EES 1030 Lecture 8 Outline of Last Lecture I. Metamorphic RocksII. Agents of Metamorphism: HeatIII. Agents of Metamorphism: PressureIV. Agents of Metamorphism: FluidsV. Metamorphic TexturesVI. Metamorphic Textures: FoliationVII. Metamorphic Rocks: Non-FoliatedVIII.Metamorphic EnvironmentOutline of Current Lecture IX. Geological Time ScaleX. Geological History of OutcropsXI. Two ways to date geological eventsXII. Principle of UniformitarianismXIII.Principle of SuperpositionXIV. Principle of Cross-Cutting RelationshipsXV. Principle of InclusionsXVI.UnconformitiesXVII. Geological History of a regionXVIII. Principle of Lateral ContinuityXIX.Fossils and CorrelationXX. Fossils and DisconformitiesXXI.The geological time scaleCurrent Lecture- Geological Time Scaleo “Calendar“ of earth history divides geologic history into units- Geological History of OutcropsThese 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.o Observations and Logical Reasoning. Can apply a series of geological principles.- Two ways to date geological eventso Relative Dating: Determine whether a rock is older or younger than surrounding rocks.o  Field relationships, fossils.o Absolute Dating: Determine actual number of years since rock was formed.o  Radioactive decay = radiometric dating.- Principle of Uniformitarianismo James Hutton “The present is the key to the past”- Principle of Superpositiono Nicolaus Steno (1669)o “In an un-deformed sequence of layered rocks, the oldest rocks are at the bottom”- Principle of Cross-Cutting Relationshipso Younger features cut across older features. Example: Igneous intrusions and faults- Principle of Inclusionso An inclusion is a piece of rock that is enclosed with another rocko Inclusions: always older than the host rock- Unconformitieso A break in the rock record produced by erosion and/or non-deposition of rock unitso Three types of unconformity Angular unconformity: tilted rocks are overlain by flat-lying rocks Disconformity: strata on either side of the unconformity are parallel Nonconformity: metamorphic or igneous rocks in contact with sedimentary strata- Geological History of a Regiono Principles of superposition, inclusions, cross-cutting relationships, and Original Horizontalityo  Fine for single location or outcrop of rock but what about across a wide region?- Principle of Lateral Continuityo Sedimentary rock layers are often laterally continuous over 10’s of km.- Fossils and Correlationo Matching of rocks of similar ages in different regions is known as correlationo Correlation often relies upon fossils- Principle of Fossil Successiono William Smith (1785) noted that sedimentary strata in widely separated areas could be identified and correlated by their distinctive fossil content- Principle of Fossil Successiono Different types of fossils always appear & disappear- Fossils and Correlationo Dating rocks using overlapping fossil ranges- Fossils and Disconformitieso Fossils can be used to recognize a break in the sedimentary record (disconformity)- The geological time scaleo A “calendar” of Earth history o Divides geologic history into units. Originally created using relative ages.o Eon: greatest expanse of timeo Phanerozoic: (“visible life”) the most recent eon, began about 540 million years agoo Proterozoic: (2500-540 million years) o Archean (3800-2500 million years)o Hadean: the oldest eon (4500-3800 Myrs)o Era: subdivision of an erao Eras of the Phanerozoic eono Know the vision of the eons, Phanerozoic and the eons***o Pigeon egg omelets make people puke often*o Classes of students detest memorizing pointless