End Daily Review #5 What 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 Boundaries Plate separate Continental Oceanic Filled by magma Volcano Continental Rift valley Oceanic Mid-ocean ridges Rift zone = deep cracks between separating plates Magma fills rift cracks due to lower density it rises up, cools and forms new crust African rift video: watch section 2

Nonexplosive Volcanoes Common near divergent boundaries Most common Produce Calm lava flows Huge amounts of lava Examples Hawaii Current eruption Not divergent boundary Ocean floor – mid ocean ridge

Hot Spots Examples Volcanically active Far from plate boundary Theories Mantle plumes Cracks in crust Move over time Due to plate movement

Yellowstone Supervolcano video http://www.photovolcanica.com/VolcanoInfo/Yellowstone/Yellowstone.html Yellowstone http://www.theepochtimes.com/n3/834488-yellowstone-volcano-eruption-effects-entire-world-would-be-at-risk-if-supervolcano-erupts/ Supervolcano video

Daily Review #6 How 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? End

Transform Boundary Plates slide past each Not usually smooth Larger, more frequent earthquakes Transform boundary: plates are sliding at angles past each other Not smooth, gets stuck, builds up pressure and eventually releases that pressure in large bursts creating large earthquakes Images are of the San Andreas Fault – one on the right is of an orchard where the rows shifted due to earthquakes over the years

Earthquakes What are they? What is it like? Seismologist Where? Plate boundary Rarely in middle of continent Occur at and create faults Varying depths Focus Epicenter Ask for student examples of experiences with earthquakes, tell of personal experiences Seismologists study earthquakes Most occur at plate boundaries especially transform boundaries New Madrid fault in middle of North American plate, 1811 earthquake, changed flow of Mississippi, evidence under river of previous faults Earthquakes occur at or create faults (cracks) of varying lengths and depths Can occur within 1 km of the surface or deeper than 300km Focus = where the earthquake originated Epicenter = surface location of the focus, usually what is referred to in the media because it is a physical location on the map

What causes an earthquake? Plates move Tension builds Energy released Travel as waves Rocks return to original shape, but different locations Some 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 scale Strength (magnitude) Measuring ground motion Used by the media Moment magnitude More precise Measures the energy released Measured at the epicenter Used by scientists Richter 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 1 An earthquake will have similar richter scale and moment magnitude numbers Strongest recorded quake = 9.5, Chile 1960, strength of 1 billion tons of TNT

Largest Recorded Earthquakes Recent earthquakes

Imaging of Earthquake Waves Seismograph Shows local movement 3 main waves P wave S wave Surface waves

Earthquake Waves P waves S waves First detected Back-and-forth Side-to-side Slower, arrive later Body waves = deeper below the surface; p and s waves All 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 crust P waves: pressure or primary, arrives first, produces a forward/backward motion, longitudinal wave like a slinky, momentarily deforms the rock S waves: secondary, moves side to side like an ocean wave, slower and arrive later

Surface Aftershocks Foreshocks Rolling Side-to-side Slowest More destructive Aftershocks Foreshocks 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 longest Aftershocks 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 situations Foreshocks are smaller earthquakes that occur before the major one, used as indicators that a major earthquake is about to occur Photo: highway overpass in Japan after 2011 earthquake

Finding the Epicenter Distance vs. time graph is constant Closest has smallest time difference Measure time difference on local seismograph Compare to graph Find distance Repeat for multiple locations Chinese 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 fell

Finding Epicenter cont. Use distances found Draw a circle from each site Overlap = epicenter

Daily 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? End

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

Earthquake Prediction Not exact Seismic gaps Area of fewer earthquakes Likely location of future earthquake Tension building Used to predict 1989 San Francisco Also use past frequency Earthquake 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 earthquakes Gap hypothesis : seismic gaps likely to have strong earthquakes in the future Gap 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 6.9 Past 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 Earthquakes Liquefaction Mixing soil with underground water Sinkholes Landslides Fire Broken gas and electrical lines Lack water to fight Building 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 down Landslides occur as unstable ground is shaken loose Fire from broken gas and electrical lines is made worse by the lack of water to fight the fires caused by broken water lines Building and highway damage caused by the shaking

Tsunami Closer to shore Slows Increases in height Causes Massive waves Underwater earthquake - ocean floor movement Landslides Volcanic eruptions Massive waves Closer to shore Slows Increases in height Tsunami means harbor wave Can travel as fast as 600 mph which is as fast as a jet plane, generally traveling at around 35mph when it hits land Largest ever recorded was 1700 ft high in 1958 in Alaska and only 2 people died 80% occur in the Ring of Fire The backwash from the tsunami is sometimes more dangerous and powerful pulling people and items out into the ocean Looks like a wall of water, does not break or curl like regular ocean waves

Tsunami warning system Only a few a year Most 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 somewhere Japan 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 damage Seiche is a tsnumai that occurs in a lake, similar to when you get into a bathtub and water sloshes around, this occurred at Quake Lake Indonesia: 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 quake

Daily Review #8 How 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?