Ch 13: Civilization as a Global Geosystem

Civilization as a global geosystem

Human society interacting with Earth systems and relying heavily on natural resources

Deepwater Horizon oil spill

2010 Gulf of Mexico disaster releasing ~200,000 gallons of oil per day for months

Human impact on Earth systems

Humans alter landscapes, atmosphere, hydrosphere, and biosphere significantly

US fossil fuel usage

~5% of world population uses ~20% of fossil fuels

Human population growth trend

Rapid increase after Industrial Revolution

Human alteration of Earth

Humans move more soil/rock than natural processes and have cleared ~1/3 of forests

River sediment trapping

Dams trap ~30% of river sediments

Atmospheric CO2 increase

Increased ~50% from ~200–300 ppm to ~420 ppm

Ozone layer damage

Caused by human-produced chemicals

Building blocks of life

Carbon, hydrogen, oxygen, water, nutrients, and energy

Water in organisms

Makes up ~50–95% of living organisms

Nutrients in life

Includes phosphorus, nitrogen, potassium, and trace elements

Society as organism concept

Civilization requires energy, materials, and nutrients like living systems

Photosynthesis equation

6CO2 + 6H2O + sunlight → C6H12O6 + 6O2

Respiration equation

C6H12O6 + 6O2 → 6CO2 + 6H2O + energy

Origin of fossil fuels

Formed from ancient biomass preserved and transformed over geologic time

Renewable energy resources

Naturally replenished (solar, wind, hydro, geothermal)

Nonrenewable energy resources

Limited supply (oil, natural gas, coal)

Btu (British thermal unit)

Energy needed to raise 1 lb of water by 1°F

US energy consumption pattern

Dominated by fossil fuels

Major Texas oil fields

Permian Basin, Barnett Shale, Eagle Ford, East Texas, Haynesville Shale

Oil and gas formation step 1

Large production of biomass

Oil and gas formation step 2

Preservation in oxygen-poor (reducing) environments

Oil and gas formation step 3

Burial increases heat and pressure causing maturation

Oil and gas formation step 4

Hydrocarbons accumulate in geological traps

Source rock

Rock where hydrocarbons form (often shale)

Reservoir rock

Rock that stores oil/gas (porous and permeable)

Cap rock

Impermeable layer that traps oil and gas

Porosity

Amount of empty space in rock (fluid storage capacity)

Permeability

Ability of rock to transmit fluids

High porosity example

Gravel

Low permeability example

Shale

Conventional oil reservoir

Oil trapped beneath impermeable rock layers

Anticlinal trap

Oil accumulates at crest of folded rock beneath cap rock

Fault trap

Oil trapped by displacement along faults

Stratigraphic trap

Oil trapped due to changes in rock type

Salt dome trap

Oil trapped around rising salt structures (common offshore)

Fracking (hydraulic fracturing)

Creating fractures in shale to release oil/gas

Tight gas

Natural gas trapped in low-permeability rocks requiring fracking

US natural gas trend

~2/3 from shale/tight formations, increasing

Natural gas composition

Mainly methane (CH4)

Natural gas advantage

Emits ~25% less CO2 than oil

Natural gas sulfur content

Very low → less acid rain

Oil as a resource

Nonrenewable and finite

Hubbert’s peak

Point where oil production peaks then declines

Global oil depletion estimate

~55 years at current rates

Coal formation sequence

Peat → Lignite → Bituminous → Anthracite

Peat

Partially decomposed plant material

Lignite

Low-grade coal (~70% carbon)

Bituminous coal

Medium-grade coal

Anthracite

High-grade coal (~90% carbon)

Coal global distribution

~85% in former Soviet Union, China, and USA

Coal energy contribution US

~22% of energy use

Coal environmental impacts

High CO2 emissions, acid rain, toxic ash

Acid rain cause

Sulfur and nitrogen emissions from coal

Coal CO2 emissions

~25% more than oil, ~70% more than natural gas

Clean Air Act (1990)

Required reduction of SO2 and NOx emissions

Acid rain region

Rust Belt states heavily impacted

Global energy production

~80% from fossil fuels (oil, gas, coal)

Future energy trend

Continued reliance on fossil fuels

Renewable energy definition

Energy sources replenished naturally

Alternative energy definition

Non-fossil fuel energy sources

Nuclear energy source

Fission of uranium-235

Nuclear energy contribution

~22% of US electricity

Nuclear energy classification

Alternative but nonrenewable

Nuclear energy risks

Radioactive waste, meltdown, weapons proliferation

Radioactive waste lifetime

~100,000 years

Nuclear meltdown examples

Chernobyl, Fukushima, Three Mile Island

Solar energy potential

Every 20 days equals all fossil fuel reserves

Incoming solar radiation

~340 W/m²

Global solar capacity leader

China (~888 GW)

US solar capacity

~177 GW

Solar panel production

China produces ~85% globally

Biofuels source

Corn, soybeans, sugarcane, algae, grass

Biofuel challenge

Requires fossil fuels to produce

Biofuel issue

Government subsidies affect sustainability

Wind energy requirement

Large open areas with consistent winds

US wind leader

Texas (#1 capacity)

Wind energy US share

~1% of national energy

Denmark wind example

Can supply 100% electricity at times

Hydroelectric energy requirement

Water + gravity

Hydroelectric advantage

Clean and inexpensive

Hydroelectric usage

Norway (~90%), Switzerland (~56%)

Geothermal energy source

Heat from Earth’s interior

Geothermal example

Iceland (~66% energy use)

Key difference renewable vs nonrenewable

Renewable replenishes quickly; nonrenewable does not

Unconventional energy sources

Fracking, shale gas, tight gas

Conventional energy sources

Easily extracted fossil fuels

Oil window

Temperature range where oil forms

Shale role in energy

Source rock and cap rock for hydrocarbons

Global change

Human-driven changes to Earth systems (climate, sea level)