geologic timeline ............................................, Slides of Biology

Download geologic timeline ............................................ and more Slides Biology in PDF only on Docsity! Geologic Time and Earth’s Biological History Designed to meet South Carolina Department of Education 2005 Science Academic Standards  What is the Geologic Time Scale? (slide 4) Standard 8-2.4 `Epochs, Eons, Eras, and Periods (slide 4)  How was the time scale and it’s divisions created? (slide 5)  A complete Geologic Time Scale with references to S.C. (slides 6-7) Table of Contents  Principles of the Geologic Time Scale (slide 8)  Principles of Superposition, Horizontality and Original lateral continuity  Principle of biologic succession (slide 9)  Charles Lyell, the Principle of cross-cutting relations & Inclusion principle (slide 10)  Charles Darwin  Relative Age Dating using unconformities (slide 10) Standard 8-2.6  Relative Age dating using cross-cutting relations and index fossils (slide 11)  Absolute Age dating (slide 13)  Isotopes and radiometric dating  Carbon dating (slide 14)  How old is old? (slide 16)  Breakdown of geologic time periods  Are we now living in the Anthropocene Era? (slide 17) 2 What is the Geologic Time Scale, continued? Due to the fact that early geologists had no way of knowing how the discoveries of the Earth were going to develop, geologist over time have put the time scale together piece by piece. Units were named as they were discovered. Sometimes unit names were borrowed from local geography, from a person, or from the type of rock that dominated the unit.  The earliest time of the Earth is called the Hadean and refers to a period of time for which we have no rock record, and the Archean followed, which corresponds to the ages of the oldest known rocks on earth. These, with the Proterozoic Eon are called the Precambrian Eon. The remainder of geologic time, including present day, belongs to the Phanerozoic Eon.  While the units making up the time scale are called geochronologic units, the actual rocks formed during those specific time intervals are called chronostratigraphic units. The actual rock record of a period is called a system, so rocks from the Cambrian Period are of the Cambrian system. Examples  Cambrian: From the Latin name for Wales. Named for exposures of strata found in a type-section in Wales by British geologist Adam Sedgwick.  Devonian: Named after significant outcrops first discovered near Devonshire, England  Jurassic: Named for representative strata first seen in the Jura Mountains by German geologist Humboldt in 1795)  Cretaceous: From the Latin “creta” meaning chalk by a Belgian geologist 5Table of Contents GEOLOGIC TIME SCALE MYA ERA PERIOD EPOCH PLATE TECTONICS LIFE 0.01 Cenozoic “Age of Mammals” Quaternary Holocene Beaches and barrier islands form -Mastadons become extinct -Human culture flourishes -Accelerating extinction of many species 1.8 Pleistocene Ice sheets form -Modern humans develop -Asians arrive and settle the Americas 5.3 Tertiary Pliocene -Volcanic activity in North America and Africa -Grand Canyon forms Hominids develop 23.8 Miocene Sandhills form in S.C. Horses, mastadons, mammoths, tigers, and camels live in South Carolina 33.7 Oligocene Appalachians uplift; erosion increases Cats, dogs, and apes appear 54.8 Eocene Sea levels rise; deposits of marine sediments – limestone in S.C.; land bridges form -Grass spreads widely -Diverse array of animals develop, including whales, rhinos, and elephants 65.0 Paleocene Earthquakes common; Georgia Embayment, Cape Fear Arch forms in Southeast -First horses appear (size of a cat) -Tropical plants dominate 144 Mesozoic “Age of Reptiles” Cretaceous Mass extinction occurs at the end of the period caused by a meteorite impact (Dinosaurs, ammonites and 25% of marine life become extinct) -T-Rex develops but number of dinosaur species decline -Snakes appear and first primates appear -Angiosperms appear 206 Jurassic Western US: orogeny of Rockies; North America continues to rotate away from Africa -First birds appear -Golden age of dinosaurs 248 Triassic -Pangea begins to break apart -Rocky Mountains and Sierra Nevada form First dinosaurs, mammals, crinoids, and modern echinoids appear 290 Permian -Pangea forms -Appalachians rise -90% of Earth’s species become extinct, including trilobites, blastoids, fish and amphibians because of heavy volcanism in Siberia 6Table of Contents Paleozoic “Age of Invertebrates” Modified after Carolina Rocks, contributed by J. Westmoreland 7Table of Contents  During the early 1800’s, English Geologist, Charles Lyell published a book called “Principles of Geology,” which became a very important volume in Great Britain. It included all of Hutton’s ideas, and presented his own contemporary ideas such as:  The principle of cross-cutting relationships: A rock feature that cuts across another feature must be younger than the rock that it cuts.  Inclusion principle: Small fragments of one type of rock but embedded in a second type of rock must have formed first, and were included when the second rock was forming.  The theory of natural selection was credited to Darwin (along with Alfred Russel Wallace) and he went on to write the famous “Origin of Species.” Darwin’s two goals in that work were: 1. To convince the world that evolution had occurred and organisms had changed over geologic time 2. The mechanism for this evolution was natural selection.  Charles Darwin (1809-1882) was an unpaid naturalist who signed up for a 5-yr expedition around the world aboard the H.M.S. Beagle. On this trip, he realized two major points. In spite of all species reproducing, no one species overwhelmed the Earth, concluding that not all individuals produced in a generation survive. He also found that individuals of the same kind differ from one another and concluded that those with the most favorable variations would have the best chance of surviving to create the next generation. Principles Behind Geologic Time, continued 10Table of Contents Standard 8-2.6: Infer the relative age of rocks and fossils from index fossils and the ordering of the rock layers.  “Relative age” means the age of one object compared to the age of another, not the exact age of an object. This method can only be used when the rock layers are in their original sequence.  All six of the original stratigraphic principles may be applied to determine the age of a rock. This process is called age dating. Correlation of strata by rock unit type (lithology) or fossil type (biology) using species, composition, or texture leads scientists to extrapolate relationships over large areas of land. Because rock layers can be “matched up,” we can guess that they were formed during the same period, so they usually are the same age.  Using the principles of original horizontality and superposition, we can conclude that oldest rock is always on the bottom because is was deposited 1st.  Deciphering the sequence of a rock outcrop is sometimes complicated by a features within the rock record called unconformities, which are specific contacts between rock layers. There are three types of unconformities that help us determine relative ages of rock layers: 1. Angular: Horizontal bed are uplifted and tilted or eroded followed by new deposition of horizontal beds. The figure to the right is an angular unconconformity. 2. Disconformity: Episodes of erosion or non- deposition between layers 3. Nonconformity: Sediment is deposited on top of eroded volcanic or metamorphic rock (indicates very long passage of time) Relative Age Dating Wikipedia (public domain) Tilted bed of sedimentary rock Horizontal bed of sedimentary rock 11Table of Contents Relative Age dating with index fossils  Biostratigraphy is the correlation of stratigraphic units based on fossil content. Biostratigraphically useful species are known as index fossils (or guide fossils) because they can be used as guides for recognition of chronostratigraphic units.  Index fossils are widespread, have short temporal durations resulting from rapid life spans, are abundant throughout their geographic and geologic ranges, and are easily recognized (unique).  Relative ages can also be determined using Lyell’s principle of cross-cutting relationships. In the figure to the right, both the gray and the yellow horizontal strata needed to be in place for the pink layer to cut them, therefore, the pink layer is the youngest. (Image from Plummer/ McGeary, 7th edition, 1996)  Trilobites are a commonly used index fossil because they are easy to recognize. We know exactly when certain species became extinct, such that we can compare rock layers that contain trilobites with a second rock layer and, based on position, determine if the second rock layer is younger. The photo to the right is a trilobite from the Mississippian period (photo courtesy of K. McCarney- Castle)  Fossils found in many rock layers have lived for long periods of time and cannot be used as index fossils. 12Table of Contents Parent Daughter half- life Mineral or Material Uranium238 Lead 206 4.56 BY Zircon, Uraninite, Pitchblende Uranium 235 Lead 207 704 MY Zircon, Uraninite, Pitchblende Potassium 40 Argon 40 1.251 BY Muscovite, biotite, hornblende, K- feldspar, volcanic rock, glauconite, conodonts Rubidium 87 Sr 87 48.8 BY K-mica, K-feldspar, Biotite, Metamorphics Thorium 230 Lead 206 75 KY Ocean sediments Thorium 232 Lead 208 1.39 BY Zircon, Uraninite, Pitchblende Carbon 14 Nitrogen 14 5730 yr Wood, bone, shell Commonly used radioactive isotopes Uranium-Lead decay series (U-Pb series)  Unlike carbon-14 dating, uranium dating cannot be used to date formerly living things; however, it is the most commonly used method in igneous rock dating because of the abundance of zircon minerals.  The subscripts of 235 and 238 are the atomic mass numbers of the element. Though each isotope has 92 protons in its nucleus, U-235 has 143 neutrons and U-238 has 146 neutrons.  Igneous rocks, or the magma from which it was formed, often intrudes overlying sedimentary rocks. By dating the magma, one can get at least a minimum age for the sedimentary rock. KY- thousand years. MY- million years. BY- billion years 15Table of Contents  From the time of Hutton, scientists were convinced that the earth was much older than the 6000 years predicted by the religious scholars.  Charles Lyell tried to estimate the age of the earth through the amount of evolution exhibited by marine mollusks in a specific time system.  Another method was to estimate the rate of deposition for sedimentary rocks.  Sir Edmund Halley proposed to estimate the age of the earth using salt content of the oceans, assuming that the oceans were once non-saline and that salt addition to the oceans corresponded in some linear fashion with time.  Lord Kelvin estimated the age of the Earth at 24-40 million years. He proposed that the Earth has been cooling since it formed, and he calculated the rate of cooling using principles of heat conduction.  It wasn’t until Henri Becquerel discovered radioactivity in 1896 and Madame Curie isolated radium 2 years later that people realized that the Earth had it’s own source of heat. Thus it became one of the most useful tools for future scientists.  The oldest rocks found so far on Earth (based on zircon grains from Australia) have been dated at 4.1-4.2 billion years.  Meteorites have also been dated at 4.6 billion years. Meteorites are considered to be remnants of a plant or asteroid that originally formed at the same time as the Earth, so that the Earth’s age is currently estimated to be 4.6 billion years.  The oldest fossils are preserved remains of stromatolites, which are layers of lithified blue-green algae, dating to approximately 3.5 billion years before present. How Old is Old? 16Table of Contents Eons: Precambrian: Earliest span of time Phanerozoic: Everything since Eras: Paleozoic Mesozoic Cenozoic Periods: Cambrian Ordovician Silurian Devonian Carboniferous (Missipp. & Pennsylvanian) Permian Triassic Jurassic Cretaceous Paleogene Neogene Quaternary Epochs: Paleocene Eocene Oligocene Miocene Pliocene Pleistocene Holocene We are living in the Phanerozoic Eon, Cenozoic Era, Quaternary Period, Holocene Epoch……..BUT Paleozoic “Age of Invertebrates” Mesozoic “Age of Reptiles” Cenozoic “Age of Mammals” 17Table of Contents Ordovician: Silurian:  The 1st animals with bones appear, though dominant animals are still trilobites, brachiopods and corals  The beginning of the construction of South Carolina  A very cold time in Earth’s history: there was a great extinction due to ice caps in present-day Africa  Four main continents: Gondwana, Baltica, Siberia and Laurentia  First land plants appear and land animals follow  Laurentia collides with Baltica and closes Iapetus Sea.  Coral reefs expand and land plants begin to colonize barren land.  First millipede fossils and sea scorpions (Euryptides) found in this period PaleoMaps used with permission from Christopher Scotese and are under copyright of C.R. Scotese, 2002 20 20Table of Contents Devonian (Age of the Fish) Mississippian:  First seed plants appear  Much of North America is covered by shallow seas and sea life flourishes (bryoza, brachipods, blastoids) Pennsylvanian:  Modern North America begins to form  Ice covers the southern hemisphere and coal swamps formed along equator.  Lizards and winged insects first appear.  Pre-Pangea forms. Dominant animal: fish  Oceans still freshwater and fish migrate from southern hemisphere to North America.  Present-day Arctic Canada was at the equator and hardwoods began to grow.  Amphibians, evergreens and ferns appear  The Acadian Orogeny, leading to S.C. metamorphism PaleoMaps used with permission from Christopher Scotese and are under copyright of C.R. Scotese, 2002 21 21Table of Contents Permian:  Last period of the Paleozoic  Pangea forms. Reptiles spread across continents.  The Appalachians rise  90% of Earth’s species become extinct due to volcanism in Siberia. This marks the end of trilobites, ammonoids, blastoids, and most fish. Triassic:  First dinosaurs appear  First mammals- small rodents appear  Life and fauna re-diversify  Rocky Mountains form.  First turtle fossil from this period  Pangea breaks apart PaleoMaps used with permission from Christopher Scotese and are under copyright of C.R. Scotese, 2002 22Table of Contents Standard 8-2.1: Explain how biological adaptations of populations enhance their survival in a particular environment. Adaptation and ‘Survival of the Fittest’  Some populations, whether mammals, amphibians, or reptiles are better adapted to living conditions than others, even within the same species, so they are better at surviving than others. Because their chances of surviving are increased, their chances of reproducing offspring are better, and their offspring will possess the same strong traits. This is the basis for natural selection over long periods of time.  Natural selection refers to the process where over long periods of time, helpful variations can appear in a species while “unfavorable” one disappear. For example, a group of frogs living on the rocky side of an island may, over time, adapt a gray skin color to help blend in with their rocky environment in while a group of frogs living on the more lush, vegetated side of the island may develop a green skin color to blend in with their particular environment. Even though the frogs are of the same species, they are able to incorporate different traits to help them survive in their environments.  The theory of natural selection, sometimes referred to as ‘Survival of the fittest,’ started with Charles Darwin’s 5-year trip around the world on the HMS Beagle. During this time, he noticed variations within the same species, especially in the Galapagos Turtles, and noted that some of the variations were favorable and some were not. He concluded that not all members of a species survive, which is why the world is not overpopulated by any one species. The practicality of their adaptation must be a determining factor for who survives and who does not. He published his findings on his return to England and wrote the classic work “The Origin of Species.” 25Table of Contents Standard 8-2.3: Explain how Earth’s history has been influenced by catastrophes (including the impact of an asteroid or comet, climatic changes, and volcanic activity) that have affected the conditions on Earth and the diversity of its life-forms. Punctuated Events Through Geologic Time  Environmental changes on earth are usually an indicator of a species extinction (or a species addition). These changes can be brought about by an asteroid or comet impact, volcanic activity, or climatic changes like the onset of ice ages. 1. Impact:  The most well-known extinction is the extinction of the dinosaurs. Scientists think that this mass extinction was caused by a large comet that impacted the earth in present-day Mexico, causing a massive quantity of dust to rise up into the atmosphere, possibly blocking out the sun and affecting the oxygen levels Earth. Many plants died, and the animals that depended on those plant for life died as well. In addition, it may have become very cold in a short period of time.  It took millions of years for the earth to recover, and when it did, the large dinosaurs were gone forever.  Certain species of birds, however, did survive and began to flourish. Birds are thought to be direct descendants of dinosaurs. 26Table of Contents 2. Climate Changes  Climate has always been a constantly changing phenomenon. The earliest atmosphere was devoid of free oxygen, and it wasn’t until the earliest life forms evolved that the present-day atmosphere began to form approximately 600 million years ago.  During the Paleozoic, warm shallow seas and tropical climates were common. Life forms that could not adapt to these conditions disappeared.  Throughout the Mesozoic era, plate movement shifted the continents and only the animals and plants with the greatest ability to adapt could survive the extreme changes in temperatures that occurred as a consequence. Plants with seed coverings and animals with constant internal temperatures (warm-blooded) lived during this era.  Climate continued to change during the Cenozoic and continues to change to this day, as issues of “Global Warming” have been on the fore-front for over a decade. It was only ~12,000 years ago that the world was in an “ice age” mode. Also, many mountain ranges formed during this era, causing climate differences due to elevation changes.  Ice ages have occurred many times in Earth’s history. Climate shifts like these may be caused by magnetic polar reversals or variation in the tilt of the earth (called Milankovitch cycles). Obviously, not all life can adapt to the extreme cold. Also, not all animals can adapt to the warming climate at the end of an ice age, which probably contributed to the extinction of the wooly mammoth. 27Table of Contents Summarize how scientists study Earth’s past environment and diverse life-forms by examining different types of fossils (including molds, casts, petrified fossils, preserved and carbonized remains of plants and animals and trace fossils) The study of Fossils  A fossil is the preserved remains of an organism that has died. Fossils tell scientists, called paleontologists, about living things such as their biology and environmental conditions over earth’s history through the rock record. In addition, they give clues to the conditions of the earth (i.e. climate) at the time that the fossil was preserved and possibly relate changes of an organism over time.  Definitions of fossil types: Mold fossils: when sediments bury an organism and the sediment hardens into rock. The organism decays slowly inside the rock, leaving an cavity in the shape of the organism.  Cast fossil: The cavity or mold mentioned above can filled in with mud. When the mud hardens, it takes on the shape of the organism.  Petrified fossil or permineralized fossil: Minerals like calcium can soak into the buried remains of an organism. The mineral replaces the remaining bone and changes it into rock.  Carbonized fossil: When organism parts are pressed between layers of mud or clay that hardens over time, squeezing the decaying organism away and leaving a carbon imprint in the rock, since all living things contain carbon.  Trace fossil: When the mud or sand hardens into rock where a footprint, trail or burrow was left behind. 30Table of Contents Standard 8-2.2  The fossil record, like the rock record, is an important record for understanding life on earth before the dawn of man.  Extinctions and new life forms are also found within the fossil record.  Fossils can also show structural similarities and differences in organisms over time revealing the diversity of life forms on earth. Nearly 90 percent of organisms that have lived on the earth are now extinct. Carbon imprint of fish remains, age unknown Belemnite fossil (cast), cut and polished. Related to present-day squid. Extinct. Brachiopods in a sandstone matrix and an individual brachiopod cast. Extinct. A trilobite cast from the Mississippian Period. Extinct. Ammonite fossil (cast), cut and polished. Related to present-day snail. Extinct. 31Table of Contents Standard 8-2: The student will demonstrate an understanding of Earth’s biological diversity over time. (Life Science, Earth Science) Indicators 8-2.1 Explain how biological adaptations of populations enhance their survival in a particular environment. 8-2.2 Summarize how scientists study Earth’s past environment and diverse life-forms by examining different types of fossils (including molds, casts, petrified fossils, preserved and carbonized remains of plants and animals, and trace fossils). 8-2.3 Explain how Earth’s history has been influenced by catastrophes (including the impact of an asteroid or comet, climatic changes, and volcanic activity) that have affected the conditions on Earth and the diversity of its life-forms. 8-2.4 Recognize the relationship among the units—era, epoch, and period—into which the geologic time scale is divided. 8-2.5 Illustrate the vast diversity of life that has been present on Earth over time by using the geologic time scale. 8-2.6 Infer the relative age of rocks and fossils from index fossils and the ordering of the rock layers. 8-2.7 Summarize the factors, both natural and man-made, that can contribute to the extinction of a species. South Carolina Science Academic Standards: Grade 8 32Table of Contents