Geology

• Geology is the study of the earth and the processes that shape it
• Engineering Geology is a branch of applied science that applies geology to design and construct civil engineering projects safely and economically
• The role of knowledge of geology in civil engineering includes providing information on construction materials, river control, foundation of faults, constructing dams and tunnels, advancing economical design, identifying nature of soil materials, and conducting soil tests before projects
• Importance of engineering geology in civil engineering:

  • To be aware of challenging ground conditions before designing and building
  • Identifying areas at risk of error
  • Establishing design specifications
  • Selecting the best site for engineering purposes
  • Choosing the best materials for construction
• Mineralogy is a science dealing with minerals, their properties, classification, and ways of distinguishing them
• Characteristics of minerals include color, streak, luster, density, crystal shape, cleavage, and fracture
• Petrology is a branch of geology that deals with the study of rocks
• Petrology is divided into three subdivisions: metamorphic, igneous, and sedimentary petrology

  • Metamorphic petrology involves the transformation of existing rock to new types of rock
  • Igneous petrology studies rocks formed from magma
  • Sedimentary petrology studies modern sediments and the processes leading to their formation
• Structural Geology deals with the study of structures found in rocks, such as anticlines and synclines
• Paleontology is the study of fossils and ancient remains of plants and animals

  • Vertebrate paleontology studies animals with backbones
  • Invertebrate paleontology studies animals without backbones
  • Paleobotany deals with plant remains
  • Palynology studies microscopic fragments of organisms
• Mining Geology involves the application of geology to mining engineering to select suitable sites for quarrying and mines
• Photogeology interprets aerial photographs to obtain geological information with minimal fieldwork
• Economic Geology studies minerals and materials of economic importance like coal and petroleum
• Earth's structure includes the crust, mantle, and core

  • Continental crust is mainly composed of granite, while oceanic crust is primarily composed of basalt
• Earth's mantle is made of solid rocks and is hot

  • Mantle heat flows through conduction and convection
  • Mantle composition includes upper mantle, transition zone, lower mantle, and D' layer
• Earth's core consists of an inner solid core mainly of iron and nickel, and an outer liquid core primarily of iron and nickel that generates the Earth's magnetic field
• Continental drift describes how continents moved over time

  • Evidences include geologic, identical rocks, fossils, and climate changes
  • Wegener's problem was not finding the force causing drift
• Seafloor spreading forms new ocean basins from volcanism

  • Plate tectonics involve lithospheric plates moving on the asthenosphere conveyor belt
  • Earth has seven major lithospheric plates
  • Three main types of plate boundaries are convergent, divergent, and transform
• Parts of continental margin include continental shelf, continental slope, and continental rise
• Parts of Continental Margin:

  • Continental Shelf: Gently sloping submerged portion of the continent
  • Continental Slope: Deep slope after the continental shelf
  • Continental Rise: Gently-sloping area after the continental slope and before the ocean floor
  • Trenches: Deepest parts of the ocean, narrow depressions caused by subduction zones
  • Mid-Oceanic Ridge: The mountain range system in the ocean
• Types of Continental Margin:

  • Active: Only has a continental shelf and a continental slope, main feature is a trench
  • Passive: Consists of continental shelf, continental slope, and continental rise, very little tectonic activities
• Earth's Geological Processes:

  Endogenic processes:

  • Magmatism, Volcanism, Metamorphism

  Exogenic processes:

  • Erosion, Mass wasting, Sedimentation, Weathering
• Endogenic Processes:

  • Associated with the energy originating in the interior of the solid earth
  • Two types of endogenic force: Slow force (over million years) and Sudden force (few hours)
  • Great mountain systems like the Himalayas are a product of the collision of lithospheric plates
  • Earth's internal heat is the driving force, originating from the decay of radioactive elements in the Earth's core
• Magmatism:

  • Formation of magma, responsible for intrusive and extrusive igneous rocks

  Volcanism:

  • Process that occurs after magma is formed, associated with Earth's internal heat and tectonic processes

  Metamorphism:

  • Process of changing the materials that make up a rock
• Stress on Rocks:

  • Geological stress is the force acting on the rock
  • Types of stress: Compressional, Tensional, Shearing, Confining
• Exogenic Processes:

  • Geological phenomena and processes that originate externally to the Earth's surface
  • Influenced or driven by gravity, water, wind, and organisms
  • Include erosion, mass wasting, sedimentation, weathering
• Weathering:

  • Breakdown of rocks and soil by various agents, unlike erosion, does not involve movement of rocks
  • Types of weathering: Physical, Chemical, Biological
• Physical Weathering:

  • Mechanical disintegration and breaking of rocks to form smaller particles
  • Reasons for physical weathering: High Speed Winds, Thermal Stress, Freezing and Thawing, Pressure Releases, Hydraulic Actions, Salt-Crystals Growth, Organisms
• Chemical Weathering:

  • Weathering in which rock minerals are attacked by water, oxygen, or by alkaline or acid materials dissolved in water
  • Processes and reactions of chemical weathering: Dissolution and Carbonation, Hydration, Hydrolysis, Oxidation
• Biological Weathering:

  • Weakening and disintegration of rocks by plants, animals, and microbes
  • Reasons for biological weathering: Burrowing animals, Organic material, Lichens
• Works of Rivers, Wind, and Sea:

  • Rivers carry water and nutrients, distribute weathering products
  • Wind is a sustainable power source, used for energy generation
  • Sea regulates Earth's temperature, provides food and drinking water
• Engineering Importance:

  • River engineering optimizes benefits and protects against flooding
  • Wind analysis and design for structures, wind energy for power generation
  • Ocean engineering preserves coastal structures, develops energy sources, and protects ports and harbors
• Origin and Occurrence of Earthquake:

  • Earthquake is an intense shaking of Earth's surface caused by movements in the outermost layer
  • Faults are fractures in rocks caused by stress or push-pull on the crust
  • Types of faults: Normal faults, Reverse faults, Thrust faults
  • Active faults are likely to have another earthquake, Inactive faults
• Inactive Fault:

  • Structures that we can identify but do not have earthquakes
• Active Fault:

  • Likely to have another earthquake in the future
• Plate Tectonic Theory:

  • Earth's outer shell divided into plates that glide over Earth's mantle
  • 7 Major Slabs: Pacific, North American, Eurasian, African, Antarctic, Indo-Australian, South American
• Primary Reasons for Tectonic Plates Movement:

  1. Mantle convection currents drive plates along

  2. Ridge Push: pushing force experienced by plates sliding down raised asthenosphere

  3. Slab Pull: older, colder plates sink at subduction zones and pull warmer plates
• Earthquake Focus:

  • Point within the earth where rock under stress breaks
• Epicenter:

  • Above the focus, where the most violent shaking of the ground occurs
• Seismic Waves:

  • Waves of energy caused by sudden breaking of rocks or an explosion