Human Interaction with the Rock Cycle

The rock cycle is the process of forming, breaking down, and reforming rocks. Humans interact with it through activities like mining, quarrying, oil and gas exploration, and geothermal energy. These activities use the Earth's resources and have major effects on the economy, environment, and society.

Case Study 1: Extraction of Building Materials – Carrara Marble Quarries, Italy

Most buildings use materials like limestone, granite, and marble, which are extracted through quarrying.

Methods of Extraction (Quarrying):

• Quarrying Process: Large pits are dug into the Earth's surface, typically open at the top. Some quarries are also located on mountain sides.
• Depth and Scale: Quarries can be up to 30 meters deep and vary widely in width.
• Techniques Used:
  1. Plug and Feather: Drill holes and use wedges (plugs) and steel rods to split the rock.
  2. Explosives: Large masses of rock are blasted apart for extraction.
  3. Channelling by Machinery: Rotating discs cut large slices of rock, which are later shaped as needed.

• Famous for producing pure white marble since Roman times, used for buildings and sculptures.
• Marble from Carrara was used by Michelangelo and Leonardo da Vinci for their art.
• The port of Marina di Carrara specializes in exporting marble worldwide.
• Marble is used in construction (e.g., public buildings, airport floors) and in homes (e.g., polished countertops and floors).

Positive Economic Impacts:

In Ireland:

• Approximately 90,000 people employed directly or indirectly in construction.
• Over 200 active quarries provide 50,000 tonnes of aggregates annually for building projects.
• Quarrying companies like Ready Mix (Offaly) and Roadstone (Clare) contribute to regional economies.

Negative Impacts:

• Noise Pollution: Blasting and machinery cause significant noise and vibrations, potentially damaging nearby structures.
• Air Pollution: Dust from quarrying can affect nearby residents.
• Water Pollution: Silt generated by quarrying affects rivers, reducing water quality and harming fish habitats.
• Road Damage: Heavy machinery transporting materials damages infrastructure.

Case Study 2: Geothermal Energy Production – Iceland

Geothermal energy is a renewable and cost-effective resource derived from the Earth's heat. This form of energy is particularly viable in tectonically active regions, such as Iceland, where magma lies close to the Earth's surface.

Methods of Extraction:

• Heat Source: Magma near the surface heats underground water reservoirs to temperatures exceeding 200°C.
• Drilling: Wells are drilled to access the superheated water.
• Usage:
  • Water is converted to steam to generate electricity.
  • Hot water is used for direct heating, greenhouses, and melting ice in urban areas (e.g., Reykjavik's car parks).

Example:

Iceland:

• 90% of homes in Iceland are heated using geothermal energy.
• Reykjavik has the lowest CO₂ levels of any major city due to its reliance on this clean energy source.
• Geothermal energy supports tourism by heating natural hot springs and pools, attracting visitors worldwide.

Positive Economic Impacts:

• Renewable Resource: Iceland benefits from a cheap, sustainable energy source.
• Job Creation: Provides employment in energy production, infrastructure maintenance, and tourism.
• Reduced Costs: Low energy costs benefit households, agriculture (heated greenhouses), and industries.

Negative Impacts:

• Land Use: Geothermal plants require significant land, which may impact natural landscapes.
• Pollution Risk: Although minimal, geothermal operations can release small amounts of greenhouse gases like CO₂ and hydrogen sulphide.
• Tourism Pressure: Increased visitors to natural hot springs can strain local infrastructure.

General Comparison

Aspect	Extraction of Building Materials	Geothermal Energy Production
Purpose	Extract rock for construction.	Harness heat for energy.
Methods	Quarrying: blasting, cutting, or drilling.	Drilling wells to access superheated water.
Example	Carrara Marble Quarries, Italy.	Iceland's geothermal plants (e.g., Hellisheiði).
Positive Impacts	Provides materials for construction; supports local economies.	Sustainable energy; reduces CO₂ emissions; boosts tourism.
Negative Impacts	Noise, air, and water pollution; road damage.	Land use; minimal pollution; tourism strain.