Class Notes: Geologic Time

Transcription

1 Name: Date: Period: Geologic Time The Physical Setting: arth Science Class Notes: Geologic Time I. Relative Dating Uniformitarianism -! The present is the key to the past Relative Dating -! Principle of Superposition -! Original Horizontality -! xtrusions -! Intrusions -! Younger then the rocks that they crosscut xception to the principle of superposition eigh-manuell - 1

2 Contact Metamorphism -! Faults -! Younger then the rocks that they crosscut Folds -! xception to the principle of superposition eigh-manuell - 2

3 Correlation -! Correlation is the most effective method when using relative dating What to look for when correlating rocks: Fossils -! xamples: bones, shells, footprints, and organic compounds (DNA) Index Fossils -! Best method for correlating rocks To be considered a good index fossil it needs to meet two criteria: 1.! arge horizontal distribution 2.! Small vertical distribution Geologic Time Markers -! xamples: volcanic ash deposits and meteorite impacts eigh-manuell - 3

4 II. Absolute Dating Absolute Dating -! Radioactive Decay -! Isotopes -! xample: Stable carbon has a mass of 12 units called Carbon-12 Isotopic carbon has a mass of 14 units called Carbon-14 Half-ife -! In a given sample of a radioactive isotope half of the atoms will decay to a! product, but the remaining half is still ach element has its own half-life that range from fractions of a second to billions of years The half-life of an isotope is not effected by any such as,, or! eigh-manuell - 4

5 Uranium-238 -! Mass: Decay: Half-ife: Carbon-14 -! Mass: Decay: Half-ife: III. arly volution 4.6 Billion Years Ago 4.5 Billion Years Ago 4.4 Billion Years Ago During early arth s melting, material separated into zones according to their densities!!! eigh-manuell - 5

6 4.2 Billion Years Ago Gases trapped inside the arth seeped out in a process called! and created a completely different second atmosphere 3.9 Billion Years Ago After the crust had cooled enough, in the atmosphere began to precipitate and form on arth 3.8 Billion Years Ago Weathering erosion, and deposition began and the first! rock was formed 3.5 Billion Years Ago Billion Years Ago Oxygen in the atmosphere reacted with iron in the soil to produce! Resembled the surface color of current day Mars 2.8 Billion Years Ago Present Billion Years Ago ife slowly evolved from single-celled bacteria to multicellular to hard parts on life forms eigh-manuell - 6

7 I (Index fossils not drawn to scale) PRCAMBRIAN ARCHAN PROTROZOIC PHANRO- ZOIC on ra Million years ago CNOZOIC AT M ID D A R Y AT M I DD A R Y First sexually reproducing organisms Oceanic oxygen begins to enter the atmosphere Oceanic oxygen produced by cyanobacteria combines with iron, forming iron oxide layers on ocean floor arliest stromatolites Oldest microfossils vidence of biological carbon Oldest known rocks MSOZOIC PAOZOIC 4600 stimated time of origin of arth and solar system PISTOCN PIOCN MIOCN OIGOCN OCN PAOCN MIDD MIDD MIDD MIDD MIDD MIDD MIDD CARBONIF- ROUS Period poch ife on arth QUATRNARY NOGN PAOGN Million years ago HOOCN Humans, mastodonts, mammoths arge carnivorous mammals Abundant grazing mammals arliest grasses Many modern groups of mammals Mass extinction of dinosaurs, ammonoids, and many land plants CRTACOUS arliest flowering plants Diverse bony fishes JURASSIC arliest birds Abundant dinosaurs and ammonoids TRIASSIC PRMIAN 251 arliest mammals arliest dinosaurs Mass extinction of many land and marine organisms (including trilobites) Mammal-like reptiles Abundant reptiles PNNSYVANIAN MISSISSIPPIAN DVONIAN SIURIAN xtensive coal-forming forests Abundant amphibians arge and numerous scale trees and seed ferns (vascular plants); earliest reptiles arliest amphibians and plant seeds xtinction of many marine organisms arth s first forests arliest ammonoids and sharks Abundant fish arliest insects arliest land plants and animals Abundant eurypterids ORDOVICIAN CAMBRIAN Invertebrates dominant arth s first coral reefs Burgess shale fauna (diverse soft-bodied organisms) arliest fishes xtinction of many primitive marine organisms arliest trilobites Great diversity of life-forms with shelly parts 580 diacaran fauna (first multicellular, soft-bodied marine organisms) 1300 Abundant stromatolites NY Rock Record Sediment Bedrock Time Distribution of Fossils (including important fossils of New York) Important Geologic vents in New York Advance and retreat of last continental ice Sands and clays underlying ong Island and Staten Island deposited on margin of Atlantic Ocean Dome-like uplift of Adirondack region begins Initial opening of Atlantic Ocean North America and Africa separate Intrusion of Palisades sill Pangaea begins to break up Catskill delta forms rosion of Acadian Mountains Acadian orogeny caused by collision of North America and Avalon and closing of remaining part of Iapetus Ocean Salt and gypsum deposited in evaporite basins rosion of Taconic Mountains; Queenston delta forms Taconian orogeny caused by closing of western part of Iapetus Ocean and collision between North America and volcanic island arc Widespread deposition over most of New York along edge of Iapetus Ocean Rifting and initial opening of Iapetus Ocean rosion of Grenville Mountains Grenville orogeny: metamorphism of bedrock now exposed in the Adirondacks and Hudson Highlands TRIOBITS AMMONOIDS GASTROPODS BRACHIOPODS CRINOIDS VASCUAR PANTS CORAS NAUTIOIDS BIRDS The center of each lettered circle indicates the approximate time of existence of a specific index fossil (e.g. Fossil A lived at the end of the arly Cambrian). C B F D G H K J N M Q P V U T X W Z Y A GRAPTOITS PACODRM FISH R URYPTRIDS Alleghenian orogeny caused by collision of North America and Africa along transform margin, forming Pangaea DINOSAURS MAMMAS O S Inferred Positions of arth s andmasses 59 million years ago 119 million years ago 232 million years ago 359 million years ago 458 million years ago eigh-manuell - 7