GEO 3

• Igneous rock


  Any of various crystalline or glassy rocks formed by the cooling and solidification of molten earth material called magma which originates deep within the Earth's crust and occasionally even in the mantle
• Earth is composed predominantly of a large mass of igneous rock with a very thin veneer of weathered material—namely, sedimentary rock
• Lava


  Magma that reaches the earth's surface
• Igneous rocks


  • If magma reaches the earth's surface, it cools quickly and forms volcanic or extrusive igneous rocks
  • If magma remains beneath the surface and cools there, it forms intrusive or plutonic igneous rocks
• Igneous rocks


  • Some cool quickly, in days or weeks which have a finer grain or glassy texture
  • Those that cool slower have larger crystals or a coarse grain
• Igneous rock classification by color and composition

  • Felsic
  • Intermediate (diorite, andesite, scoria)
  • Mafic (gabbro, basalt, scoria)
• Texture of igneous rocks

  Dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals
• Igneous activity on Earth


  • Majority is confined to a small region closely linked to the movements of the lithospheric plates
  • Plate tectonics plays a major role in controlling the properties of intrusions, the forms of volcanism, and the makeup of the magma
• Sedimentary rocks


  Formed through continuous compression and cementation of existing rocks, fossil fragments, and marine sediments through time
• Secondary rocks


  Sedimentary rocks are products of older pre-existing rocks
• Sedimentary rocks cover the greater part of the Earth's land surface and occur as layers or strata
• Types of sedimentary rocks

  • Clastic
  • Chemical/Biochemical
• Clastic sedimentary rocks


  • Composed of fragments (clasts) of pre-existing rocks that have been weathered, transported and deposited by various geological processes
  • Classified based on size, shape, and composition
• Clastic sedimentary rocks


  • Sandstone
  • Shale
  • Conglomerate
  • Breccia
• Chemical/Biochemical sedimentary rocks


  • Primarily composed of minerals that have precipitated out of solution
  • Often formed through chemical processes like evaporation or biological activity
• Chemical/Biochemical sedimentary rocks


  • Limestone
• Properties of sedimentary rocks

  • Mineral composition
  • Textures (grain size, particle shape, fabrics)
  • Sedimentary bedding and structures
  • Biogenic structures (fossils)
  • Color
• Formation of sedimentary rocks

  1. Weathering (mechanical, chemical)

  2. Transport

  3. Deposition

  4. Compaction and cementation
• Sedimentary rocks formed by compaction and cementation

  • Sandstone
  • Limestone
  • Shale
  • Conglomerate
  • Breccia
• Metamorphism


  The process of transforming rocks into new types through heat and pressure
• Metamorphism affects rocks' composition and texture, revealing their history based on mineral composition and orientation
• Metamorphic rocks


  A type of rock that has undergone transformation from pre-existing rocks due to high temperatures, pressures, or chemically active fluids
• Classes of Metamorphism


  • Contact or Thermal Metamorphism
  • Dislocation or Dynamic Metamorphism
  • Regional Metamorphism
• Contact or Thermal Metamorphism


  • Occurs when hot stuff like lava touches other rocks, or when layers of rocks are squeezed down into the hot parts of the Earth
• Dislocation or Dynamic Metamorphism


  • Occurs when strong forces push and pull on rocks, causing them to change shape
• Regional Metamorphism


  • Occurs when rocks change over a big area due to lots of pressure and heat everywhere
• Common Types of Metamorphic Rocks

  • Quartzite
  • Marble
  • Slate
  • Gneiss
  • Schist
• Quartzite


  Primarily composed of quartz, forms from the metamorphism of sandstone under intense heat and pressure, known for its high resistance to chemical weathering and smooth, glassy texture
• Marble


  Mainly composed of calcite or dolomite minerals, forms from the metamorphism of limestone or dolostone, known for its distinctive veining and variety of colors, smooth texture
• Slate


  Primarily composed of clay minerals, forms from the metamorphism of shale or mudstone, has a fine-grained texture, excellent cleavage, and is commonly gray in color
• Gneiss


  Composed of alternating layers of different minerals, giving it a banded appearance, forms from the metamorphism of igneous or sedimentary rocks under high temperature and pressure
• Schist


  Composed of platy minerals such as mica and chlorite, forms from the metamorphism of shale or mudstone, has a foliated texture with visible mineral grains aligned in layers, often has a shiny appearance due to the presence of mica
• Understanding the attitude of beds, outcrops, geological maps, and the study of geological structures such as folds, faults, and joints are essential aspects of geology that have significant implications for engineering construction projects
• Attitude of Beds


  The orientation of rock layers or strata in the Earth's crust, described by strike (the compass direction of a horizontal line in the plane of the beds) and dip (the angle of inclination of the beds from the horizontal)
• Attitude of Beds


  • Crucial for determining the stability of rock formations, assessing the potential for landslides, and planning the excavation and construction of structures such as tunnels and foundations
• Outcrops


  Locations where rock formations are exposed at the Earth's surface, provide valuable information about the geological structure and composition of the subsurface
• Outcrops


  • Engineers use outcrop observations to understand the geological conditions of a site, assess rock quality for construction materials, and plan infrastructure projects accordingly
• Geological Maps


  Depict the distribution of rock units, structures, and geologic features in a specific area, using symbols, colors, and patterns to represent different rock types, faults, folds, and other geological elements
• Geological Maps


  • Engineers rely on geological maps to evaluate the subsurface conditions, identify potential hazards such as faults or unstable formations, and make informed decisions during the design and construction of infrastructure projects
• Geological Structures


  • Folds
  • Faults
  • Joints