Deep Time and the Geologic Time Scale

Transcription

1 Deep Time and the Geologic Time Scale Prior to the 1700 s deep time did not exist... According to Genesis the Earth was created in 6 days about 6000 years ago. Earth history = Biblical history Dinosaurs did not exist. The Geologists (1700 s) Cuvier ( ) Hutton ( ) Rock layers show that the Earth is ancient and has a long pre-human history, including extinct species preserved as fossils.

2 circa 1790 Earth History, 1700 s post-diluvial Diluvial Flood Gravels Layers composed of unconsolidated sediment Secondary Secondary Hard rock layers with abundant fossils Trans. Transitional Hard rock layers with sparse fossils Primary Primary Crystalline rock Secondary Fossil Reptiles Dinosaur fossils were found in the upper part of the Secondary rock layers.

3 The Earth is 4.6 billion years old Now 31st The Age of the Earth One Year Earth Forms 4,600,000,000 years ago January 1st ajor Subdivisions of Geologic Time 3.45 Ga 2.3 Ga ay June July April September August arch October February November January 0 Ga 1.15 Ga Origin of life? 3.45 Ga Earth is cooling. Heavy meteoric bombardment. Crust, oceans, and atmosphere are forming and reforming. No surviving rock. 2.3 Ga ay June July April August September arch October February November January 1.15 Ga

4 2.3 Ga ay June July April August September arch October February November 3.8 Ga January Hadean 1.15 Ga Evolution of Bacterial Life! Formation of large continents. Oxygenation of the atmosphere. 2.3 Ga ay June July April August 3.45 Ga September arch October Oldest rock formations. February November January 1.15 Ga 2.5 Ga Archean ay June July April August September arch October February November 3.8 Ga January Hadean 1.15 Ga

5 3.45 Ga 2.3 Ga Evolution of Eucaryotic Life ay June July April August September arch October 1.15 Ga February November January First animal fossils. Evolution of most animal phyla. 2.5 Ga Archean Proterozoic ay June July April August September arch October February November 3.8 Ga January 540 a Hadean abundant fossils of animals with shells

6 Archean ua ry ay Fe br 2.5 Ga Apr il arch 3.8 Ga June ry Janua r be em er Octob gu Dece mbe r ov Au N st Septem ber July Haikouichthys Phanerozoic evolution of vertebrates late Nov. - Proterozoic Acanthostega Dimetrodon 1 formation of Pangea synapsids rule first tetrapods largest mass extinction first amniotes s cte e d Di Permian - Age of Synapsids (pre-mammals) 31

7 formation of Pangea continents drift into their modern positions coal swamps first tetrapods first amniotes largest mass extinction Age of Dinosaurs first birds formation of Pangea continents drift into their modern positions coal swamps first tetrapods first amniotes largest mass extinction Age of Dinosaurs first birds evolution of modern mammals formation of the Alps and Himalayas

8 What about us? 31st midnight Ice Ages Hominids evolve noon 11:59:59 - First Geologists 11:59:57 - Columbus sets sail 11:59:45 pm - Roman Empire 11:59 pm - Agriculture develops 11:48 pm - First modern humans evolve 10:00 pm - Hominids migrate out of Africa 5:00 pm - First hominids evolve

9 Subdivisions of Human Time illennium Century Decade Year onth Day longer shorter Subdivisions of Geologic Time Era Period Epoch Stage Substage longer shorter 0 a Phanerozoic 540 a Proterozoic 2500 a Archean 3800 a Hadean C P 2.5 Ga Archean Proterozoic ay June July odern Geologic Time Scale April August September arch October February November 3.8 Ga January 540 a Hadean Phanerozoic 4600 a

10 0 a Phanerozoic 540 a Proterozoic 2500 a Archean 3800 a Hadean 4600 a C P Cenozoic esozoic Paleozoic Quat. Carb. Paleogene Neogene Cretaceous Jurassic Triassic Permian Pennsylvanian ississippian Devonian Silurian Ordovician Cambrian Quat. = Quaternary Carb. = Carboniferous odern Geologic Time Scale Holocene Pleistocene Pliocene iocene Oligocene Eocene Paleocene a RIP Eras 0 a Phanerozoic 540 a Proterozoic 2500 a Archean 3800 a Hadean 4600 a C P Cenozoic esozoic Paleozoic Quat. Carb. Paleogene Neogene Cretaceous Jurassic Triassic Permian Pennsylvanian ississippian Devonian Silurian Ordovician Cambrian Quat. = Quaternary Carb. = Carboniferous odern Geologic Time Scale Holocene Pleistocene Pliocene iocene Oligocene Eocene Paleocene a RIP Periods 0 a Phanerozoic 540 a Proterozoic 2500 a Archean 3800 a Hadean 4600 a C P Cenozoic esozoic Paleozoic Quat. Carb. Paleogene Neogene Cretaceous Jurassic Triassic Permian Pennsylvanian ississippian Devonian Silurian Ordovician Cambrian Quat. = Quaternary Carb. = Carboniferous odern Geologic Time Scale Holocene Pleistocene Pliocene iocene Oligocene Eocene Paleocene a RIP Epochs

11 What records the passing of geologic time? Formation of rock layers Sediments are deposited over time in layers. Each layer traps and records information about the time during which it formed. Sedimentary layers are analogous to the pages that compose the book of Earth History. Problem - how do you determine the order in which rock layers formed? At a single place, layers can be ordered using the law of Superposition. youngest even less old time younger less old The same rock type repeats through time. oldest East Devonshire Secondary Flood Gravels Layers composed of unconsolidated sediment Hard rock layers with abundant fossils Transitional Hard rock layers with sparse fossils Primary ary post-diluvial Diluvial Earth History, 1700 s Second circa 1790 Crystalline rock Trans. Primary

12 Cretaceous System D Omalius d Halloy, 1822 circa 1790 circa 1820 post-diluvial Diluvial British Isles alluvium gravels London clay Continental Europe Sicilian strata Parisian gypsum beds English chalk Parisian chalk Secondary Oolites Lias Coal easures agnesian Limestone New Red Sandstone Perm strata Jura t. strata uschelkalk - Trias Geologic Systems Transitional Old Red Sandstone Devonshire strata Welsh Greywackes ountain Limestone Wenlock Limestone Primary Crystalline (metamorphic) strata

13 Within a local region, rock layers can be correlated on the basis of their lithology (physical characteristics) to define a geologic system. East Devonshire West Devonshire Correlation - the matching-up of rock layers between different places. We can put local rock layers in the correct time order because we can see how they are stacked on each other. We can use the physical features of rock layers to correlate them into a regional system. The Problem: How can we correlate different regional systems so that they are in the correct time order if we can t directly match their layers? How can we correlate different systems if the layers cannot be correlated based on their physical features??? Great Britain Continental Europe

14 William Smith ( ) surveyor, civil engineer Smith made the first large scale geologic map showing the distribution and order of rock layers in Great Britain. In his work as a surveyor, Smith noticed that the rock layers seemed to contain a unique sequence of fossil species that appear and disappear through time. Even when the rocks look different, the sequence of fossils is always the same.

15 Location A Location B Fossils provide the key to correlating rock strata. Location A Location B Location A Location B Location C

16 The evolution and extinction of species define unique intervals of time. Goes Extinct T I E Unique interval of time Exists Evolves Goes Extinct Exists T I E T I E Evolves

17 T I E T I E Fossils are the key to correlating regional systems Great Britain Continental Europe

18 Geologic Systems and Geologic Time Once a particular regional system was formally named and its fossils described, other regional systems with the same fossils were correlated to it and given the same name. The original system names thus came to stand for particular intervals of geologic time. Geologic Systems and Geologic Time For example, the Jurassic System was originally named for the rocks and fossils of the Jura ountains between France and Switzerland. Now the Jurassic Period refers to the time interval during which the fossil species of the Jurassic System lived. Any rock layers with these fossils can be identified as Jurassic in age. circa 1790 circa 1870 post-diluvial Diluvial British Isles alluvium gravels Continental Europe odern Time Scale Quaternary Sicilian strata London clay Parisian gypsum beds English chalk Parisian chalk Cretaceous Secondary Oolites Lias Jura t. strata Jurassic New Red Sandstone uschelkalk - Trias Triassic agnesian Limestone Perm strata Permian Transitional Coal easures ountain Limestone Old Red Sandstone Devonshire strata Carboniferous Devonian Wenlock Limestone Silurian Welsh Greywackes Ordovician Cambrian Primary Crystalline (metamorphic) strata Precambrian

19 How do we subdivide geologic time and assign sedimentary layers to their correct position in time? fossils each time interval in Earth history is defined by a unique set of species that existed at that time. Species evolve, live for a short time, and go extinct. The same species never evolves twice (extinction is forever). Evolution provides a biological calendar that geologists use to keep track of time. ass extinctions create the boundaries that define most geologic time intervals.