Introduction to Geology

• Geology is the study of the Earth, its structure, its history, and the processes that shape it

Branches of Geology

• Geomorphology studies the Earth's surface and the processes that create and modify landforms.
• Mineralogy focuses on the chemical composition, crystal structure, and physical properties of minerals.
• Petrology is the study of rocks, their composition, origin, and alteration.
• Structural geology deals with the deformation of the Earth's crust.
• Stratigraphy studies the layering of rocks (strata) and their interpretation in terms of geological time.
• Paleontology is the study of fossils and ancient life forms.
• Economic geology focuses on the study of ore deposits, mineral resources, and their economic exploitation.
• Geophysics uses physical principles to study the Earth's subsurface.
• Geochemistry studies the chemical composition of the Earth and its rocks, minerals, and fluids.
• Engineering geology applies geological principles to engineering works.

Earth Structure

• The Earth consists of the inner core, outer core, mantle, and crust.
• The crust is the outermost layer, divided into oceanic and continental crust.
• The mantle is a thick layer beneath the crust, composed mainly of silicate rocks.
• The outer core is liquid and composed mainly of iron and nickel.
• The inner core is solid and also composed mainly of iron and nickel.

Plate Tectonics

• The Earth's lithosphere is divided into several plates that move relative to each other.
• Plate boundaries are classified as divergent, convergent, or transform.
• Divergent boundaries are where plates move apart, such as mid-ocean ridges.
• Convergent boundaries are where plates collide, leading to subduction or mountain building.
• Transform boundaries are where plates slide past each other horizontally.
• Plate tectonics drives volcanism, earthquakes, and mountain formation.

Rock Cycle

• The rock cycle is a continuous process where rocks are transformed from one type to another.
• Igneous rocks form from the cooling and solidification of magma or lava.
• Sedimentary rocks form from the accumulation and cementation of sediments.
• Metamorphic rocks form when existing rocks are changed by heat, pressure, or chemical reactions.

Geological Time Scale

• The geological time scale divides Earth's history into eons, eras, periods, and epochs.
• Eons are the largest division of time, followed by eras, periods, and epochs.
• The Phanerozoic eon is the current eon, characterized by abundant visible life.

Weathering and Erosion

• Weathering is the breakdown of rocks at the Earth's surface through physical and chemical processes.
• Erosion is the removal and transport of weathered material by wind, water, ice, or gravity.
• Physical weathering includes processes like freeze-thaw and abrasion.
• Chemical weathering involves chemical reactions that alter the composition of rocks.

Hydrogeology

• Hydrogeology is the study of the occurrence, distribution, and movement of groundwater in the Earth's subsurface.

Groundwater Occurrence

• Groundwater occurs in the saturated zone beneath the water table.
• The water table is the boundary between the saturated and unsaturated zones.
• Aquifers are geological formations that store and transmit significant quantities of groundwater.
• Aquitards are geological formations that restrict the flow of groundwater.
• Unconfined aquifers are directly overlain by permeable soil or rock.
• Confined aquifers are bounded above and below by impermeable layers.

Groundwater Flow

• Groundwater flows from areas of high hydraulic head to areas of low hydraulic head.
• Hydraulic head is the sum of elevation head and pressure head.
• Darcy's Law describes the flow of groundwater through porous media.
• Hydraulic conductivity measures the ability of a material to transmit water.
• Groundwater recharge is the process by which water infiltrates into an aquifer.
• Groundwater discharge is the process by which water leaves an aquifer.

Groundwater Chemistry

• Groundwater chemistry is influenced by the composition of rocks and soils, as well as biological activity.
• Dissolved ions in groundwater can include calcium, magnesium, sodium, potassium, chloride, sulfate, and bicarbonate.
• Groundwater pH affects the solubility of minerals and the mobility of contaminants.

Groundwater Resources

• Groundwater is an important source of drinking water, irrigation, and industrial use.
• Overpumping of groundwater can lead to water level decline, land subsidence, and saltwater intrusion.
• Groundwater contamination can occur from various sources, including industrial waste, agricultural runoff, and leaking underground storage tanks.
• Sustainable groundwater management is necessary to ensure the long-term availability and quality of groundwater resources.

Groundwater Exploration

• Geological mapping helps delineate potential aquifer locations.
• Geophysical surveys, such as seismic refraction and electrical resistivity, can characterize subsurface properties.
• Well drilling and testing are used to assess the hydraulic properties and water quality of aquifers.

Groundwater Modeling

• Groundwater models are used to simulate groundwater flow and contaminant transport.
• Models can be used to predict the impact of pumping, recharge, and contamination on groundwater resources.
• Modeling helps develop sustainable groundwater management strategies.

Interaction of Groundwater and Surface Water

• Groundwater and surface water are interconnected resources.
• Groundwater can discharge into streams, lakes, and wetlands, providing baseflow.
• Surface water can infiltrate into the ground and recharge aquifers.
• Pumping of groundwater near surface water bodies can reduce streamflow or lake levels.