Nat hazards
Volcanic pressure and hazards
4.0 intro to volcanism
Volcanism in our solar system
4.0 introduction to volcanism: volcanic eruptions
50 to 60 volcanoes erupt each year
Most eruptions are in sparsely populated areas
Nearly 100,000 people have been killed by eruptions in the past 100 years
500 million people live in the vicinity of volcanoes
Japan, mexico, philippines, indonesia
Western north america
4.0 introduction to volcanism- distribution of volcanoes
Volcanoes are not randomly distributed but occur in well defined zones or belts
⅔ of all active volcanoes on land are located along the ring of fire which surrounds the pacific ocean
Tectonic setting determines the type of volcano
Mid- ocean ridges, subduction zones and hot spots
4.1 properties of igneous rocks;
Molten rock material below the earth's surface is called magma. It becomes lava when it reaches the surface
The viscosity of magma is controlled primarily by silica content
Silica content affects viscosity
Silica rich magma does not flow easily and has a high viscosity
Viscosity affects the flow of lava and therefore the shape of the resulting volcano
In explosive eruption tephra is ejected
Small fragments of pyroclastic debris
An accumulation of tephra is a pyroclastic deposit
4.1 properties of igneous rocks: rock classification⭐⭐⭐⭐⭐
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Exctrusive igneous rocks (lava) incisive igneous rocks
4.1 properties of igneous rocks: silica content
Rhyolite
High silica content (70-75%)
High viscosity
Andesite
Intermediate silica content (60-65%)
Intermediate viscosity
Basalt
Low silica content (50-55%)
Low viscosity
Komaite
Limited silica (below 40%)
Very low viscosity
4.1 properties of igneous rocks: lava flows
Rhyollitic lava flows
Flows have broken and blocky surface
Lava dome
Andestic lava flows
Advances slowly 1-5 m/day
Typically flows are < 10km long
Breaks into angular blocks
Basalitic lava flows
Average flow rates- 30km/hr
Most flows travel between 10-50km from the source
Komaltite lava flows
Has not erupted in about 2.5 billion years
4.2 types volcanoes
The shape and eruptive style of volcanoes are related to the chemistry and viscosity of their magmas
Lava dome
Type of material- rhyolite
Shape- domed shaped
How explosive- very explosive (super dangerous
Location- around venus or cracks
composite volcano
type of materials- andesite- layers pireplastic (ash)
Shape- cone
how explosive - explosive
Location- ring of fire
Shield/ basaltic volcano 1
Type of materails- saltic lava
Shape- gentle slopes rounded shapes
How explosive- non explosive
Location hawaiian islands
Shield volcano 2 (extremely rare)
Type of materails- komite
Shape- extremely low profiles
How explosive- non explosive
Location- plate boundaries
. cinder cone
Type of materails- pyrocalastic- little chunks of lava that cools so quickly thats like rock
Shape- steep cones
How explosive- doesnt explode at all
Location- bents
.
4.3 products of volcanic eruptions and landforms; pyroclastic materials
Pyroclastic materials Are magma fragments that are explosvely ejected by volcanoes most are solid
Ash <2mm
Lapili 2-64mm
Bombs partially molten >64 mm
Blocks solids >64mm
4.3 products of volcanic eruption and landforms: volcanic gases
Primarily water vapour
Lesser amounts of carbon dioxide nitrogen sulfur dioxide and hydrogen sulfide
Erupted sulfur can have widespread significant effects on climate
4.3 products of volcanic eruption and landforms:
Craters
Depressions formed by explosion or collapse of volcano top
4.3 products of volcanic eruption and landforms:
Calderas
The summit of a volcano collapses into its magma chamber following voluminous eruptions (violent explosions)
Thousands of meters across hundreds of meters deep
4.3 products of volcanic eruption and landforms:
Lava tubes
Forms when the margins and upper surface of the flow solidify
Can move up to 50 km/hr
In some cases they drain and become empty tunnels
4.3 products of volcanic eruption and landforms:
Vents
Any opening for lava and debris (may be circular or thin fissures)
Can produce flood basalts
4.3 products of volcanic eruption and landforms:
Hot springs
Hot rocks heat groundwater discharged at surface
4.3 products of volcanic eruption and landforms:
Geysers
Groundwater boils erupting steam at surface
4.3 products of volcanic eruption and landforms:
Pyroclastic sheet deposits -
ejected from the volcano ash can reach up to 10,000m
Thick sequences
Huge sheet like eruptions by pyroclastic materials
4.3 products of volcanic eruption and landforms:
Lava lake- a volcano that oozes down the side
4.3 products of volcanic eruption and landforms:
Jokulhaups
Ice contact volcanoes
Erupt beneath or against a glacier
Subglacial volcanoes erupt rapidly melting ice and produce huge floods known as Jokulhlaups
Ex iceland mt garibaldi
4.4 volcanic hazards
What are the most dangerous manifesations of volcanos
⭐ Primary effects
Lava flows, ash fall, volcanic bombs and pyroclastic flows,
pyroclastic surges lateral blasts and poisonous gases
⭐ Secondary effects
Lahars, debris avalanches, landslide, groundwater and surface contamination
floods fires and tsunamis
The size of an eruption can be quantified using a scale called the volcanic explosvitu index (VEI)
4.4 volcanic hazards: ash
Ash is blown high into air and falls onto areas
Ash can produce its own lightning
Health hazards: respitory problems (can get into lungs need to wear masks)
Example- vegetation destroyed no ability to grow
Burn the skin off mammals
Contaminates surface water- drinking wate will be contaminated for a while
Damage to buildings- roof can cave in- ash covers every square inch
Aircraft engine failure- it will eat away
4.4 volcanic hazards: ash
The biggest flight distruptioj since 9/11
British airways flight 009
Flew into a cloud of volcanic ash (Mt Gaulungger near Jakarta indoniessa)
4.4 volcanic hazards
Occur when magma reaches the surface
Can move slowly or rapidly depending on viscosity and temperature
High viscosity moves more slowly
4.4 volcanic hazards: lava flows
Basaltic lava flows are most common
Pahoehoe
Harden with a smooth ropy texture
Travel at speeds of up to a few km per hour
Aa
Harden with rough blocky texture
More viscous travels at rates of a few meters per day
4.4 volcanic hazards: diverting lava flows (iceland)
Bombing
Block channels to cause lava flows to take a less damaging route
Hydraulic chilling
Water used to chill and control water flows
Wall construction
Water are used to redirect lava flows
4.4 volcanic hazards:
Kills the most people
Flows- avalanches of hot rock ash volcanic rock fragments
Hot and race down side of volcano at speeds exceeding 400km/hr (250 mph)
Surges- dens clouds of hot gas and rock debris produced by explosive interaction of water and magma
Catastrophic if populated area in path
4.4 volcanic hazards: pyroclastic flows and surges
The eruption of Vesuvius and the resulting destruction of Pompeii (italy)
Pyroclastic flows covered 6km from summit
4.4 volcanic hazards: pyroclastic flows and surges
4.4 volcanic hazards: pyroclastic flows and surges
In 1902 the city of st Pierre on Martinque in the caribbean
2 surrivors - in jail
Obliterated by an incandescent pyroclastic flow
Nuee ardentes
4.4 volcanic hazards: lateral blast
Rock fragrments, gas and ash that are blown horizontally from side of volcano
Mt St Helens: may 18 1980 8:32 am- A M 5.1 earthquake triggers a landslide/debris avalanche of the bulge area
4.4 volcanic hazards: lateral blast
57 people were killed
Flooding destroyed over 100 homes
Forests to the north of the mountain were flattened
Damage exceeds U.S $1 billion
September 23, 2004 mt st helens reawakened
Magma began moving up towards the crater floor
The mountain is monitored with seismographs to continuously record events
They jumped to see and should have never done that they died
Harry truman (spirit lake lodge)
Belived the situation was over exaggerated
4.4 volcanic hazards: poisonous gas
Gas emission usualy accompanies lava and ash but sometimes acts alone
Carbon dioxide (CO2)
Oderless, heavy gas that can displace breathable air
Sulfur dioxide
Odourous gas that causes acid rain and can contaminate rock and soil
4.4 volcanic hazards:
Debris flows and other mass movement
Lahars - large amounts of loose volcanic ash and other pyroclastic material become saturated with water and rapidly move downslope
4.5 linkages between volcanoes and other natural hazards
Earthquakes
Commonly precede or accompany volcanic eruptions
Landslide
Sector collapses can cause tsunamis if they enter water
Fire
Hot lava may ignite plants structures
Climate change
Volcanic ash from an eruption can temporarily cool climate
4.6 why do people live near volcanoes
People live near volcanoes for a variety of reason
Place of birth
On some islands all land is volcanic
Fertile land for farming
Believe in eruption is unlikely
Unware of risk
Economic limitations
4.6 why do people live near volcanoes
Volcanic soils
Good for coofeen maize pinapples sigar cane and grapes
Geothermal power
Can create energy for nearby urban areas
Mineral resources
Gold silver etc. and non metallic rocks
Used for soap building stone aggregate for roads railroads etc
4.6 why do people live near volcanoes
Natural service functions
recreation
Health spas and hot springs
Hiking snow sports and education
Kilauea national park
Creation of new land
Hawaiian islands
4.7 volcanic monitoring and forecasting
Is it possible for forecast eruptions
Monitoring involves recording and anaylizing both physical and chemical changes at volcanoes
Titmeters and geodimeters to detect changes in slope elevation and shape
Seismoteres to detect harmonic tremors
Gas emission, thermal magnetic and hydrologic monitoring are also measured
Rivers and flooding
5.0 introduction
Severe flooding in pakistan
Heavy rains during the monsoon season
Killed over 2000 people
21 million people displaced
Floods inundated crops
7 million had submerged
200,000 livestock killed
Crippled infrastructure
Bridges, roads, 10,000 transmission lines damaged
Limited rescue and aid
Red river flood 1997- winnipeg
One of many floods in 100 years
Heavy snowpack- warming weather and rain
Covered 2560 km2 (southern Manitoba and parts of North Dakota)
Worst in 50 years
3 people died- $815 million in damages
5.1 river flow and sediment transport processes: hydrologic cycle
Streams and rivers are part of the hydrologic cycle
Evaporation of water from Earth's surface
Water returns to ocean underground or across the land
5.1 river flow and sediment transport processes: gradient
Gradient
Slope of the land over which the river flows
Steepest at high elevations
Levels off as river approaches its base
Show on longitudinal profile
Cross-sectional profile
Steeper-sided and deeper valleys near headwaters
Wide floodplain usually present at base level
Differences due to higher flow velocity at higher elevations
5.1 river flow and sediment transport processes: longitudinal profiles
Normally as one goes down a river:
Discharge increases (as more triburtiares join):
River width increases;
River depth increases ;
River velocity stays about the same or slightly increases (offsetting effects of lower slope but higher discharge)
Sediments size decreases;
Sediment amount increases; and
River slope decreases
5.1 river flow and sediment transport processes: discharge
Discharge (Q= AxV) (AREA X VELOCITY)
Water volume flowing through a cross section per unit time constant along river if no additions or deletions
Canadians rivers are dominated by the freshet , the period of snowmelt in the spring
5.4 drainage basins and rivers
A is a land that slopes toward the sea separated by topographic ridges
Four maor drainage basins:
The atlantic basin
The hudson bay basin
The arctic basin
The pacific basin
5.1 river flow and sediment transport processes
(pic)
Zone of erosiom the river model - zone number 1
Zone of transport= zone number 2 - floodplain
Zone of deposition- zone number 3
Zone 1
Typically v shaped
Generally in upper parts where there is steeper topography and more percepipitation
Water velocity is fast, downcutting and erosion occur
Coarse material in river
River often flowing over rock
River dominates bottom of valley- no wide floodplain
5.1 river flow and sediment transport processes: the river model
Intense rainfall over short duration-
found in arid environment and steep slopes (arid is little vegetation
Most people who die in this region during flash floods are in cars
In zone ll
the broad valley bottom is occupied by the floodplain
Broad valley and floodplain
Sediment frequently deposited in river bars or on flood plain
Braided or meandering or combination of both
Areas that are able to be flooded periodcallu by the rivers
Covers a wide area
Storms with long duration
Damaged to buildings
Zone 3
When the river essentially loses its load may have either fans or deltas as depositional landforms although in many cases where rivers flow into larger rivers or into a lake or the sea the sediment is simply swept away
Storm of long duration
N ever gona be the same but dangerous because
5.1 river flow and sediment transport processes: transportation
Total load consists of:
Bed load
Materials that roll bounce along bottom
About 10% of what's in the river
Suspended load
Silt and clay particles that are carried in the water
90% of material
Dissolved load
Materials carried as chemical solution
Rocks dissolve less than a percentage
5.2 flooding
Flooding is a normal and necessary part of the fluvial system
It is human occupation of flood plains that creates the problem
Magnitude and duration of a flood are determined by:
Amount and distribution of precipitation in drainage basin
Rate at which the precipitation soaks into earth
How quickly surface runoff reaches river
Amount of moisture in soil
5.3 the effects of flooding: primary effects
Primary
Injury and loss of life
Damage caused by currents, debris and sediment to farms, homes, buildings, railroads, bridges, roads
Erosion and deposition of sediment related to loss of soil and vegetation
Examples being river pollution in texas USA in 2010
Secondary
Short term river pollution of rivers
Hunger and disease
Homelessness
New orleans cemeteries pop up
Example mold in new orleans
5.4 human interactions: service functions
Fertile lands
Periodic deposits of minerals enriches the soil for agriculture
Aquatic ecosystem
Floods clear rivers of debris and sweep in nutrients
Sediment supply
Periodic flooding builds up elevation
5.4 human interactions: land use changes
For 300 years the sea has been closing in on new orleans
Coastal erosion and land use changes
The levees designed to protect the city may have actually made in vulnerable
Subsidence and lack od sediments
City will be offshore in 90 years
5.4 human interactions: dam construction
Upstream
As water enter reservoir, it slows deposits sediment, and forms a delta
Downstream
As water leaves dam, it is devoid of sediment and can erode sediment to transport instead of depositing
Slope of the stream will decrease until equilibrium is reached
Colorado river
Methylmercury poisoning
5.4 human interactions: urbanization
Increases magnitude and frequency of floods
Urban areas have impervious cover and greater storm sewers
Urban areas have impervious cover and greater storm sewers
Carries water to stream channels more quickly
Decrease lag time
Reduces stream flow during dry season
Urban runoff can be 5 times more that preurban conditions
Bridges block debris, creating dams
5.4 human interactions: urbanization
Rivers and flooding
Winnipeg floods
All the major floods on the red river have occurred in the spring runoff period. The most devastating was in 1950. The flood of 1997 was second in size only to the flood of 1826
Following in the 1950 flood, major flood protection works and diversions have been constructed to protect Winnipeg (left) the 1997 flood was a real test of the winnipeg floodway it worked
5.5 minimizing the flood hazard: physical barriers
Levees are barriers built to keep flood water contained
Earthen, concrete flood wall, reservoirs, storm water basins
Levee breaks cause higher energy flows
Levees can produce bottlenecks in upstream areas
Levees need to be maintained
False sense of security
5.5 minimizing the flood hazard: channelization
Straightening, deepening, widening, clearing, or lining existing stream channels
Have adverse effects on fish and wetland wildlife
Can cause benefits to some urban and rural areas, and improves navigation
Create a natural channel by allowing the stream to meander and reconstruct variable water flow conditions by:
Cleaning urban waste to allow channel to flow freely
Protecting existing channel banks by not removing trees
Planting additional trees or vegetation where necessary
5.5 minimizing the flood hazard: adjustments- flood insurance
Maps of 100 year floodplain were created to determine risk
Area where there is 1% chance of floods in any given year
New property owners are required to purchase flood insurance
Building codes limit new construction on floodplain
Codes prohibit on 20 year floodplain
5.5 minimizing the flood hazard: adjustments
Flood- proofing
Raising foundations of building above the flood hazard level
Constructing flood walls or mounds around buildings
Using waterproof construction
Installing improved drains and pumps
Floodplain Regulation
Land use specification for floodplains in urban areas
Relocation
Government purchasing and removing homes damaged by floodwaters
Subsidence and sediments
6.0 introduction to subsidence and soil volume change
subsidence
Is slow or rapid nearly vertical downward movement of earth's surface
Karst
Landscape resulting from dissolution of limestone, dolostone, marble, gypsum or rock salt
Soil expansion and contraction
Changes in water content of soil
Freezing and thawing
Not usually life threatening but are some of the most widespread and costly natural hazards
6.1 Karst Topography: sinkholes
Can range from one to several hundred metres in diameter
Solutional sinkholes
Collapse sinkholes- a cave system roof will collapse
6.1 karst topography: cave system
If you can fit in it, it's a cave
Cave can only form when there’s no water in it
Stalagmite (g stands for ground)
Stalactite (c stands for ceiling)
When stalagmite and stalactite meet its called a colum
Flowstone flows along the ceiling
6.1 Karst Topography; tower karst, disappearing streams and springs
Karst towers
Can only find in hot, humid environments
Disappearing streams
Groundwater and surface water in karst areas are intimately connected, This waterfall discharges groundwater from falling spring, northwest of Iowa (from textbook)
6.2 Permafrost and thermokarst
Active layer refreezes in winter, thaws in summer
When permafrost thaws it can create land subsidence
Extensive thawing creates uneven soil called thermokarst
Frost-susceptible sediments expand when they freeze
Causes frost heaving
- ⅔ of Canada is covered by permafrost (1000 m thick)
6.2 permafrost and thermokarst
Continuous permafrost
In the polar dessert
Discontinuous permafrost
Heading south
Sporadic permafrost
Individual pockets of permafrost
6.3 sediments and soils
Ice within or underneath soil when it starts to warm up
6.3 sediments and soils: expansive soils
Cracks occur when building on clay, must use sands, etc
6.4 regions at risk
Climate controls the amount and timing of rainfall and duration of freezing temperatures
Sinkholes are common in humid climates
Expansive soils are common in areas with wet and dry seasons
Collapsible soils are found in arid and semi arid climates
Areas with extensive below freezing temperatures can host frost heaving
6.5 effects of subsidence and soil volume change
Sinkhole formation
Damage highways, homes, sewage facilities etc.
Probably triggered by fluctuations in water table
Groundwater use and contamination
Caves create direct access between surface and groundwater
This access can make water vulnerable to pollution, especially during drought and when sinkholes are used as landfills
6.5 effects of subsidence and soil volume change
Soil volume changes
Causes billions of dollars is damage annually to highways, buildings and structures
Swelling of expansive soils and frost heaving
Damage caused by soil volume change exceeds the cost of all other natural hazards combined
6.5 effects of subsidence and soil volume change
(New Orleans will be surrounded by the Gulf eventually)
Underground mining
Coal mine structures have collapsed
Water is used to dissolve and pump out salt leaving behind cavities
Flooding in salt mines can also cause sinkholes
6.7 natural service functions
Water supply- best quality water
6.6 natural service functions
Aesthetic values and scientific resources
6.6 natural service functions
Unique Ecosystems- Troglobites (have no eyes because they evolved as there is no sunlight)
6.7 perception and adjustments to hazard
Few people are aware of subsidence and soil volume change hazard
People who live in dramatically affected areas are more than others
Best solution is to avoid buildings in vulnerable areas through:
Geologic and soil mapping
Surface features
Subsurface surveys
Mass movements
Landslides and mass movements
Landslide and mass wasting
Terms used to describe the downslope movement of rock or sediment due to gravity
What is a snow avalanche
Masses of snow, generally more than a few cubic metres in volume that separate from the intact snowpack and slide or follow downslope
Types of landslides are determined by:
Mechanism of Movement (is it a fall, slide, flow?)
Type of Material (is it solid rock, sand, gravels?)
Amount of Water Present
Rate of Movement (if can see, move its fast, if can’t see it, its slow)
7.0 introduction to mass movements: geographic locations
Anywhere that have significant slopes and mountains
Ex. British Columbia
7.1 types of mass movements
One can distinguish between
Fall (steep and vertical drops)
Slide (enclined movements, intact/coherent movement of a block)
Flow (Individual particles moving relative to each other)
7.1 types of mass movements: Fall
Rock Fall
Bounding of rock or blocks of sediment from the face of a cliff
Blocks pile up at the bottom to form talus
Falls vertically
7.1 types of mass movements: Slides
Rock Slide
Downslope movement of a coherent block of rock or sediment along a discrete failure plane
7.1 types of mass movements: The frank slide
7.1 types of mass movements: Slides (soil slip)
Slump
Failure plane is curved upward
7.1 types of mass movements: Flows
Flow
Downslope movement of sediment in which particles move semi- independently of one another, often with the aid of water
Debris flows
Typically move rapidly; mixtures of mud debris and water
7.1 types of mass movements: Flows
Creep
Very slow flow of rock or sediment
Sackung- slow movement of large masses of rock
Topple- a rock mass pivots about a point
7.1 types of mass movements: Flows
Earthflows : are the downslope viscous flow of saturated fine grain materials
Resemble mudflows however slower moving and covered with nonfluid material
7.1 types of mass movements: Flows
Avalanches
Rapid downslope movement of snow and ice (mixed with air)
Depend on steepness of slope, stability of snowpack weather
Avalanches move down chutes
Avoiding these areas minimize hazard
7.1 types of mass movement: Flows
Avalanches
Point-release Avalanche
Begin with failure of a small amount of loose fluffy snow
Widens as it moves downslope
Commonly happen after a heavy snowfall
Slab Avalanches
Snowpack fractures along a weak layer at depth
Moves as a cohesive block
More dangerous than point release avalanches
7.1 types of mass movement: Complex
Most large mass movements consist of several elements. For example a rock fall can lead into a debris avalanche which can in turn become a debris flow
7.2 slope processes
Driving and resisting forces are not static
As local conditions change these forces may change
Factor of safety may increase or decrease
Forces on slope are determined by:
Type of Material (what is it made of?)
Slope, angle, and topography
Climate (arid regions, less vegetation, less succession to slope movements)
Vegetation (makes slope stable due to roots in trees acting as anchors)
Water (can influence failure of slope, directly or indirectly)
Time (Acted on physical weathering, etc)
7.2 slope processes
Role of Earth Material
Can affect both the type and frequency of movement
Important characteristics
Mineral composition
Degree of cementation or consolidation
Presence of zones of weakness
Ability of material to transmit water
Slope
Slope steepness
Steeper the slope the greater the driving force
Steep slopes are associated with falls
Moderate slopes are associated with flows
Gentle slopes are associated with creep
Topographic relief
Height of hill above land
Mass wasting occurs more in high relief areas
7.2 slope processes: avalanche movements
2. avalanche movements
Slope angle
The most important terrain factor for avalanche formation
Avalanches tend to occur on slope with angles between 25 and 60 degrees
30 and 45 degrees
Slope orientation
Leeward slopes are more likely to have avalanches
Sun- facing slopes are more prone to avalanches during sunny, warm weather; shaded slopes are more prone to avalanches in cold weather
7.2 slope processes: the role of slope and topography
the role of slope and topography
Influences
Amount and timing of water that infiltrates or erodes slope
Type and abundance of hillside vegetation
Arid regions: rock falls, debris flows and soil slips
Humid regions: complex landslides, earth flows and creep and debris flows
The role of vegetation
Function of climate, soil type topography and fire history
Significant factor in slope stability
Vegetation provides protective cover (slows surface erosion) (positive)
Roots adds strength to the slope materials (positive)
Vegetation adds weight to the slope (negative)
5. The role of water
Almost always directly or indirectly involved
Saturated slopes: shallow soil slips and debris flows
Deep infiltration: slumps develop months or even years after
Water erosion: erosion of base of slope decreases stability
Water can cause spontaneous liquefaction or quick clay
Fine grained material that loses strength when distributed and flows like a liquid
6. The role of time
Forces change with time
Driving and resisting forces change with season due to changes in moisture content or water table
Chemical erosion occurs slowly over time
7.3 effects of mass movements: landslides
30 people are killed each year on average in north america; damage exceeds $1 billion
Slides may damage homes, roads and utilities constructed at the top, base, or side of a hil
People hit with or buried in falling debris
Slides may block roads and railways impeding travel or may block streams causing flooding
7.3 effects of mass movements: avalanche
Human deaths (600 in Canada since mid 1800s)
Economic losses (destruction and blockage of roads property damage)
Damage to forests soil removal
Avalanche safety
Survival depends on the length of time the person is buried and the burial and burial depth
92% survive if recused within 15 min only 30% survive after 35 mins, almost 0% after 2 hours
Only 5-10% survive burial in more than 1.5 m of snow
Rescue
Avalanche cords
Avalanche transceivers
Probes
Shovels
Avalanche dogs
7.3 effects of mass movements: roads
7.3 effects of mass movements: rails
7.4 human interaction
Landslides are a natural phenomenon
Humans increase though:
Expansion of urban areas, transportation networks, and natural resource use
Grading of land surfaces that increase instability of surfaces
Humans can decrease incidence through
Building stabilizing structures
Improving drainage
7.4 human interactions
Major environmental and economic issue in some regions
Two controversial practices
Clear cutting
Removing all of the trees from a defined area
Road building
Increase erosion (soil slips) on geologically unstable land
Interrupts surface drainage alters subsurface movement of water, and changes distribution of earth's materials
7.5 prevention of mass movements
Drainage control (don’t want water on surface or trickle in, but want water to go away fast)
Keeps water from infiltrating a slope
Drains can divert water
Impermeable layers can keep water from infiltrating
Slope supports
Steel mesh on top of surface, idea is to block chunks of rock from coming on the roads
Rock bolts, found on betting planes tilted on an angle, once you put the bolt in ur drilling through the layers squeezing them together
Drain, water drain, within rock there are fractures with water flowing inside, idea is to get water out but putting tubes in rock to get water out
Avalanche barrier (shed)
V shaped with community on side
Area prone to avalanches
Idea to make it wedged shape so that material is deflected to the sides
Or can be concrete structure (shed or tunnel) that covers highways from avalanches
Triggering Mechanism (A gun that points to avalanche and causes it to happen to prevent chaos)
Retaining walls
Concrete rocks wood, over 100 yrs old, deep prevents roads from deteriorating
Terracing or Grating
Idea is to make slope more stable by making series of steps (areas are typically prone to landslides and mass movements)
7.6 perception of an adjustment to landslide hazards
People continue to build in landslide- prone areas
Need to find adjustments
Movements of critical facilities
Hospitals schools and police stations should be placed in safe locations
Landslide correction
Landslide may be stopped after it starts using drains
7.6 perception of and adjustment to mass movement hazards
Be wary of leaks in swimming pools or septic tanks, trees or fences that tilt or sagging or taut utility wires
Be wary of small springs
Look for linear or curved cracks
Look for surface features
Don't buy a home that has a landslide hazard
7.6 perception of and adjustment to mass movement hazards
Location of infrastructure
Risk is estimated by determining avalanche frequency distribution size
Structures
Fences nets berms and avalanche sheds are used for protection
Triggering
Explosive charges are projected from cannons fired by artillery or dropped from helicopters