Geology Chapter 18

Saltation

(geology) the leaping movement of sand or soil particles as they are transported in a fluid medium over an uneven surface

Competence

A flow's ability to carry material of a given particle size

Delta

A landform made of sediment that is deposited where a river flows into an ocean or lake

Alluvial Fan

A large cone or fan-shaped accumulation of sediments when stream velocity slows, like at a mountain front.

Antecedent stream

A stream that continued to downcut and maintain its original course as an area along its course was uplifted by faulting or folding.

Superposed Stream

A stream that cuts through a ridge lying across its path. The stream established its course on uniform layers at a higher level without regard to underlying structures and subsequently downcut.

Longitudinal profile

An intentional change in the base level of a stream caused bu human activities, such as the construction of a dam, alter's the stream's.....

Dendritic Drainage

An irregular stream drainage network that resembles the limbs of a branching tree.

cohesiveness

At intermediate velocities, particles may erode or settle depending on their grain size and...

Distributaries

At the head of a delta, the major channel splits into smaller channels that follow different paths to the sea. These smaller channels are known as_____

large, small

At the highest velocities, currents erode both _____ and _____ particles from the streambed

settle

At the lowest velocities, particles of all sizes ______ onto the streambeds

Ripples

At very low velocities, _______ form, which migrate downstream and have cross-bedded structures

Turbulent flow

Flow velocities are randomly distributed, not very smooth

clay

For small but cohesive particles such as ____, a stronger current is required to erode them

quartz

For small non-cohesive particles such as quartz, the gentlest current can erode them

Dune

Higher flow velocities produce a larger bed form, a ____. Then, smaller ripples may piggyback up the dune; they migrate faster, so they tend to climb over the backs of dunes.

Foreset Beds

In a delta, which of the following sediment layers forms gentle inclines?

Rectangular Drainage

Looks like all of the streams met at right angles; small streams converge into a single river; common in rock that has cracks at right angles

Abrasion

One of the major ways a stream breaks apart and erodes rock; the sand and pebbles the stream carries create a sandblasting action that wears away even at the hardest rock.

Laminar flow

Simplest type of liquid flow through a tube where thin layers of liquid slide over one another, occurring as long as the flow rate remains below a critical velocity Vc

adjusts

The base level of a stream controls the lower end of its longitudinal profile. If the base level of a stream changes, the longitudinal profile _______ to the new base level over time

Velocity, geometry (primarily depth), viscosity

Whether a fluid is laminar or turbulent depends on three factors

Radial Drainage

a system of streams running in all directions away from a central elevated structure such as a volcano

Bottomset beds

a thin, horizontal bed of mud deposited seaward of the delta and then buried by continued delta growth

Trellis Drainage

developed in folded topography like that found in the Appalachian Mountains of North America. Down turned folds called synclines form valleys in which the main channel of the stream resides.

Drainage Network

interconnected system of tributaries, creeks, streams, rivers, etc. in an drainage basin that feed into a main waterway

Topset Beds

materials deposited on top of the delta, made up of sand

Bed load

sand, pebbles, and boulders that are moved along the bed of a stream and that are too heavy to be carried in suspension

Tributaries

small river or stream that flows in to a larger river or stream; a branch of the river

Drainage Basin

the area from which a single stream or river and its tributaries drains all of the water

Potholes

the geological feature that occurs when rocks that are part of the bed load get restricted to one spot. the river spins the rock around fast, and holes are gouged into the river floor.

Suspended load

The load contains small rocks and soil in suspension, which can make the river look muddy.

climate of region, width of floodplain, size of the channel

The recurrence interval of floods of a certain discharge depends on three factors:

Longitudinal profile

The smooth, concave-upward curve that represents a cross-sectional view of a stream, from notably steep near its head to almost level near its mouth.

Settling velocity

The speed at which a particle falls through a still fluid. The size, shape, and specific gravity of particles influence settling velocity.

Dischare

The volume of water that passes a given point in a given time as it flows through a channel of a certain width and depth.

Terraces

These form when the land surface is uplifted, causing a stream to erode into its floodplain and establish a new floodplain at a lower level. The ________ are remnants of the former floodplain.