1. Rocks & Landforms I-3 Notes

2. Introduction

3. Physical Weathering Takes place over tens to hundreds of years
Processes that take place in the surface environment of the Earth
Causes solid rock to be broken down into loose pieces of minerals and rocks

4. Chemical Weathering
Rocks from deep in the Earth (are at higher temperature and pressure)
When these rocks are brought near the surface (different chemical environment). The change in conditions makes some of the minerals chemically unstable
Some minerals may breakdown chemically

5. Physical weathering and chemical weathering act together
Physical weathering and chemical weathering act together. However, they will be studied separately.

6. Physical Weathering
Breaks rocks apart without changing their mineral composition

7. Ice Wedging Water seeps into cracks in rocks
Temp. drops, water freezes & expands
The expansion puts enormous pressure on the surrounding rocks
Frozen water acts like a wedge, making cracks wider

8. After repeated freezing and thawing, the rocks break apart.
Expansion and contraction of water also causes potholes in streets.

9. Plant Roots Plants take root in cracks of rocks
Roots become larger and exert pressure
Cracks in rocks become larger and rocks break apart

10. Chemical Weathering
Minerals in the rock dissolve in water forming a weak acid (Acid Rain)
Acidic water makes some rocks dissolve even faster
Rocks made of the mineral calcite (for example, limestone, are most easily dissolved by acidic water
Without water, chemical reactions that weather rocks happen slowly

11. Biological Processes in Weathering
Lichens

12. Lichens (continued)
Among the first organisms that establish themselves on bare rocks
Produce a diluted acidic solution which break down the minerals in rocks slowly

13. Weathering of the mineral material in soil
Microorganisms are present in the soil in amazingly large numbers

14. Larger animals, like earthworms and rodents also live in the soil

15. As plants and animals die, they add organic material to the soil

16. This organic material decays and is converted into carbon dioxide
Carbon dioxide forms more weak acid (carbonic acid) promoting more weathering

17. The Earth Systems and Weathering

18. Formation of karst landform

19. Formed by chemical weathering
Carbon dioxide is produced naturally by animals, the use of fossil fuels and the decay of organic matter in soil
Some of this carbon dioxide is dissolved in surface waters forming an acid
In areas where pure limestone bedrock and lots of rainfall, karst topography often develops

20. Happens both on rock surfaces and cracks and fractures in limestone, as acidic groundwater percolates downward

21. Leads to large underground networks of caverns

22. Sometimes whole blocks of homes will collapse, forming a sinkhole

23. Copy Chart
The Atmosphere
The Biosphere
The Geosphere
The Hydrosphere

24. In boxes, write how karst topography occurs in each of the four Earth Systems