Rock Outcrop on Rte. 12 Depauville Unit V: Earth s History Review Book pp.97-112. Original photo taken by Mr. O on 8/11/10.
Objective #1 Describe processes that formed the atmosphere and oceans of early Earth. Objective #2 Explain the difference between relative and absolute age.
Evidence suggests that the atmosphere and oceans of the early Earth began to form from gases emitted by volcanic eruptions from the Earth s interior through a process called outgassing. Outgassing was thought to add the gases water vapor (H 2 O), carbon dioxide (CO 2 ) and nitrogen (N 2 ). Image taken from http://www.globalchange.umich.edu/gctext/inquiries/inquiries_by_unit/unit_8_files/image011.jpg on 8/9/10.
Image taken from http://www.fossilmuseum.net/tree_of_life/stromatolites.htm on 8/11/10. The Earth s hot surface was cooled by precipitation that fell over millions of years and formed the oceans. Sedimentary rocks of marine origin dating back approximately 4 billion years provide evidence for the presence of an early ocean.
What percent of today s atmosphere is oxygen? 21% (ESRT p.1) If outgassing/volcanic eruptions did not add oxygen to the atmosphere and oceans, how do scientists think it got there? Photosynthesis from algae and simple producers in the ocean. Image taken from http://www.scitizen.com/cachedirectory/htmlcontributions/img/algae20 100408.jpg on 8/11/10.
Image taken from McGuire, Thomas. Earth Science: The Physical Setting. New York: Amsco, 2005.
Relative Age Concerned with sequence of events that have occurred, comparing the ages of objects. Relative age is not concerned with actual age. Example: Rock Layers along Rte. 12 Image taken from http://academic.brooklyn.cuny.edu/geology/leves on/core/topics/time/graphics/bracketing.gif on 8/11/10. Clayton near Spicer s Bay Original photo taken by Mr. O on 8/11/10.
Actual age Absolute Age The most accurate method of determining the absolute age of geologic events and rock is by radioactive dating. Image taken from http://en.wikipedia.org/wiki/radiometric_dating on 8/11/10.
Objective #3 In a section of rock, determine order of geologic events by using chronology of layers, intrusions/extrusions, faults, folds, joints, unconformities and internal characteristics.
Principle of Superposition Idea that the oldest rock layers in a series of horizontal sedimentary rock are found at the bottom. Image taken from http://www.astrofoto.ca/stuartheggie/grand_canyon/grand_canyon_23.jpg on 8/11/10.
What type of geologic events cause the principle of superposition to not remain true? Faulting Folding Overturning of rocks Image taken from http://geomaps.wr.usgs.gov/socal/geology/inland_empire/images/san_andreas_fault.jpg on 8/11/10. Image taken from http://www.nps.gov/history/history/online_books/geology/publications/state/tx/1968-7/images/fig26.jpg on 8/11/10.
Image taken from http://www.indiana.edu/~geol105/images/gaia_chapter_5/dike&sill.jpg on 8/11/10. Image taken from http://www.gangiteach.com/practice%20tests/geohist6.gif on 8/11/10. The rock layers through which igneous intrusions or extrusions cut are older than the intrusions or extrusions themselves, since the rock layers must be formed prior to the intrusion of magma or extrusion of lava.
Contact Metamorphism Process of rock changing due to contact (being touched) with hot magma or lava. Image taken from http://www.nvcc.edu/home/cbentley/geoblog/2009_10_01_archive.html on 8/11/10. Contact metamorphism is younger than the rock layers that were metamorphosed.
Faults Cracks in rock along which movement has occurred. Joints Immovable cracks Folds Bends in the rock strata. Image taken from http://www.geology.wisc.edu/courses/g112/images/salv_faults.jpgon 8/11/10. Image taken from http://farm3.static.flickr.com/2327/2212321452_7dec0280d0.jpg on 8/11/10.
Folding and faulting associated with the San Andreas fault, along highway 14 near Palmdale, California. Faults, joints and folds are younger than the rocks in which they appear. Image taken from http://strike-slip.geol.ucsb.edu/kessel/palmdaleroadcut.html on 8/11/10. These distortions in rock occur due to changes in temperature and pressure. Image taken from http://www.gangiteach.com/practice%20tests/geohist4.gif on 8/11/10.
Practice Diagram #1 Image taken from
Practice Diagram #2 Image taken from
Fragments that occur inside a rock are older than the rocks in which they are found, since they were already around before the rock was made. Image taken from http://www.answersincreation.org/curri culum/geology/images/conglomerate.j pg on 8/11/10. Image taken from http://www.babble.com/cs/blogs/strollerderby/2009/06/chocolate_chip_cookie.jpg on 8/11/10.
Quartz vein in quartzite(metamorphosed sandstone) rock in Killarney, Ontario ESRTp.7 Image taken from http://www.flickr.com/photos/31856336@n03/galleries/72157623975198 336/ on 7/19/10. However, cracks and veins are younger than the rocks in which they occur. Veins- Mineral deposit that have filled a rock crack or permeable zone
Sedimentary rocks are younger than the sediments and the cements that formed them. Image taken from http://www.empr.gov.bc.ca/mining/geoscience/publicationscatalogue/inform ationcirculars/ic1987-05/pages/key.aspx on 8/11/10.
Unconformity A gap in the geologic rock record due to erosion or nondeposition. An unconformity indicates that a portion of the rock record is missing. Image taken from http://lams.slcusd.org/pages/teachers/saxby/wordpress/wp-content/uploads/2010/03/syncline_unconformity.jpg on 8/11/10.
#1 #2 #3 #4 Image taken from http://stevekluge.com/geoscience/images/unconformity1.jpg on 8/11/10.
PreCambrian-Cambrian Unconformity (Rte. 12 Alex Bay near Schemerhorn Landing) Original photo from Mr.O taken on 8/11/10.
Close up of Unconformity near Schemerhorn
Objective #4 Explain how rocks and geologic events in one place can be matched to another by using correlation of rock layers, fossils and volcanic ash. Objective #5 Identify two characteristics of a good index fossil.
The determination of the relative age of rock in geologic history can be accomplished through the use of correlation techniques. Correlation Process of determining that rock layers or geologic events in two separate areas are the same. Correlation involves observing similarity and continuity of rock layers in different locations, comparing fossil evidence and using volcanic time markers. Images taken from http://academic.brooklyn.cuny.edu/geology/leveson/core/topics/time/froshlec8.html on 8/12/10.
Outcrop at Aqua Zoo in Alex Bay Outcrop- Bedrock exposed at earth s surface. Scientists can make observations about an area and the landscape by walking the outcrop. Original Photo taken by Mr. O on 8/11/10.
Rock Outcrops Rte.12 Depauville An example is matching up sedimentary rock strata on opposite sides of a valley. Rocks can be matched on the basis of similarities in appearance, color and composition. Original photo taken by Mr. O 8/11/10.
Correlation of Rock Layers between Three National Parks Image taken from http://www.fas.org/irp/imint/docs/rst/sect2/correlation.jpg on 8/12/10.
Fossils Remains or traces of once living organisms found in sedimentary rock. Amphibian tracks from Oklahoma about 300 million years old that show it was raining at time of preservation Image taken from http://www.flickr.com/photos/31856336@n03/galleries/72157623975198336/#photo_236128744 on 8/11/10.
B Original photo taken by Mr. O on 8/11/10. Outcrop @ 6 th Hole C-Way Golf Course Fossils found in rocks at lower levels are considered to be older than fossils found in rocks at higher levels. A
Presence of marine fossils indicates that the rock was formed in the sea and can be inferred that the area was submerged at some time during geologic history. Original photo taken by Mr. O on 8/27/10.
Index or Guide Fossils Fossil characteristics of a certain geologic time used to correlate rock layers. Image taken from http://www.geology.ohio-state.edu/~vonfrese/gs100/lect29/xfig29_04.jpg on 8/12/10.
Index fossils are used because of widespread horizontal distribution (geographical) in sedimentary rocks and their relatively short period of existence on Earth (narrow vertical distribution). ESRT p.8&9 Image taken from http://www.cartage.org.lb /en/themes/sciences/ear thscience/geology/about Geology/GeologicTime/I ndexfossils/fossils.gif on 8/12/10.
Volcanic Time Markers A volcanic eruption is relatively short in duration when compared to the many years necessary to form sedimentary rock or build up the Earth s surface. When a volcano erupts, a layer of volcanic ash is rapidly deposited over a large area. Image taken fromhttp://regentsearth.com/graphics/thumbs.htm on 8/12/10.
Volcanic Ash Image taken from http://geology.com/articles/volcanicash/volcanic-ash-column.jpg on 8/12/10. Image taken from http://www.livescience.com/imageoftheday/siod_080509.html on 8/12/10. Fine particles of igneous rock ejected during a volcanic eruption. Since volcanic ash is quickly deposited over a large area, it serves as an excellent time marker.
Objective #6 Using pages 8 & 9 of ESRT, interpret geologic history and tell important events in each Era, Period and Epoch.
C. GEOLOGIC TIME SCALE Geologists have subdivided geologic time into units called eons. Eons are subdivided into eras. Eras are split into periods and periods are broken into epochs. Image taken from http://www.cerritos.edu/esci/tutor/on-line_lecture_notes/earth_history/unit_7_time_scale.htm on 8/12/10.
The eons, eras, periods and epochs of geologic history are found in the ESRT on page 8&9. The three eons are Phanerozoic, Proterozoic, Archean. ESRT p8&9
I. Geologic Eras The four eras are Cenozoic, Mesozoic, Paleozoic, Precambrian. Interactive Geologic Timeline
Precambrian or Pre-Paleozoic Era about 85% of total geologic time of Earth s history very little fossil evidence from this era since the living organisms were small, simple and soft bodied like algae and bacteria. Bacteria Magnified 20,000 times Image taken from http://blog.syracuse.com/healthfitness/2009/01/large_staphaureus_bacteria.jpg on 8/12/10.
Paleozoic Era about 8 or 9% of geologic time of Earth s history progressed from Age of Invertebrates to Age of Fishes to Age of Amphibians first vertebrates and land plants and animals develop begins with Cambrian period and ends with Permian period. Image taken from http://www.astrobio.net/albums/origins/agb.jpg on 8/12/10.
Mesozoic Era about 3 or 4% of geologic history fossils show dinosaurs and earliest birds and mammals develop Three periods: Triassic, Jurassic, Cretaceous Image taken from http://www.palaeos.com/vertebrates/units/unit310/images/diplodocus.jpg on 8/12/10.
Cenozoic Era about 2 or 3% of geologic history modern era with fossils of modern plants and mammals with appearance of humans. Image taken from http://static.howstuffworks.com/gif/willow/cenozoic-era-info0.gif on 8/12/10.
Human existence is infinitesimal (.04% of geologic history) compared to entire history of Earth (4.6 billion years) Image taken from http://upload.wikim edia.org/wikipedia/ commons/thumb/2/ 28/Geologic_Clock _- _with_events_and_ periods_- _remake.png/475p x- Geologic_Clock_- _with_events_and_ periods_- _remake.png on 8/12/10. http://www.youtube.com/watch?v=yxseyttblmi Interactive Geologic Timeline
Plate motions and orogeny (mountain building) events are also placed in this time sequence on page 9 of ESRT. Image taken from http://www.lakegeorgeassociation.org/images/adirondack_uplift2.gif on 8/12/10.
II. Erosional Record Why is there no place on earth that contains a complete rock and fossil record for the entire geologic history of the Earth? There are destructional forces such as weathering and erosion that remove rock record and there is NO PLACE on Earth that has always been underwater and removed from earth s destructional forces at all times in Earth s history. Image taken from http://upload.wikimedia.org/wikipedia/commons/c/c7/sidari_eroded_rock.jpg on 8/12/10.
Principle of Uniformitarianism Implies that geologic events and processes currently changing the earth have also changed the earth in the past Original photo taken by Mr. O on 8/11/10.
III. The Geologic History of NYS The Geologic Map of NYS on ESRT p. 3 shows the remaining rock and geologic record of our state. What eras are well represented in the NYS bedrock? Paleozoic, some Precambrian What eras are not well represented? Mesozoic & Cenozoic ESRT p.8&9
Objective #7 How can geologic ages be measured using radioactive decay? Objective #8 Be able to solve the different types of radioactive decay problems (may use p.1 of ESRT).
Absolute or actual age can be determined by the process of radioactive dating. Process of determining age of rock by measuring half-life of radioactive materials in the rock. Image taken from http://wikis.lib.ncsu.edu/images/8/84/carbondating.gif on 8/11/10.
This radioactive decay is unaffected by external factors such as pressure and temperature that would normally affect chemical reactions. Image taken from http://www.my-stuffonline.com/arozpad-alfa.gif on 8/12/10. Image taken from http://www.teachersource.com/images/product/md/tim500.jpgon 8/12/10.
Some, but not all, rocks contain atoms whose nuclei undergo radioactive decay. This decay occurs as a random event and is not influenced by other changes occurring in the rock at the same time. Image taken from http://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/thorium_decay_chain_from_lead-212_to_lead- 208.svg/300px-Thorium_decay_chain_from_lead-212_to_lead-208.svg.png on 8/12/10.
Half-life Amount of time taken for radioactive decay to reduce total amount of radioactive substance to one half of its original amount. Image taken from http://accelerateu.org/graphic_resources/q42,43rev.jpg on 8/12/10. Therefore by knowing the original content of a radioactive material and comparing it to the present content of the same radioactive material, the age of the material can be determined.
Radioactive Isotope Materials that decay from unstable to stable forms. The half-lives of radioactive isotopes are different for different substances. Isotope half-lives are found in ESRT on page 1.
Some radioactive isotopes such as Carbon-14 have short half-lives and are good for dating recent organic remains (between 1,000 and 50,000 years.) ESRT p.8 In 1991 hikers in the Alps found the Otzi iceman in a crevasse of a retreating mountain glacier. Carbon-14 dating revealed his age to be about 5,300 years old. Image taken from http://www.age-of-the-sage.org/archaeology/otzi_the_iceman.html on 7/19/10.
Other radioactive isotopes such as Uranium-238 which decays to stable Lead-206 have very long half-lives and are good for dating older rock formations (more than 10 million years.) Uranium-238 has a half-life of about 4.5 billion years. The Earth is estimated to be 4.6 billion years old so Uranium-238 that formed at the same time the Earth was formed has had time to undergo only 1 half-life. ESRT p.8
Each half-life, the amount of atoms gets cut in half.
Since you don t know how many atoms you started with, a ratio between parent to daughter will tell you how many half-lives have gone by. 100% parent 0% daughter 0 half lives
One half-life. 50% parent 50% daughter 1 half-life
Two half-lives. 25% parent 75% daughter 2 half-lives
Three half-lives. 12.5% parent 87.5% daughter 3 half-lives
Four half-lives. 6.25% parent 93.75% daughter 4 half-lives
Don t worry about the last atom. You start with so many trillions that you never really get there. (It will just decay and then they re all gone.)
Radioactivity Decay Graph Image taken from http://www.kgs.ku.edu/extension/gifs/halflife.gif on 8/12/10.
Try Sample Radioactive Decay Problems on p.7 of note packet. Example 1 Example 2 Image taken from http://academic.brooklyn.cuny.edu/geology/leveson/core/topics/time/graphics/radio1.gif on 8/12/10.
Objective #9 What are fossils, where are they found and what do they suggest about ancient life?
Important fossils of NYS are found in ESRT on pp.8 & 9. This chart contains NYS index fossils that can be used in correlation.
Fossils give evidence that a great many kinds of plants and animals have lived in the past on the Earth in a great variety of environmental conditions. Image taken from http://la-brea-tar- pits.visit-los-angeles.com/saber- Tooth-Cat.jpgon 8/12/10. Image taken from http://skywalker.cochise.edu/wellerr/students/sabercat/project_files/image0 20.jpg on 8/12/10. Cambrian sea Image taken from http://www.search4dinosaurs.com/burgess_shale.html on 8/12/10. Burgess shale fossil image taken from http://www.nmnh.si.edu/rtp/students/2006/images/paleo_day89.jpg on 8/12/10.
Most of these life forms have become extinct which means that they do not exist on the Earth today. It is highly probable that in addition to the fossil types that have been found, there existed an even greater number of life forms that left no traces or fossils in the rock record. Image taken from http://www.aerospaceweb.org/question/nature/evolution/archaeopteryx.jpg on 8/12/10.
The similarity among some fossil forms of various time periods suggests a transition that may be a result of evolutionary development. Image taken from http://darwiniana.org/equid2t.gif on 8/11/10.
Generally the older rock formations contain more simple and marine life forms. The younger rock formations have the fossils of more complex land dwelling organisms. Image taken from http://www.mbmg.mtech.edu/graphics/time-line.gif on 8/11/10.