Introduction Geology 357

Focus of this class Learn about natural disasters, and the geologic processes that are responsible Examine how natural disasters affect the urban environment

What is Environmental Geology? environmental concerned with the ecological effects of altering the environment; “environmental pollution” geology The science which treats: (a) Of the structure and mineral constitution of the globe; structural geology. (b) Of its history as regards rocks, minerals, rivers, valleys, mountains, climates, life, etc.; historical geology. (c) Of the causes and methods by which its structure, features, changes, and conditions have been produced; dynamical geology. Source: Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.

What is a Natural Disaster? An event of nature that releases energy upon an area, causing destruction of property and loss of human life. A subdiscipline of Environmental Geology

What is a Natural Hazard? A hazard that arises from geological or weather-related occurrences. Includes: Earthquakes Volcanoes Floods Storms / Hurricanes / Tornadoes

Terms to Know Magnitude The size of the event Frequency How often the event happens Return Period The time between two events of the same size

Terms to Know Disaster A natural event, such as a flood or earthquake. Catastrophe A natural event that causes significant damage to property and harms/kills a large number of people.

Terms to Know Hazard Occurs when a natural event is likely to cause harm Risk Hazard + recurrence interval + costs Ex.: great hazard potential + short recurrence interval + high cost = high risk

Plate Tectonics

The Theory of Plate Tectonics Continental Drift + Sea-Floor Spreading + Paleomagnetism = Plate Tectonics

Plate Tectonics Earth’s lithosphere is broken up into plates Hot, weak asthenosphere allows for plates to move Plates are in motion and continually changing in shape and size Move very slowly – 5 cm/yr

Structure of the Earth Layers – by composition Crust Mantle Core

Structure of the Earth Layers – by physical properties Lithosphere Asthenosphere Mesosphere Outer Core Inner Core

Structure of the Earth Crust Continental crust Average rock density about 2.7 g/cm3 Composition = the felsic igneous rock granodiorite

Structure of the Earth Crust Oceanic crust Density about 3.0 g/cm3 Composed mainly of the igneous rock basalt

Structure of the Earth Mantle Contains 82% of Earth’s volume Solid, rocky layer Upper portion has the composition similar to peridotite Two parts Mesosphere (lower mantle) Asthenosphere or upper mantle

Structure of the Earth Core Larger than the planet Mars Mostly iron with some nickel Average density is nearly 11 g/cm3 Two parts Outer core - liquid Inner core - solid

Structure of the Earth Core Responsible for Earth’s magnetic field Made of material that conducts electricity Core is mobile

Structure of the Earth Seismic waves P waves Travels through liquids as well as solids In all materials, P waves travel faster than do S waves S waves Cannot travel through liquids

Structure of the Earth Seismic waves Seismic waves refract as they pass from one material to another P & S wave shadow zones P-Wave Shadow Zone

Structure of the Earth Seismic waves Seismic waves refract as they pass from one material to another P & S wave shadow zones S-Wave Shadow Zone

Plate Boundary Features Plate Boundary Features

Plate Tectonics Plate boundaries Types of plate boundaries Divergent plate boundaries Convergent plate boundaries Transform fault boundaries

Motion at Plate Boundaries Motion at Plate Boundaries

Tectonic Settings and Volcanic Activity Tectonic Settings and Volcanic Activity

Hot Spot Volcano Tracks Hot Spot Volcano Tracks

Energy Sources of Disasters

Primary Sources Impacts with Asteroids and Comets Gravity Internal Heat The Sun

Energy Sources of Disasters Impacts with Asteroids and Comets Origin of the Sun & Planets

Nebular Hypothesis of Solar System Formation Nebular Hypothesis of Solar System Formation

Energy Sources of Disasters Gravity Attraction between two or more objects Interaction between the sun, moon and Earth produces tidal energy

Energy Sources of Disasters Spring Tides During the period of a new moon, the moon and sun are lined up on the same side of the Earth Produces the greatest range between high water and low water Neap Tides Produced when the moon is at a right angle to the line of centers of the Earth and the sun The range between high and low water is small

Energy Sources of Disasters Internal Heat Impact energy from the formation of the planet Gravitational energy Radioactive Elements

Energy Sources of Disasters The Sun Small percentage of total solar energy reaches the Earth More than 3500 times greater than Earth’s interior heat flow

Energy Sources of Disasters The Sun Where does the energy go? 30%  Albedo (reflection) 47 %  Absorbed by air, sea and land 23 %  Evaporation / begin hydrologic cycle

Hydrologic Cycle Hydrologic Cycle

Losses from Natural Disasters

Losses from Natural Disasters - Human Fatalities Worst Disasters: Floods Hurricanes Earthquakes Severe Weather Least: Tsunami and Volcanic eruptions

Losses from Natural Disasters - Human Fatalities Amount varies from year to year The population density of a region affects number of fatalities

Losses from Natural Disasters - Economic Sources Buildings and other structures Industry and businesses

Losses from Natural Disasters - Economic Insured Portion of Economic Losses Amount covered by insurance Dollar amount lost is different than lives lost US, Europe and Japan have fewer lives lost but higher damage costs

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