1. Geology and geological cycle
Lecturer:
Assoc. Professor Hj. Dr. Ir. ACHMAD FAUZI
Faculty of Civil Engineering & Earth Resources, 2014

2. Geology and geological cycle
Figure 1.1 The rock cycle

3. Igneous Rocks as Primordial Sources for Soils,
James Hutton (1727–1797) was the author the concept of the rock cycle, which depicts the inter- relationships between :
igneous rocks;
sedimentary rocks;
metamorphic rocks.
The weathering processes:
Physical Weathering:
disintegration of rocks and minerals by a physical or mechanical process.
Chemical Weathering;
chemical alteration or decomposition of rocks and minerals.

4. Physical Weathering process:
Takes place by a variety of processes:
Development of Joints
Crystal Growth
Heat
Plant and Animal Activities
Frost Wedging
Chemical weathering processes:
Since many rocks & minerals are formed under conditions present deep within the earth, when they arrive near the surface as a result of uplift & erosion, they encounter conditions very different from those under which they originally

5. Chemical weathering processes: (cont.)
The main agent responsible for chemical weathering reactions is water and weak acids formed in water.
H+ is a small ion and can easily enter crystal structures, releasing other ions into the water
Types of Chemical Weathering Reactions

6. Chemical weathering processes: (cont.)
Types of Chemical Weathering Reactions
Hydrolysis - H+ or OH- replaces an ion in the mineral.
Leaching - ions are removed by dissolution into water.  In the example above we say that the K+ ion was leached
Oxidation - Since free oxygen (O2) is more common near the Earth's surface, it may react with minerals to change the oxidation state of an ion
Dehydration - removal of H2O or OH- ion from a mineral.
Complete Dissolution – all of mineral is completely dissolved by the water.

7. Clay Minerals + Hematite + Goethite
Weathering of Common Rocks
ROCK
PRIMARY MINERALS
RESIDUAL MINERALS1)
LEACHED IONS
Granite
Feldspars
Clay Minerals
Na+, K+
Micas K+
Quartz
 ---
Fe-Mg Minerals
Clay Minerals + Hematite + Goethite
Mg+2
Basalt
Na+, Ca+2
Magnetite
Hematite, Goethite
  ---
Limestone
Calcite
None
Ca+2, CO3-2
1) Residual Minerals = Minerals stable at the Earth's surface and left in the rock after weathering

8. Groups of rocks: 1. Igneous Rocks
were formed from originally molten states (see lava mountain).
2. Sedimentary Rocks
were formed initially through the accumulation of sediment /new minerals formed through the result of chemical precipitation or organic activity
3. Metamorphic Rocks
Pre-existing rocks that are affected by pressure, substantial changes in temperature or by chemically active fluids (e.g., hot water)

9. Igneous Rocks:
are primary rocks formed by the cooling of molten magma's, or by the recrystallization of older rocks under heat & pressure great enough to render them fluid.
1. Extrusive Igneous Rocks or Volcanic Igneous Rocks (poured out at the surface) were formed initially through the accumulation of sediment /new minerals formed through the result of chemical precipitation or organic activity. Those formed as molten rock that flows from a volcano
2. Intrusive igneous rocks or plutonic igneous rocks, (large rock masses which have not been formed in contact with the atmosphere or rock forms directly within magma chambers).

10. Igneous Rocks Classification

11. (c) Obsidian Exhibits a Glassy (d) Porphyritic
(a) Coarse-Grained
(b) Fine-Grained
(c) Obsidian Exhibits a Glassy
(d) Porphyritic

12. Sedimentary Rocks (SR)
1. Silici-clastic SR:
particles came from eroded pre-existing rocks
2. Chemical (SR):
Biochemical SR: particles came from the remains of organisms that left behind mineralized shells, tests or skeletons and
Chemical SR: particles came from minerals precipitated from water. The color varies from dark-grey to black.
3. Organic sedimentary rocks: particles came from
the remains of plants

13. Sedimentary Rocks Classification

14. Silici-clastic SR Chemical SR Organic SR (a) Shale with Plant Fossils
(b) Conglomerate
Fossiliferous limestone
Organic SR
(a) lignite/brown coal
(b) bituminous coal

15. There are two main categories of MR:
Metamorphic Rocks MR:
These solid state changes that Sedimentary/igneous rocks undergo at elevated pressure and/or temperature are known as metamorphism and the rocks that result are metamorphic rocks.
Example: a sedimentary rock (shale) has been changed into a metamorphic rock (slate).
There are two main categories of MR:
1. Foliated MR, has a banded or layered appearance, Fig. a
2. Non-foliated MR, does not have a banded texture, Fig. b

16. Displays a Banded Appearance b. Marble—A Non-foliated Metamorphic Rock
a. Gneiss Typically
Displays a Banded Appearance
b. Marble—A Non-foliated Metamorphic Rock

17. Major Metamorphic Rocks Classification

18. General type of soil
Residual and Transported Soils
Residual soils are those that remain at the place of their formation as a result of the weathering of parent rocks
Transported soils are soils that are found at locations far removed from their place of formation. The transporting agencies of such soils are glaciers, wind and water.
Organic and Inorganic Soils
Soils of organic origin are chiefly formed either by growth and subsequent decay of plants such as peat, or by the accumulation of fragments of the inorganic skeletons or shells of organisms.

19. Hence a soil of organic origin can be Organic and In- organic Soils
Organic soil ordinarily refers to a transported soil consisting of the products of rock weathering with a more or less conspicuous admixture of decayed vegetable matter.
Some Soils that are commonly used practice
Bentonite,
is a clay formed by the decomposition of volcanic ash with a high content of montmorillonite.
It exhibits the properties of clay to an extreme degree.

20. Varved Clays,
consist of thin altemating layers of silt and fat clays of glacial origin. They possess the undesirable properties of both silt and clay. The constituents of varved clays were transported into fresh water lakes by the melted ice at the close of the ice age.
Kaolin, china clay
is very pure forms of white clay used in the ceramic industry.
Boulder Clay
is a mixture of an un-stratified sedimented deposit of glacial clay, containing unsorted rock fragments of all sizes ranging from boulders, cobbles, and gravel to finely pulverized clay material.

21. Calcareous Soil
is a soil containing calcium carbonate. Such soil effervesces when tested with weak hydrochloric acid.
Marl
consists of a mixture of calcareous sands, clays/loam.
Hardpan
is a relatively hard, densely cemented soil layer, like rock which does not soften when wet. Boulder clays or glacial till is also sometimes named as hardpan.
Caliche
is an admixture of clay, sand, and gravel cemented by calcium carbonate deposited from ground water.
Loam
is a mixture of sand, silt and clay.

22. Peat
is a fibrous aggregate of finer fragments of decayed vegetable matter. Peat is very compressible and one should be cautious when using it for supporting foundations of structures.
Loess
is a fine-grained, air-borne deposit characterized by a very uniform grain size, and high void ratio. The size of particles ranges between about 0.01 to 0.05 mm. The soil can stand deep vertical cuts because of slight cementation between particles. It is formed in dry continental regions and its color is yellowish light brown.

23. Shale
is a material in the state of transition from clay to slate. Shale itself is sometimes considered a rock but, when it is exposed to the air or has a chance to take in water it may rapidly decompose.