemical weathering

• changes in rock by chemical processes

• raindrops absorb CO2 from air

makes carbonic acid makes caves

stalactites & stalagmites

The stalactite formed over the

bat before the bat

decayed.

Weathering [06:58]

soil• mixture of sediments :

– weathered rock

– decayed organisms

– gases from air

– water

parts of soil

topsoiltopsoil= fertile b/c large = fertile b/c large amt. decayed materialamt. decayed material

subsoilsubsoil= less decayed = less decayed materialmaterial

bedrockbedrock= nearly solid rock= nearly solid rock

sediments in soilsediments in soil