The Dynamic Crust Topic 12
Principle of Original Horizontality: The assumption that sedimentary rocks form in horizontal layers. Drawing: Then how do you explain this?
Evidence of Crustal Change Folding, faulting, tilting of rock strata (layers) Drawings: Displaced rocks and fossils Volcanoes/ Earthquakes
“Continental Drift”- Alfred Wegener Theory: the continents are sliding across the Earths’ surface. Evidence: Shape of the continents. Warm water fossils in Greenland. Similar rocks and fossils Similar mountain ranges Pangea- “All lands”
Pangea
Pillow Lavas
Plate Tectonics Theory: Earth’s crust is made up of a variety of plates that are moving.
Divergent Sea floor spreading Alfred Wegener Plate tectonics Volcano Convergent Mid ocean ridge Transform Boundary Mantle Convection Currents Trench Subduction
Mid Ocean Ridge Underwater mountain range that wraps around the Earth Evidence of Sea Floor Spreading 1.Age of rocks 2.Temperature of Rocks 3.Basalt Pillow lavas (igneous extrusive) 4.Paleomagnetism
Drawing:
Crustal plates move due to convection currents in the Earth’s mantle (asthenosphere)!!!
Plate Boundaries Oceanic Crust Thinner More dense basaltic Continental Crust Thicker Less dense granitic Vs.
Convergent Boundaries 1.Oceanic – Continental Drawing Features E-quakes Volcanoes Trenches Mountains Examples: South America Cascades
2.Oceanic – Oceanic Drawing Features E-quakes Volcanoes Trenches Mountains Examples: Japan Aleutian Islands (Alaska)
3.Continental – Continental Drawing Features E-quakes Mountains Volcanoes (extinct) Examples: Himalayas
Divergent Boundaries: 1.Mid Ocean Ridges 2.Rift Zones
Transform Boundary: Boundary where plates slide by each other. Drawing: Example: San Andreas Fault
“Hot Spots” Regions of volcanic (magmatic) activity usually away from plate edges. Example: Hawaii
Earthquakes, volcanoes and mountains are usually associated with plate boundaries.
BONUS: What is the relationship between the distance a planet is from the Sun and the gravitational force between the planet and the Sun?
Earthquakes The shock wave produced by the sudden movement of rocks in the Earth’s crust. Seismograph- instrument used to detect and record earthquake waves.
Focus- point below the surface where the earthquake originates. Epicenter- point at the Earth’s surface directly above the focus.
Seismic Waves Primary Waves “P-Waves” Compressional waves Faster Travel through liquids and solids Secondary Waves “S-Waves” Transverse waves. Slower Travel through solids only!
The difference between the P & S wave arrival times can be used to calculate the distance from the epicenter. To find the epicenter, one must find the distance from at least 3 seismic stations.
Earth’s Interior: See diagram p. 10 in the Earth Science Reference Tables. Evidence: Seismic Data Meteor Composition Earths Magnetic Field Moon Composition
Earthquake Damage Depends on… Magnitude of the earthquake Distance from the epicenter Building structure Type of surface Richter Scale vs. Mercalli Scale
Brain teaser A seismic station is located 5,200 km away from the epicenter of an earthquake. What will be the difference in the arrival time between the P and S waves at this station?
Earthquake Emergency Planning Individual- “Drop, Cover and Hold” Drop down under strong object (desk, table) Cover your eyes Hold onto the strong object you are under. Earthquake drills Have emergency supplies on hand. Do not try to run out of buildings!!!
Earthquake Emergency Planning Community Proper planning of building sites Proper building construction Retrofitting older buildings to make them safer
Tsunami Large wavelength ocean wave produced by disruption of the ocean floor.
Volcanoes A mountain composed of igneous extrusive rock. Violent Eruptionsvs. Non-Violent Eruptions Mt. St. HelensHawaii
BONUS: What was the name of the scientist who developed the Theory of Continental Drift?
BONUS: The epicenter of an earthquake is 4800 km away from a seismic station. What is the difference in arrival time of the P and S waves at that station?
In Loving Memory of Ebony