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GEOLOGY I LIKE TO MOVE IT MOVE IT Part 1 Age of Earth and scientific classification Part 2 Plate tectonics and water 1

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CONTINENTAL DRIFT

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Theory 1912 Alfred Weagner proposed the theory that Earth's crust is slowly drifting on a liquid core. His theory was not accepted in his lifetime...but now there is a lot of evidence National Geographic Continental Drift http://www.youtube.com/watch?v=3uBcq1x7P34

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Pangea 250 million years ago

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Evidence Fit of continents

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Evidence Distribution of rocks & mountains

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Evidence -Paleoclimates- Rocks deposited at the Earth's surface (sedimentary) reflect the climate and latitude of which they form -Glacial sediments -Fossils

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Plate Movement Plates of lithosphere are moved around by the underlying hot mantle convection cells

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Spreading ridges As plates move apart new material is erupted to fill the gap Effect: Underwater mountains Divergent Boundaries

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Age of Oceanic Crust Courtesy of www.ngdc.noaa.gov

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Evidence:Earths Magnetic Field Movement of Fe (l) in the outer core as the planet rotates. Behaves like permanent magnet near center of Earth Magnetic north (compass measures) differs from geographic north of planets axis of rotation.

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How can it be monitored? Basaltic lava with iron minerals act like compasses. When they cool, they are magnetized in the direction of the surrounding magnetic field. Paleomagnetism = Study of ancient magnetism

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Earth s Magnetic Field http://nsdl.org

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BUT..Magnetic North is NOT at the North Pole http://nsdl.org

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ANDthe Magnetic Field Reverses Field reverses ~1 time every 200,000 years on average. 400 times in last 330 million years. Last reversal was 780,000 years ago. NORMALREVERSE

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WHICH FAULT IS AT FAULT?!

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What is a fault? A fault is a fracture in the Earth's crust that occurs when stress is applied to quickly or when stress is too great. It can be either vertical or horizontal A vertical fault is comprised of a footwall and a hanging wall

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Normal Fault Tension pulls rocks apart causing the hanging wall block to be pulled down. Normal does not mean most common! Why do you think it is called a normal fault? At what type of plate boundary do normal faults occur?

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Reverse Fault Opposite of the normal fault Compression pushes rocks together and causes the hanging wall to be pushed up At what plate boundary do reverse faults occur?

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Strike-Slip Fault A strike-slip fault happens when rocks slide past each other (shearing) Moves left or right laterally with very little horizontal movement At which plate boundary do strike slip faults occur? What is a common example of a strike slip fault?

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The Himalaya Mountains contain many of these faults.

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EARTHQUAKES

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Earthquakes Earthquake is the vibration of Earth caused by a rapid release of energy Often caused by slippage along a break in Earths crust Focus & Epicenter Focus is point w/in Earth where earthquake starts Energy is released in waves Epicenter is location on surface directly above the focus

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Faults Earthquakes are usually associated w/large fractures in Earths crust & mantle called faults Faults are fractures in Earth where movement has occurred

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Causes of Earthquakes Scientists studied 1906 San Francisco quake along San Andreas fault Some areas moved 4.7 m on one side of fault compared to the other Hypothesis was developed force causes rocks to bend & store elastic energy, eventually friction which holds rocks together is overcome, rocks slip at the weakest point (focus) releasing energy allowing rocks to return to original shape

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Elastic rebound hypothesis Explains that when rocks are deformed, they bend then break, releasing stored energy Most earthquakes are produced by the rapid release of elastic energy stored in rock that has been subjected to great forces When strength of rock is exceeded, it suddenly breaks, causing vibrations of an earthquake

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Aftershocks & foreshocks Aftershocks are smaller earthquakes produced after a major earthquake Foreshocks are small earthquakes produced before a major earthquake; can be days or years before quake

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Earthquake waves Surface waves Travel along Earths outer layer Move up-down & side-to-side Causes ground & anything on it to move Most destructive AKA L waves or Rayleigh waves

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Body waves P waves Push-pull waves Compression waves Change volume of material they pass through Earthquake waves

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S waves Most particles @ right angles to their travel Transverse waves Change shape of material they pass through, SOLIDs only Earthquake waves

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Seismogram shows all 3 types of waves P waves arrive first fastest traveling S waves arrive second Surface waves (L waves) arrive last slowest traveling Earthquake waves

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Locating an Earthquake Compare arrival times of P & S waves Greater the difference = greater distance to focus Earthquake distance Developed using seismograms from earthquakes w/identifiable epicenters 2 steps 1. Find time interval btwn 1 st P wave & 1 st S wave 2. Find on travel-time graph the equivalent time spread btwn P & S wave curves

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Earthquake direction Travel-time graphs from 3 or more seismographs can be used to find exact location of earthquakes epicenter Draw circle w/diameter in distance, where they intersect = epicenter

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Earthquake zones 95% of earthquakes occur in narrow zones Most on outer edge of Pacific called circum-Pacific belt Second belt Mediterranean-Asian belt

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TSUNAMIS

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Tsunamis Wave caused by earthquake on ocean floor Causes of tsunamis Slab of ocean floor is displaced vertically along a fault Vibration can also set an underwater landslide into motion Waves travel 500-950 km/hr Height in ocean is less than 1m but can reach 30m when it hits land

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Tsunami warning system Tsunami warning center in Honolulu HI Receives info about large earthquakes in Pacific Use water level in tide gauges Warnings are issued w/in 1 hr of report Only 1-2 destructive tsunamis per year

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Other Dangers Landslides Greatest damage to structures is from landslides & ground subsidence, or sinking of ground triggered by the vibrations Fire Start when theres damage to gas & electric lines

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Emergency Situations What should you do in a Tsunami? Follow the evacuation order issued by authorities and evacuate immediately. Take your animals with you. Move inland to higher ground immediately. Pick areas 100 feet (30 meters) above sea level or go as far as 2 miles (3 kilometers) inland, away from the coastline. If you cannot get this high or far, go as high or far as you can. Every foot inland or upward may make a difference. Stay away from the beach. Never go down to the beach to watch a tsunami come in. If you can see the wave you are too close to escape it. CAUTION - If there is noticeable recession in water away from the shoreline this is nature's tsunami warning and it should be heeded. You should move away immediately. Save yourself - not your possessions. Remember to help your neighbors who may require special assistance - infants, elderly people, and individuals with access or functional needs.

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Emergency Situations What should you do in an Earthquake? If Indoors DROP to the ground; take COVER by getting under a sturdy table or other piece of furniture; and HOLD ON until the shaking stops. If there isnt a table or desk near you, cover your face and head with your arms and crouch in an inside corner of the building. Stay away from glass, windows, outside doors and walls, and anything that could fall, such as lighting fixtures or furniture. If Outdoors Stay there. Move away from buildings, streetlights, and utility wires. Once in the open, stay there until the shaking stops. The greatest danger exists directly outside buildings, at exits and alongside exterior walls.

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VOLCANOES Vulcan- Roman God of Fire

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What is a volcano? Volcano- Areas of earths surface through which magma and volcanic gases pass Volcano comes from the Roman word Vulcan, which means fire

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Whats inside a volcano? MMagma Chamber- molten rock that feeds a volcano VVents- cracks in the crust WWhat is the difference between magma and lava?

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Types of Volcanoes Shield Volcano a) Built from layers of lava b) Non-explosive eruptions c) Not very steep, but can be big

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Types of Volcanoes Cinder Cone Volcano a) Built from pyroclastic material b) Moderately explosive, short eruptions c) Small in size, steep slopes

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Types of Volcanoes Composite Volcanoes a) Most common type b) Explosive eruptions and lava flow c) Built from pyroclastic material AND lava

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Types of Volcanoes

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VOLCANIC ERUPTIONS AND HAZARDS

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What is a volcano? Magma Chamber- molten rock that feeds a volcano Vents- cracks in the crust (chimney) What is the difference between magma and lava? vent cone magma chamber conduit

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How and why do volcanoes erupt? Hot, molten rock (magma) is buoyant (has a lower density than the surrounding rocks) and will rise up through the crust to erupt on the surface. Same principle as hot air rising, e.g. how a hot air balloon works When magma reaches the surface it depends on how easily it flows (viscosity) and the amount of gas (H 2 O, CO 2, S) it has in it as to how it erupts. Large amounts of gas and a high viscosity (sticky) magma will form an explosive eruption! Think about shaking a carbonated drink and then releasing the cap. Small amounts of gas and (or) low viscosity (runny) magma will form an effusive eruption Where the magma just trickles out of the volcano (lava flow).

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Explosive Eruptions Mt. Redoubt Explosive volcanic eruptions can be catastrophic Erupt 10s-1000s km 3 of magma Send ash clouds >25 km into the stratosphere Have severe environmental and climatic effects Hazardous!!! Above: Large eruption column and ash cloud from an explosive eruption at Mt Redoubt, Alaska

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Three products from an explosive eruption Ash fall Pyroclastic flow Pyroclastic surge Explosive Eruptions Pyroclastic flows on Montserrat, buried the capital city.

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Direct measurements of pyroclastic flows are extremely dangerous!!!

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Effusive Eruptions Effusive eruptions are characterised by outpourings of lava on to the ground. Hawaii Courtesy of www.swisseduc.ch

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Pyroclastic flow Lahars/Mud flows Pyroclastic fall Lava flow Noxious Gas Earthquakes Volcanic Hazards Courtesy of www.swisseduc.ch

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Pyroclastic Flow Hot, fast moving, high particles concentration flows of gas, rock and ash For example, eruption of Vesuvius, Italy in 79 AD destroyed the city of Pompeii

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Pompeii (79AD) On August 24, 79AD Mount Vesuvius literally blew its top, erupting tonnes of molten ash, pumice and sulfuric gas miles into the atmosphere. Pyroclastic flows flowed over the city of Pompeii and surrounding areas.

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Pompeii (79AD) Pyroclastic flows of poisonous gas and hot volcanic debris engulfed the cities of Pompeii, Herculaneum and Stabiae suffocating the inhabitants and burying the buildings.

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Pompeii (79AD) The cities remained buried and undiscovered for almost 1700 years until excavation began in 1748. These excavations continue today and provide insight into life during the Roman Empire.

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Vesuvius today Vesuvius remains a hazardous volcano with heavily populated flanks: around 1.5 million people live in the city of Naples alone Naples is situated approx. 30 km from Vesuvius Pyroclastic flows can flow up to 100 km from source! Bay of Naples Vesuvius Naples Courtesy of www.swisseduc.ch

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An eruption of Mt Pele in 1902 produced a pyroclastic flow that destroyed the city of St. Pierre. beforeafter Mt Pele, Martinique (1902)

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29,000 people died. Only 2 survived! Why?

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Pyroclastic Flow - direct impact Courtesy of www.swisseduc.ch

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Pyroclastic Fall Ash load Collapses roofs Brings down power lines Kills plants Contaminates water supplies Respiratory hazard for humans and animals

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Lava Flow It is not just explosive volcanic activity that can be hazardous. Effusive (lava) activity is also dangerous.

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Earthquakes Large volumes of magma moving through the shallow crust can cause large earthquakes. This can lead to building collapse, slope failure and avalanches

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So. How do we minimize the risk of active volcanoes?

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*Volcano Monitoring Volcano Observatories are set up on all active volcanoes that threaten the human population. These are designed to monitor and potentially to predict the eruptive behaviour of the volcano in question.