Download Understanding Natural Hazards: Processes, Risks, and Mitigation and more Exams Advanced Education in PDF only on Docsity!
ERTH 2415 - Midterm Test With
Complete Solution
Processes: Internal and External - ANSWER • Physical, chemical, and biological ways in which events affect Earth's surface Internal processes come from forces within Earth
- Plate tectonics
- Result of internal energy of Earth External processes come from forces on Earth's surface
- Atmospheric effects
- Energy from the Sun Hazard, Disaster, or Catastrophe - ANSWER Hazard
- Natural process or event that is a potential threat to human life or property Disaster
- Hazardous event that occurs over a limited time in a defined area
- Criteria:
- Ten or more people killed
- 100 or more people affected
- State of emergency is declared
- International assistance is requested Catastrophe
- Massive disaster that requires significant amount of money or time to recover Mitigation - ANSWER • Reduce the effects of something
- Natural disaster preparation Death and Damage caused by Natural Hazards - ANSWER • Effects of hazards can differ and change with time because of changes of patterns of human land use
- Natural hazards that cause the greatest loss on human life may not cause the most property damage
- Hazards vary greatly in their ability to cause catastrophe Greatest damage - ANSWER Where would you expect the greatest damage/economic losses from natural disasters?
- Industrial nations suffer the most economic challenges Where would you expect the greatest death toll from natural disasters?
- Poorest Nations Case Study: Earthquake in Haiti, 2010: - ANSWER • Earthquake became a catastrophe
- Eighty-five percent of people in Port-au-Prince lived in slum conditions
- Poor conditions lead to 190,000 destroyed or damaged homes
§^ Biogeochemical cycle
The Tectonic Cycle - ANSWER • Refers to large-scale processes that deform Earth's crust and produce landforms
- Driven by forces within Earth (internal energy)
- Involves the creation, destruction, and movement of tectonic plates The Rock Cycle - ANSWER • Rocks are aggregates of one or more minerals
- Recycling of earth materials linked to all other cycles o Tectonic cycle: heat and energy o Biogeochemical cycle: materials o Hydrologic cycle: water for erosion and weathering
- Rocks classified according to how they were formed in the rock cycle
- Igneous rocks o Form from crystallization of magma
- Sedimentary rocks o Rocks are weathered into sediment by wind and water o Deposited sediment undergoes lithification
- Metamorphic rocks o Rocks are changed through extreme heat, pressure, or chemically active fluids
The Hydrologic Cycle - ANSWER • Movement of water between atmosphere and oceans and continents driven by solar energy
- Processes include evaporation, precipitation, surface runoff, and subsurface flow
- Water is stored in compartments such as oceans, atmosphere, rivers, groundwater, etc. o Residence time is estimated average time that a drop of water spends in any compartment o Only a small amount of water is active at any given time
Biogeochemical Cycle - ANSWER • Transfer of chemical elements through a series of reservoirs - o Atmosphere, lithosphere, hydrosphere, biosphere
- Related to the three previous cycles - o Tectonic cycle: water from volcanic processes; heat and energy required - o Rock and hydrological cycles: involved in transfer and storing of chemical elements
- Rates of transfer of important chemical elements are only approximate - o Carbon, Nitrogen, Phosphorus
Fundamental Concepts for Understanding Natural Processes as Hazards - ANSWER 1. Hazards are predictable from scientific evaluation
- Risk Analysis - ANSWER Risk = (probability of event) x (consequences) →Live in northern Saskatchewan? →Live inside the crater of an active volcano? →Live on the San Andreas fault?
- Consequences: damages to people, property, economics, etc.
- Acceptable Risk is the amount of risk that an individual or society is willing to take
- Problem: lack of reliable data for either the probability or consequences
- Linkages - ANSWER - Hazards may be linked to or cause one other -Hazards linked to earth materials For example:
- Earthquakes can cause landslides
- Earthquakes and landslides can cause tsunamis
- Volcanic eruptions may be preceded by earthquakes
- Hurricanes can cause flooding
- Drought can make fires worse
- Global warming (climate change) could lead to more hurricanes
- Some rock types are prone to landslides
- Disasters are now becoming Catastrophes - ANSWER The world's population is growing exponentially
- Grows by the addition of a constant percentage of current population
- Has more than tripled in the past 70 years The Problems:
- Increases number of people at risk
- Reduced availability of food & clean drinking water
- Greater need for energy and waste disposal Examples:
- Mexico City: 10,000 killed in 1985 8.0 earthquake
- Izmit, Turkey: >17,000 killed in 1999 earthquakes
Magnitude and Frequency of Hazardous Events - ANSWER • Impact of hazards depend on: o Magnitude: Amount of energy released (how large is the event) o Frequency: Interval between occurrences o Other factors: climate, geology, vegetation, population, and land use
- Magnitude-frequency concept o Frequency of an event inversely related to magnitude
- Land use affects magnitude and frequency of events
o Search and rescue - o Firefighting - o Providing emergency food, water, and shelter
- Need to increase efforts to anticipate disasters and their effects - o Land-use planning limitations - o Hazard-resistant construction + building codes - o Hazard modification or control - o Disaster preparedness (e.g. Evacuation plans, insurance) - o Control through artificial structures
- Total losses are direct losses and losses related to human actions
Reducing Risk - four pillars of emergency management - ANSWER 1. Response Short-term - Immediate actions to put event under control
- Recovery Middle-term - Put situation back to normal
- Mitigation Long-term - Actions taken to minimize risk, damage
- Preparedness Long-term - Actions taken in advance to ensure people are ready
- New term added in response to climate change issues -
- Adaptation Long-term
"The Big One" (2015-2045) - ANSWER • The US Geological Survey's Third Uniform California Rupture Forecast (UCERF3) predicts earthquake eruptions and states that a magnitude 8.0 or larger earthquake has a 7 percent chance of occurring in the next 30 years, at present.
- The odds of a magnitude 6.5-7.0 earthquake hitting went up 30 percent.
Wildfires in Canada and the United States (2015-2050) - ANSWER • Environmental scientists from the Harvard School of Engineering and Applied Sciences (SEAS) predict that by 2050, wildfire seasons will be three weeks longer, twice as smoky, and will burn a larger portion of the West per year
- 30,000-50,000 wildfires predicted to occur annually
Canadian trends - ANSWER • The # of natural disasters is increasing with time
- Communities are increasingly vulnerable: o Population growth o Development in risky areas o Degradation of natural ecosystems o Over-reliance on technology Canadian Trends
- The # of natural disaster fatalities is decreasing with time
- Economic losses are mostly due to weather-related disasters
Earth is differentiated into layers based on:
The Geoid - ANSWER - The shape that the surface of the oceans would take under the influence of Earth's gravity and rotation alone
Internal structure of Earth - ANSWER • Internal processes have incredibly important impacts on the surface of the Earth
- Responsible for continents and ocean basins
- Oceans' currents and distribution of heat carried by seawater controlled by configuration of continents and ocean basins
- Responsible for regional landforms
- Earth is layered and dynamic
- Internal structure of Earth o By composition and density o By physical properties (strength)
Earth structure - ANSWER • Outer core
- Liquid
- 2,000 km (1,243 mi.) in thickness -
- Composition similar to inner core
- Density (10.7 g/cm3)
- Inner core
- Solid - 1,300 km (808 mi.) in thickness
- High temperature
- Composed of iron (90 percent by weight) and other elements (sulfur, oxygen, and nickel)
The core is a heat battery - ANSWER • The Earth is cooling down
- Cooling of the liquid outer core
- The inner core is growing over time as the outer core cools and solidifies!
- Tremendous heat is given off as the liquid outer core solidifies and the inner core cools. >10,000 Giga-watts!
Internal Structure of Earth, cont. - ANSWER • Mantle
- Solid - 3,000 km (1,864 mi) in thickness
- Composed of iron- and magnesium-rich silicate rocks
- Average density 4.5 g/cm
- Crust
- Shear stress = parallel to surface
Responding to stress - ANSWER a) Elastic -recovers: when stress stops in recovers b) Ductile-deforms stress deforms from original c) Brittle-breaks: if stress is applied it will break
Outer surface of the earth - ANSWER The outer surface of the Earth consists of several lithospheric plates moving relative to each other as rigid bodies on a fluid substratum called the asthenosphere
- Lithosphere
- Cool, strong outermost layer of Earth (crust and upper mantle)
- Crust embedded on top
- Asthenosphere
- Below lithosphere
- Hot, soft/ductile slowly flowing layer of weak rock
- Higher water content and hotter
Buoyancy - ANSWER • Earth can be described as a series of layers where less dense material floats on top of denser material
- Low-density crust floats on top of the denser mantle
- Mantle floats on top of the very dense core
Isostasy - ANSWER Surface elevation represents a balance between forces:
- Gravity: pushes plate into mantle
- Buoyancy: pushes plate back to float higher on mantle Isostatic equilibrium describes this balance.
- Isostasy is compensated after a disturbance.
- Adding weight pushes lithosphere down
- Removing weight causes isostatic rebound
- Compensation is slow, requiring asthenosphere to flow.
heat transfer - ANSWER Heat can be transmitted through solids and fluids by conduction, through fluids by convection, and by radiation. Heat Transfer On a planetary scale, the same processes are active!
- Heat from the interior of Earth flows to the surface by conduction
- In the mesosphere and asthenosphere, heat is redistributed by flow of plastic solids
- Hot, less-dense materials rises
- Cold, denser material sinks creating convection cells
- This is how we infer that the outer core is liquid
- S-waves do not propagate through the outer core
Movement of the Tectonic Plates - ANSWER • Lithosphere is broken into pieces o Lithospheric plates or tectonic plates
- Plate tectonics o Plates move relative to one another o Plates are created and destroyed o Boundaries between lithospheric plates are geologically active areas o Responsible for several of the most devastating natural hazards, such as earthquakes and volcanoes
Earth's Plates - ANSWER o THREE types of plate boundaries: 1. Divergent 2. Convergent 3. Transform o Location of volcanoes and earthquakes is not random!
Fit of the Continents - ANSWER • Antonio Snider-Pelligrini (1858), a geographer cut out a map of Africa and South America suggesting they were connected at one time
- Other physical evidence based on observation (maps, fossils etc.) was used
by Wegener
Continental Drift Hypothesis - ANSWER • Alfred Wegener proposed the hypothesis of continental drift in 1915
- Theory based on congruity of the shape of the continents and similarity of fossils in South America + Africa
- Theory not accepted because could not explain how continents moved
Subduction Zones - ANSWER • Plate collides with another plate
- Denser plate dives under the less-dense plate and is recycled
- Denser plate: subducting plate
- Less-dense plate: overriding plate
Divergent Boundaries - ANSWER • Plates move apart during seafloor spreading
- Magma from asthenosphere rises
- Plates are pulled apart under tension at divergent zones: o Reduction in pressure on superheated asthenosphere rock o Liquifies and rises o Buildup of magma and heat causes expansion and elevation of overlying lithosphere
