8/28/16. Introduc)on to Natural Disasters III. Introduc)on to Natural Disasters III. Introduc)on to Natural Disasters III

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1 Popula)on Growth (anthropogenic hazard) - Con)nuously increasing number of people on our planet is THE number one environmental problem. Why? Popula)on Growth - Environmental problems As popula)on increases: Needs increase (food, clean water, energy, minerals/ rock), depletes non- renewable resources (used faster than nature produces), greater environmental impact (pollu)on, global warming, ozone hole, acid rain) Drama)c pictures of overpopula)on + overconsump)on, (The Guardian, hnps:// development- professionals- network/gallery/ 2015/apr/01/over- popula)on- over- consump)on- in- pictures) Stark photos involving resource extrac)on (Edward Burtynsky, hnps://thesocietypages.org/socimages/2008/12/21/burtynsky- resource- extrac)on/) Popula)on Growth - Environmental problems As popula)on increases: Greater impact of natural disasters (more death and destruc)on) Damage from Natural Disasters ( ) Popula)on Growth - Current rate of popula)on growth is exponen)al, therefore annual growth rate is ~constant percentage of popula)on, not constant number of people So, increasing number of people added to world each year Number of Natural Disasters ( ) Popula)on Growth - Annual rate of world popula)on growth is only ~1.1%, but Popula)on Growth - With 1.1% growth, s)ll have exponen)al curve 1

2 Popula)on Growth - Recent Trends Popula)on Growth - Annual popula)on increase is star)ng to drop! Eventually Earth will reach its carrying capacity (maximum number of people it can support due to finite resources), things will get worse as we reach Earth s carrying capacity Popula)on Growth- Growth is occurring (+ will occur) mainly in underdeveloped parts of world (India, Asia, Africa) Popula)on Growth - Annual popula)on increase is dropping due to decreasing % growth rate Earth s Carrying Capacity - Case History Easter Island - In southeast Pacific Ocean, inhabited 1,500 years ago by Polynesian islanders. Rich culture flourished (famous large carved statues) Moai 2

3 Earth s Carrying Capacity - Easter Island PopulaJon soared to 7,000 around 1400 AD before declining due to poverty by 1722 when first Europeans arrived. Island reached carrying capacity by stripping Jmber; culture collapsed, cannibalism, tribal warfare, subsistence farming, cave dwellers Earliest known painjng of Easter Island (1775) Solu)on to Popula)on Crisis? Zero populajon growth (death rate balances birth rate) Religious, polijcal, cultural roadblocks Sun's energy and Earth's gravity drive all weather, floods, landslides, sinkholes, and waves/coastal erosion Earth s Carrying Capacity? Current age of mass exjncjon; ~thousands of species go exjnct every year What is Earth's carrying capacity? Hard to determine exactly, perhaps between current populajon (7.35 billion) and ~9.3 billion populajon projected for 2050 All processes on Earth require energy, comes from many sources. Natural disasters occur when there is sudden release of energy near Earth's surface Energy for natural disasters: External sources (Sun, meteorite impacts) Internal sources (radioac)ve decay, gravity) Earth's internal heat and gravity drives tectonic plate mo)on (earthquakes, volcanic erup)ons, mountain uplid/ landslide) 3

4 Intro Natural Disasters III - External Energy 1) Energy from Sun - radiant (light) energy, 99.98% of energy received by Earth; ~30% reflected into space by atmosphere, oceans; ~50% absorbed (by water, Earth), converted to heat (drives circulajon in atmosphere, oceans), eventually escapes back into space 23% evaporates water, begins hydrologic (water) cycle. Tiny amount absorbed/stored in plants. Intro Natural Disasters III - Internal Energy Geothermal energy = Jny amount of energy to Earth's surface (~0.02%) 1) RadioacJve Decay - Unstable/radioacJve isotopes (U, Th, K) change to stable form radioacjve decay, releases energy, heats rock in Earth's interior, heat slowly moves to Earth's surface 2) Gravity - All objects at Earth's surface (rain, snow, earth in landslide) are pulled toward Earth's center by gravity. Some internal energy caused by gravitajonal compacjon of Earth's interior. Hydrologic Cycle: movement of water through reservoirs (where water resides): oceans, atmosphere (clouds), glaciers, lakes, streams, groundwater, biosphere. Ocean is largest reservoir. Main pathway water moves is atmosphere. Solar energy causes evapora)on and atmospheric circula)on; gravity causes water to flow back to oceans (precipita)on and river, glacial, groundwater flow). Intro Natural Disasters III - External Energy 2) Meteorite impact energy - meteorites have enormous kinejc energy (fast- moving, can be very large), transferred to Earth during impact; impact generates very high temperatures (10,000 C or more) and pressures ( million atmospheres); meteorite collisions much more common during early history of Earth (generated lots of heat, sjll escaping from Earth's interior) Earth s systems: atmosphere, hydrosphere (water), lithosphere (rock, soil), biosphere (living organisms); Interact with each other exchanging both maner and energy on cyclical basis; geologic cycles important to natural disasters Chemical Cycle: Movement and reservoirs of specific elements, e.g., carbon = carbon cycle (N, P, O, S, others); 4 major reservoirs in carbon cycle = biosphere (building block of life), lithosphere (in carbonate minerals, rocks, fossil fuels, coal, oil), hydrosphere/oceans (dissolved ions), atmosphere (carbon dioxide, CO2, gas). 4

5 8/28/16 Intro Natural Disasters III - Geologic Cycles Rock Cycle: Cycling of elements among igneous, sedimentary, metamorphic rocks; mostly involves lithosphere (also hydrologic, chemical cycles). Geologic processes convert one rock to another. Energy near surface = solar energy and gravity (erosion, weathering); energy subsurface processes = geothermal energy and gravity (control uplid, burial, mel)ng, metamorphism) 5