Geology Basics

Igneous Rocks

• Formed from the cooling and solidification of magma or lava
• Can be either intrusive (forms below the Earth's surface) or extrusive (forms above the Earth's surface)
• Characteristics:
  • Coarse-grained texture (intrusive)
  • Fine-grained texture (extrusive)
  • May contain gas bubbles or mineral crystals
• Examples:
  • Granite (intrusive)
  • Basalt (extrusive)

Sedimentary Rocks

• Formed from the accumulation and compression of sediments, such as mineral and rock fragments, plant and animal remains, and precipitated minerals
• Can be further divided into three categories:
  1. Clastic sedimentary rocks: formed from clastic sediments, such as sandstone and conglomerate
  2. Chemical sedimentary rocks: formed from the precipitation of minerals, such as rock salt and gypsum
  3. Organic sedimentary rocks: formed from the accumulation of plant and animal remains, such as coal and limestone
• Characteristics:
  • Layered or bedded appearance
  • May contain fossils or other sedimentary structures
• Examples:
  • Sandstone
  • Limestone

Metamorphic Rocks

• Formed from the alteration of existing rocks under high pressure and temperature conditions
• Can be formed from any type of rock, including igneous, sedimentary, and other metamorphic rocks
• Characteristics:
  • Foliated texture (layered or banded appearance)
  • May contain minerals not found in the original rock
• Examples:
  • Marble (formed from limestone)
  • Slate (formed from shale)

Mineral Identification

• Minerals can be identified by their physical and chemical properties, including:
  • Color
  • Streak (color of powder produced by scratching the mineral on a porcelain plate)
  • Luster (appearance of the mineral's surface)
  • Hardness (resistance to scratching)
  • Cleavage (pattern of breaking along flat surfaces)
  • Density (mass per unit volume)
• Mineral identification is important for understanding the composition and properties of rocks

Geological Processes

• Processes that shape the Earth's surface and form rocks and minerals, including:
  • Plate tectonics: movement of the Earth's lithosphere (outer layer) that drives geological activity
  • Weathering: breakdown of rocks into sediments through exposure to wind, water, and temperature fluctuations
  • Erosion: removal of sediments and rocks through natural forces, such as wind and water
  • Deposition: accumulation of sediments and rocks in a new location
  • Metamorphism: alteration of rocks under high pressure and temperature conditions
  • Magmatic activity: formation of igneous rocks through the cooling and solidification of magma or lava