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ESC1000 Exam 3 Study Guide

ESC1000 Exam 3 Study Guide - CHAPTER 4 GEOLOGIC TIME Three...

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CHAPTER 4 GEOLOGIC TIME Three hypotheses for mass extinction -extraterrestrial impacts : alvarez and alvarez: suggested 65 million years ago a meteorite 10 km in diameter hit the Earth -Volcanic eruptions : volcanic eruptions blasted massive amounts of volcanic ash and sulfur aerosols into the air: aerosols blocked the sun, and the temp of Earth plummeted Supercontinents and Carbon Dioxide : one huge continent, development of a single global ocean, preventing mixing of surface water and the ocean depths, carbon accumulated in the deep oceans, causing above temps to drop, the cool air cooled the surface of the sea causing the surface water to sink and the carbon-filled deep water to rise to the surface, releasing tons of carbon, killing life Geologic Time Earth is approx. 4.6 billion years old Relative Age : refers only to the order in which events occurred -in order for an event to affect a rock, the rock must exist first Absolute Age : measured in years, tells us both the order in which events occurred and the amount of time that has passed since they occurred Relative Geologic Time The Principle of Original Horizontality : based on the observation that sediment usually accumulates in horizontal layers Principle of Superposition : states that sedimentary rocks become younger from bottom to top -younger layers of sediment always accumulate on top of older layers The Principle of Crosscutting Relationships : based on the obvious fact that a rock must first exist before anything can happen to it -(ex. A dike cutting across layers of sandstone, the sandstone must have been there first) The Principle of Faunal Succession : states that species succeeded one another through time in a definite and recognizable order and that the relative ages of sedimentary rocks can therefore be recognized from fossils Fossils : the remains and other traces of prehistoric life that are preserved in sedimentary rock Layers of sedimentary rock are conformable is they were deposited without interruption An unconformity represents an interruption in deposition, usually a long duration -represents a long time interval for which no geologic record exists in that place
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Disconformity : the sedimentary layers above and below the unconformity are parallel Angular conformity : tectonic activity tilted older sedimentary rock layers, and erosion planed them off before younger sediment accumulated Nonconformity : an unconformity in which sedimentary rocks lie on igneous or metamorphic rocks Correlation : the matching of rocks of the same age from different localities to assemble a complete and continuous record of time Types of Correlation Time correlation : age equivalence Lithographic correlation : continuity of a rock unit Evidence Used to Correlate Rocks Index Fossils : produced by an organism that is abundantly preserved in rocks, was geographically widespread, existed as a species or genus for only a short time, and is easily identified in the field Key bed
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