The Basics
From GeoClasses
Contents |
Chapter 1
What is Environmental Geology:
- applying geological information to guide humans' use and preservation of the land
Fundamental Concepts
Human population
- exponential growth (fig. 1.4, table 1.2; Keller, 2005)
- growth rate (G) - percentage that population is growing
- doubling time (D) - time it takes for population to double
- General Rule - D = 70/G
Let's make a graph:
- 40,000 - 9000 BC = hunter-gatherers - total population say 2,000,000, G about 0.0001%
- 9000 BC - AD 1600 = agricultural (preindustrial) - (total population 500,000,000) - G about 0.03%
- 1600-1800 = early industrial - (total population 1,000,000,000) - G about 0.1%
- 1800-2000 = modern - (total population in 2000 6,100,000,000) - G about 1.4% in 2000
Sustainability
How to define it?
- development so that future generations have something left?
- OR development that is economically viable but environmentally sound?
- must be a long-term concept - over several 100 years and many generations
- renewable resources vs. nonrenewable
- development/use vs. recycling/replacement vs. substitution/conservation (of forests, mines, fossil fuels, wind, water, groundwater, soil)
 development: an open pit copper mine |
 use: copper wiring, a common use for Cu metal |
 recycling: crushed steel waiting to be recycled |
 substitution: fiberoptics replace wired methods of communication |
 conservation: reclaiming land over old Pb and Zn mines in Wales; the pennycress plant absorbs metals into itself and reclaims the soil |
- we are responsible not only to other humans but to the total environment (plants, animals, land, water, air
- this is inconsistent with allowing economics (profit) to determine our behavior
Earth as a System
- input vs. output (bank account)
- input = output (reservoir does not change)
- input > output (reservoir grows - ex: pollution level in a lake)
- input < output (reservoir shrinks - ex: amount of fossil fuel remaining underground)
- input vs. output (bank account)
Residence time
Residence time = time that one unit (of whatever) remains in a reservoir before leaving
- ex: residence time in river = 2 weeks, in groundwater = 10,000 years
- so if pollution occurs in river (oil spilled from barge) - short time to naturally clean itself
- BUT if pollution occurs in groundwater (oil spill from broken pipeline) - long time to naturally clean itself
- Which reservoir will spread the pollution faster? Which reservoir will be easier for humans to clean?
| Reservoir | Average residence time |
|---|---|
| Oceans | 3,200 years |
| Glaciers | 20 to 100 years |
| Seasonal snow cover | 2 to 6 months |
| Soil moisture | 1 to 2 months |
| Groundwater: shallow | 100 to 200 years |
| Groundwater: deep | 10,000 years |
| Lakes | 50 to 100 years |
| Rivers | 2 to 6 months |
| Atmosphere | 9 days |
- Atmosphere
- Ocean
- Ice caps
- Groundwater
- example from published data from NIWA, on fish and residence time in some New Zealand lakes
Hazards
- what hazards will we cover?
- Anything geological! Earthquakes, volcanoes, floods, landslides, as well as pollution hazards
- what hazards will we cover?
Scientific method
- Observations, hypothesis, testing, conclusion and (almost always) revision of hypothesis - over time, theories
- early questions: how fast can land move? (table 1.3)
- slow rates:
- uplift of mountains (up to 2mm/yr)
- erosion of land (up to 1mm/yr)
- incision of rivers into bedrock (up to 10mm/yr)
 Rocky Mountains in western U.S. |
 severe erosion in a wheat field |
 river incision at Victoria Falls in Zambia |
- intermediate rates:
- gravitational creep of rock down a mountain (up to 1.2mm/yr)
- coastal erosion by waves (up to 1 m/yr)
 hillside creeping over a sidewalk |
 coastal erosion: houses shown did not survive the 1997 storm season |
- fast rates:
- glacier movement (up to few m/day)
- lava flows (up to few m/second)
- floodwater flow (up to few m/second)
- mudflow or avalanche (up to 62 mi/hr)
- earthquake rupture/fault (up to several km/second)
 glaciers in the Himalayas |
 lava flow in Hawaii |
 flooding of the streets in Alicante, Spain |
 avalanche on Mount Timpanogos, Utah |
 earthquake faulting |
- it takes up to:
- 300 my to erode 3 km of landscape away
- 600 my to create 3 km river canyon
- 100 years to erode backwards 100 m of beach
- BUT humans can:
- increase erosion of land by clearcutting and increasing erosion
- increase river incision by building dams which inrease downcutting underneath
This brings up geologic time: make a timeline with above processes marked
