Geology Final Water

Geo 20

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.