GEOL 1301 1st Edition Lecture 4 Outline of Last Lecture I.Theory of Plate Tectonicsa.Divergentb.Convergentc.Transform-faults boundariesOutline of Current LectureII.Geological Characteristics of Plate Boundariesa.Volcanismb.Earthquakesc.Mid-ocean ridgeIII.Seafloor spreading agea.Magnetic anomaliesCurrent LectureWhat are some of the geologic characteristics of plate boundaries? Many geologic features develop at plate boundaries. Divergent boundaries are typically marked by volcanism and earthquakes at the crest of a mid-ocean ridge. Convergent boundaries are marked by deep-sea trenches, earthquakes, mountain building, and volcanism. Transform faults, along which plates slide horizontally past each other, can be recognized by earthquake activity and offsets in geologic features.How can the age of the seafloor be determined? We can measure the age of the seafloor by using thermoremanent magnetization. Magnetic anomaly patterns mapped on the seafloor can be compared with a magnetic time scale that was established using the magnetic anomalies of lavas of known ages on land. Seafloor ages have been verified through dating of rock samples obtained by deep-sea drilling. Geologists can now draw isochron maps for most of the world’s oceans, which allow them to reconstruct the history of seafloor spreading over the past 200 million years. Using thismethod and other geologic data, geologists have developed a detailed model of how Pangaea brokeapart and the continents drifted into their present configuration.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.magnetic anomaly: One in a pattern of long, narrow bands of high or low magnetic intensity on the seafloor that are parallel to and almost perfectly symmetrical with respect to the crest of a mid-oceanridge.magnetic time scale: The detailed history of Earth’s magnetic field reversals as determined by measuring the thermoremanent magnetization of rock samples whose ages are known.mantle plume: A narrow, cylindrical jet of hot, solid material rising from deep within the mantle, thought to be responsible for intraplate volcanism.mid-ocean ridge: An undersea mountain chain at a divergent boundary, characterized by earthquakes, volcanism, and rifting, all caused by the tensional forces of mantle convection that are pulling the two plates
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