Stream and River Dynamics Quiz

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Questions and Answers

What is the definition of a stream?

A stream is a body of running water confined to a channel that flows downhill due to gravity.

Where is the headwaters of a stream typically located?

The headwaters are located in the upper part of the stream near its source in the mountains.

What is the purpose of a drainage basin?

A drainage basin is the total area drained by a stream and its tributaries.

Explain the relationship between stream velocity and sediment transport.

Higher stream velocities promote erosion and the transport of coarser sediments. Signup and view all the answers

What are tributaries?

Tributaries are small streams that flow into a larger stream. Signup and view all the answers

What is the term for the ability of a stream to pick up and move sediment?

The term is hydraulic action. Signup and view all the answers

What is the distinction between the channel and streambed?

The channel refers to the long, narrow depression eroded by a stream, while the streambed is the bottom of that channel. Signup and view all the answers

What role does the Continental Divide play in drainage basins?

The Continental Divide separates streams that flow into the Pacific Ocean from those flowing into the Atlantic and Gulf of Mexico. Signup and view all the answers

What is a delta and how is it formed?

A delta is a body of sediment deposited at the mouth of a river when flow velocity decreases. Signup and view all the answers

How does the shape of a delta change in response to different dominant forces?

The shape of a delta varies based on whether it is wave-dominated, tide-dominated, or stream-dominated. Signup and view all the answers

Describe the formation of an alluvial fan.

An alluvial fan forms when stream velocity decreases as it emerges from a narrow canyon onto a flat plain. Signup and view all the answers

What characterizes the sediment distribution in larger alluvial fans?

Larger alluvial fans exhibit grading from larger sediments near the mountains to finer sediments farther away. Signup and view all the answers

What role do valleys play in the landscape, and how are they formed?

Valleys are significant landforms on Earth formed by stream erosion. Signup and view all the answers

Explain the term 'downcutting' in the context of stream valley development.

Downcutting refers to the process where streams erode the ground beneath them, deepening the valley. Signup and view all the answers

Why are alluvial fans particularly common in desert regions?

Alluvial fans are most developed in desert regions due to the occurrence of sudden and intense flash floods. Signup and view all the answers

How do distributary channels affect the surface of a delta?

The surface of a delta is marked by shifting distributary channels that redirect sediment flow. Signup and view all the answers

What are the primary causes of flood erosion?

High velocity and large volume of water cause flood erosion. Signup and view all the answers

How does urbanization contribute to increased flood risk?

Urbanization creates impermeable surfaces, which increase runoff and hasten the occurrence of floods. Signup and view all the answers

Define flash floods and identify their typical triggers.

Flash floods are sudden, local floods of large volume and short duration, typically triggered by heavy thunderstorms. Signup and view all the answers

What is the purpose of dams in flood risk reduction?

Dams are designed to trap flood waters in reservoirs upstream and release them gradually over time. Signup and view all the answers

What are some environmental concerns associated with dam construction?

Environmental concerns include habitat destruction, trapping of sediment and nutrients, and destabilizing the river valley. Signup and view all the answers

What percentage of the hydrosphere is represented by groundwater?

Groundwater represents 1.7% of the hydrosphere. Signup and view all the answers

List two reasons why groundwater is considered a tremendously important resource.

Groundwater is generally cleaner than surface water and is accessed by wells, making it vital for drinking water supplies. Signup and view all the answers

What impact does a growing population have on groundwater resources?

A growing population leads to increasing rates of groundwater removal and escalating pollution impacts. Signup and view all the answers

What is abrasion in the context of stream channels?

Abrasion is the grinding away of the stream channel caused by the friction and impact of the sediment load. Signup and view all the answers

Describe the characteristics of bed load in stream transportation.

Bed load consists of large or heavy particles that travel along the streambed, primarily through traction. Signup and view all the answers

What role do meander cutoffs play in stream dynamics?

Meander cutoffs form when a new, shorter channel is created through a narrow neck of a meander, often triggered by flooding. Signup and view all the answers

How do braided streams differ from meandering streams?

Braided streams contain multiple interconnected channels with numerous bars, while meandering streams develop pronounced curves or meanders. Signup and view all the answers

What are point bars and where do they form?

Point bars are formed on the inside of meander bends where sediment is deposited as water flows slower in these areas. Signup and view all the answers

What are natural levees and how do they form?

Natural levees are slightly raised banks alongside the main channel of a floodplain, formed by sedimentation as floodwaters recede. Signup and view all the answers

Define placer deposits and their significance in streams.

Placer deposits are concentrations of heavy sediment that accumulate in specific areas of a stream, often due to gravity. Signup and view all the answers

What is suspended load in a stream and how does it behave?

Suspended load consists of small or light sediment that remains floating above the stream bottom due to turbulent flow. Signup and view all the answers

What is geothermal energy and how is it characterized?

Geothermal energy is produced using natural steam or superheated water and is characterized as a clean energy source with no CO2 or acid rain production. Signup and view all the answers

Describe the two main types of glaciers and their locations.

The two main types of glaciers are alpine glaciers, found in mountainous regions, and continental glaciers, which cover large parts of continents, especially in polar regions. Signup and view all the answers

What are the critical conditions for glacier formation?

Glaciers can only form where more snow accumulates in winter than melts in spring and summer. Signup and view all the answers

Approximately what percentage of the Earth's surface is covered by glaciers?

Approximately 10% of Earth's surface is covered by glaciers. Signup and view all the answers

How does the melting of Antarctic ice affect global sea levels?

If all the ice on Antarctica were to melt, it would cause sea levels to rise approximately 65 meters (213 feet). Signup and view all the answers

What role does snowfall play in glacier formation?

Snowfall initiates glacier formation by providing the necessary accumulation of snow that compacts to form glacial ice. Signup and view all the answers

In what ways can geothermal energy be utilized directly?

Geothermal energy can be used directly to heat buildings. Signup and view all the answers

What defines the water table in terms of its relation to the saturated zone?

The water table is the top of the saturated zone where all rock openings are filled with water. Signup and view all the answers

How does porosity differ between loose sand and compacted sandstone?

Loose sand has approximately 30-50% porosity, while compacted sandstone has only about 10-20% porosity. Signup and view all the answers

What is firn in the context of glacier formation?

Firn is the transitional substance formed between granular snow and glacial ice during the glacier formation process. Signup and view all the answers

Explain the concept of a perched water table.

A perched water table is a localized layer of saturation above the main water table, separated by an unsaturated zone. Signup and view all the answers

What factors influence the movement of groundwater through rock and sediment?

The movement of groundwater is influenced by the slope of the water table and the permeability of the rock or sediment. Signup and view all the answers

Differentiate between unconfined and confined aquifers.

Unconfined aquifers have a water table and are only partially filled, while confined aquifers are completely filled with water under pressure. Signup and view all the answers

What role do aquitards play in groundwater flow?

Aquitards are layers of rock or sediment that slow down groundwater flow due to their low porosity and permeability. Signup and view all the answers

How does the permeability of different rocks affect groundwater movement?

Rocks like sandstones and conglomerates have high permeability which allows water to flow easily, while granites and schists are typically impermeable. Signup and view all the answers

What is the primary purpose of a well in terms of groundwater extraction?

The primary purpose of a well is to access water from an aquifer, specifically using the water level at the water table before pumping. Signup and view all the answers

Study Notes

Exogenic Processes of the Earth

Course Outcome 4
GEO01 - Earth Science

Mass Wasting

Mass wasting is the downhill movement of masses of bedrock, rock debris, or soil driven by gravity.
With proper planning, mass wasting is one of the most easily avoidable geologic hazards.

Controlling Factors in Mass Wasting

Driving Force: Gravity
Contributing Factors:
- Slope angle: Gentle slopes are more stable, steep slopes are more unstable.
- Local relief: Low relief is more stable, high relief is more unstable.
- Thickness of soil over bedrock: Thin layers are more stable.
- Orientation of planes of weaknesses in bedrock: Planes at right angles to hillside slopes contribute to stability.
- Temperature: Temperature stays above freezing for stability.
- Water in soil or debris: Saturation leads to instability
- Precipitation: Frequent light rainfall contributes to stability, heavy rainfall to instability.
- Vegetation: Heavier vegetation leads to more stability.

Gravity

Gravity is the driving force for mass wasting.
Normal force is the force perpendicular to a surface.
Shear force is the force parallel to a surface.
Shear resistance is the resistance to movement.
If shear resistance is less than shear force, landslides occur.
Steep slopes maximize shear forces due to gravity.

Shear Strength and Water

Shear strength is the resistance to movement or deformation.
Saturated soil has reduced shear strength due to increased pore water pressure.
A small amount of water can prevent downslope movement, like a sandcastle.

Mass Wasting Triggers

Seismic activity (earthquakes)
Heavy Rainfall
Construction
Lack of vegetation (no roots to hold rock/soil in place)

Classification of Mass Wasting

Rate of movement: Less than 1 cm/year to more than 100 km/hour.
Type of material: Solid bedrock or debris (unconsolidated material on Earth's surface).
Type of movement: Flow, slide, or fall.

Some Types of Mass Wasting

Flows: Creep (soil), Debris flow, Earthflow, Mudflow, Rock avalanche (Debris)
Slides: Debris slide (debris) / Earthslide, Rockslide (bedrock)
Falls: Rockfall (bedrock)

Creep (or soil creep)

Very slow downslope movement of soil.
Major contributing factors include water in soil and daily freeze-thaw cycles.
Can be costly to maintain homes, etc., on creeping ground as foundations, walls, pipes, and driveways crack and shift downslope over time.

Flows: Earthflow and Solifluction

Earthflow: Debris moves downslope, slowly or rapidly, as a viscous fluid.
Solifluction: Flow of water-saturated soil over impermeable material, common in colder climates.

Flows: Debris Flow, Mudflow, Avalanche

Debris flow and mudflow are flowing mixtures of debris and water, usually down a channel.
Mudflow is only soil and water.
Debris avalanches are very rapid and turbulent.

Falls

Material falls or bounces down a cliff.
Rockfall - a block of bedrock breaks free and falls or bounces down a cliff.
Commonly an apron of fallen rock fragments (talus) accumulates at cliff base.

Slides

Descending mass remains relatively intact and descends along well-defined surfaces.
Translational slide: Movement along a plane parallel to motion.
Rotational slide (slump): Movement along a curved surface.
Rockslide and Rock Avalanche: Rapid sliding of bedrock along an inclined surface of weakness.
Underwater Landslides: Turbidity currents, these can create tsunamis.

Preventing Landslides

Preventing Rockfalls and Rockslides on Highways: Remove loose material, stitch slopes together.
Preventing Mass Wasting of Soil: Construct retaining walls with drains, don't oversteepen slopes during construction, remove rock prone to sliding, add vegetative cover, cover roads.

Streams and Floods

Hydrologic Cycle: Movement and interchange of water between sea, air, and land; involves evaporation, precipitation, transpiration, runoff, and infiltration.

Running Water

Stream: Body of running water, confined to a channel, flows downhill under the influence of gravity.
Headwaters: Upper part of a stream near its source in the mountains.
Mouth: Where a stream enters a sea, lake, or larger stream.
Channel: Long, narrow depression eroded by a stream into rock or sediment.
Stream banks: Sides of a channel.
Streambed: Bottom of a channel.
Floodplain: Flat valley floor composed of sediment deposited by the stream.

Drainage Basins

Drainage basin: Total area drained by a stream and its tributaries.
Tributary: Small stream flowing into a larger one.
Divide: Ridge or high ground that divides one drainage basin from another.
Continental Divide: Separates streams flowing into the Pacific from those into the Atlantic and Gulf of Mexico.

Factors Affecting Stream Erosion and Deposition

Velocity: Maximum velocity near center of channel. Higher velocity promotes erosion and transport of coarser sediments.
Gradient (slope): Higher gradient leads to higher erosion.
Channel Shape and Roughness: Shape and roughness affect the flow and therefore erosion and deposition.
Discharge: Volume of water passing a point in a stream over time.

Stream Erosion

Streams cut and widen valleys over time.
Hydraulic action: Ability to pick up and move rock and sediment.
Solution: Dissolving of rocks (chemical reaction).
Abrasion: Grinding away of stream channel by the impact and friction of sediment load.
Potholes are eroded into stream beds by the abrasive action of sediment load.

Stream Transportation of Sediment

Bed load: Large particles travel on the streambed by rolling, sliding, or dragging.
Saltation load: Medium particles bounce along inside the stream.
Suspended load: Small/light sediment that remains above stream bottom by turbulent flow.
Dissolved load: Dissolved ions produced by chemical weathering.

Stream Deposition

Bars: Sediments temporarily deposited along stream course.
Placer Deposits: Concentrated heavy sediment.

Braided Streams

Contain sediment deposited as numerous bars around which water flows in interconnected rivulets, resembling braids of hair or rope.
Common in streams carrying a lot of sediment.

Meandering Streams

Rivers that develop pronounced, sinuous curves called meanders.
Water flows faster along the outside of bends causing erosion and creating cut banks.
Slower flow along the inside leads to deposition of point bars.

Meandering Cutoffs

Meander cutoffs may form when a new, shorter channel is cut forming a meander neck through the meander, as during a flood. This creates oxbow lakes.

Floodplains

Broad strips of land built up from sedimentation on either side of a stream channel.
Left behind when floodwaters slow and recede.
Main channel often has slightly raised banks called "natural levees."

Deltas

Body of sediment deposited at the mouth of a river when flow velocity decreases.
Marked by shifting distributary channels.
Shape depends on whether it's wave-dominated, tide-dominated, or stream-dominated.

Alluvial Fans

Large, fan- or cone-shaped piles of sediment that forms where stream velocity decreases as it emerges from a narrow mountain canyon onto a flat plain.
Well-developed in desert regions (like the southwestern U.S.).
Larger fans show grading from large sediments nearest the mountains to finer sediments farther away.

Stream Valley Development: Downcutting

Valleys are the most common landform on Earth and formed by stream erosion.
Different valley morphologies depend upon erosional processes.
Downcutting is the process of deepening a valley by erosion of the streambed.
V-shaped valleys typically form from downcutting combined with mass wasting and sheet erosion.
Streams cannot erode below their base level.

Stream Valley Development: Grading, Later Erosion, Headward Erosion

Graded streams have a concave-up longitudinal profile, lack rapids and waterfalls, and represent a balance.
Lateral erosion widens stream valleys.
Headward erosion slowly grows a valley uphill.

Stream Valley Development: Terraces

Step-like landforms found above a stream and its floodplain, occur when a river rapidly cuts downward into its own floodplain.
Represents a relatively sudden change from deposition to erosion.
Can be caused by rapid uplift, drops in base level, or climate changes.

Stream Valley Development: Incised Meanders

Retain sinuous pattern as they cut vertically downward.
Can occur when rapid tectonic uplift alters base levels.

Flooding

When water levels rise and overtop the banks of a river, flooding occurs, a natural process on all rivers.
Floods are described by recurrence intervals and can cause great damage in heavily populated areas.
High velocity and large volume of water during floods causes severe erosion.
Floods deposits are deposited in floodplains as the flooding ends..

Flooding and Urbanization

Urbanization increases runoff by creating impermeable surfaces.
This leads to water being delivered to streams faster, increasing peak discharge and hastening flood occurrence

Flash Flooding

Local, sudden floods of a large volume and short duration.
Typically triggered by heavy thunderstorms.

Reducing Flood Risk

Dams: Trap floodwaters in reservoirs for gradual release.
Artificial levees: Increase river channel capacity.
Wise land-use planning: Preventing development within 100-year floodplains.

Impact of Dams

Societal benefits: Electricity production, flooding control, and reservoir for drinking water.
Environmental concerns: Trapping sediment and nutrients, habitat destruction, destabilizing the river valley, leading to landslides.

Groundwater

Importance of Groundwater

Lies beneath the ground surface fills voids in sediments, sedimentary rocks and fractures.
Represents 1.7% of the total hydrosphere.
Resupplied by precipitation
Generally cleaner than surface water; readily accessed through wells
Tremendously important resources that face increasing withdrawal and pollution.

The Water Table

Saturated zone: Subsurface zone where rocks' pores are filled with water.
Water table: Top of the saturated zone, equivalent to water level in lakes and rivers.
Unsaturated zone: Region above the water table.
Perched water table: Body of groundwater separated from the main water table by an unsaturated layer.
Formed from impermeable layers above the main water table.

Springs and Streams

Spring: Place where water flows naturally from rocks or sediments onto the ground surface.
Gaining streams: Receive water from saturated zone, stream surface is at water table level.
Losing streams: Lose water to saturated zone, stream beds lie above the water table.

Contamination of Groundwater

Infiltrating water can bring pollutants to the water table, including pesticides, fertilizers, landfill pollutants, heavy metals, bacteria, viruses, parasites, industrial chemicals, acid mine drainage, radioactive waste, and oil and gasoline.

Pollution Caused by Pumping Wells

Depletion of water tables, leading to cone of depression in water table, causing saltwater intrusion.

Balancing Withdrawal & Recharge

High rate of ground water pumping exceeding recharge that can affect water tables and leads to ground subsidence (sinking of land).
Subsidence can crack foundations, roads, and pipelines.
Areas of high irrigation often suffer severe subsidence.

Geologic Effects of Groundwater

Groundwater dissolves soluble bedrock, such as limestone.
This creates caves, sinkholes, karst topography and related effects.

Caves

Naturally-formed underground chambers.
Acidic ground water dissolves limestone, along joints and bedding planes.
Stalactites: form when water drips from cave ceilings
Stalagmites: dripstone formations that grow upward from the cave floor.
Columns: fused stalagmites and stalactites.

Karst Topography

Karst Topography: Area characterized by rolling hills, disappearing streams, and sinkholes.

Sinkholes and Karst Topography

Caves near the surface collapse to form sinkholes.
Common in karst topographies.

Other Effects of Groundwater

Preservation of Fossils: Water-filled voids can replace organic matter to produce fossils.
Petrified Wood: Infiltration of groundwater can dissolve wood, which is then replaced by minerals.
Concretions: Deposits of minerals around a central nucleus which can form in rock layers.
Geodes: Voids in rock layers filled with crystals

Hot Water Underground

Hot springs: Springs whose water is warmer than human body temperature.
Water is heated by nearby magma, often rises back to surface on its own.
Geysers: Hot springs that periodically erupt hot water and steam through fractures, due to fluctuating pressure.
Minerals precipitate around geysers as hot water cools.

Geothermal Energy

Utilizing natural steam or superheated water for energy production.
Clean energy source, with minimal CO2 or acid rain.
Some toxic gases from some sites, like sulfur compounds.
Superheated water may be corrosive to pipes and equipment

Glaciers & Glaciation

What is a Glacier?

Glacier: Large, long-lasting mass of ice formed on land which moves downhill under its own weight.
Glaciated terrains: Alpine (mountain), continental (large portions of continents).
~70% of fresh water is locked in glacial ice.

Types of Glaciers

Develop from snow that is compacted and recrystallizes into firn then glacial ice.
Alpine glaciation: Occurs in mountainous regions (valley glaciers).
Continental glaciation: Covers large land masses in polar regions (ice sheets).

Distribution of Glaciers

Most extensive in polar climates, but occurs anywhere with more snow falling than melting.
Approximately 10% of Earth's surface is covered by glaciers.
About 85% of the world's glacial ice is in Antarctica.

Formation and Growth of Glaciers

Snowfall, compaction of snow removes air, snow flakes recrystallize into granules (firn).
Firn – a transitional state between snow and ice.
Glacial ice: Formed after further compaction and removal of air, has a granular, crystal-like texture.
Gravity causes downslope movement of glaciers.
Ablation: Loss of glacier from melting, evaporation, or icebergs calving.

Glacial Erosion

Glaciers erode underlying rocks by plucking and abrasion as they are dragged along.
Basal abrasion polishes and striates the underlying rock surface producing abundant fine rock powder called rock flour.

Landscapes Associated with Continental Glaciation

Rounded topography is more common
Weight and thickness of continental ice sheets produce rounded knobs
Grooved or striated rock (several meters deep and kilometers long)
Thick enough to bury mountains rounding off ridges and summits

More Indirect Effects

Lowering and rising of sea levels: Fiords - coastal inlets formed by drowning of glacially carved valleys by rising sea levels.
Crustal rebound: Occurs after ice sheet removal, crust adjusts as it rebounds from weight of ice.
Great Lakes region as an example of this.

Deserts & Wind Action

Deserts

Desert: Arid region receiving less than 25 cm annual precipitation.
Running water is predominant force shaping desert landscapes.
Rare but often violent flash flood events produce most desert erosion.

Where and How Deserts Form

Deserts can be found anywhere where the atmosphere is usually dry (air is descending)
Most common near 30° north or south latitudes.

Rain Shadow Deserts

Form downwind of high mountain ranges as moist air rises over mountains, leading to precipitation on the windward side, and dry air (rain shadow) on the leeward side.

Some Characteristics of Deserts

Intermittent Stream Flow: Streambeds are typically dry most of the year due to lack of significant rainfall.
Internal Drainage: Streams flow into landlocked basins rather than reaching larger bodies of water.
Flash Floods: Common in arid regions due to short-lived but high-volume rain storms.
Desert Washes/Arroyos: Steep-sided with flat floors covered by loose sediment deposited from rare, highly erosive flash flood events.

Wind

Large daily temperature and pressure differences lead to strong winds.
Dust storms can occur when fine-grained sediments are easily available.
Wind can transport dust thousands of kilometers (e.g., the Dust Bowl).
Saharan dust can be transported across the Atlantic Ocean.
Volcanic ash is another example of wind-transported material.

Wind Erosion and Transportation

Wind can keep dust suspended.
Larger sand grains move by saltation.
High-speed winds can effectively sandblast rocks into ventifacts.
Deflation: A process where wind removes fine sediments (e.g., blowouts and desert pavements).

Wind Deposition: Sand Dunes

Sand dunes are mounds of loose sand piled up by the wind, most likely to develop in areas with a large sand supply and generally blowing in the same direction.
Small patches are found, but large expanses exist in deserts near seas and large lakes.

Shaping Dunes

Shapes are determined by: Wind velocity and direction, amount of available sand, and vegetation cover.

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Test your knowledge on streams, rivers, and their dynamics with this quiz. Explore topics like headwaters, drainage basins, sediment transport, and alluvial formations. Perfect for students studying environmental science or geography.