Daily Review #1

Daily Review #5What happens at a convergent boundary?What feature is formed at each type of convergent boundary?Why is a pyroclastic flow so dangerous?Would you ever live near an active volcano? Why or why not?

End

Divergent BoundariesPlate separateFilled by magmaVolcanoContinentalRift valleyOceanic Mid-ocean ridges2Rift zone = deep cracks between separating platesMagma fills rift cracks due to lower density it rises up, cools and forms new crustAfrican rift video: watch section 2

Nonexplosive VolcanoesCommon near divergent boundariesMost commonProduceCalm lava flowsHuge amounts of lavaExamplesHawaiiCurrent eruptionNot divergent boundaryOcean floor mid ocean ridge

3Hot SpotsExamplesVolcanically activeFar from plate boundaryTheoriesMantle plumesCracks in crustMove over timeDue to plate movement

Yellowstone

http://www.photovolcanica.com/VolcanoInfo/Yellowstone/Yellowstone.html

http://www.theepochtimes.com/n3/834488-yellowstone-volcano-eruption-effects-entire-world-would-be-at-risk-if-supervolcano-erupts/Supervolcano videoDaily Review #6How are convergent and divergent boundaries similar? Different?What causes a hotspot?Why do hotspots appear to move?What do you observe about this volcanic eruption? Hypothesize why this volcanic eruption is so different than most?

EndTransform BoundaryPlates slide past eachNot usually smoothLarger, more frequent earthquakes

Transform boundary: plates are sliding at angles past each otherNot smooth, gets stuck, builds up pressure and eventually releases that pressure in large bursts creating large earthquakesImages are of the San Andreas Fault one on the right is of an orchard where the rows shifted due to earthquakes over the years7EarthquakesWhat are they? What is it like?SeismologistWhere?Plate boundaryRarely in middle of continentOccur at and create faultsVarying depthsFocusEpicenter

8Ask for student examples of experiences with earthquakes, tell of personal experiencesSeismologists study earthquakesMost occur at plate boundaries especially transform boundariesNew Madrid fault in middle of North American plate, 1811 earthquake, changed flow of Mississippi, evidence under river of previous faultsEarthquakes occur at or create faults (cracks) of varying lengths and depthsCan occur within 1 km of the surface or deeper than 300kmFocus = where the earthquake originatedEpicenter = surface location of the focus, usually what is referred to in the media because it is a physical location on the mapWhat causes an earthquake?Plates moveTension buildsEnergy releasedTravel as wavesRocks return to original shape, but different locations

9Some rocks exhibit plastic behaviors which is more elastic, when under pressure it just keeps stretching and stays that shape, no earthquakes are formed (photo)Elastic rebound hypothesis= stretch to breaking point, breaks, releases energy, return to original shape

How are earthquakes measured?Richter scaleStrength (magnitude)Measuring ground motionUsed by the mediaMoment magnitudeMore preciseMeasures the energy releasedMeasured at the epicenterUsed by scientists

10Richter scale = original scale of measurement for earthquakes, still frequently used in the media, each number is a factor of 10, 2 is 10 times more powerful than 1An earthquake will have similar richter scale and moment magnitude numbersStrongest recorded quake = 9.5, Chile 1960, strength of 1 billion tons of TNT

Largest Recorded EarthquakesRecent earthquakes11Imaging of Earthquake WavesSeismographShows local movement3 main wavesP waveS waveSurface waves

12Earthquake WavesP wavesFirst detectedBack-and-forthS wavesSide-to-sideSlower, arrive later

13Body waves = deeper below the surface; p and s wavesAll waves are created at the same time when the earthquake occurred, but travel at different rates because of how they move and where they are at in the crustP waves: pressure or primary, arrives first, produces a forward/backward motion, longitudinal wave like a slinky, momentarily deforms the rockS waves: secondary, moves side to side like an ocean wave, slower and arrive laterSurfaceRollingSide-to-sideSlowestMore destructiveAftershocksForeshocks

Surface waves occur in the upper few km of the surface, 2 types = rolling and side to side (like S wave), slowest so arrives last, most destructive because it is closest to the surface and last the longestAftershocks occur after the largest earthquake and there can be many of them and sometimes they are more destructive because structures are already damaged or people are in more dangerous situationsForeshocks are smaller earthquakes that occur before the major one, used as indicators that a major earthquake is about to occurPhoto: highway overpass in Japan after 2011 earthquake14Finding the EpicenterDistance vs. time graph is constantClosest has smallest time differenceMeasure time difference on local seismographCompare to graphFind distanceRepeat for multiple locations

15Chinese earthquake detector, 132 ce, bronze urn with 6 dragons heads holding bronze ball in mouth, pendulum inside urn, in a tremor pendulum strikes urn causing a ball to fall into mouth of a toad below, creates a large noise, could supposedly tell where earthquake was by which ball fellFinding Epicenter cont.Use distances foundDraw a circle from each siteOverlap = epicenter

16Daily Review #7

Which type of boundary do you think has a bigger impact on its surrounding environment? Why?What is an epicenter and how is it found?What kind of damage can an earthquake cause and how do you think we could prevent that damage?

If the P wave from an earthquake arrives at 10:45 am and the S wave arrives 10:55 am, how far are you from the epicenter?

EndEarthquake Hazard Map

18Hazard: how likely a damaging earthquake to occur in an area, determined by past and present earthquake activity

Earthquake PredictionNot exactSeismic gapsArea of fewer earthquakesLikely location of future earthquakeTension buildingUsed to predict 1989 San FranciscoAlso use past frequency

19Earthquake prediction is not and probably will never be perfect (able to predict exact size, time and location of an earthquake)Seismic gaps areas in an active fault that have relatively few earthquakesGap hypothesis : seismic gaps likely to have strong earthquakes in the futureGap identified in 1988 predicted a 30% chance of at least a 6.5 earthquake in that area; Loma Prieta earthquake occurred in 1989 and measured 6.9Past frequency and size of earthquakes is also used to predict future earthquakes; example if an area usually has a major earthquake every 100 years, that pattern could possibly continue and if the last major earthquake was 100 years ago then one is likely to happen in that area (if the pattern continues)Destruction from EarthquakesLiquefactionMixing soil with underground waterSinkholes LandslidesFireBroken gas and electrical linesLack water to fightBuilding and highway damage

Liquefaction is created when the shaking of an earthquake causes groundwater and soil to mix liquefying the soil which creates sinkholes because liquid soil takes up less space and shrinks downLandslides occur as unstable ground is shaken looseFire from broken gas and electrical lines is made worse by the lack of water to fight the fires caused by broken water linesBuilding and highway damage caused by the shaking

20TsunamiCausesUnderwater earthquake - ocean floor movementLandslidesVolcanic eruptionsMassive wavesCloser to shoreSlowsIncreases in height

Tsunami means harbor waveCan travel as fast as 600 mph which is as fast as a jet plane, generally traveling at around 35mph when it hits landLargest ever recorded was 1700 ft high in 1958 in Alaska and only 2 people died80% occur in the Ring of FireThe backwash from the tsunami is sometimes more dangerous and powerful pulling people and items out into the oceanLooks like a wall of water, does not break or curl like regular ocean waves21Tsunami warning systemOnly a few a yearMost recent (major)Indonesia (Dec. 2004)Japan (Mar. 2011)Seiche

Tsunami warning system: series of buoys out in the Pacific Ocean (where most tsunamis occur), monitor ocean height especially after a major earthquake somewhereJapan 2011: created a wave 131ft. high in some areas, killed over 15,000 people (some not directly from the wave), will cost $232 billion to rebuild and repair all the damageSeiche is a tsnumai that occurs in a lake, similar to when you get into a bathtub and water sloshes around, this occurred at Quake LakeIndonesia: killed over 200,000 people in 14 countries, earthquake was 9.0 located entirely under the ocean, land moved over 30 feet because of this quake22Daily Review #8How are earthquakes created?How are P, S and surface waves similar? Different?What is a tsunami and how is it made?Look at the Ring of Fire on the map below. Why is it unique and what is causing it to have those features?