Geology Basics

Igneous Rocks

• Formed from the cooling and solidification of magma or lava
• Can be either intrusive (plutonic) or extrusive (volcanic)
• Characteristics:
  • Coarse-grained texture in intrusive rocks
  • Fine-grained texture in extrusive rocks
  • May contain gas bubbles or mineral crystals
• Examples: granite, basalt, obsidian

Metamorphic Rocks

• Formed through the alteration of existing rocks under high pressure and temperature
• Process involves mineral recrystallization and changes in texture and composition
• Characteristics:
  • Foliated texture in rocks that have been subjected to differential stress
  • Non-foliated texture in rocks that have not been subjected to differential stress
  • May exhibit mineral banding or layering
• Examples: marble, slate, quartzite

Sedimentary Rocks

• Formed through the accumulation and compression of mineral and organic particles
• Can be classified into three types:
  1. Clastic sedimentary rocks: formed from the cementation of clastic sediments (e.g. sandstone, conglomerate)
  2. Chemical sedimentary rocks: formed through chemical precipitation (e.g. rock salt, gypsum)
  3. Organic sedimentary rocks: formed from the accumulation of organic matter (e.g. coal, limestone)
• Characteristics:
  • May exhibit bedding planes or cross-bedding
  • Can contain fossils or other sedimentary structures

Mineral Identification

• Minerals can be identified through a combination of physical and chemical properties
• Key properties:
  • Color and streak
  • Luster and transparency
  • Hardness and cleavage
  • Density and specific gravity
  • Crystal form and habit
• Techniques:
  • Hand lens examination
  • Streak plate analysis
  • Acid testing
  • X-ray fluorescence (XRF) or X-ray diffraction (XRD) analysis

Geological Processes

• Plate tectonics: the movement of the Earth's lithosphere and the resulting geological activity
• Weathering and erosion: the breakdown and transportation of rocks and sediments
• Diagenesis: the conversion of sediment into sedimentary rock
• Metamorphism: the alteration of rocks under high pressure and temperature
• Magmatic activity: the formation and movement of magma and lava