Geology and Earth Science Quiz

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Questions and Answers

Which type of dune is characterized by a crescent shape with horns pointing downwind?

Barchan dunes (correct)

Transverse dunes

Longitudinal dunes

Parabolic dunes

What factor is NOT mentioned as influencing the formation of dune shapes?

Wind velocity

Direction of the wind

Amount of available sand

Mineral composition of sand (correct)

What type of dune forms in areas with large sand supply and a single dominant wind direction?

Parabolic dunes

Transverse dunes (correct)

Longitudinal dunes

Barchan dunes

What is the primary process causing the formation of potholes in a streambed?

Abrasive action of sediment load Signup and view all the answers

Which dune shape is known to curve deeply and have horns anchored by vegetation?

Parabolic dunes Signup and view all the answers

What type of sediment load consists of small/light particles that remain suspended in water for long periods?

Suspended load Signup and view all the answers

Which type of dune is characterized by being extremely long, high, straight, and regularly spaced?

Longitudinal dunes Signup and view all the answers

What indicates the presence of braided streams?

Numerous interconnected rivulets with sediment bars Signup and view all the answers

Where do point bars form in meandering rivers?

Inside the bends of the river Signup and view all the answers

What characterizes a floodplain?

Flat land built up by sedimentation during floods Signup and view all the answers

What is the nature of a delta?

A body of sediment deposited at a river's mouth Signup and view all the answers

What happens during a meander cutoff?

The river creates a new channel across the neck of a meander Signup and view all the answers

What kind of load is characterized by heavy particles that move along the streambed by rolling, sliding, or dragging?

Bed load Signup and view all the answers

What is geothermal energy primarily produced from?

Natural steam or superheated water Signup and view all the answers

What characteristic primarily differentiates a glacier from other forms of ice?

It moves downhill under its own weight. Signup and view all the answers

What type of glaciation is specifically found in mountainous regions?

Alpine glaciation Signup and view all the answers

What term describes the steep-sided, half-bowl-shaped recesses carved into mountains at the heads of glacial valleys?

Cirques Signup and view all the answers

What happens to hot water as it rises back to the surface from underground layers?

It rises because it is less dense than cool water. Signup and view all the answers

Which feature is described as sharp peaks resulting from cirques cutting back into a mountain on three or more sides?

Horns Signup and view all the answers

What is the transitional form of snow called during the formation of glaciers?

Firn Signup and view all the answers

What do we call the unsorted, unlayered glacial sediment deposited by glaciers?

Till Signup and view all the answers

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

10% Signup and view all the answers

What is a potential environmental consequence of using geothermal energy?

Release of toxic gases Signup and view all the answers

Which type of moraine is characterized by being trapped between adjacent ice streams?

Medial Moraines Signup and view all the answers

What would be the effect on sea levels if all the ice in Antarctica were to melt?

Increase by approximately 65 meters Signup and view all the answers

What is an esker?

A sinuous ridge of sediment Signup and view all the answers

What do varves represent in glacial lakes?

Annual sediment deposition Signup and view all the answers

Which of the following best describes a recessional moraine?

Successive end moraines from a retreating glacier Signup and view all the answers

Who was initially a major opponent of the hypothesis regarding extensive past glaciation in Europe?

Louis Agassiz Signup and view all the answers

What is the primary driving force behind mass wasting?

Gravity Signup and view all the answers

Which of the following is NOT a trigger of mass wasting?

Vegetation growth Signup and view all the answers

What happens to the shear strength of saturated soil?

It decreases due to increased pore pressure Signup and view all the answers

Which type of mass wasting movement is characterized by very slow downslope movement?

Creep Signup and view all the answers

What type of mass wasting occurs when debris moves downslope as a viscous fluid?

Earthflow Signup and view all the answers

What effect does adding weight to the upper part of a slope have?

It can trigger mass wasting Signup and view all the answers

Which mass wasting process is common in colder climates due to water-saturated soil over impermeable material?

Solifluction Signup and view all the answers

Which factor contributes to enhancing shear forces on steep slopes?

Gravity Signup and view all the answers

What is the definition of the water table?

The top of the saturated zone. Signup and view all the answers

What is the primary difference between an aquifer and an aquitard?

An aquifer has high porosity, while an aquitard has low porosity. Signup and view all the answers

What characterizes a perched water table?

It is disconnected from the main water table by an unsaturated zone. Signup and view all the answers

How does permeability differ from porosity?

Porosity indicates fluid retention, while permeability indicates fluid movement. Signup and view all the answers

What effect does pumping water from a well in an unconfined aquifer have?

It lowers the local water table, a process called drawdown. Signup and view all the answers

What distinguishes gaining streams from other streams?

Gaining streams receive additional water from underground sources. Signup and view all the answers

Which type of rock or sediment is most likely to act as an aquitard?

Clay. Signup and view all the answers

What factors most influence the flow velocity of groundwater?

Slope of the water table and permeability of the rock. Signup and view all the answers

Study Notes

Exogenic Processes of the Earth

Course Outcome 4, GEO01 - Earth Science
Materials prepared by Ryo Jerome C. Tuzon, LPT
Video lecture prepared by Perseval S. Pineda, LPT
Website: www.mapua.edu.ph

Mass Wasting

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

Driving Force: Gravity

Contributing Factors (Most Stable Situation):
- Gentle slopes or horizontal surface
- Low slope angle
- Local relief
- Low thickness of soil over bedrock
- Planes at right angles to hillside slopes
- Temperature stays above freezing (climatic factor)
- Film of water around fine particles (climatic factor)
- Frequent but light rainfall (climatic factor)
- Heavily vegetated (climatic factor)
Contributing Factors (Most Unstable Situation):
- Steep or vertical surface
- High slope angle
- Great thickness of soil over bedrock
- Planes parallel to hillside slopes
- Freezing and thawing for much of the year (climatic factor)
- Saturation of soil with water (climatic factor)
- Episodes of heavy precipitation (climatic factor)
- Sparsely vegetated (climatic factor)

Gravity

Driving force for mass wasting
Normal Force
Shear Force
Shear Resistance
Shear resistance < shear force = landslide
Steep slopes - shear forces maximized by gravity

Shear Strength and Water

Shear strength – resistance to movement or deformation
Saturated soil has reduced shear strength due to increased pore pressure.
A small amount of water in soil can prevent downslope movement.

Mass Wasting Triggers

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

Classification of Mass Wasting

Rate of movement: < 1 cm/year - >100km/hour
Type of material: Solid bedrock or debris (unconsolidated material at Earth's surface)
Type of movement: flow, slide, or fall

Some Types of Mass Wasting

Flow: Creep (soil), Debris Flow, Earthflow, Mudflow, Rock avalanche (debris), Rock avalanche (bedrock)
Slide: Debris slide or earthslide, Rockslide (bedrock), Landslides
Fall: 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, foundations, walls, pipes and driveways as creeping ground cracks and shifts over time.

Flows: Earthflow and Solifluction

Flow – descending mass moves downhill as a viscous fluid
Earthflow – debris moves downslope, slowly or rapidly, as a viscous fluid.
Solifluction Permafrost – flow of water-saturated soil over impermeable material. This is common in colder climates

Flows: Debris Flow, Mudflow, Avalanche

Debris Flow and Mudflow – flowing mixture of debris and water, usually down a channel
Mudflow is only soil and water
Debris Avalanches are very rapid and turbulent.

Falls

Material free-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 a mass of bedrock along an inclined surface of weakness
Underwater Landslides
- Turbidity Currents
- 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 all rock that is prone to sliding
- Add vegetation cover
- Cover roads

Streams and Floods

Hydrologic Cycle

Movement and interchange of water between the sea, air, and land
Evaporation – solar radiation provides energy
Precipitation – rain or snow
Transpiration – evaporation from plants
Runoff – water flowing over land surface
Infiltration – water soaking into the ground

Running Water

Stream – body of running water, confined to a channel, that runs downhill under the influence of gravity
Headwaters – upper part of a stream near its source in the mountains
Mouth – place 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 that flow into the Atlantic and Gulf of Mexico

Drainage Patterns

Dendritic - resembles the branches of a tree
Radial - streams diverge outward like spokes of a wheel, such as on conical mountains
Rectangular - tributaries with frequent 90° bends and join other streams at right angles
Trellis - parallel streams with short tributaries meeting at right angles

Factors Affecting Stream Velocity and Deposition

Velocity - Maximum velocity near center of channel. Higher stream velocities promote erosion and transport of coarser sediments. Floods involve increased velocity and erosion.
Gradient (slope)
Channel shape and roughness
Discharge (volume of water passing a particular point in a stream over time)

Stream Erosion

Streams cut their own valleys
Hydraulic action - ability to pick up and move rock and sediment
Solution - dissolving of rocks
Abrasion - grinding away of stream channel by the friction and impact of sediment load
Potholes are eroded into streambed by abrasive action of sediment load

Stream Transportation of Sediment

Bed load – large or heavy particles that travel on the streambed (traction load – large particles that travel by rolling, sliding or dragging; saltation load – medium particles that travel by bouncing along)
Suspended load – small/light sediment that remains above stream bottom by turbulent flow for an indefinite period of time
Dissolved load – dissolved ions produced by chemical weathering of soluble minerals upstream

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
Resembles braids of hair or rope
Common for streams carrying a lot of sediment

Meandering Streams

Rivers that develop pronounced, sinuous curves (meanders)
Water flows faster along the outside of bends causing erosion and created cut banks.
Flows slower along the inside, depositing point bars on the insides of the meanders

Meandering Cutoffs

Meander cutoffs may form when a new, shorter channel is cut through the narrow neck of a meander (as during a flood)

Floodplains

Broad strips of land built up by sedimentation on either side of a stream channel.
Floodplain sediments are left behind as flood waters slow and recede at the end of flood events.
Main channel has slightly raised banks with respect to the floodplain, known as natural levees.

Deltas

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

Alluvial Fans

Large, fan- or cone-shaped pile 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.
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
Formed by stream erosion
Different valley morphologies depend on the erosional processes that created them
Downcutting – 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 concave-up longitudinal profile, lack rapids and waterfalls, represent a balance between available sediment load and transport capacity
Lateral erosion – widens stream valleys by undercutting of stream banks and valley walls as stream swings from side to side across the valley floor
Headward erosion – the slow uphill growth of a valley above its original source by gullying, mass wasting, and sheet erosion

Stream Valley Development: Terraces

Step-like landforms found above a stream and its floodplain
Occurs when a river rapidly cuts downward into its own floodplain
Represents 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
May be produced by profound base level changes
Can occur when there's rapid tectonic uplift

Flooding

When water levels rise and overtop the banks of a river, flooding occurs
Natural process on all rivers
Described by recurrence intervals
Can cause great damage in heavily populated areas
High velocity and large volume of water causes flood erosion
Water slowing as flood ends causes flood deposits to be deposited in the floodplain

Flooding and Urbanization

Urbanization creates many impermeable surfaces, increasing runoff flooding
Water is delivered to streams faster, increasing peak discharge and hastening flood occurrence

Flash Flooding

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

Reducing Flood Risk

Dams – designed to trap flood waters in reservoirs upstream and release them gradually over time
Artificial levees – designed to increase capacity of river channel and works well until stream overtops, leading to extremely rapid flooding and erosion
Wise land-use planning – including prevention of building within 100-year floodplains, is most effective

Impact of Dams

Societal Benefits
- Electricity production
- Flooding control
- Reservoir for drinking water
Environmental Concerns
- Trapping of sediment and nutrients behind the dam
- Habitat destruction
- Destabilizing the river valley when the reservoir fills
- Can lead to landslides

Groundwater

The Importance of Ground Water

Lies beneath the ground surface, filling pores in sediments and sedimentary rocks, and fractures in other rock types
Represents 1.7% of the hydrosphere (100x the fresh water in all lakes and rivers combined)
Resupplied by slow infiltration of precipitation
Generally cleaner than surface water
Accessed by wells
Tremendously important resource, being removed at ever-increasing rates
Pollution impacts are increasing

The Water Table

Saturated zone – subsurface zone in which all rock openings are filled with water
Water table – top of the saturated zone
Water level at surface of most lakes and rivers corresponds to local water table
Unsaturated zone – unsaturated region above the water table
Perched water table – above and separated from main water table by an unsaturated zone; commonly produced by thin lenses of impermeable rock (for example, shale or clays) within permeable ones

Springs and Streams

Spring – place where water flows naturally from rock or sediment onto the ground surface
Gaining streams – receive water from the saturated zone; surface is local water table
Losing streams – lose water to the saturated zone; stream beds lie above the water table
Streambed infiltration produces a permanent “mound” of water in the water table beneath a dry channel

Contamination of Groundwater

Water may bring contaminants to the water table, including pesticides/herbicides, fertilizers, landfill pollutants, heavy metals, bacteria, viruses, parasites, industrial chemicals, acid mine drainage, radioactive waste, and oil and gasoline.
Contaminated groundwater is difficult and expensive to clean up.

Pollution Caused by Pumping Wells

Balancing Withdrawal & Recharge

If ground water is withdrawn more rapidly than it's recharged, the water table will drop
Dropping water table can lead to ground subsidence and cracking of foundations, roads, and pipelines
Areas with extremely high ground water pumping have subsided several meters

Geologic Effects of Groundwater

Dissolves soluble bedrock, such as limestone, creating cave systems, sinkholes, karst topography, and other effects

Caves

Naturally-formed underground chambers
Acidic groundwater dissolves limestone along joints and bedding planes
Stalagmites – dripstone that forms on cave floors
Stalactites – dripstone formations that hang from cave ceilings

Cave Formation

Karst Topography

Area with rolling hills, disappearing streams, and sinkholes

Sinkholes and Karst Topography

Caves near the surface that have collapsed

Other Effects of Groundwater

Preservation of Fossils
- Petrified Wood
- Concretions
- Geodes

Hot Water Underground

Hot springs – springs in which the water is warmer than human body temperature
Heated by nearby magma bodies or circulation to unusually deep levels in the crust
Hot water is less dense than cool water and thus rises back to the surface on its own
Geysers – hot springs that periodically erupt hot water and steam; minerals often precipitate around geysers as hot water cools rapidly in the air

Geothermal Energy

Produced using natural steam or superheated water
No CO₂ or acid rain are produced (clean energy source)
Some toxic gases (e.g., sulfur compounds) are given off
Can be used directly to heat buildings
Superheated water can be very corrosive to pipes and equipment

Glaciers & Glaciation

What is a Glacier?

Large, long-lasting mass of ice formed on land, moving downhill under its own weight
Glaciated Terranes
- Alpine - found in mountainous regions
- Continental – large parts of continents covered by glacial ice.
Approximately 70% of the world's fresh water is locked up in glacial ice.

Types of Glaciers

Develop as snow is compacted and recrystallized, first into firn and then glacial ice
Alpine glaciation occurs in mountainous regions as valley glaciers; continental glaciation covers large land masses in Earth's polar regions in the form of ice sheets.

Distribution of Glaciers

Extensive in polar climates, but can occur anywhere where snowfalls more than melts
Approximately 10% of Earth's surface is covered by glaciers
Approximately 85% of all glacial ice is in Antarctica
Melting all Antarctic ice would raise sea level by approximately 65 meters, flooding coastal cities

Formation and Growth of Glaciers

Snowfall
Compaction removes air from the snow
Snowflakes recrystallize into granules
Firn – transitional between granular snow and glacial ice
Glacial ice formed when firn is compacted and more air removed, creating similar texture to quartzite
Gravity causes the glacier to move downslope
Ablation – loss of glacier due to melting, evaporation, or calving of icebergs

Glacial Budgets

Advancing glacier - more snow gain than loss
Receding glacier – more snow loss than gain
Zone of accumulation – snow added
Zone of ablation – melting and calving of icebergs
Equilibrium line – separates zones

Movement of Valley Glaciers

Move downslope due to gravity
Basal sliding – glacier slides over underlying rock
Plastic flow – movement within glacial ice due to its plastic nature
Rigid zone – upper part of glacier that moves rigidly downslope
Crevasses – fractures formed in the upper rigid zone during glacier flow
Glacier flow fastest at top center and slowest along margins due to friction

Movement of Ice Sheets

Downslope and outward from a central high area due to gravity
Basal sliding, plastic flow and rigid zone
Antarctica - two ice sheets separated by Transantarctic Mountains
Outlet glaciers – mountain valley glaciers that occur where mountains are higher than ice sheet
Ice streams – flow zones much faster than adjoining ice

Glacial Erosion

Glaciers erode underlying rock by plucking and abrasion
Basal abrasion polishes and striates underlying rock surface, producing fine rock powder (rock flour)

Glacial Valleys

Associated with Alpine Glaciation
Several types
- U-shaped valleys
- Hanging valleys – smaller tributary glacial valleys left stranded above more quickly eroded central valleys
- Truncated Spurs – ridges that have triangular facets

Cirques, Horns, and Arêtes

Cirques - steep-sided, half-bowl-shaped recesses carved into mountains at the heads of glacial valleys
Horns - sharp peaks remaining after cirques have cut back into a mountain on 3+ sides
Arêtes - sharp ridges separating glacial valleys

Landscapes Associated with Continental Glaciation

Rounded topography is more common
Weight and thickness of continental ice sheets produce more pronounced effects
Rounded knobs
Grooved or striated rock
Thick enough to bury mountains, rounding off ridges and summits

Glacial Deposition

Till – general name for unsorted, unlayered glacial sediment
Lateral, medial and end moraines are deposits of till left behind at the sides and end of a glacier.

Glacial Deposition: Moraines

Lateral moraines – elongate, low mounds of till along sides of valley glaciers
Medial moraines – lateral moraines trapped between adjacent ice streams
End moraines – ridges of till piled up along the front end of a glacier
Recessional moraines – successive end moraines left behind by a retreating glacier
Ground moraine – thin layer of till at the base of the glacier

Glacial Deposition: Outwash

Outwash – sediment deposited by large amounts of meltwater flowing over, beneath, and away from the ice at the end of a glacier
Sediment-laden streams emerging from ends of glaciers have braided channel drainage patterns
Has related landforms: Eskers, Kettles, Kames

Outwash Landforms

Eskers – sinuous ridge
Kettles – glacial depression
Kames – low glacial mound

Glacial Deposition: Lakes and Varves

Glacial Lakes and Varves - annual sediment deposition in glacial lakes produces varves, which can be counted like tree rings

Past Glaciation

Extensive glaciation of Europe was first hypothesized in the early 1800s, considered outrageous at first.
Observations in Swiss Alps by Louis Agassiz led to the theory of glacial ages.
Most recent glacial age peaked ~18,000 years ago.
Earth has undergone episodic climate changes over the last 2-3 million years.

Direct Effects of Past Glaciation

Large-scale glaciation of North America scraped off soil and sedimentary rocks, excavating lake basins out of bedrock
Extensive recessional moraines left by retreating ice sheets in the upper Midwestern US and Canada.

Indirect Effects of Past Glaciation

Glacial Lakes
- Lake Agassiz
- Lake Missoula
Pluvial lakes – formed in periods of abundant rainfall
Lake Bonneville
Lake Missoula

More Indirect Effects

Lowering and rising of sea level
- Fiords - coastal inlets formed by drowning of glacially carved valleys by rising sea level
Crustal rebound - Great Lakes region continues to rebound as crust adjusts to the removal of the last ice sheet.

Evidence for Older Glaciation

Tillites - lithified glacial till featuring distinctive textures
Paleozoic era in portions of southern continents indicate that these landmasses were once joined
Snowball Earth hypothesis - Late Precambrian glaciation when the oceans were frozen over
Oldest glaciation evidence dates back to 2.3 billion years ago ; strong evidence supporting plate tectonics

Deserts & Wind Action

Deserts

Desert - any arid region that receives less than 25 cm of precipitation per year
Running water is the predominant force shaping most desert landscapes (rare and often violent flash flood events produce most desert erosion)

Where and How Deserts Form

Found anywhere atmosphere is usually dry
Most deserts associated with descending air (subsiding air is compressed and warms, causing dry climate over land, while rising air expands and cools, causing clouds and precipitation)
Rain shadow deserts form downwind of high mountain ranges (moist air rises over mountains, cools, and precipitates, leaving drier air on the downwind side)

Some Characteristics of Deserts

Intermittent stream flow – streambeds are dry most of the year; exceptions include the Colorado and Nile Rivers.
Internal drainage – streams flow to landlocked basins
Flash floods – common in arid regions due to short periods of high-volume rain storms
Desert washes (arroyos) – steep-sided, with flat floors covered by loose sediments, a result of rare but highly erosive flash flood events.

Desert Features in the Southwestern United States

Two distinct landscapes
- Colorado Plateau
- Basin and Range Province
Colorado Plateau – centered on the four corners region of Utah, Colorado, Arizona, and New Mexico, 1500 meters above sea-level
Flat-lying sedimentary rocks, heavily eroded into plateaus, mesas, and buttes

Desert Landforms of the Southwestern United States

Basin and Range province – rugged, linear, fault-bounded mountain ranges separated by flat-floored valleys; narrow canyons carry sediment into valley floors during heavy rains; alluvial fans overlap to form a bajada; finest sediments travel to basin center where water ponds and evaporates in playas

Wind

Large daily temperature and pressure differences lead to strong wind.
Dust storms may occur if fine-grained sediments are readily available.
Dust can be transported across thousands of kilometers by atmospheric winds.
Dust Bowl – continuing dust storms in the prairie states during droughts of the 1930s
Saharan Desert sediments carried across the Atlantic Ocean; volcanic ash.

Wind Erosion and Transportation

Wind can keep dust in suspension, but larger sand grains move by saltation
High-speed winds can effectively sandblast rocks into ventifacts
Deflation of fine sediments; blowouts and desert pavement

Wind Deposition: Loess

Loess – deposit of wind-blown silt and clay composed of unweathered grains of quartz, feldspar, and other minerals
Sediment sources include glacial outwash plains and desert playas
Thick loess deposits are in China and the United States
Loess forms very fertile soils, but easily eroded

Wind Deposition: Sand Dunes

Sand dunes – mounds of loose sand piled up by the wind
Most likely to develop in areas with large sand supply and winds blowing in the same direction
Small patches of dunes common in southwestern U.S., but huge sand seas in Sahara and Arabian deserts
Dunes may form just inland of beaches along coasts of seas and large lakes

Shaping Dunes

Shapes depend on wind velocity and direction(s), amount of available sand, and distribution of vegetation cover.

Types of Dunes: Barchan

Crescent-shaped, with horns that point downwind and a steep slip face on the concave side
Form in areas with one dominant wind direction and a limited sand supply
Exist on Mars

Types of Dunes: Transverse

Relatively straight, elongate dunes that form in areas with a large sand supply and one dominant wind direction

Types of Dunes: Parabolic

Deeply curved dunes convex in the downwind direction, forming around blowouts and with horns anchored by vegetation

Types of Dunes: Longitudinal

Form in areas with large sand supply, parallel to the prevailing wind direction
Extremely long, high, straight, and regularly spaced
Crosswinds may play a part in their development
Area between parallel dunes is swept clean of sand by winds
Formation mechanism is not fully understood

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on various geo-physical processes including dune formations, sediment loads, and river dynamics. This quiz covers essential concepts like braiding streams, floodplains, and energy production. Perfect for students in geology or earth science courses.