Format of exam About 35 multiple choice 10 true false completion of geologic time column matching relative age of layers of rock oldest to youngest Physical Geography Exam 3 Earth s internal structure Crust what we are on Mantle 80 of earths volume Core 1 3 of earths mass only 1 6 of volume Inner core is solid iron outer core is liquid Outer core generates 90 of earths magnetic field We know these exist because of seismic activity indirect evidence Idea formed by Wagner Supporting evidence fossils of Mesosaurus found in South Africa and Brazil and distribution of glacial sediments Magnetic Pole Movement apparent polar wandering when put on moving continents Continental Drift matches up Plate Tectonics Lithosphere crust and uppermost mantle Broken into tectonic plates Asthenosphere weaker hotter deeper part of mantle Involved in tectonic movements the mobile part of the mantle Supporting evidence Crustal plate boundaries match up with earthquake epicenters as well as magnetic pole movements Convection complex convection within the Earth s mantle allows material to rise to the base of the lithosphere beneath each divergent plate boundary Convection cells drive motion of the plates on the surface Divergence two plates moving away from each other Within continents they produce rifts and rift valleys The most active ones exist as mid oceanic ridges Form volcanic islands and produce gaps where molten lava rises to fill Convergence two or more plates move toward one another and collide Forms subduction zone or continental collision The subducting plate usually with oceanic crust moves below the other plate Large mountain ranges can be formed Minerals Working definition Element or group of elements naturally occurring crystalline solid inorganic origins Example A wooden desk is not a mineral because it has organic origins create by a person Rocks Three families Igneous from magma cooling and solidifying Sedimentary weathering erosion transportation of igneous rocks turns into sediment Compaction cementation Lithification of sediment makes sedimentary rocks Metamorphic heat and intense pressure on sedimentary rocks metamorphism turns them into metamorphic Continental rock is mostly granite and lighter but thicker rocks Oceanic is mostly basalt and more dense heavy and thin rocks Geologic Time Geologic Time Column Paleozoic Era contains Cambrian Ordovician Silurian Devonian Mississippian Pennsylvanian Miss and Penn together are the Carboniferous period and Permian periods Periods listed oldest to youngest Dominant life form invertebrates Mesozoic Era contains Triassic Jurassic and Cretaceous periods Dominant life form Dinosaurs reptiles Cenozioc Era contains Tertiary and Quaternary periods Dominant life form mammals us Relative ages of rock layers The oldest will be at the bottom Any breaks in the rock an igneous dike or igneous batholith will be younger than the layers they are going through An earthquake fault is younger than the layers it is going through as well Volcanism Effusion eruption produces a shield volcano which is the largest type of volcano example Hawaii Explosive eruption makes a composite volcano Layers of ash and lava Fissure lava comes up through cracks fissures in earths crust and spreads Cinder cone from lava coming from one vent more simple than composite The mist of particles fall down around the vent to make the volcano Caldera formed by collapse of land after volcanic eruption Big measured in miles Crater depression in ground caused by volcanic activity Vents in center where magma erupts Pyroclastic debris Fragments blown out by explosive volcanic eruptions and subsequently deposited on ground Include ash cinders lapilli blocks bombs and pumice Gas coming from volcano is made up mostly of water in the form of steam Magma the molten material beneath Earth s crust This material consists of rock gases and mineral crystals Lava the molten rock that comes out of a volcano or from a fissure in Earth s surface A fissure is a crack The molten rock comes from the underground magma Lava is the magma that has broken through Earth s surface Folding Along the ridge of the fold layers slope downward away from the axis anticline In the trough of the fold layers slope downward towards the axis syncline Monocline would be just one leg of the curve Faulting Normal when forces pull rocks apart tension causes a normal fault Reverse compressional forces associated with converging plates force rocks to move upward causes reverse fault Strike slip moving alongside each other Earthquakes Causes generally occur along plate boundaries Result from faults plate tectonics and the internal heat of the earth displacement of plates causes rock to move past rock which creates energy this energy is the earthquake Focus where motion initiates seismic waves Epicenter point on surface right above focus Occurrence locations at plate boundaries Very large ones occur at convergent boundaries when ocean plates move below other plates aka subduction zones Richter amplitude magnitude scale from 1 10 Tsunami reverse fault generates tsunamis below subduction zone P wave primary wave Fastest velocity of all seismic waves so arrive at seismometer station first They are longitudinal or compression waves S secondary Move more slowly than P but faster than surface second to arrive at station They are transverse or shear waves L Surface wave Have the largest magnitude and cause majority of damage