Natural Disasters Exam 1 PITT

Age of the Earth

4.57 Billion Years

Most Common Silicate

quartz

Atomic Number

# of protons in an atom

Return Period

# of years between between the same sized event

Silica Tetrahide (SiO4)

-"building block" of most rocks and minerals -defines the crystal shape, properties, appearance, etc.

Solid Earth Circulation

-Earth's crust moves horizontally and vertically -Produces large amount chemical recycling with erosion, weathering & lithification

Scientific Method

-allows hypotheses to be tested and debated -good ones hold up and weak ones die out -not a closed door/minded approach

P (primary) Waves

-compressional particle motion -fastest avg. speeds in the crust -behave similar to sound waves in air -can pass through solid, liquid and gas

Surface Waves

-confined to the very upper surface of the crust -slower than body waves -most damaging to structures -2 types: -Love-waves: similar to the motion of S waves -Rayleigh-waves: rotating particle motion

Upper Layer (Lithosphere)

-defines a tectonic plate -brittle behavior: does not flow, fractures under stress -all of the crust and part of the upper mantle

Rock Cycle

-describes pathways of rock-formation process -consequence of plate tectonics -estimated time of about 100 million years per cycle

Seismometer

-device that measures the ground vibrations -anchored to bedrock and moves with the ground motion -complex version of a simple mass on a spring device -can measure horizontal/vertical motion -transmits data to a remote seismogram

Sedimentary Rocks

-form on/near the Earth's surface or under the oceans -accumulation of the fragments of other rocks -fragments of organic remains -solids precipitated from liquids (salt)

Oxygen

-dominates Earth's crust -Si is much more abundant than the other elements (O is 3* more abundant!) -minerals naturally grow from whatever elements are available, a lot of O and Si -called Silicate minerals

Normal (extensional)

-due to tensional forces; generally, the smallest EQ's -hanging wall moves down with respect to the footwall

Continental Drift Hypth. to Theory of Plate Tectonics

-early 1960s: sea floor appeared to be spreading from its center -younger rocks toward center -discovered that the mantle of earth was convecting much like water boiling on a stove

Seismic Waves

-energy in the form of waves (causing particle motion) radiating out from a fault rupture (break) -change speeds when they pass through the earth -seismologists can model these changes -2 types of waves: Body (P and S) and Surface

Core

-enriched in iron and nickel, more dense -inner core: solid (caused by very high pressure), known because of seismic wave behavior -outer core: liquid (caused by the very high temperatures), known because of seismic wave behavior [ROTATION of metallic liquid creates the Earth's magnetic field]

Chemical Formation

-evaporation, precipitation of minerals from a liquid like water -ex. limestone (CaCO3), gypsum (CaSO4 - 2H20), salt (NaCl)

Mantle

-extends from asthenosphere/lithosphere down to the outer core -most information comes from seismic profiles -uniform composition of rock -P and T increase with depth THIS ZONE ALLOWS PLATE TECTONICS TO HAPPEN

Metamorphic Rocks

-form when an existing rock of any type re-crystalizes (but does not melt) -experiences elevated temperatures and pressures ("solid state transformation")

Reverse (thrust)

-from compressional stress -generally, the largest M, but can also be the deepest

Seismogram

-generally located in a place away from the seismometer -records on paper or digitally (seismograph)

Earthquakes

-ground movement caused by the release of seismic energy -seismic energy is usually caused by the brittle failure of rocks under stress

Seismograph

-instrument that detects and records ground motion (comprised of two parts, seismometer, seismogram)

Transform

-lateral movement caused by shearing stress -not as strong as trust faults -but usually shallower and thus more damaging

Fault Trace

-line where the fault/fracture intersects the surface

Mechanical Formation

-lithification of sediments/rock fragments (sandstone, mudstones, shales, breccia)

Skeptics of Continental Drift

-no explanation of the energy source -no ability to refute a claim that plants and animals may have just migrated -no inclusion of the sea floor

Asthenosphere Below

-plastic behavior: flows when stress is applied -contains a "low velocity" zone - some amount of partial melting -all mantle material

Convergent Plate Boundaries

-plates come together -subduction zones -increased volcanic activity -large earthquakes (ex. South America)

Transform Plate Boundaries

-plates slide past one another -moderate earthquakes (San Andreas fault)

Divergent Plate Boundaries

-plates spreading apart -small earthquakes (ocean floors)

Intensity Scale

-qualitative measurement based on human perception and property damage (only scale available before 1935) -12 levels of detailed descriptions of damage (Limitations: bias toward populated regions (need man-made structures))

Richter Scale

-quantitative, relates seismograph reading to a number (Open Ended Scale: Rocks are not strong enough to accumulate that much strain energy Limitations: expensive to set up and man seismometers, can not describe historic or very distant EQ's)

S (secondary/shear) Waves

-second fastest wave (~ 3.5km/s) -shearing particle motion (side to side movt. with respect to the wave propagation direction) -only passes through solids -more damaging to structures because of the shearing ground motion

Silica Tetrahedra Combinations

-single, isolated: "Olivine" (no shared oxygen atoms) -chain structure: "Pyroxene" (2 shared oxygen atoms) -double chain structure: "asbestos" (2 shared oxygen atoms) -sheet structure: "mica" (3 shareDIEd oxygen atoms) -framework structure: quartz" (all 4 shared oxygen atoms)

Solidification of Igneous Rocks

-solidifies slowly: large mineral crystals form -solidifies quickly: glass forms -solidifies slowly THEN erupts: large mineral crystals in a finer-grain matrix -with a large amount of water present in the magma (very explosive volcanoes) -with little water present in the magma (very effusive (non-explosive) volcanoes

Seismology

-study of seismic waves as they move through the crust -formed by earthquakes -can be VERY destructive -can be used to "image" the structure of the Earth

Earthquakes & Faults

-sudden release of stored energy as a result of rapid movement between two blocks (plates) -energy stored bc of plate movement and friction

Kinetic Energy

.5mv^2

General Stages of the Scientific Method

1) Observation & Data Collection 2) Hypothesis 3) Prediction 4) Testing and Debating 5) Formulate a TheoryTheory

Theory

AS CLOSE TO A SCIENTIFIC FACT AS POSSIBLE

Early Observations: Continental Drift

Alfred Wegener (1924) -continents seemed to fit together if the oceans were removed -similar fossils and species on both continents

Phosphates

Ca5(PO4)3(OH,Cl,F)

Carbonates

CaC03, FeCO3, (Ca,Mg)(CO3)2

Sulfates

CaSO4, BaSO4

Magnitude

How powerful an event is (amount of energy released, high M hazards happen with low F, much more destructive)

Crust Types

Continental Crust: thicker, less dense (granitic rocks), older Oceanic Crust: thinner, more dense (gabbroic rocks), much younger

Internal Heat

Early impacts of comets and asteroids, tremendous amount of heat created and stored during Earth's formation High density materials pulled toward earth's core (caused from radioactive decay)

Geohazard

Earth process involving the lithosphere, hydrosphere and/or atmosphere, which releases large amounts of energy

Components of Human Element

Economic Losses Population Increase (hyper-concentrated)

Energy Sources for Disasters

External Heat Internal Heat Force of Gravity

Igneous Rocks

Form when molten (melted) rock cools and solidifies either UNDER or ON the Earth's surface

Oxides/Hydroxides

Fe2O3, Al2O3, H2O (Ice)

Native Elements

Gold (Au), Copper (Cu), Diamond (C), Sulfur (S)

Fault Terminology (walls)

Headwall: rock layers above the fault plane Footwall: rock layers below the fault plane

Regional Metamorphism

High T and P -occurs where continental collisions form mountain belts -deep core of mountains experience elevated temperatures and pressures -foliation of minerals (light/dark bands)

Contact Metamorphism

High T, Low P -occurs where a hot magma intrudes colder rocks -"cooks" the surrounding host rocks -no foliation (banding)

Frequency

How often a given event occurs in a certain region

Hallides

NaCl, KCl, CaF2

Sulfides

PbS, ZnS, FeS2

4 Earthquake Classifications

Shallow Focus (0-70km) - 85%of the total energy released per year Intermediate Focus (70-300km) - 12% of the total energy released per year Deep Focus (300-800km) - 3% of the total energy released per year, only at convergent plate boundaries

External Heat (3)

Solar Output - very small fraction reaches the Earth's surface Solar Energy - wavelength related to frequency (delta = speed of light/frequency [c/v]) Solar Flux - amount of energy over a given area (w/m^2), measured perpendicular to incoming energy

Element

Substance that cannot be broken down into other substances (can be mineral too)

Common Misconceptions

Thinking the earth is NOT a closed system Displaced Problems Frequency of the Event

Natural Disaster

a geohazard interaction with human activity causing loss of life and property (important to understand the human element)

Rock

a naturally occurring solid made of one or more minerals or other solid substances

Mineral

a naturally occurring, inorganic solid with a specific regular arrangement of atoms

isotope

an element with varying amount of neutrons

Scope

area affected by a given hazard

Range of Igneous Rock Types

from light to dark minerals, extrusive vs. intrusive cooling Granite = intrusive, average composition of the continental crust, slow cooling, light colored Gabbro = intrusive, average composition of the oceanic crust, slow cooling, dark colored

Potential Energy

mgh

Half-life

time required for 1/2 the number of atoms of the parent element to decay into the daughter element

Radioactive Minerals

unstable and over time decay (radioactive decay = releasing neutrons, protons, or particles from the atom's nucleus, changes atomic #/isotope and therefore the element)