GENERAL GEOLOGY

• Geology


  The study of the earth. It came from the Greek word "Geo" meaning earth or land and "logos" meaning the study of.
• Engineering geology


  The scientific discipline concerned with the application of geological knowledge to engineering problems to reservoir design and location, determination of slope stability for construction purposes, and determination of earthquake, flood, or subsidence danger in areas considered for roads, pipelines, or other engineering works.
• Main branches of geology

  • Physical Geology
  • Mineralogy
  • Petrology
  • Structural Geology
  • Historical Geology (Stratigraphy)
  • Paleontology
  • Economic Geology
  • Engineering Geology
• Allied branches of geology

  • Mining Geology
  • Geophysics
  • Geohydrology
  • Geochemistry
• Physical Geology


  Deals with the study of different physical features of the earth, such as mountains, plateaus, valleys, rivers, lakes, glaciers, and volcanoes in terms of their origin and development.
• Mineralogy


  Deals with the detailed mode of formation, composition, occurrence, types, association properties uses etc. of minerals.
• Petrology


  Deals with the study of rocks.
• Structural Geology


  Deals with the form, arrangement, and internal structure of rocks, and especially with the description, representation, and analysis of structures, chiefly on a moderate to small scale.
• Historical Geology (Stratigraphy)


  The study of the earth's history through the sedimentary rocks. It is also called stratigraphy (strata = a set of sedimentary rocks and graphy = description).
• Paleontology


  Includes the study of fossils to classify organisms and study their interactions with each other and their environments.
• Economic Geology


  Focuses on earth materials that can be used for economic or industrial development purposes, often to identify new ore deposits for excavation as well as understanding how ore deposits are generated and localized within Earth's crust.
• Engineering Geology


  Concerned with the application of geological knowledge in civil engineering for the construction of safe, stable, and cost-effective structures such as dams, bridges, and tunnels.
• Mining Geology


  Relates to the use of geological knowledge in the mining industry.
• Geophysics


  Is the study of physical properties such as density and magnetism of the earth or its parts in order to learn about their interior.
• Geohydrology


  Is the study of groundwater and is sometimes referred to as groundwater hydrology.
• Geochemistry


  Is the study of the chemical composition of and the chemical changes in the solid material of the Earth or other celestial bodies.
• The three major parts/layers of the Earth

  • The Crust
  • The Mantle
  • The Core
• The Crust


  The outside layer of the earth made of solid rock, mostly basalt and granite. Two types: Oceanic Crust (denser and thinner, mainly basalt) and Continental Crust (less dense, thicker, mainly granite).
• The Mantle


  Lies below the crust, up to 2900 km thick, consists of hot, dense, iron and magnesium-rich solid rock.
• The Core


  The very hot, very dense center of the planet, made of a liquid outer core and solid inner core.
• Continental Drift


  A theory that explained how continents shift position on Earth's surface, proposed by Alfred Wegener in 1912. It explained why look-alike animal and plant fossils, and similar rock formations, are found on different continents.
• Plate Tectonics


  A scientific theory that explains how major landforms are created as a result of Earth's subterranean movements. It transformed the earth sciences by explaining many phenomena, including mountain building events, volcanoes, and earthquakes.
• Two main types of tectonic plates

  • Oceanic plates (oceanic crust called "sima")
  • Continental plates (continental crust called "sial")
• Weathering


  The process of decay, disintegration and decomposition of rocks under the influence of certain physical and chemical agencies.
• Three main types of weathering

  • Mechanical weathering
  • Chemical weathering
  • Organic or biological weathering
• Mechanical weathering


  The physical breakdown of rocks into smaller and smaller pieces.
• Chemical weathering


  The chemical changes that alter the composition of rocks over time.
• Organic or biological weathering


  Weathering caused by organisms such as animals, plants, fungi and microorganisms.
• The importance of weathering in engineering is that it causes a loss in the strength of rocks or soil, which is an important consideration when constructing civil structures using stone masonry and concrete.
• River erosion


  The disintegration and decomposition of rocks and soil material by a natural agent through mechanical, chemical, and other physico-chemical processes, accompanied by removal of the disintegrated or decomposed product.
• The geological work of rivers is divided into three phases: erosion, transport, and deposition.
• Features of stream erosion

  • Potholes
• Structures


  • Constructed using stone masonry and concrete work
  • Constructed on good, strong and unweather rock surface
• The importance of weathering in engineering
• Works of rivers
• Method of river erosion

  1. Disintegration and decomposition of rocks and soil material by natural agents through mechanical, chemical, and other physico-chemical processes

  2. Removal of the disintegrated or decomposed product to far off places by the same agent
• Geological work of rivers

  • Erosion
  • Transport
  • Deposition
• Features of stream erosion

  • Potholes
  • River valleys
  • Waterfalls
  • Stream terraces
• Types of sediment transport by rivers

  • Suspended load
  • Bed load
  • Dissolved load
• Types of deposition by rivers

  • Alluvial fans and cones
  • Natural levees
  • Deltas
  • Channel deposits