disasters10.07notes

disasters10.07notes - 1 4.1: Ch. 4 Earthquake Geology and...

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4.1: Ch. 4 – Earthquake Geology and Seismology Date:_________ Lisbon Earthquake of 1755: a series of three major earthquakes in a little over 2 hours struck Lisbon, Portugal, killing nearly 70,000 and destroying or seriously damaging about 90% of the houses and churches in the city! This great natural disaster occurred at a time in history when Europe was enjoying “an air of prosperity and tranquility in an ordered world.” It changed the prevailing philosophies of the era. What is an Earthquake? Stresses build up in near-surface rocks until the stress is so great that the rocks fracture and shift along a fault ; the shock waves sent off as the rock ruptures and moves are what we experience as an “earthquake.” Niels “Steno” Steensen, 1669 , set forth several laws that are fundamental in interpreting geologic history: Law of original horizontality : sediments (sands, gravels, muds) are originally deposited or settled out of water in horizontal layers . ● Law of superposition : in an undeformed sequence of sedimentary rock layers, each successive layer is deposited on top of a previously formed, and hence, older layer . ● Law of original continuity
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disasters10.07notes - 1 4.1: Ch. 4 Earthquake Geology and...

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