1. Chemical Weathering
SAPROLITE

2. Chemical Weathering

3. Chemical Weathering
I. Introduction

4. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
Decomposition alters minerals into more stable minerals or substances at the earth’s surface.

5. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction

6. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
an element loses electrons to an Oxygen ion

7. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
an element loses electrons to an Oxygen ion
2Fe2++ 4HCO /2O2 + 2H20 >>>> Fe2O3 + 4H2CO3

8. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
an element loses electrons to an Oxygen ion
2Fe2++ 4HCO /2O2 + 2H20 >>>> Fe2O3 + 4H2CO3
Ferrous bicarbonate ferric carbonic acid
Iron Iron

9. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution

10. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution
The process of chemical weathering by which earth material passes into solution by removal of its atoms.

11. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution
The process of chemical weathering by which earth material passes into solution by removal of its atoms.
Most well-known:
CO H2O = H2CO3
Carbon dioxide water carbonic acid

12. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution
The process of chemical weathering by which earth material passes into solution by removal of its atoms.
Most well-known:
CO H2O = H2CO3
Carbon dioxide water carbonic acid
CaCO H2CO = Ca HCO3-
Limestone + carbonic acid = calcium ions + bicarbonate

13. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution
The process of chemical weathering by which earth material passes into solution by removal of its atoms.
Most well-known: Limestone + water + carbonic acid = calcium ions + CO2 + bicarbonate
pH controls solubility….

14. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution
D. Hydrolysis
Describes the reaction between minerals and hydrogen
“converting primary minerals into secondary minerals”

15. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution
D. Hydrolysis
Describes the reaction between minerals and hydrogen
“converting primary minerals into secondary minerals”
2 KAlSi3O8 + 2H+ + 9H2O >>>> H4Al2Si2O9 + 4H4SiO4 + 2K+
orthoclase kaolinite silica acid

16. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution
D. Hydrolysis
E. Ion Exchange
involves the substitution of ions in solution for those held by mineral grains.

17. Cation exchange capacity (CEC): the capability for absorbing cations
“High Base Saturation”…..the % of exchange sites occupied by cations
other than H+.”
In acid soils, H+ replaces the cations; but in basic soils, H+ replace by cations.

18. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution
D. Hydrolysis
E. Ion Exchange
III. Mobility
A. Overview

19. III. Mobility
A. Overview
* Mobility of cations
(Ca+2, Mg2+, Na+) > K+ > Fe2+ > Si4+ > Ti 4+> Fe 3+> Al 3
* All related to the ionic potential
valence (z) / ionic radius

20. valence (z) / ionic radius
very mobile = less than 3
very immobile + greater than 9.5

21. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution
D. Hydrolysis
E. Ion Exchange
III. Mobility
A. Overview
B. Leaching
“The separation, selective removal, or dissolving out of soluble constituents from a rock by the natural action of percolating water”
The process is dependent on CLIMATE and SOIL PROPERTIES

22. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution
D. Hydrolysis
E. Ion Exchange
III. Mobility
A. Overview
B. Leaching
C. pH

23. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution
D. Hydrolysis
E. Ion Exchange
III. Mobility
A. Overview
B. Leaching
C. pH
* The mobility of ions is controlled by pH

24. pH controls solubility….

26. Chemical Weathering
III. Mobility
A. Overview
B. Leaching
C. pH
D. Fixation/Retardation

27. Chemical Weathering
III. Mobility
A. Overview
B. Leaching
C. pH
D. Fixation/Retardation
E. Chelation

28. Chemical Weathering
IV. Degree and Rate of Decomposition
A. Mineral Stability

30. Chemical Weathering
I. Introduction
II. Process of Decomposition
A. Overview:
B. Oxidation and Reduction
C. Solution
D. Hydrolysis
E. Ion Exchange
III. Mobility
A. Overview
B. Leaching
C. pH
D. Fixation/Redardation
E. Chelation
IV. Degree and Rate of Decomposition
A. Mineral Stability
B. Secondary Minerals

32. IV. Degree and Rate of Decomposition A. Mineral Stability
Chemical Weathering
IV. Degree and Rate of Decomposition
A. Mineral Stability
B. Secondary Minerals
C. Estimates based on chemical analysis