Lecture Notes: Rocks

Introduction

• Earth is surrounded by rocks (buildings, mountains, rivers, valleys).
• Rocks are the solid surfaces on Earth where we live.
• Soil is formed from the weathering of rocks.
• Rocks contain minerals.
• Over 2000 types of minerals exist, but only a few are abundant.
• Most abundant minerals: Silicon (Si), Aluminum (Al).
  • Earth's crust first layer: Sial (silica + aluminum).
  • Second layer: Sima (silica + magnesium).

Types of Rocks

• Igneous Rocks

  • Formed from cooling, solidification, and crystallization of molten material (magma/lava).
  • Examples: Granite (used in kitchen platforms), Marble (used in flooring).
  • Characteristics: Hard, compact, crystalline.
  • Two main types:
    • Extrusive (volcanic): Formed from lava cooling outside Earth.
    • Intrusive (plutonic): Formed from magma cooling inside Earth.

• Sedimentary Rocks

  • Formed from sediment accumulation and compaction.
  • Layered appearance due to continuous deposition of sediments.
  • Characteristics: May contain fossils.
  • Processes:
    • Lithification: Loose sediments compacted into rock.
    • Common example: Sandstone (compacted sand).
  • Types based on formation:
    • Mechanically formed (clastic): From fragments of other rocks.
    • Chemically formed: From precipitated minerals.
    • Organic: From remains of plants and animals.

• Metamorphic Rocks

  • Formed from alteration of existing rocks under high pressure and temperature.
  • Examples: Marble (from limestone), Slate (from shale).
  • Characteristics: Hard, compact, nearly impermeable, typically do not contain fossils.
  • Types based on metamorphism:
    • Thermal: High temperature influence.
    • Dynamic: High pressure influence.
    • Contact: Small area around hot magma.

Rock Cycle

• Continuous process of transformation of rocks from one type to another.
• Never-ending cycle involving Igneous, Sedimentary, and Metamorphic rocks changing forms.

Importance of Rocks

• Construction of buildings, bridges, roads.
• Source of minerals and metals (gold, silver, platinum, etc.).
• Fossil fuels like coal are extracted from rocks.

Conclusion

• Rocks are essential for various constructions and materials.
• Continuous exploration and understanding of rocks help in geological studies and applications.

Action Points

• Observe different types of rocks around your environment.
• Ask questions and provide examples of rocks you have seen.