Introduction to Geology

• Geology is the study of Earth, including its materials, processes, and history.
• It studies the solid Earth, its waters, and the surrounding atmosphere.

Branches of Geology

• Geomorphology focuses on landforms and their formation.
• Mineralogy studies minerals, their composition, and properties.
• Petrology is the study of rocks, their origin, composition, and classification.
• Structural Geology examines rock deformation and resulting structures.
• Stratigraphy studies layered rocks (strata), their sequences, and correlation.
• Paleontology focuses on fossils and ancient life forms.
• Economic Geology studies mineral resources and their economic value.
• Engineering Geology applies geological principles to engineering projects.
• Hydrogeology studies groundwater and its movement.
• Geophysics studies Earth's physical properties using methods like seismic, gravity, and magnetism.
• Geochemistry studies the chemical composition of Earth, rocks, and minerals.

Earth's Structure

• Crust: The outermost layer divided into continental and oceanic types.
• Continental crust is thicker and less dense compared to oceanic crust.
• Mantle: The layer beneath the crust, making up most of Earth's volume and composed mainly of silicate rocks.
• Core: The innermost layer divided into a liquid outer core and a solid inner core.
• Earth's magnetic field is generated by the outer core.
• Iron and nickel primarily compose the inner core.

Minerals

• Minerals are naturally occurring, inorganic solids, possessing a definite chemical composition and a crystalline structure.
• Identification properties:
• Hardness is measured using the Mohs scale.
• Cleavage and fracture behavior.
• Luster (metallic, non-metallic descriptions).
• Color as a visual property.
• Streak when powdered.
• Specific gravity as a density measure.

Rocks

• Igneous Rocks: Formed from magma or lava cooling and solidifying.
• Intrusive igneous rocks cool slowly beneath the surface.
• Extrusive igneous rocks cool quickly on the surface.
• Sedimentary Rocks: Formed from sediment accumulation and lithification.
• Clastic sedimentary rocks are formed from fragments of other rocks.
• Chemical sedimentary rocks are formed from precipitation of minerals from solution.
• Organic sedimentary rocks are formed from the accumulation of organic matter.
• Metamorphic Rocks: Formed when existing rocks transform due to heat, pressure, or chemically active fluids.
• Foliated metamorphic rocks have a layered appearance.
• Non-foliated metamorphic rocks do not have a layered appearance.

Plate Tectonics

• The Earth’s lithosphere is divided into moving and interacting plates.
• Types of plate boundaries:
• Divergent boundaries: Plates move apart from one another.
• Convergent boundaries: Plates collide into one another.
• Transform boundaries: Plates slide past each other horizontally.
• Plate tectonics causes geological phenomena:
• Earthquakes.
• Volcanoes.
• Mountain building.
• Seafloor spreading.

Weathering and Erosion

• Weathering breaks down rocks at the Earth's surface.
• Physical weathering is the mechanical breakdown of rocks.
• Chemical weathering alters rocks via chemical reactions.
• Erosion removes and transports weathered materials through water, wind, and ice.

Geomorphology

• Geomorphic processes shape the Earth's surface features.
• Fluvial processes are related to rivers and streams.
• Glacial processes are related to glaciers and ice sheets.
• Eolian processes are related to wind activity.
• Coastal processes are related to the coastlines.
• Karst topography describes landscapes formed by the dissolution of soluble rocks like limestone.

Structural Geology

• Folds: Rock layers that bend.
• Anticlines are upward folds.
• Synclines are downward folds.
• Faults: Fractures in rocks involving movement.
• Normal faults: The hanging wall moves down relative to the footwall.
• Reverse faults: The hanging wall moves up relative to the footwall.
• Strike-slip faults: Movement occurs horizontally.
• Joints: Fractures in rocks without any significant movement.

Stratigraphy

• Law of Superposition: Oldest layers are at the bottom, youngest at the top, in undisturbed rock sequences.
• Law of Original Horizontality: Sedimentary layers are initially deposited horizontally.
• Law of Lateral Continuity: Sedimentary layers extend laterally until they thin or meet a barrier.
• Fossils: Preserved remains or traces of ancient organisms.
• Index fossils: Date rock layers as they are widespread and existed for a short time.
• Unconformities: Gaps in the geologic record from erosion or non-deposition.

Paleontology

• Fossils offer evidence of Earth's life history.
• Fossil types:
• Body fossils: Preserved organism remains.
• Trace fossils: Imprints of organism activity.
• Fossilization processes:
• Petrification.
• Mold and cast formation.
• Carbonization.
• Preservation within amber or ice.

Economic Geology

• Mineral resources: Naturally occurring concentrations of minerals with economic value.
• Ore deposits: Deposits of metallic minerals mined at a profit.
• Types of ore deposits:
• Magmatic deposits.
• Hydrothermal deposits.
• Sedimentary deposits.
• Placer deposits.
• Non-metallic resources: Resources for construction, like limestone, sand, and gravel.
• Energy resources: Resources like coal, oil, and natural gas used in energy production.

Engineering Geology

• Geological principles are applied to engineering for structural stability and safety.
• Site investigation: Geological conditions are assessed at construction sites.
• Slope stability analysis: Slope and hillside stability are evaluated.
• Foundation design: Building and structure foundations are designed.
• Groundwater management: Groundwater resources are managed to prevent contamination and depletion.

Hydrogeology

• Groundwater, its movement, and surface interaction are studied.
• Aquifers: Store and transmit groundwater through permeable rock or sediment.
• Aquicludes: Prevent groundwater movement through impermeable layers.
• Groundwater flow: Groundwater movement through aquifers.
• Water table: The upper surface of the saturated zone.
• Groundwater contamination: Pollution of groundwater from human activities.

Geophysics

• Use of physical methods to study the Earth's subsurface.
• Seismic surveys: Use of seismic waves to image the subsurface.
• Gravity surveys: Measurement of variations in Earth's gravity field.
• Magnetic surveys: Measurement of variations in Earth's magnetic field.
• Electrical surveys: Measurement of electrical properties of rocks.
• Remote sensing: Use of satellite or aerial imagery to study the Earth's surface.

Geochemistry

• Study of the chemical composition of the Earth and its rocks and minerals.
• Chemical weathering: Alteration of rocks by chemical reactions.
• Geochemical cycles: Movement of chemical elements through the Earth's systems.
• Isotope geochemistry: Use of isotopes to date rocks and trace the origin of materials.

Geological Time Scale

• Eons: The largest divisions in geological time.
• Eras: Subdivisions of eons.
• Periods: Subdivisions of eras.
• Epochs: Subdivisions of periods.
• Key events in Earth's history:
• Formation of the Earth.
• Origin of life.
• Evolution of major groups of organisms.
• Mass extinction events.