1.1-1.2: Formation of Rocks and Extraction Notes:

Formation of Rocks

Types of Rocks:

1. Igneous: 

• • Formed from cooling magma/lava. They can be either:

    • Intrusive: Granite (slow cooling inside Earth)

    • Extrusive: Basalt (fast cooling on surface/exterior) 

2. Sedimentary: 

• Formed from compressed sediments over time.

• Examples: Limestone (marine shells), Sandstone (quartz grains), Shale (mud/silt) 

3. Metamorphic: 

• Formed when existing rocks are changed by heat and pressure.

• Examples: Marble (from limestone), Slate (from shale) 

The Rock Cycle:

• Continuous transformation between rock types via weathering, erosion, heat, pressure, and melting.

Rock Cycle Explained:

• No starting point or end point—each rock type can lead to any other via one or more processes.

• Main Pathways:

1. Magma → Cooling & Crystallization → Igneous Rock 

• Deep slow cooling → Granite (intrusive) 

• Surface rapid cooling → Basalt (extrusion)

2. Igneous/Sedimentary → Weathering & Erosion → Sediments 

• • • • Broken fragments carried by wind, water or ice

3. Sediments → Compaction & Cementation (Lithification) → Sedimentary Rock 

• • • • Layers of sand, mud or biological debris become sandstone, shale or limestone

4. Sedimentary/Igneous → Burial + Heat & Pressure → Metamorphic Rock  

• • • • Shale → Slate, Limestone → Marble

5. Metamorphic → Melting → Magma 

• Extreme conditions melt rock back into magma, restarting the cycle

Extraction of Rocks and Minerals:

Mining Methods:

1. Surface Mining

• Digging minerals from the Earth's surface where the overlying soil and rock (overburden) are removed to access the deposit..

• Types include opencast, open-pit, open-cut or strip mining.

• Used when: Minerals are close to the surface.

• Steps:

  1. Survey the land – Check if valuable minerals are present.

  2. Clear the area – Remove trees and plants (deforestation).

  3. Remove top layers – Use machines to strip soil and rocks.

  4. Extract minerals – Dig out minerals using trucks and excavators.

  5. Transport – Move minerals to processing plants.

• Examples: Coal, sand, gravel, and some metals.

• Pros:

  1. Cheaper

  2. Safer for workers

  3. Faster

• Cons:

  1. Damages the environment

  2. Creates large holes (open pits)

2. Subsurface Mining

• Definition: Digging deep tunnels or shafts to reach minerals/ore buried far below the surface.

• Includes: 

  1. Vertical shafts (lift or cage to the zones)

  2. Inclined shafts/declines (spiral ramps for vehicles)

  3. Adits/drifts (horizontal tunnels into a hillside)

• Used when: Minerals are deep underground.

• Steps:

  1. Explore underground – Use geology tools to find mineral locations.

  2. Build access tunnels – Create shafts or drifts to reach the ore.

  3. Ventilation & safety setup – Install air systems and safety gear.

  4. Extract minerals – Use machines or manual labor to mine.

  5. Bring minerals to surface – Transport using lifts or carts.

• Examples: Gold, diamonds, copper, coal (deep seams).

• Pros:

  1. Less surface damage

  2. Can reach deeper, richer minerals

• Cons:

  1. Expensive

  2. Dangerous for miners

  3. Slower process

Factors Affecting the Decision to Mine

• When deciding whether and how to extract, companies weigh many interlinked factors:

1.  Type of Rock & Mineral

• Hardness and composition affect how easy it is to mine.

• High-grade ores are more profitable than low-grade ones.

2. Depth of Deposit

• Shallow deposits = surface mining (cheaper).

• Deep deposits = subsurface mining (costly and risky).

3. Location & Accessibility

• Remote areas need roads, transport, and infrastructure.

• Easier access = lower cost.

4. Cost of Extraction

• Includes labor, equipment, energy, and safety measures.

• If costs are too high, mining may not be worth it.

5. Environmental Impact

• Mining can damage ecosystems, water sources, and air quality.

• Companies must plan for restoration and waste management.

6. Legal & Government Rules

• Permits, land rights, and environmental laws affect operations.

• Some areas are protected and cannot be mined.

7. Market Demand & Prices

• High demand = more profit = more mining.

• If prices drop, mining may stop or slow down.

8. Climate & Weather

• Harsh climates (e.g., extreme cold or rain) make mining harder.

• Seasonal changes can affect productivity.

9. Technology Available

• Advanced tools and machines make mining faster and safer.

• Poor technology = slower and more expensive mining.

NOTES DONE BY FARIDA SABET

CLICK HERE TO GO TO THE NEXT TOPIC

CLICK HERE TO GO BACK TO THE NOTES MENU