Fluvial Systems, Coastal Geology, and Climate Change Practice Flashcards

A set of vocabulary flashcards covering fluvial systems, sediment transport, coastal dynamics, and geologic climate proxies based on the lecture material.

Laminar Flow

A type of flow where water moves in parallel, non-crossing streamlines, which is rarely found in open channels.

Turbulent Flow

Water flow characterized by chaotic, crossing streamlines and continuous mixing, which is highly efficient at eroding channels and keeping sediment in suspension.

Bed (Traction) Load

Coarse particles like boulders and gravel that roll or slide along the river bottom without leaving the substrate.

Saltating Load

Sand-sized grains that move by bouncing or hopping along the stream bed.

Suspended Load

Fine silt and clay particles that are kept aloft by turbulent eddies within the water column.

Dissolved Load

Soluble ions carried in chemical solution within a stream.

Competence

A metric measuring the maximum particle size a stream can carry, which is determined by the stream's velocity.

Capacity

A metric measuring the total volume of sediment a stream can transport, determined by the stream's discharge.

The Thalweg

The path of fastest water velocity within a channel, which swings to the outside of river bends and dictates where erosion occurs.

Cut Banks

The outer bank of a river loop where dynamic erosion occurs due to high water velocity.

Point Bars

The inner loop of a river bend where deposition occurs because the water slows down.

Oxbow Lakes

Crescent-shaped lakes that form when the neck of a meander is breached and then abandoned.

Graded Stream

A river system in dynamic equilibrium where $sediment\ delivered = sediment\ removed$, characterized by a concave-up profile.

Base Level

The lowest elevation to which a stream can erode, typically represented by sea level.

Stream Terraces

Stranded, incised former floodplains left behind after a river adjusts to profile disruptions.

Alluvial Fans

Fan-shaped aprons of coarse sediment dropped by ephemeral streams exiting steep mountain fronts onto flat plains.

Deltas

Tri-part sedimentary wedges formed where a river drops its sediment load as it enters a standing body of water like an ocean or lake.

Wave Base

The depth below which orbital wave motion vanishes, roughly equal to $\frac{1}{2}$ the horizontal wavelength.

Refraction

The bending of wavefronts as they slow down in shallow water, focusing energy onto headlands and dissipating it in bays.

Longshore Drift

The shore-parallel transport of sand caused by waves striking the beach at an angle, involving incoming swash and gravity-driven backwash.

Spring Tides

Extreme tidal ranges that occur during full or new moons when the gravitational forces of the Moon and Sun reinforce each other.

Tsunamis

Long-period waves generated by sudden sea floor displacements, such as megathrust earthquakes, which grow into high-amplitude walls of water in shallow areas.

Thermohaline Circulation

A global "ocean conveyor belt" driven by density differences resulting from water temperature (thermo) and salinity (haline) variations.

Recurrence Interval ($R$)

The statistical average time elapsed between floods of a given size, such as a "100-year flood" having a 1% annual chance.

Greenhouse Effect

The process where greenhouse gases like $H_2O$, $CO_2$, and $CH_4$ capture and reflect longwave, infrared radiation back to Earth, warming the lower atmosphere.

Benthic Foraminifera

Deep-sea organisms that build calcium carbonate $CaCO_3$ shells using oxygen from seawater, providing climate proxies through $^{18}\text{O}/^{16}\text{O}$ ratios.

Eccentricity

A Milankovitch cycle lasting approximately $100,000$ years where the shape of Earth's orbit alternates between nearly circular and mildly elliptical.

Obliquity (Tilt)

A Milankovitch cycle lasting approximately $41,000$ years involving the tilt angle of Earth's axis, ranging from $21.5^\circ$ to $24.5^\circ$.

Precession

A Milankovitch cycle lasting approximately $23,000$ years involving the wobble of Earth's axis, which changes the seasonal timing of perihelion and aphelion.