Weathering refers to the breakdown of rocks into smaller pieces through mechanical, chemical, or biological processes without transportation, while erosion includes the transportation of weathered rock material by agents such as wind, water, or ice. This document describes three types of weathering - mechanical, chemical, and biological - and provides examples of specific weathering processes, including freeze-thaw action, salt crystallization, carbonation, hydration, oxidation, and hydrolysis. Images show examples of weathering patterns from these processes in various rock formations around Ireland.

1. Chapter 6
Weathering and
Erosion

2. Junior Cert Recap
1. What is Weathering?
2. What is Erosion?
3. Describe two types of Weathering
4. What type of weathering is happening in this picture?
5. Where was this picture taken?

3. Weathering and Erosion
 Weathering refers to the breaking down of rocks into smaller
pieces
 Erosion refers to the breaking down of rocks into their smaller
pieces and the transportation away of the rock fragments,
usually by moving wind, sea currents, rivers or glaciers.

4. Weathering
 Three types of weathering:
 Mechanical – breaking down of larger rock into smaller
rocks. No chemical change to rock. Example – Freeze thaw
action
 Chemical – a chemical reaction occurs in the rock causing it
to dissolve and forming new substances. Example –
Limestone dissolved by rainwater, forming calcium
carbonate in caves
 Biological – disintegration of rocks due to the actions of
plants/animals

5. Freeze thaw weathering – p71

6. Freeze Thaw in action creating straight
fractures in rock – the Burren

7. Onion weathering (exfoliation)
 Surface of the rock is peeled away layer by layer – like an
onion
 Caused by heat (causing expansion) and cold (causing
contraction)
 If a rock has different minerals (e.g. Granite, sandstone) can
wear more quickly as different particles expand and contract
at different rates

8. Onion Weathering (Exfoliation)

9. Salt Crystillisation
 Water drying out leaves salt traces behind (basic process
behind the creation of chemically formed sedimentary rocks)
 If water gets into a crack (like what happens with freeze thaw
action) and evaporates instead of freezing, the salt gets left
behind.
 Over time this salt can build up, putting pressure on the rock,
and the rock can crack
 (Like freeze thaw action, except with salt instead of ice)

10. Honeycomb patterns caused by
Salt Crystillisation

11. Chemical weathering
 Rocks are dissolved (usually by rainwater)
 Rainwater contains chemicals and is slightly acidic from
picking up CO2 from the atmosphere
 Sedimentary rocks are most easily weathered –
cementing agents in the rock are most easily weathered
 The Burren in Co. Clare is a landscape created by
Chemical Weathering.

12. The Burren – Chemical Weathering
– no straight fracture lines

14. 2010 Leaving Cert

15. Chemical Weathering (processes)
 Four processes of chemical weathering
 Carbonation (rainwater becomes acidic & dissolves rock)
 Hydration (Minerals in rock react with water)
 Oxidisation (Minerals in rock react with oxygen)
 Hydrolysis (acidic water on certain minerals esp feldspar)

16. Hydration

17. Oxidisation & Hydrolysis

18. Biological Weathering
 The action of animals and plants
 Roots breaking up rocks
 Burrowing animals

19. Biological weathering

20. Biological weathering – burrowing
animals

21. Biological weathering – rat vs
concrete

22. 2007 Leaving Cert Hons

23. Erosion
 Erosion involves the breaking down (weathering) of rocks
and also the transportation of weathered material away.
 Agents of Erosion are
 Rivers
 Moving Ice
 The Sea
 Wind

24. 2007 Ordinary Level LC
 MARKING SCHEME: 10 SRPs at 3 Marks each

25. Chemical Weathering (processes)
 Write 5 SRPs on each of the following processes of chemical
weathering
 Carbonation
 Hydration
 Oxidisation
 Hydrolysis