GEOS 212 1st EditionFinal Exam Study Guide Lectures: 1 - 25The questions will take advantage of: - content from slides or videos or maps or diagrams we have seen/used in class or HW - simple velocity calculations (no measuring required) - content from HW#1-3Lecture 1: Ocean basins- Characteristics of layers in Earth (crust, mantle, lithosphere, asthenosphere diagram) CRUST: part of chemical layeringMANTLE: part of chemical layeringLITHOSPHERE: Strong, solid = Plates= crust plus uppermost mantle. ASTHENOSPHERE: Weak but NOT MOLTEN = Rest of mantle and coreDiagram- Thicknesses of continental crust and oceanic crustCONTINENTAL: 30kmOCEANIC: 7kmLecture 2: Spreading Center -- factory for making oceanic crust (profile view diagram) - Height of the spreading center is 2km above surrounding sea floor- Divergent boundaries are the longest (about 28,000 miles) mountain range on Earth.Subduction zones – how removes oceanic crust and creates continental crust- Continents collide (convergent boundary). The friction of the two continents pressing against each other eventually breaks. One plate dives, or "subducts", under the other down into the athenosphere where is melts into magma which will eventually resurface at a spreading center somewhere to create new crust.Subduction zone profile view (know diagram)How magma forms- Is heated and melted in the athenosphere where it then rises to the surface to flow from volcanoes and form new crust.Lecture 3: II. History of spreading in South Atlantic, North Atlantic, Eastern Pacific, Labrador Sea, and Indian Ocean- All continents used to be together in one mass: Pangea- We can look at the oldest sea floors near mid-ocean ridges to estimate time two continents diverged.- Oldest sea floor 140mya, anything older we must estimate with other methodsIII. Rates of spreading- rate is distance / time, usually km/my or cm/yri. Distance = total length between continentsii. Time = age of oldest sea floor- The edge of the continent is usually not sea level, but the edge of the continental shelf (measure from there for calculations:IV. Pacific Plate also has chain of islands from hot spot = Hawaii!- Connection between mantle plume, hot spot, island chaini. Plate moves over hot spot, youngest island largest, eventually re-submerges as it ages and moves away from hot spot- Rate of motion calculation: distance / time, usually km/my or cm/yrV. Subduction zones in continental and oceanic settings- Oceanic crusts can subduct under either oceanic OR continental crust- Continental crust never subducts under- Subduction zones are deepest portions of ocean (Trench)- Large earthquakes generally occur hereVI. Plate tectonics is:- The most efficient way for the earth to lose heat … that’s the simple reason that plates move.VII. Early idea was that conveyor-belt convection ‘drives’ plate, but it has problems:- Problems: o 1. Cells ‘like’ to have sides of same dimensions. o 2. Upper and Lower mantle at least partially isolated. o 3. Would predict larger plates would go faster; no correlation. o 4. Spreading centers, and all plate boundaries, move with respect to each other.o 5. Hard to explain sudden changes in plate motionVIII. Some people now believe that plates slide away from ridges and toward subduction zonesIX. World Tour of subduction zones (HW review)Lecture 4Volcanoes: 1500 could erupt, ~20 erupting most of the timeVOLCANOES Occur in four tectonic settings:o Spreading centerso Hot Spotso Subduction Zoneso Continents Pulling ApartTwo main types of volcanoes:o Shield Volcanoes:o On oceanic crusto Not steep sideso Basalt (high iron); very hoto Not explosiveo Not Hazardouso Lava flows (runny)o Strato Volcanoes: o On continental crusto Steep sideso Andesite (lower iron), cooler, stifo Explosiveo Hazardouso Lava flows, ash/cinders, pyroclastic flowsDiagrams of Shield & Strato VolcanoesVideos of shield volcano eruptionso % of volcanoes below sea surface: 80%o Importance of Kilauea: Most ACTIVE, largest on eartho Temperature of lava?: 2,000 degreeso Key to forecasting eruptions? : Eruptionhistoryo Nature of magma: Hot, runny, NOT very explosiveo Nature of basalt (color, texture): Black,smooth, igneouso What else comes from volcanoes besides magma?  Magma Lava Andesite Basalt Ash Cinderso Pyroclastic flow made up of: rock, ash, gaseso Nature of andesite ash (color, texture): Porous, heterogeneous, gray, pockets of minerals o How many potentially active volcanoes?: 1,500o How many people live at risk from volcanoes? MANY (ex: san andres fault, California)- Cascade volcanoes in Oregon & Washington: Stratos for by subduction- Eruption history of the Cascade volcanoes: Cascade volcanoes are some of the most dangerous, due to their eruptive history and potential for future eruptions- Caldera eruptions: Yellowstone sits on top of four overlapping calderas. ... explosive eruptions have occurred in and near the Yellowstone calderaLecture 5- Review of volcanoes: ~1500 could erupt (dormant), ~20 erupting today - Shield volcanoes versus stratovolcanoeshazards: Strato = very hazardous, explosive; Shield = Barely hazardous and not explosiveprediction: Strato= less predictable, erratic; Shield = relatively predictable, consistantsetting : Strato = Subduction zones; Shield = Hot spots - Transform fault = 3rd type of plate boundary Two types of plates just slide past each other, not creating or destroying plate, Friction builds up and break, causing "jump" and earthquake- Atlantic example : San Andres fault- Pacific example : Haiti = edge of Caribbean plate- San Andreas fault = transform fault = North America-Pacific plate boundary - Animations of earthquake process = stick, build up stress, then slip - Earthquakes along San Andreas fault 922 earthquakes along fault in last week! Many too small too reportMagnitude threshold for detection: MAGNITUDE 3- Sizes (magnitudes) of earthquakes < 3 = not detectable2.5 to 5.4 Often felt, but only causes minor damage. 30,0005.5 to 6.0 Slight damage to buildings and other structures. 5006.1 to 6.9 May cause a lot of damage in very populated areas. 1007.0 to 7.9 Major earthquake. Serious damage. 208.0 or greater Great earthquake. Can totally destroy communities near the epicenter. One every 5 to 10 years- Earthquake history along San Andreas fault : 1857 Los Angeles roughly 8.3. occur on "bendy" part of fault1898 quake in CA most famous in US history- Global Earthquakes:- Sumatra & Japan earthquake & tsunami - Global