Dynamic Planet/Earthquakes, Volcanoes, and Tectonics

This page is for the 2009 and 2010 Dynamic Planet topic,Earthquakes and Volcanoes. For the current topic, go to Earth's Fresh Water.

Earthquakes and Volcanoes is the 2009 and 2010 topic for Dynamic Planet.

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Overview

The topic for this event varies from year to year, so in an effort to retain useful content for when topics cycle back in, yearly topics will be set up as sections within the page.

Links

GMOA Notes

General Dynamic Planet notes

Earthquake Notes

Earthquake Notes2

Crave the Wave (seismic wave section)

General Advice

A good way to start studying this event is by reading Earth Science, Ecology, and Weather books. Simple as they are, it might be worth your time to start with the Macmillan books. Their 'Dynamic Earth' gives you a background on earth science if you know little or none to start with. Learning some plate tectonics basics and information on ocean floor spreading out of this book will only take you a few minutes.

Demystified and For Dummies books are good to start out. They usually simplify the topics, but give a good overview of the material. College textbooks are best to use to prepare for state or regional competitions, because usually it is a college professor writing the test, and they will base it off a textbook. Cheap textbooks can be found at Amazon.com, Abebooks.com. Half-priced books are at Ebay and at library book sales. Also, a general geology textbook seems to have most of the stuff listed in the rules.

For topics which are not covered by these books, Wikipedia is a good souce of information.

For 2009 and 2010 only one 8.5" by 11" sheet of paper, front and back will be allowed as a resource. Therefore, you should be careful of what you put on the sheet. Only put on what you need. Don't waste space with information that you have memorized. It is advised to type the notesheet and to have important vocabulary and information highlighted.

Earthquake hazards

• Ground breaking- where the rocks are sliding past each other (slip-strike) or moving under/on top of each other (normal or reverse). Buildings or other structures built on or very close to the fault can be damaged or ripped apart by the movement of the ground.
• Ground shaking- where the ground is shaken by seismic waves. Affects areas up to 65 miles or more (depending on earthquake) from the epicenter. May cause sloshing around of bodies of water, landslides, avalanches, can liquefy soil, causing buildings to sink and utilities (water, gas, etc.) to rupture
• Subsidence- the motion of a surface as it shifts downward. This process can cause the destruction of roads, buildings, etc.
• Liquefaction- the movement of the earth mixes certain types of soil and groundwater, basically turning it into quicksand, making buildings tilt, tip over, or sink
• Ground displacements- destroys homes
• Flooding-destroys homes
• Rupture of dams and levees- Ground shaking can cause dams to crack, releasing the water being held in the resevoir and flooding a large area downstream
• Tsunamis- one giant wave crashing down onto land due to the result of an earthquake off the coast. These can cause buildings to be destroyed, they cause flooding, etc.
• Fire- Earthquakes can rupture gas lines and cause a fire; electrical lines can also snap and cause fires

Volcano Hazards

• Lahars
• Pyroclastic Flows
  • Fluid mass of rock fragments and gases
• Pyroclastic surges
  • Low density flows of pyroclast
• 3 types
  • Base
    • Base of eruption column
  • Ash cloud
    • During main eruption column
  • Ground surges
    • Base of pyroclastic flow
    • Debris avalanches landslides and tsunamis
• Lava flows
  • Least dangerous
  • Slow
  • Destruction of property
  • May produce floods
• Volcanic gases
  • C02 - Carbon Dioxide
  • S02 - Sulfur Dioxide
  • HCI - Hydrogen Chloride
  • H2S - Hydrogen Sulfide
  • CO - Carbon Monoxide
  • CH4 - Methane
  • Produce acid rain
  • Lake poisoning
• Directed Blast
  • Large area of damage
  • Very hot blast of air
  • Common

Types of eruptions

• Strombolian
  • Huge clots of molten lave
  • Luminous arcs
  • Can/has been used to describe many different types of eruptions
• True stombolian
  • Short explosive outbursts of pasty lava
  • No eruption Columns
  • Ejects Bombs
  • No Peles tears/hair
  • Little or no flowing lava
  • A'a flows common
  • Can form from a Funarole

• Vulcanan
  • Dense ash laden clouds
  • High rising eruption column
• Peleon or Nuee Ardente
  • Large amount of gas
  • Glowing pyroclatic flow

• Hawaiian
  • Incandescent lava spurts
  • Calmest eruptions
  • Long eruptions
  • Fire fountains

• Pilian (or vesuvian)
  • Volatile rich dactia lava
  • Variable duration
  • Longest eruption with felsic lava types
  • Large eruption columns
  • Dangerous

• Lava lakes
  • Lava forms ponds or lakes in vents craters or depressions
  • The longest lasting lava lake was in the Halemaumau crater from 1823 to 1924

Volcanoes and Climate Change

• Two thing that can be changed
  

  VEI
  • Dust veil Index (DVI)
    • Estimation of dust in air
  • Volcanic explosivity index (VEI)
• Volcanic eruptions emit two (major) things
  • Tephra
  • volcanic gases
• Eruptions can spew large amount of gasses into the atmosphere, these gasses contribute to a concept know as global cooling. Where the gas particles reflect sunlight before it even reaches Earth's surface. Global cooling can help offset Global Warming, and has been know to induce periods of cooling.
• Negative Factors
  • Major solar radiation change
  • Changes in El Nino and southern ossilation

Tsunamis

• Tsunamis
  • Generated when sea floor abruptly changes
  • When it approaches shore
    • Slows
    • Grows
    • Erodes

What is an earthquake?

• A vibration of the earth produced by rapid release of energy.
• Energy radiates out from focus
• Focus is where the rock breaks creating an earthquake
• Energy moves outward from focus in seismic waves

What causes the rock to break? Stress-a force or pressure acting on a rock Types of stress

1. Compression (fault type- reverse)
2. Tensional (fault type- normal)
3. Shear (fault type- strike-slip)

Strain-the result of stress of deformation

• Elastic deformation-when stresses are removed,rock returns to original shape
• Plastic deformation-permanent deformation. when stress is removed rocks stay bent
• Rupture-breakage and fracturing of the rock causing an earthquake.

brittle materials break during elastic deformation

Seismograph

Sample of a Siesmograph

Seismograph

• A fault is a break or crack in the rock along which movement has occurred.
• movement along the fault produces earthquakes and seismic waves.
• A seismograph detects seismic waves.
• First seismograph developed by the Chinese about 2000 years ago.
• Invented by Zhang Heng

Modern seismographs are normally electronic

• Basic components
  • Drum with paper
  • Bar with two hinges
  • Weight
  • Pen

The bar is attached to the weight, which is on the pen. when there is an earthquake The vibrations move the paper creating a record of the earthquake

seismograph

Houfeng Didong Yi

Houfeng Didong Yi was the name given to the first seismoscope. Houfeng Didong Yi was created by Zhang Heng in 132 CE. According to the Book of the Later Han (a compilation of Chinese Historical works by Fan Ye) Houfeng Didong Yi was bronze, had a radius of approximately 1 meter, and had 8 dragons spaced on its top, each holding bronze balls.

When there was a earthquake/tremor the ball would fall from the dragons mouth to the mouth of the toad below making noise. The dragon who's ball fell out would indicate the direction from which the earthquake came.

A replica of what Houfeng Didong Yi would have looked like according to Historical Sources

Types of Seismic Waves

• Body waves
  • P-waves- have the same motion as sound waves (as they spread out, P-waves alternately push (compress) and pull (dilate) the rock). P-waves can travel through both solids and liquids. In most earthquakes, the P waves are felt first. (The effect is similar to a sonic boom.)

• • S-waves- shear the rock at right angles to the direction of travel. S waves cannot travel through liquid because if a liquid is sheared sideways or twisted, it will not spring back. After the P-waves, the S waves arrive with their up-and-down and side-to-side motion, shaking the ground surface vertically and horizontally, causing the wave motion that is damaging to structures.

• Surface waves (l-waves)- Two types: Love waves and Rayleigh waves. Can only affect areas of the ground near the surface, hence the name.
  • Love waves- have the same motion as S waves but without the vertical movement. Love waves move the ground from side to side horizontally at right angles to the direction of travel. The horizontal shaking is damaging to the foundations of structures.
  • Rayleigh waves- move both vertically and horizontally, like ocean waves. Rayleigh waves generally travel slower than Love waves.

Detection in Seismographs

• The arrivals of the different seismic waves can be observed in a seismograph.
  • Small oscillations representing P waves arrive first.
  • Larger S waves show next.
  • Largest surface waves arrive last.

• This helps to find the epicenter of an earthquake.
  • You can subtract the time between the P and S waves, and this corresponds to distance on a special chart.
  • This is then compiled with three or more values from other stations that recorded the tremor.
  • The distances from these stations is a circle representing all of the possible locations the epicenter could be in.
  • Where the circles from the stations meet is the location of the epicenter.

Hazards

1. Ground motion-shaking of the ground, depends on

• Local geological positions such as loose unconsolidated sediment which is worst
• Size
  • Distance from epicenter farther away the less damage
• Construction
  • Concrete structures are brittle and will damage more easily
  • Wood and steel less are susceptible to damage

1. Faulting and Ground Rupture-occurs along the fault zone that moves during an earthquake
2. After Shocks- dangerous because they can further collapse structures that are damages
3. Fire- started by power lines,gas lines rupturing. more dangerous in the water lines break
4. Landslides-quakes may trigger landslides
5. Liquefaction- turning the ground into a substance similar to a liquid which will make structures sink
6. Changes in ground level
7. Tsunamis-giant ocean waves
8. Flooding-may be due to rupture of dams and levees

Glossary

This is a basic glossary of terms that I have been compiling.

Aa: A blocky and fragmented form of lava occurring in flows with fissured and angular surfaces.

Batholith: A great irregular mass of coarse-grained igneous rock with an exposed surface of more than 100 square kilometers, which has either intruded the country rock or been derived from it through metamorphism.

Block fault: A structure formed when the crust is divided into blocks of different elevation by a set of normal faults.

Caldera: A large, circular depression in a volcanic terrain, typically originating in collapse, explosion, or erosion.

Central vent: The largest vent of a volcano, situated at the center of its cone.

Cinder cone: A steep, conical hill built up about a volcanic vent and composed of coarse pyroclasts expelled from the vent by escaping gases.

Density: The mass per unit volume of a substance, commonly expressed in grams/ cubic centimeter.

Earthquake: The violent oscillatory motion of the ground caused by the passage of seismic waves radiating from a fault along which sudden movement has taken place.

Elastic rebound theory: A theory of fault movement and earthquake generation that holds that faults remain locked while strain energy accumulates in the country rock, and then suddenly slip and release this energy.

Epicenter: The point on the Earth's surface directly above the focus or hypocenter of an Earthquake.

Fault: A planar or gently curved fracture in the Earth's crust across which there has been relative displacement.

Fault-block mountain: A mountain or range formed as a horst when it was elevated between parallel normal faults.

Fault plane: The plane that best approximates the fracture surface of a fault.

Flood basalt: A plateau basalt extending many kilometers in flat, layered flows originating in fissure eruptions.

Focus (earthquake): The point at which the rupture occurs; synonymous with hypocenter.

Fold: A planar feature, such as a bedding plane, that has been strongly warped, presumably by deformation.

Fumarole: A small vent in the ground from which volcanic gases and heated groundwater emerge, but not lava.

Hypocenter: The point below the epicenter at which an earthquake actually begins; the focus.

Igneous rock: A rock formed by congealing rapidly or slowly from a molten state.

Intrusion: An igneous rock body that has forced its way in a molten state into surrounding country rock.

Intrusive rock: Igneous rock that is interpreted as a former intrusion from its cross-cutting contacts, chilled margins, or other field relations.

Isostasy: The mechanism whereby areas of the crust rise or subside until the mass of their topography is buoyantly supported or compensated by the thickness of crust below, which "floats" on the denser mantle. The theory that continents and mountains are supported by low-density crustal "roots."

Joint: A large and relatively planar fracture in a rock across which there is no relative displacement of the two sides.

Laccolith: A sill-like igneous intrusion that forces apart two strata and forms a round, lens-shaped body many times wider than it is thick.

Lahar: A mudflow of unconsolidated volcanic ash, dust, breccia, and boulders mixed with rain or the water of a lake displaced by a lava flow.

Lava: Magma or molten rock that has reached the surface.

Lava tube: A sinuous, hollow tunnel formed when the outside of a lava flow cools and solidifies and the molten material passing through it is drained away.

Left-lateral fault: A strike-slip fault on which the displacement of the far block is to the left when viewed from either side.

Lithosphere: The outer, rigid shell of the Earth, situated above the asthenosphere and containing the crust, continents, and plates.

Magma: Molten rock material that forms igneous rocks upon cooling. Magma that reaches the surface is referred to as lava.

Magma chamber: A magma-filled cavity within the lithosphere.

Magnitude: A measure of earthquake size, determined by taking the common logarithm base 10) of the largest ground motion observed during the arrival of a P-wave or seismic surface wave and applying a standard correction for distance to the epicenter.

Mantle: The main bulk of the Earth, between the crust and core, ranging from depths of about 40 to 3480 kilometers. It is composed of dense mafic silicates and divided into concentric layers by phase changes that are caused by the increase in pressure with depth.

Mesophere: The lower mantle.

Mohorovic discontinuity: The boundary between crust and mantle, marked by a rapid increase in seismic wave velocity to more than 8 kilometers per second. Depth: 5 to 45 kilometers. Abbreviated "Moho" or "M-discontinuity."

Monocline: The S-shaped fold connecting two horizontal parts of the same stratum at different elevations. Its central limb is usually not overturned.

Normal fault: A dip-slip fault in which the block above the fault has moved downward relative to the block below.

Oblique-slip fault: A fault that combines some strike slip motion with some dip-slip motion.

Outgassing: The release of juvenile gases to the atmosphere and oceans by volcanism.

Pahoehoe: A basaltic lava flow with a glassy, smooth, and undulating, or ropy, surface.

P-wave: The primary or fastest wave traveling away from a seismic event through the solid rock, and consisting of a train of compressions and dilations of the material.

Right-lateral fault: A strike-slip fault on which the displacement of the far block is to the right when viewed from either side.

Sea-floor spreading: The mechanism by which new sea floor crust is created at ridges in divergence zones and adjacent plates are moved apart to make room. This process may continue at 0.5 to 10 centimeters/year through many geologic periods.

Seismic refraction: A mode of seismic prospecting in which the seismic profile is examined for waves that have been refracted upward from seismic discontinuities below the profile. Greater depths may be reached than through seismic reflection.

Seismic surface wave: A seismic wave that follows the earth's surface only, with a speed less than that of S-waves. There are Raleigh waves (forward and vertical vibrations) and Love waves (transverse vibrations).

Stratovolcano: A volcanic cone consisting of both lava and pyroclastic rocks, often conical.

Stress: A quantity describing the forces acting on each part of a body in units of force per unit area

Strike-slip fault: A fault whose relative displacement is purely horizontal.

Subduction zone: A dipping planar zone descending away from a trench and defined by high seismicity, interpreted as the shear zone between a sinking oceanic plate and an overriding plate.

S-wave: The secondary seismic wave, traveling slower than the P-wave, and consisting of elastic vibrations transverse to the direction of travel. It cannot penetrate a liquid.

Syncline: A large fold whose limbs are higher than its center; a fold with the youngest strata in the center.

Thrust fault: A dip-slip fault in which the upper block above the fault plane moves up and over the lower block, so that older strata are placed over younger.

Transform fault: A strike-slip fault connecting the ends of an offset in a mid-ocean ridge. Some pairs of plates slide past each other along transform faults.

Tsunami: A large destructive wave caused by sea-floor movements in an earthquake.

Volcanic ash: A volcanic sediment of rock fragments, usually glass, less than 2 millimeters in diameter that is formed when escaping gases force out a fine spray of magma.

Volcanic block: A pyroclastic rock fragment ranging from about fist- to car-sized.

Volcanic bomb: A pyroclastic rock fragment that shows the effects of cooling in flight in its streamlined or "bread-crust" surface.

Volcanic cone: The deposit of lava and pyroclastic materials that has settled close to the volcano's central vent.

Volcanic dome: A rounded accumulation around a volcanic vent of congealed lava too viscous to flow away quickly; hence usually rhyolite lava.

Volcanic ejecta blanket: A collective term for all the pyroclastic rocks deposited around a volcano, especially by a volcanic explosion.

Volcanic emanations: Gases, especially steam, emitted from a vent or released from lava.

Volcanic glass: Can refer to either Obsidian or Pumice.

Volcanic pipe: The vertical chamber along which magma and gas ascend to the surface; also, a formation of igneous rock that cooled in a pipe and remains after the erosion of the volcano.

Volcano: Any opening through the crust that has allowed magma to reach the surface, including the deposits immediately surrounding this vent.

Links

Student Center's Earth Science Study Sites - lots of links

Frank Potter's Science Gems - Earth Science II

TWC - Weather Glossary - Yes, the folks at the Weather Channel actually have a good site with an amazing list of terms.

New York Coaches Conference

Earth Quake Map

US Geological Survey

USGS Photo Glossary of Volcanic Terms

Michigan Tech UPSeis program

Earth and Environmental Systems podcast, look for episodes 3-13

Black Hawk College Physical Geography course

http://facweb.weber.edu/bdattilow/shknbk/notes/fltstlds.htm possibly dead link

http://www.onep.go.th/tsunamis/Tsunamis_Eng/menu1.asp another possibly dead link

Robotman's page used for the event Compute This

USGS Volcanoes

San Diego State Volcano site

A good site for practice in finding epicenters