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Relative Dating
Establishes the sequence of events without providing specific numerical ages, based on principles like superposition and cross-cutting relationships.
Numerical Dating
Specifies the actual number of years since an event occurred, determined through radiometric dating techniques.
Principle of Superposition
States that in an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below.
Principle of Original Horizontality
Indicates that sedimentary layers are typically deposited in a horizontal position, and tilting suggests post-depositional deformation.
Principle of Lateral Continuity
Asserts that sedimentary beds extend laterally until thinning out at basin edges or transitioning into different sediment types.
Principle of Cross-Cutting Relationships
Describes that geologic features cutting across rocks must form after the rocks they cut through.
Principle of Inclusions
States that a rock mass containing inclusions is younger than the inclusions themselves, which are from an older rock mass.
Unconformities
Represent gaps in the rock record due to erosion or non-deposition, with types like angular, disconformity, and nonconformity.
Fossil
Preserved remains or traces of prehistoric life, providing evidence of past environments, evolution, and geologic time.
Index Fossils
Widespread but short-lived fossils used for dating rock layers of the same age.
Radiometric Dating
Uses ratios of parent to daughter isotopes to determine the age of a sample, based on the concept of half-life.
Alpha Decay
Emission of alpha particles from the nucleus, decreasing the mass number by 4 and atomic number by 2.
Beta Decay
Emission of an electron from the nucleus, leading to an increase in atomic number by 1 while mass number remains unchanged.
Electron Capture
Capture of an electron by the nucleus, decreasing the atomic number by 1 while the mass number remains unchanged.
Radiocarbon Dating
Uses carbon-14 to date organic materials up to around 70,000 years ago, valuable for studying recent Earth history.
Radiometric Dating
Determining the numerical dates of sedimentary layers by dating igneous rocks like volcanic ash beds and intruding dikes.
Sedimentary Strata Dating
Establishing numerical dates for sedimentary layers based on their relationship to nearby igneous rocks.
Geologic Time Scale
Dividing Earth's history into eons, eras, periods, and epochs to understand the timeline of geological events.
Precambrian Time
The period before the Cambrian period, challenging to subdivide due to limited knowledge and fossil evidence.
Hydrologic Cycle
The continuous circulation of water through Earth's land, oceans, and atmosphere driven by solar energy.
Evaporation
Process where liquid water changes into water vapor and enters the atmosphere from oceans and land.
Transpiration
Release of water vapor by plants into the atmosphere.
Infiltration
Movement of precipitation into the soil to become groundwater or flow into lakes and streams.
Evapotranspiration
Combined process of evaporation from soil, lakes, and streams, along with transpiration from plants, returning water vapor to the atmosphere.
Humid Regions
Streamflow from overland flow and groundwater.
Arid Regions
Stream loses water to groundwater due to lower water table level.
Drainage Patterns
Dendritic Pattern
irregular tributary
Irregular tributary streams resembling tree branches. Determined by land slope.
Drainage Patterns
Radial Pattern
Radial drainage pattern
Streams diverge from a central area like spokes on a bike tire, common in volcanic regions.
Drainage Patterns
Rectangular Pattern
Trellis drainage
Streams with right-angle bends due to underlying structural features.
Drainage Patterns
Trellis Pattern
parallel tributary
Parallel tributary streams, common in areas with alternating bands of resistant rock.
River Zones and Sediment Dynamics
Zones
Fluvial processes
Areas for sediment production, transport, and deposition in river systems.
River Zones and Sediment Dynamics
Sediment Production
headwater erosion
Erosion and weathering in headwaters leading to sediment contribution.
River Zones and Sediment Dynamics
Sediment Transport
sediment transport in trunk streams
Movement of sediment through trunk streams.
River Zones and Sediment Dynamics
Sediment Deposition
delta formation
Sediment settling at river mouths forming deltas or coastal features.
River Evolution
Headward Erosion
headward erosion
Lengthening of streams by erosion of their heads upslope.
River Evolution
Antecedent Streams
stream capture/ uplift
Streams maintaining course despite uplift.
River Evolution
Superposed Streams
structural erosion
Streams eroding through existing structures due to sedimentary layering.
Streamflow Characteristics
Streamflow
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Water movement in river channels influenced by gravity.
Streamflow Characteristics
Laminar Flow
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Smooth water flow in parallel layers with low turbulence.
Streamflow Characteristics
Turbulent Flow
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Chaotic water movement with high turbulence, common in natural streams.
Factors Influencing Streamflow
Flow Velocity
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Speed of water movement influenced by channel characteristics.
Factors Influencing Streamflow
Gradient
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Slope change affecting flow velocity and erosional power.
Factors Influencing Streamflow
Channel Shape
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Cross-section shape impacting flow characteristics.
Factors Influencing Streamflow
Discharge
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Volume of water passing a point influencing erosion and transport.
Monitoring Streamflow
Longitudinal Profile
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Cross-sectional view of a stream from source to mouth.
Monitoring Streamflow
Changes from Upstream to Downstream
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Variations in channel width, depth, velocity, and discharge along a stream.
Stream Erosion
Raindrop Erosion
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Dislodging sediment particles by raindrops, initiating erosion.
Stream Erosion
Channel Erosion
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Erosion in confined flow channels influenced by slope and discharge.
Transport of Sediment
Dissolved Load
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Minerals dissolved in water with minimal velocity effect.
Transport of Sediment
Suspended Load
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Fine particles carried in suspension influenced by flow velocity.
Transport of Sediment
Bed Load
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Coarser sediment moving along the streambed influenced by channel characteristics.
Deposition of Sediment
Sorting
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Separation of sediment particles during transport based on size.
Deposition of Sediment
Alluvium
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Sediment deposited by streams forming various features.
Alluvial Channels
Channels composed of unconsolidated sediment that change shape due to erosion, transportation, and deposition.
Meandering Channels
Streams with sweeping bends (meanders) that evolve over time, leading to oxbow lake formation.
Braided Channels
Complex networks of channels with multiple paths separated by bars, formed in high sediment supply environments.
Bedrock Channels
Channels cut into solid rock, common in headwaters with steep slopes.
Base Level
The lowest point a stream can erode, including ultimate (sea level) and local levels.
Stream Load
Sediment transported by a stream, including bed load, suspended load, and dissolved load.
Floodplain
Broad, flat valley floor covered with alluvium, inundated during floods.
Deltas
Landforms at river mouths with sediment deposition into still waters, forming distributaries.
Natural Levees
Elevated ridges parallel to river channels, formed by successive floods depositing coarse sediment.
Alluvial Fans
Fan-shaped sediment deposits at the base of steep mountain slopes, formed by high-gradient streams.
Natural Levees
Elevated ridges formed by successive flood deposits of coarse sediment adjacent to a river channel during overflow.
Back Swamps
Areas behind natural levees with poor drainage conditions.
Yazoo Tributaries
Tributaries that flow through back swamps before rejoining the main river channel.
Aquitards
Impermeable layers above and below the aquifer, restricting the flow of groundwater.
Aquifers
Permeable layers that allow the transmission of groundwater.
Pressure Surface
Represents the level to which water would rise if not confined in an artesian system.
Frictional Losses
Reduction in pressure due to friction between flowing water and surrounding rock, causing non-flowing artesian wells.
Hydraulic Gradient
Increased distance from recharge areas leading to higher friction, reducing pressure and flow at the surface.
Depleted Reservoirs
Aquifer overuse causing lowered water table, reduced pressure, and non-flowing artesian wells.
Groundwater Contamination
Pollution from various sources threatening groundwater quality.
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