Physical Geography Final Exam 5

Karst Topography

A cornerstone concept that describes the special landforms that develop on exceptionally soluble rocks, although there is a broad international vocabulary to refer to specific features in specific regions

Floodplains

A low-lying, nearly flat alluvial valley floor that is periodically inundated with floodwaters

Capacity

A measure of the amount of solid material a stream has the potential to transport, normally expressed as the volume of material passing a given point in the stream channel during a given time interval.

Competence

A measure of the particle size a stream can transport, expressed by the diameter of the largest particles that can be moved

Collapse Sinkhole

A sinkhole that results from the collapse of the roof of a subsurface cavern; these may have vertical walls or even overhanging cliffs

Geyser

A special form of intermittent hot spring, hot water usually issues out of it sporadically, and most or all of the flow is an eruption, in which hot water and steam spout upward

Furmarole

A surface crack directly connected to a deep seated heat source

Yazoo Stream

A tributary stream entering a floodplain that has prominent natural levees cannot flow directly into the main channel and so flows down valley in the backswamp zone, running parallel to the main stream for for some distance before finding an entrance

Desert Fluvial Deposition

Almost all streams are ephemeral, flowing only during and immediately after rain. Such streams are effective agents of erosion, shifting enormous amounts of material in a short time

Examples of Equilibrium Theory

Alps and the Himalayas

Intermittent Streams

Also known as seasonal streams, only flow for part of the year and are impermanent streams

Stream Capture

Also known as stream piracy, is relatively uncommon in nature, but evidence that it does sometimes occur is found in many places

Drainage Basins

Also known as watershed of a particular stream; all the area that contributes overland flow, streamflow, and groundwater to that stream.

Desert Rainfall

Although rainfall is limited in desert areas, much of the rain that does fall comes from intensive convective thunderstorms.

Rills

As Overland flow moves downslope and its volume increases, the resulting turbulence tends to break up the sheet flow into multitudinous tiny channels

Lateral Erosion

As the stream sways from side to side, THIS begins: the main flow of the current swings from one bank to the other, eroding where the water speed is greatest and and depositing where it is least

Third-order stream

At the confluence of two second-order streams

Desert Impermeable Surfaces

Caprocks (resistant bedrock surfaces) and hardpans (hardened and generally water-impermeable subsurface soil layers) of various types of are widespread, and what soil is formed is usually thoroughly compacted and often does not readily absorb water

Undercutting

Causes landslides that dump more loose material into water to be swept downstream

Stream Order

Concept that describes the hierarchy of a drainage network

Braided channels

Consist of a multiplicity of interwoven and interconnected channels separated by low bars or islands of sand, gravel, and other loose debris

Stream Load

Contains three fractions or three loads

Desert Soil Creep

Creep is a smoothing phenomenon in more humid climates, and its lack in deserts accounts in part for the angularity of desert slopes

Thalweg

Deepest parts of the channel

Graded Streams

Defined as one in which the gradient just allows the stream to transport its load. More theoretical than actual because equilibrium is so difficult to achieve and so easy to upset

Fluvial processes

Defined as those that involve running water

Desert Basis of Interior Drainage

Desert areas contain many watersheds that do not drain ultimately into any ocean. In dry lands drainage networks are frequently underdeveloped, and the terminus of a drainage system is often a basis or valley with no external outlet

Desert Vegetaton

Desert plant cover consists mostly of widely spaced shrubs or sparse grass, which provide little protection from the force of raindrops and function inadequately to bind the surface material with roots

Trellis Pattern

Develops as a response to underlying structural control-in this case, alternating bands of of tilted hard and soft strata, with long, parallel streams linked by short, right angled segments

Erosion by Overland Flow

During heavy or continued rain, however, particularly if the land is sloping and has only a sparse vegetation cover, infiltration is greatly diminished and most of the water moves downslope as Overland Flow.

Centripetal Pattern

Essentially the opposite of a radial one, is usually associated with streams converging in a basin

Meandering channels

Exhibit an extraordinarily intricate pattern of smooth curves in which the stream flows as a serpentine course, twisting and contorting and turning back on itself, forming tightly curved loops and then abandoning them, cutting a new, different, and equally twisting course

Delta

Flowing water slows down whenever it enters the quiet water of a lake or ocean and deposits its load. Most of this debris is dropped right at the mouth of the river in a landform called this

Interfluve

Higher land above the valley walls that separates adjacent valleys

Desert Soil and Regolith

In deserts, the covering of soil and regolith is either thin or absent in most places, a condition that exposes the bedrock and erosion, and contributes to the stark, rugged, rocky terrain

Perennial Stream

In humid regions the large rivers and tributaries are permanent

Process

Is concerned with the internal and external forces that shape the landforms

Headward erosion

It is the basis of rill, gully, and valley formation and extension

Desert Wind

Landforms in deserts are not produced largely by wind action. Although, high winds are a characteristic of most deserts and sand and dust particles are easily shifted

Soda Straws

Little more than one drop wide, these delicate hollow tubes may eventually grow into stalactites

Ephemeral Streams

Makes up more than 99% of all desert streams. The period in which these streams flow are times of intense erosion, transportation, and depostion

Natural Levees

Merge outwardly and almost imperceptibly with the less well drained lower portions of the floodplain, generally referred to as backswamps

Desert Weathering

Moisture is required for nearly all kinds of chemical weathering, in many desert regions mechanical weathering is dominant

Sinkholes

Most common feature of Karst Landforms, which occur by the hundreds and sometimes the thousands. Rounded depressions formed by the dissolution of surface carbonate rocks, typically at joint intersections

Desert Sand

Most deserts are covered in sand but not all are filled with sand. The relatively high proportion of sand in some deserts has three important influences

Example of Knickpoint Migration

Niagara Falls

Consequent Stream

Normally the first to develop on newly uplifted land, and many streams remain this way through their evolutionary development

Cutoff meanders

Often a meander loop is bypassed as the stream channel shifts through lateral erosion and cuts a new channel across its neck and starts meandering again, leaving the old meander loop as this

Point Bar

On the inside of a curve where water is moving most slowly, alluvium is likely to accumulate

Erosion by Streamflow

Once surface flow is channeled, its ability to erode and transport material is greatly enhanced by the increased volume and velocity of water. Channel banks can also be undercut by streamflow, particularly at times of high discharge.

Ephemeral Streams

Only carry water during and immediately following rain

Hydrothermal Activity

Outpouring of hot water, often accompanied by steam, and usually takes the form of either a hot spring or geyser

Valley Bottom

Partially or totally occupied by the channel of a stream

Exotic Streams

Permanent streams in dry lands are few, far between, and, with scarce exceptions, exotic, meaning they are sustained by water that originates outside the desert

Mechanical Weathering

Processes such as salt wedging are more common in arid regions than in humid ones

Splash Erosion

Rain starts to fall. Unless the impact is absorbed by vegetation or some other protective covering, the collision of raindrops with the ground is strong enough to blast fine soil particles upward and outward, shifting them a few meters laterally.

Structure

Refers to the type and arrangement of the underlying rocks and surface materials

Tower Karst

Residual karst features, in the form of very steep-sided hills, dominate some parts of the world; almost vertical sides and conical or hemispheric shapes

Valley Walls

Rise above the valley bottom on both sides

Bedload

Sand, gravel, and larger rocks make up this load

Ultimate Base Level

Sea level is the absolute or lower limit of downcutting for most streams

Straight Channels

Short and uncommon channels, and usually indicative of strong control by the underlying geologic structure

Caverns

Solution along joints and bedding planes in limestone beneath the surface often creates these large open areas

Dissolved Load

Some minerals, mostly salts, are dissolved in the water and carried in solution

Antecedent Stream

Some streams seemed to "defy" the structure with courses that cut through ridges or other significant structures. One way this can occur is when an established stream is interrupted by an uplift of land that is so slow that the stream is able to maintain its previously established course by downward erosion, leaving a deep gorge carved through hills or mountains

Column

Stalagmites and Stalactites may extend until they meet to form this

Alluvium

Stream-deposited sediment

Subsequent Streams

Streams that are developed along zones of structural weaknesses

Superimposed Stream

Such stream originally existed when the landscape was higher; this older, higher landscape has since been entirely or largely eroded away, so that the original drainage pattern becomes incised into an underlying sequence of rocks of quite different structure

Disappearing Streams

Surface runoff that does become channeled does not usually go far before it disappears into a sinkhole or joint crack

Hot Springs

The appearance of hot water at Earth's surface usually indicates that the underground water has come in contact with heated rocks or magma and has been forced upward through a fissure by the pressures that develop when water is heated

Streamflow

The channelled movement of water along a valley bottom

Stage

The length of time during the which the processes have been at work

Base Level

The lower limit of how much downcutting a stream can do. An imaginary surface extending from sea level at the coasts

Dendritic Pattern

The most common drainage pattern over the world is a treelike branching, which consists of a random merging of streams, with tributaries joining larger streams irregularly but always at an angle smaller than 90 degrees

Valley

The portion of the terrain in which a drainage system is clearly established

Overland Flow

The unchannelled downslope movement of surface water

Sheet Erosion

The water flows across a surface as a thin sheet, transporting material already loosened by Splash Erosion

Cutbanks

The water moves fastest on the outside of curves, and there is undercuts the bank

Swallow holes

The water that collects in sinkholes generally percolates downward, but some sinkholes have distinct distinct openings at their bottom, through which surface drainage can pour directly into an underground channel, often to reappear at the surface through another hole some distance away

Sinuous channels

These are winding channels and are found in almost every type of topographic setting. Their curative is usually gentle and irregular

Davis's Geomorphic Cycle

This first, and in many ways most influential, model of landscape development was propounded by William Morris Davis; Sometimes called the cycle of erosion

"Decoration Stage"

This initial excavation is followed, often after a drop in the water table, by this stage in which ceilings, walls, and floors are decorated with a wondrous variety of speleothems

Rill Erosion

This more concentrated flow picks up additional material and scores the slope with numerous parallel seams; this is a sequence of events

Annular Pattern

This ring-shaped drainage pattern can develop either on a dome or in a basin where dissection has exposed alternating concentric bands of tilted hard and soft rock.

Equilibrium Theory

This theory suggests that slopes are adjusted to geomorphic processes so that there is a balance of energy-the energy provided is just adequate for the work to be done

Karst Landforms

Typical landforms in karst regions include sinkholes, disrupted surface drainage, and underground drainage networks that have openings formed from solution action

Radial Pattern

Usually found when streams descend from sort of concentric uplift, such as an isolated volcano

Suspended Load

Very fine particles of clay and silt are carried in suspension, moving along with the water without ever touching the stream bed

Penck's Theory of Crustal Change and Slope Development

Walther Penck pointed out in the 1920's that slopes assume various shapes as they erode and his ideas have been substantiated by subsequent workers, and his ideas have been called this theory

Knickpoint Migration

Waterfalls and rapids are often found in valleys where downcutting is prominent. They occur in steeper sections of the channel, and their faster, more turbulent flow intensifies erosion.

Uvala

Where sinkholes occur in profusion, they often channel surface runoff into the groundwater circulation, leaving networks of dry valleys as relict surface forms

Stalagmite

Where the drip from a stalactite hits the floor, a companion feature grows upward

Second-order stream

Where two first-order streams unite

Stalactite

Where water drips from, a pendant structure grows slowly downward like a icicle

Initial Excavation

Wherein percolating water dissolves the carbonate bedrock and leaves voids

Downcutting

Wherever it has either a relatively rapid speed or a relatively large volume, a stream expends most of its energy doing this. Produces a valley with steep sides and often a V-shaped cross section

Davis's stages of development

Youth, Maturity, Old Age, Rejuvination

First-order stream

smallest unit in the Stream Order System, a stream without tributaries

Corrosion

soluble rock being dissolved by water