Chapter #7 Flashcards
Stealth disasters occur ____
Slowly
Sinkholes
Land collapsing into circular depressions
Land Subsidence
Land gradually sinking over a broad area
Soil destruction is caused by….
Nutrient depletion, Soil contamination, Erosion
Hydrologic Cycle
The water cycle.
The 4 main components
Evaporation, Convection, Precipitation and Collection.
Water cycles through…
Land and Organisms
Lakes and Streams
Oceans and ice
Earth’s atmosphere
Surface Water examples
Lakes, streams, wetlands, snow, and glaciers
Soil moisture
Water clinging to minerals or organic material
Ground water
Water underground in rock and sediment pores
Most surface water is, drinkable or undrinkable?
undrinkable salt water
Water consumption growth is caused by…
Growing human population
Improving living standards
Fresh water withdrawals, list the main sectors
70% Agricultural
19% Industry
11% Municipally
Fresh water consumption concerns for society
Political and economic factors can drive shortages.
Productivity disruptions
Military conflicts
Watershed
An area that refills fresh water reservoirs
Depletion
When extraction exceeds replenishment
Pollution Sources (For water)
Garbage
Chemicals
Fertilizer
Pesticides
Animal Waste
Eutrophication
Nutrients form fertilizer and sewage cause algal blooms.
Algae depletes water and oxygen when it dies
occurs when the environment becomes enriched with nutrients, increasing the amount of plant and algae growth to estuaries and coastal waters.
Eutrophication is considered to be a serious environmental concern since it often results in the deterioration of water quality and the depletion of dissolved oxygen in water bodies. Eutrophic waters can eventually become “dead zones” that are incapable of supporting life.
Salinification
Evaporation > addition
Diverted freshwater inputs
Irrigation leaches soil salts
Groundwater
water in pores of sediment and bedrock
Recharge area
The region where water enters the ground
Discharge area
The region where water returns to the surface
Pores
Open spaces between mineral grains
Porosity
percentage volume of open space
Permiability
The degree of pore connectivity
Permeable Rock
Open conduits allow ground water flow
Impermeable rock
Cement between minerals blocks groundwater flow
Aquifer
Sediment or rock with high permeability and porosity
Aquitard
Sediment or rock with low permeablity
Unsaturated zone
pores contain just air, or both air and water
Saturated zone
water completely fills pores
Water table
Boundary between saturated and unsaturated zones
When does a water table rise and sink?
Rises during wet season, and sinks during dry season
Springs
Natural outlets where groundwater seeps to surface
Aquitards may produce….
perched water tables
Wells
Pits or holes into which groundwater seeps
Producing wells
Penetrate aquafers and produce water
Dry wells
Do not penetrate aquafers
Ordinary wells
Water is lifted by buckets or pumps
Artesian wells
water rises under its own pressure
Depleting ground water supplies can cause a specific threat, which is called
A societal threat
Drawdown
Water is pumped from a well faster than it can replenish. Causes the water table to sink
Groundwater depletion
May occur due to over extraction.
May occur due to damaged recharge areas
Recharging a depleted reservoir can take how long?
could take a millennia
Ground water should be viewed as a renewable or nonrenewable source?
Nonrenewable
Effects of ground water depletion
Shallow wells, lakes, reservoirs,
rivers, and wetlands dry up.
Pores in weakly cemented rock
collapse, causing land to sink.
Natural contamination
Can occur from minerals in an aquifer, Ex: Arsenic from pyrite may leach into groundwater.
Anthropogenic contamination
Injection wells
Chemical and sewage spills
Leaking underground oil tanks
Water security
Access to safe and affordable water.
Currently we have a growing lack of water security
Physical Scarcity (Water)
There is not enough water
Economic Scarcity
There is enough water, but economic reasons make water unfit or unobtainable/unavailable
Conservation
Decreases consumption
Lifestyle changes
Crop and irrigation changes
Can conservation and economic growth occur together?
Yes
What causes Water stress(Like what can cause us to be scared):
- Agriculture and urban use
- Surface water pollution
- Paved and/or deforested recharge areas
- Wetlands filled for housing
- Inadequate rainwater harvesting
- Inadequate purification and distribution
- Dropping precipitation rates
Caverns
Open underground spaces without sunlight
Cavern collapse
When the roof of a cavern collapses
Sinkholes
Circular pits caused by cavern collapse
Karst terrain
a landscape with numerous sinkholes
Caverns form at water table, because of:
Highest acidity at water table
Fastest flow at water table moves dissolved minerals
Caverns develop when?
Water tables drop
Speleothems
Calcite formations within caverns
How to Karst landscapes develop
as caverns collapse
Dissolution sinkholes
Water dissolves surface rock and creates a depression
Cover-subsidence sinkholes
Loose sediment washes into underground space
Collapse Sinkholes
The roof of the cavern suddenly falls to the cavern floor
Collapse can be triggered by…
Heavy rain
Building construction
Lowering water table
Does expanding communities increase sinkhole disaster risk?
Yes
LIDAR
Light detection and ranging
Is used to detect sinkholes, even those covered by vegetation
Resistivity survey
Measures underground electricity flow.
Air-filled voids have lower-relative conductivity
Gravity survey
Measures local gravity field.
Air-filled voids have lower relative gravity.
Ground-penetrating radar
Radar may reveal a cavers roof and floor
Seismic reflection profiling
Seismic waves may reveal air filled voids
Sediment liquefaction
When soil is transformed into a liquid-like slurry.
Due to sudden ground shaking or influx of water.
Evaporites
- Sedimentary rock containing halite and gypsum.
- Halite and gypsum quickly dissolve in water.
- Evaporite sinkholes can develop in just hours.
What will the government do and not do regarding sink holes?
Does Not: Asses sinkhole likelihood, does not fill sinkholes on private land
Will do: Buy sinkhole insurance
What are the signs of an evolving sinkhole?
- Cracks in sidewalks
- A growing ground depression
- Ill-fitting doors and windows
- Cloudy well water
- Dropping well water level
- Tilting telephone poles
Subsidence
When land sinks over a broad area
Water in pore spaces supports what?
unconsolidated sediment
Removing water from pores casues?
sediment to pack together
Pore collapse decreases..
rock and sediment porosity, as well as thickness of sedimentary beds
Subsidence is not uniform:
- Some areas may begin tilting.
- Large fissures, hundreds of meters long, may open.
- Flooding may increase.
- Slope changes may cause streamflow and ecosystem disruptions.
- Sewer lines and water mains may stop flowing properly.
Deltas
Wedges of sediment deposited by a river
Flood Plains
Flat lands bordering a river that regularly flood
Coastal Plains
Low-lying lands along some continental margins
Subsidence occurring for 3 reasons:
- Dams and levees prevent flooding and thus sediment deposition.
- Surface sediment has dried out, shrunk, and oxidized.
- Groundwater, oil, and gas extraction have caused pore collapse.
Longwall coal mining (Subsidence):
- Mine collapses as grinder and enclosure move.
- Overlying land sinks.
Roof-and-pillar coal mining (Subsidence):
- Weak pillars may fail, causing overlying land to sink.
Coal bed fires also cause….
subsidence
Salt mines may collapse if…
water dissolves halite
Modifying agents of soil(Good things):
Rain, air, organisms and decaying organic matter
Soil destruction is a ______disaster. Which can create problems of…
stealth disaster.
* Food production is at risk.
* Famine may result.
3 processes form soil:
- Weathering breaks rock into sediment.
- Rain percolates through sediment.
- Organisms physically and chemically alter sediment.
Zone of leaching
Where percolating water picks up ions and clay flakes
Zone of accumulation
- Where minerals precipitate from percolated water
- Where clay is deposited
Topsoil
- Modified by leaching
- Contains the most organic matter and nutrients
- Supports plant growth
Subsoil
- Lacks significant carbon
- Poor soil for plant growth
Soil diversity caused by many interacting factors:
- Climate
- Source rock
- Slope
- Vegetation
- Time
Soil degradation includes:
- A reduction in the quantity
- A reduction in fertility
Soil depletion:
- Crops absorb soil’s nutrients.
- Fertility declines over time.
Soil texture. Good example and what can ruin the texture
- Good soil is porous, permeable, and a bit sticky.
- Plowing, heavy equipment, and animals can ruin texture.
Soil contamination
- Chemicals, overfertilization, oil spills, and landfills
- Salt deposits
Soil Erosion
Wind and water pick up and carry away soil particles.
Deforestation removes soil’s protective vegetation cover
Soil Erosion effects on Agriculture
- Commercial crops have lower root densities.
- Farm fields lie exposed to wind and water most of the year.
- Heavy farm equipment breaks surface soil particles.
Dust storms
- A wall of dust up to 1.5 km high
- Reduce visibility and coat everything in fine sediment
- May cause silicosis (damaged lungs) from repeated exposure
- May contain toxic agricultural chemicals
Mitigation measure against dust storms
- Prevent intensive farming
- Change plowing methods
- Leave post-harvest stubble
- Grow windbreaks
- Plant cover crops
Soil Conservation techniques
- Constructing fewer impervious (asphalt and concrete) surfaces
- Modifying plowing techniques
- Rotating crops
- Planting cover crops
- Practicing no-till farming
Expansive Soil
Soil that expands and shrinks due to wetting and drying
Potential problems with expansive soil
Unequal wetting and drying may crack foundations
Buildings, homes, roads, and pipelines may be damaged.
Protection for buildings against Expansive soil
- Build foundations on deep piles, below movement layer
- Improve drainage around buildings.
