Chap. 1
Rocks & Minerals Formation
Key Definitions
Rock : naturally occurring solid material made up of minerals. Mineral : naturally occurring inorganic substance with a definite chemical composition (e.g. gold, iron, diamond). Rock cycle : continuous movement and transformation of rocks from one type to another over time.
Chap. 2
The Three Types of Rocks
| Igneous | Sedimentary | Metamorphic | |
|---|---|---|---|
| Origin | Molten magma cools & solidifies | Particles of other rocks or organic materials | Existing rocks changed by heat & pressure |
| Layers? | No | Yes | No |
| Fossils? | No | Possible | No |
| Hardness | Hard & crystalline | Usually softer | Hard & dense |
| Example | Granite | Limestone | Marble |
Igneous Rock — Two Subtypes
- Intrusive : forms below Earth's surface (slow cooling → large crystals) — e.g. granite
- Extrusive : forms above Earth's surface (fast cooling) — e.g. volcanic rock
Sedimentary Rock — Formation Steps
- Weathering breaks rocks into smaller pieces
- Erosion transports the sediments
- Deposition — sediments settle in layers
- Compaction & cementation turn sediments into solid rock
Metamorphic Rock — Formation
Existing rocks are subjected to heat and pressure deep inside the Earth → structure changes completely.
Chap. 3
Extraction of Rocks & Minerals
Extraction : process of removing rocks and minerals from the Earth for use.
Methods of Extraction
| Method | When used | Examples |
|---|---|---|
| Quarrying | Surface, building materials | Limestone, granite, marble |
| Surface mining (open-cast) | Minerals near the surface, topsoil removed | Coal, iron ore |
| Underground mining | Minerals deep below surface, tunnels & shafts dug | Gold, diamonds |
| Drilling | Liquid or gaseous minerals | Crude oil, natural gas |
Importance of Extraction
- Provides minerals for industries
- Supports construction of roads and buildings
- Creates employment
- Generates income for countries
Environmental Impacts
| Impact | Details |
|---|---|
| Land degradation | Destruction of land & vegetation; large open pits left behind |
| Pollution | Air (dust & gases), water (chemicals & waste) |
| Loss of biodiversity | Habitats of plants and animals destroyed |
| Noise pollution | Caused by blasting and machinery |
| Soil erosion | Removal of topsoil destabilises the land |
⚠️ Sedimentary rocks are the only type that can contain fossils — a common exam question!
