Flashcards About Geology – Geology
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Earth formation
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about 4.6 billion years ago.
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Homo sapiens appeared on Earth
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between about 300,000 and 150,000 years ago. We are new creatures to earth!
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organisms have evolved
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(changed) through genetic recombination, mutation, and natural selection!
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Key to Geologic Time Travel:
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Geological Time Scale
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how much do we know?
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The entire world and universe is in motion! Rocks are moving!
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Big Bang Theory
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(cosmology) the theory that the universe originated 20 billion years ago from the cataclysmic explosion of a small mass of matter at extremely high density and temperature how the universe formed
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nebula hypothesis
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A model that explains the formation of the solar system from a large cloud of gas and dust floating in space 4.56 billion years ago. how the earth formed
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what lies below the land and ocean floor
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Rocks and Minerals (& Some Fluids)
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homer
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wrote about geology and water, curiosity leads to exploration
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principle of uniformitarianism
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Earth processes occurring today are similar to those that occurred in the past James Hutton -science scholar- defined earth as a place where: "We find no vestige of a beginning, no prospect of an end. (James Hutton, 1785)"
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past geologic events
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Earthquakes and volcanoes: Plate Tectonics. Volcanic eruptions Continents flooded by inland seas. True/False Drifting and colliding continents. Glaciers have covered large parts of continents. In US also-yes: Climate Change! Meteorite and asteroid impacts. One every 1000 yr Changes in chemistry of oceans and atmosphere. Changes to life on Earth through time - sometimes slow, sometimes swift and deadly. Evolution?
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geology
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Science dealing with the earth's history as recorded in rocks. Study of the earth Two main major branches of geology: Physical Geology Historical Geology
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physical geology
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deals with Earth materials and processes
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historical geology
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deals with origin and changes of Earth and life through time and space.
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3 Major Themes in this class
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Deep time, Plate tectonics, Evolution
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what do geologists do
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Study the structure of mountain ranges &Forces Attempt to predict geologic hazards &Links. Identify minerals - Earth's Composition. Study rivers, floods, glaciers, and water Geologic events & causes of those events - Uniformitarianism applied! Search for fossil fuels and minerals.
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scientific method in geology
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Science operates through the use of this- to answer geologic questions & puzzles. Three parts! Hypothesis Setting Data Collection Draw Conclusion The data may be obtained through: observations and/or experiments, which can be repeated and verified by others.
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hypothesis setting
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Question is formulated
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observations
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collect samples and study data Use and Develop multiple working hypotheses ideas to explain the observations
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conclusion
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draw from test of the hypothesis: by experimenting and either accept, reject, or modify the hypothesis.
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principle of parsimony
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The principle of applying the simplest possible explanation to any set of observations; also called Occam's razor.
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theory
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A hypothesis that survives repeated tests, and is supported by a large body of evidence, may be elevated to the status of a theory. not just an wild idea or a guess. Examples the theory of relativity (physics) plate tectonics theory (geology) evolutionary theory (biology) atomic theory (physics).
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deep time
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Recognition of immensity of geologic time i.e., 4.6 byrs ( earth - not born 4004 BCE or 7000 yrs ago - doctrine wrong!) geochronology. Same thing as deep space, brain cannot understand how old earth is, can memorize a number but don't actually understand, concept beyond brain Age of Earth
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plate tectonics
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theory that the lithosphere is made up of plates that float on the athenosphere and that the plates posible are moved by convection currents Movement of earth features it has revolutionized the understanding of geology. THE EARTH MOVES! explains many large scale patterns in the Earth's geological record. It is a "great unifying theory" in geology. The Earth's surface or lithosphere is divided into plates (about 7 large plates and 20 smaller ones) Plate movement is due to convectional flow of molten rock material --(circular movement of the material in asthenosphere due to hot material rising and cooler material sinking). The plates only move a few centimeters per year - about the rate at which your fingernails grow.
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evolution of life
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Inherited characteristics within the populations change over generations. Helps them adapt to their surroundings origin of earths creatures
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geochronology
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The science that deals with determining the ages of rocks, fossils, earth
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earth history in brief
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Universe-12-14 Bil.yrs 2. Earth Origin: 4.6 billion years old 3. Major Geologic Changes over time: use of Geologic Time scale
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geologic time scale
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has been determined over the years by: 1. relative dating techniques, 2. correlation, 3. examination of fossils 4. radiometric dating techniques. Boundaries are drawn where important changes occur in the fossil record, such as extinction events (organisms die out quickly).
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geochronologic units.
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From the largest to the smallest units, : Eons - largest amount of time Eras Periods Epochs - smallest amount of time These units are time units.
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eons
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longest time units Phanerozoic Eon (13%) - has three eras "Phaneros"=evident; "zoo"=life Latin terms used: 1.paleo+zoic=ancient life; 2. meso+zoic=middle life; 3. ceno+zoic=recent life Precambrian Eon (87%)- Before Cambrian Life (before 542 mil years ago) includes two below: Proterozoic Eon Archean Eon
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era
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Three eras in the Phanerozoic (Evident life) Eon. In order from oldest to youngest, the three eras are: Paleozoic Era - "ancient life" (such as trilobites-now extinct) Mesozoic Era - "middle life" (such as dinosaurs-now extinct) Cenozoic Era - "recent life" (such as mammals-thriving today/"age of humans")
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derivation of period
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"Cambrian Period-1830s" -Latin for "Wales"-named by A. Sedgwick "Ordovician-after 1835-1871"-Celtic tribe "Ordovices" -(long dispute settled by combination of lower Cambrian and upper Silurian into Ordovician) "Silurian-1835" - Inhabitants of Silures -by Sir R.I. Muchison "Devonian-1839" - Named for Devonshire, England - by Murchison "Carboniferous-1822" - named for coal beds of north-cent. England (Miss. & Penn. In NA); "Permian-1840" - after Permia = ancient Russian Kingdom -by Murchison "Triassic-1834" - after tri-fold division of rocks in Germany "Jurassic-<1859"-after Jura Mtns of France and Switzerland "Cretacceous"-named after Creta: is Latin for chalk of France, Belgium, Holland;White Cliffs of Dover, England "Paleogene" -Age of mammals (Oligocene+Eocene+Paleocene) "Neogene" Younger (Miocene and Pliocene) "Quarternary" Pleistocene" Age of glaciers +"Holocene" Age of Man
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methods of dating rocks
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Absolute age-dating methods Relative age-dating methods -
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absolute age
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The actual age +/-. Quantifying the age of the rock or mineral in years. The discovery of radioactivity in 1896 gave us the tools to find the absolute age of a rock - Bequerel. Radiometric dating
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relative age
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Determining which rocks are older and which are younger. "Rock unit A is older than rock unit B". The geologic time scale was developed primarily through relative age-dating methods and radiometric age-dating!
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cambrian period
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1830s" -Latin for "Wales"-named by A. Sedgwick
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ordovician period
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after 1835-1871"-Celtic tribe
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ordovices period
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(long dispute settled by combination of lower Cambrian and upper Silurian into Ordovician)
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silurian period
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1835" - Inhabitants of Silures -by Sir R.I. Muchison
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devonian period
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1839" - Named for Devonshire, England - by Murchison
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carboniferous period
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-1822" - named for coal beds of north-cent. England (Miss. & Penn. In NA);
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permian period
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-1840" - after Permia = ancient Russian Kingdom -by Murchison
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triassic period
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1834" - after tri-fold division of rocks in Germany
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jurassic period
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<1859"-after Jura Mtns of France and Switzerland
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cretacceous period
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named after Creta: is Latin for chalk of France, Belgium, Holland;White Cliffs of Dover, England
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paleogene period
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Age of mammals (Oligocene+Eocene+Paleocene)
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neogene period
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Younger (Miocene and Pliocene)
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Quarternary/ Pleistocene period
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age of glaciers
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Holocene period
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age of man
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radiometric dating
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involves analysis of the breakdown of unstable radioactive elements in rocks. Radioactive elements decay by releasing subatomic particles from their nuclei. Through this process, the unstable radioactive "parent element" is converted to a stable "daughter" element. Example: Uranium-235 decays to form lead-207
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radioactive decay
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Many radioactive elements can be used as geologic clocks. Each radioactive element decays at its own nearly constant rate. The rate of decay can be measured in a lab. 2. Once this rate is known, geologists can determine the length of time over which decay has been occurring by: measuring the amount of radioactive "parent" element and the amount of stable "daughter" elements
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half life
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the time it takes for half of the parent radioactive element to decay to a daughter product. Each radioactive element has its own unique one (Decay = Nucleus gives off alpha particles, beta particles, and gamma radiation-creating new daughter elements) Example: Uranium-235 has a half-life of about 704 million years.
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uranium 235 decays to form lead-207.
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Uranium-235 has a half-life of about 704 million years. After 704 million years, only half (50%) of the uranium atoms in the mineral remain. (The rest have decayed to lead-207.) After another 704 million years, only half of that amount (or 25%) of the uranium atoms remain. So, a rock with 25% uranium-235 and 75% lead-207 must be 1,408 million years old (or 1.408 billion years old).
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oldest rocks in world
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some rocks found in Canada's Northwest Territories have been dated at 4.04 billion years old
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earth layers
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criteria 1- composition- chemical crust layer one- 25 miles mantle layer 2 core layer 3 criteria 2- physical properties lithosphere- layer 1, rocky and rigid athenosphere- layer 2, molten mesosphere- layer 3, rigid core- layer 4
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lithosphere
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A rigid layer made up of the uppermost part of the mantle and the crust. The lithosphere is about 100 km thick and consists of the rigid, brittle crust layer and uppermost mantle layer. Rigid lithospheric plates rest (or "float") on the asthenosphere, (the easily deformed, or partially molten part of mantle below the lithosphere.) The plates are moving, but their rates (3-5 cm/year) and directions of movement vary
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athenosphere
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The soft layer of the Mantle on which the tectonic plates move
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mesosphere
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Beneath the asthenosphere is the strong lower part of the mantle (from the bottom of the asthenosphere to the earth's core)
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core
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Iron-nickle alloy with small amounts of oxygen, silicon, and sulfur
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convectional flow
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of molten rock material --(circular movement of the material in asthenosphere due to hot material rising and cooler material sinking)
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types of plate boundaries
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Divergent Convergent Transform
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divergent
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where plates move apart from one another.
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convergent
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where plates move toward one another.
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transform
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where two plates slide past one another
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evolution
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In biology and science, "evolution" is the "great unifying theory" for understanding the history of life thru fossils and age-dating. As a result of evolution, plants and animals living today are knwn to be different from their ancestors. Notes: 1. The organisms differ in appearance, genetic characteristics, body chemistry, and in the way they function. 2. These differences appear to be a response to: changes in the environment and competition for food. Key: Fossils record the changes in organisms over time.
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natural selection process
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Charles Darwin and Alfred Wallace were the first scientists to assemble a large body of convincing observational evidence in support of evolution. Any given species produces more offspring than can survive to maturity. Variations exist among the offspring - genes. Offspring must compete with one another for food and habitat - some cannot compete. Offspring with the most favorable characteristics are more likely to survive to reproduce (this does not mean you will!). Beneficial traits are passed on to the next generation through genetic recombination
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fossils
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provide direct evidence for changes in life in rocks of different ages.
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homologous structures
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Certain organs or structures - but they are modified to function differently , Structures in different species that are similar because of common ancestry.
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vestigial organs
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appear to have little or no use. (These structures had a useful function in ancestral species)
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lines of evidence for evolution
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Genetics (study of DNA molecule) Biochemistry (Biochemistry of closely-related organism is similar, but very different from more distantly related organisms). Molecular biology (sequences of amino acids in proteins)
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organic evolution
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-The study of fossils in geology: indicate that plants and animals of each geologic era arose from earlier species by the process we call "organic evolution". - Organic evolution refers to changes that have occurred in organisms with the passage of time. - Darwin's Book: "On the Origin of Species by..........." published: 24 November 1859, republished in 1872, with shorter name.
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relativity of age to a geologist
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As such, never loan a geologist money to be paid back in the recent future, Because to a geologist - "Recent" is a few hundred thousand years
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fossils definition
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the remains or traces of prehistoric life. They can tell us much about the history of the Earth and life. The Remains of past life or evidence of life!
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early interpretation of fossils
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Greek philosopher, Herodotus, 450BC 1.noticed fossil seashells in outcrops of sedimentary rocks that were far from the sea, and high above sea level. 2.concluded that the area had once been beneath the sea. This is true!!!! 3. Seas have once covered the continents. To some, the seashells on mtns: maybe: suggested the Biblical flood of Noah. But why would animals that lived in the water be killed by a flood??? They would not!!!! ICE TOO! KEY Question?: Why are different types of fossil animals and plants found in the different sedimentary layers?
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relative age dating
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produces a more valid interpretation of fossils and sedimentary rocks. The "fossils" are the record of plants and animals "which lived and died" over an "immense span of geologic time".
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how do fossils form
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These characteristics are "most favorable" for fossil preservation: - Rapid burial with sediment to prevent destruction of the dead organism by scavenging or bacterial decay. - Presence of hard parts like bones, teeth, or shell.
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time definition- fossils in rocks
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When plants and animals -dead or alive - are covered by sediment and buried, they may become preserved as fossils. For example: People of Pompeii - Other: Santorini Island, Krakatoa ?- volcanic eruption can preserve also
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burial in sediment
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When plants and animals are covered by sediment and buried, they may become preserved as fossils.
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fossils types
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Soft parts: may be preserved as fossils by: Freezing (wooly mammoths) Desiccation (drying or mummification) Preservation in tree sap (amber) - Lab Book! Preservation in tar (LaBrea tar pits) Preservation in peat bogs (Lindow man - England; Tollund man - Denmark) Carbonized imprints in fine-grained sediment.
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3 main types of rocks
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Igneous Rocks = Fire rocks - Hawaii Metamorphic Rocks = Changed rocks by heat/pressure Sedimentary Rocks = From sediment Note: Atoms form "Chemical elements" that form "Minerals" that form "Rocks"
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igneous rocks
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Form directly from cooling of magma or lava. Ex: granite (magma) and obsidian (lava)
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metamorphic rocks
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Made when heat, pressure, or fluids change one type of rock into another type of rock
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sedimentary rocks
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Formed when particles of broken rock and organic materials are pressed and cemented together to form new rocks. Sediment is deposited worldwide on earth. Sediment includes: Gravel, sand, silt, mud and clay from rivers and streams Clay and organic debris settling to the seafloor Dust and volcanic ash carried by the wind and deposited rock groups = clastic or chemical rocks Most occur in the form of layers called: beds" = "strata" = "layers".
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clastic sedimentary rocks
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(also called "detrital" = based on size Conglomerate or Breccia - largest size pieces Sandstone ---sand size Siltstone ---silt size Shale or Claystone ---clay size
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Chemical/biochemical sedimentary rocks
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(mostly limestone, but evaporites or rocks precipitated from water) ------ Organic sedimentary rocks (coal)
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grain size
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Gravel forms Conglomerate = rounded pieces or Breccia = angular pieces Sand forms Sandstone Silt forms Siltstone Clay forms Shale (= fissile - laminations) Claystone = massive = very thick layer
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gravel
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forms conglomerate- rounded pieces, or breccia- angular pieces
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sand
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sandstone
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silt
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siltstone
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clay
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Clay forms Shale (= fissile - laminations) Claystone = massive = very thick layer
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chemical sedimentary rocks
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Evaporites Carbonate rocks Siliceous rocks
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evaporites
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form during the evaporation of water and precipitation of chemicals
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carbonate rocks
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form both by chemical processes and biochemical processes
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siliceous rocks
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form from chemical processes: (silica from water) or biochemical processes (shells of silica-secreting organisms)
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biochemical or organic
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sedimentary rocks from plant burial Peat Lignite - soft coal Bituminous coal Anthracite coal
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foliated metamorphic rocks
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Preferred alignment of platy mineral particles Types = Slaty vs schistosity vs gneissic banding Typically classified by texture Slate (low grade), phyllite, schist, gneiss (high grade) Minerals: low to high grade: Chlorite-Biotite-Garnet-Sillimanite (depicts different metamorphic zones)
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nonfoliated metamorphic rocks
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Randomly arranged crystals and interlocked mineral particles Fine-grained, coarse-grained Typically classified by composition as: Marble, quartzite
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igneous rocks types
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Depends on the composition of magma 1. Felsic/granitic: 2. Intermediate/andesitic: 3. Mafic/basaltic
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felsic/ granitic
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Silica rich, typically related to continental or land crust
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mafic/ basaltic
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Silica poor, usually related to the oceanic (sea) crust
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intermediate/ andesitic
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Commonly associated with convergent plate boundaries along the rim of Pacific
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igneous rocks composition
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Mineral Makeup FELSIC= Light Minerals Fe/Alum/Si INTERMEDIATE = Light and Dark Minerals - Mafic= Dark Minerals
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igneous rocks texture
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Size of Mineral Grains Intrusive Rocks - Coarse Grained Texture - Phaneritic Granite -Felsic Minerals Diorite - Felsic and Mafic Minerals Gabbro - Mafic Minerals Extrusive Rocks - Fine-grained Texture - Aphanitic Rhyolite Andesite Basalt
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intrusive igneous rocks
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Coarse Grained Texture - Phaneritic Granite -Felsic Minerals Diorite - Felsic and Mafic Minerals Gabbro - Mafic Minerals
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extrusive igneous rocks
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Fine-grained Texture - Aphanitic Rhyolite Andesite Basalt
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bowen's reaction series
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The simplified pattern that illustrates the order in which minerals crystallize from cooling magma according to their chemical composition and melting point
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faults
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Break and movement of blocks of rock (shown later)
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anticlines and synclines
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bending of layers of rock (shown later)
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unconformites
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area of rock layer showing erosion or nondeposition (shown later)
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steno's laws
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basis of statigraphy Principle of Superposition Principle of Original Horizontality Principle of Original Lateral Continuity
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principle of superposition
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Oldest rocks on the bottom -Younger rocks on top
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principle of original horizontality
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Sediments are deposited in flat, horizontal layers (beds or strata).
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principle of lateral continuity
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Sediments are deposited over a large area in a continuous sheet.
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stratigraphy
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the study of layered rocks. allows geologists place rock units into a layered sequence (oldest rock layer to youngest rock layer), to help interpret Earth history.
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cross cutting relationships- faults
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Where a fault cuts across a sequence of sedimentary rock, the fault is younger than the rocks it cuts. The sedimentary rocks are older than the fault which cuts them, because they had to be there first, before they could be faulted
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cross cutting relationships- intrusions
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Where an igneous intrusion cuts across a sequence of sedimentary rock, the sedimentary rocks are older than the igneous rock which intrudes them. The intrusion is younger than the rocks it cuts. Igneous Intrusions = Dikes and Sills
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cross cutting relationships- unconformity
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The irregular erosional surface is an unconformity. The unconformity is younger than the rocks that have been eroded. 3 unconformities: 1. angular unconformity (sed/tilted), 2.disconformity (sed/sed), 3. nonconformity (sed/ign.-rk Or meta-rk)
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principle of inclusions
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sedimentary rocks Fragments of eroded rock overlie the unconformity. These are gravel clasts or inclusions. The "pieces of gravel" are older than the bed in which they are found. igneous rocks A "xenolith" is a fragment of the surrounding rock which has broken off during an intrusion and fallen into the magma. The xenolith is older than the igneous rock which contains it.
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xenolith
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a piece of rock of different origin from the igneous rock in which it is embedded
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gravel clasts
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Metaconglomerate
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abraham werner
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"Neptunists" All rocks from water: Named after Neptune -Roman God of sea contributed to the geologic time scale. He recognized but not true that: Neptunists = "of ocean formation of rocks" ideas were criticized because he could not explain what had happened to such an immense volume of water, and because he insisted that lava flows were precipitated from water.
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james hutton
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"Plutonists" All rocks from magma: Named Roman god of Underworld (wrote Theory of the Earth -1785) - Gave us "Principle of Uniformitarianism" igneous origins Other geologists showed the "volcanic origin of lava flows". disagreed with Werner (Netunist). Saw Earth as a dynamic, ever changing place where rocks and mountains form slowly, and are slowly weathered and eroded. Recognized that "the present is the key to the past". Recognized uniform natural laws govern geologic processes, later called "uniformitarianism". Published "Theory of the Earth" in 1785. Realized the immensity of geologic time. "No vestige of a beginning, no prospect of an end." First interpretation of sequence of events in an unconformity. Saw a world dominated by cycles - rock cycle, sedimentation cycles, etc. recognized the significance of the unconformity at Siccar Point in Scotland
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charles lyell
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- opposing view of Catastrophism; Wrote "Principles of Geology" -Said that seemingly abrupt changes in the fossil record were interpreted to result from missing strata that were eroded along the unconformity. -Said that the ancestors of the "new" fossil groups were actually present in the underlying strata.
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uniformitarianism
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means that geologic processes are uniform through time. --Physical and chemical laws that govern nature are uniform. --Uniform natural laws govern weathering, erosion, glacial movement, earthquakes, volcanic eruptions, and the transport of sediment by moving water.
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events not occurring today
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Huge meteorite impacts? Extensive volcanism? Large glacial ice sheets accompanied by much lower sea levels? Differences in atmospheric chemistry? - Earth's original atmosphere lacked oxygen, so chemical process acting in the weathering environment did not include oxidation
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actualism
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Many geologists prefer to use this term to emphasize the importance of natural laws to the concept of uniformitarianism. the principle that natural laws governing past and present processes on Earth have been the same.
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unconformity
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is an ancient surface of erosion (or non-deposition), separating older rocks from younger rocks.
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angular unconformity
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If the older rocks are folded or tilted
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william smith
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(1769-1839) was an English surveyor and civil engineer who was working to site canals to transport coal in England. He saw that layers of rocks: (1) occurred in a definite order, and (2) that rock units could be differentiated on the basis of the fossils they contain.
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principle of fossil succession
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Fossils occur in a consistent vertical order in sedimentary rocks all over the world. This is the Principle of Fossil Succession. Geologists interpret fossil succession to be the result of "evolution" - the natural appearance and disappearance of species through time.
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baron george leopold cuvier
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(1769-1832), a French vertebrate paleontology expert (along with Alexander Brongniart), --confirmed William Smith's findings that fossils display a definite vertical succession in the rock record, and that the succession is basically the same in widely separated areas. also noted that the fossils changed across unconformities. He concluded that there had been a series of catastrophic floods. ?????? Sea level change actually. This viewpoint became known as: catastrophism.
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catastrophism
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comes into play episodically with events such as asteroid impacts, or sudden, severe climatic changes that cause extinctions, and other unusual events.
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catastrophism vs uniformitarianism
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Both uniformitarianism and catastrophism probably operate jointly. Uniformitarianism dominates the day-to-day processes. Catastrophism: episodic events
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charles darwin
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English biologist and geologist. provided a hypothesis to account for the observed fossil succession. He served as a naturalist in a 5-year mapping expedition around the world on the H.M.S. Beagle. He gathered volumes of data to support his hypothesis of the evolution of organisms by natural selection.
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natural selection
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based on the following observations: A given species produces more offspring than can survive to maturity. Variations in morphology (form and structure) and physiology (organs and functions) exist among individuals of a species. The individuals of a species must compete with one another for food and habitat. Individuals with the most favorable traits are more likely to survive to reproduce. Beneficial traits are passed on to the next generation.
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cause of variation
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Darwin did not know the cause of the variations among individuals in a species. ---Many years later, after Darwin's death, scientists determined that variations within a species are caused by new gene combinations that occur during reproduction, and from genetic mutation.
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louis aggasiz
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(1807-1873) was a Swiss paleontologist who arrived in North America in 1846 and founded the Harvard Museum of Comparative Zoology. He studied glaciers and proposed that ice sheets once covered much of North America and Europe ("Ice Age hypothesis").
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ice age hypothesis
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Evidence includes: Glacial striations (scratches on rock) Glacial erratics (huge boulders transported by ice) Glacial moraines (mounds of rock debris deposited by melting glaciers) Lakes scoured by glacial erosion The "Ice Age" was recognized as the main event of the Pleistocene Epoch (1.5 million years ago to 8000-10,000 years ago). Ice blanketed one third of Earth's land area.
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james hall
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(1811-1898) was the director of New York's first geological survey. He recognized that fossils in 40,000 ft (7.5 mi) thick sedimentary rock sequence in NY were deposited in shallow water, and concluded that the seafloor had subsided during deposition & The Appalachian Mountains were later raised from a marine basin.
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ferdinand V. hayden
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(1829-1887) - mapped geology of Badlands of South Dakota and other areas in the west. *****Helped convince Congress to establish Yellowstone National Park, the oldest national park in the US-"Site of one of largest ancient volcanoes in the world, with caldera-~43 miles across-630k yrs ago". At end of dead volcanoes of Snake River Plain (like Hawaiian Chain)
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John Wesley Powell
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(1834-1902) - journeyed by boat through Grand Canyon on Colorado River to map geology despite having lost an arm in Civil War. 2nd Director of the U.S. Geological Survey.
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cope and marsh
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were rivals who competed to hire professional collectors to discover, describe, and name dinosaur bones in the western U.S.
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O.C. Marsh
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(1831-1899) - first professor of paleontology at Yale University, and later founded the Peabody Museum of Natural History.
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Edwin D. Cope
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(1850-1897) - wealthy Quaker who taught at the University of Pennsylvania. The "Bone Wars" 80 new species-O.C.&56E.D
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The Bone Wars
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These geologist were fairly wealthy initially, but spent their entire fortune on fighting "The Bone Wars" - Criticizing each other! E.D. Cope stated his brain was "larger" than O.C. Marsh He sent his brain to be studied after death to see who had larger brain - Was it he or O.C. Marsh.- his life long combatant O.C. Marsh never took challenge!
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results of work of cope and marsh
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Thousands of specimens of dinosaurs were collected for study and as museum exhibits. Enhanced our understanding of life in the Mesozoic Era. Provided evidence for evolution. Established paleontology as a science with a spirit of discovery.
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sedimentary rocks contain
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the fossil record, which preserves the evolving story of life on Earth. examples: archimedes- bryozoan trilobite ammonoid cephaloid
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mineral definition
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A mineral composes rocks! a substance that is: 1. naturally occurring 2. Solid and inorganic 3. has a specific chemical composition 4. specific crystalline structure
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mineral properties
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1. color - how it looks in light 2. streak - color of powder on porcelain 3. luster - how it shines in reflected light 4. cleavage - tendency to break along planes 5. Hardness - Moh's hardness scale 6. crystalline system - cubic, or hexagonal 7. Other secondary- magnetic, taste, feel, flexibility Silicates vs non-silicate minerals = silica vs no silica in chemical formula
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mineral types
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Silicates - contain silica in chemical structure Clay minerals - weathered minerals Carbonates - calcite minerals Evaporites - salt minerals
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characteristics of sediment
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depend on: Tectonic setting - "Mountain" or "sedimentary basin" or "ocean basin" Physical, chemical, and biological processes in the depositional environment Method of sediment transport - how far have sediments moved and how?
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principle tectonic elements of a continent
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Craton - Shield - Platform Orogenic belt
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depositional environments
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All of the physical, chemical, biological and geographic conditions under which sediments are deposited. By comparing modern sedimentary deposits with ancient sedimentary rocks, the depositional conditions can be interpreted.
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sediment grain size or texture
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The texture of a sedimentary rock can provide clues to the depositional environment.
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texture
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size, shape, sorting, and arrangement of grains in a sedimentary rock.
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fine grained textures
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typically indicate deposition in quiet water or deep water.
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coarse grained textures
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In general, it takes higher energy and velocity of water
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3 categories of depositional environments
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(earth locations): 1. Marine environments (ocean) 2. Transitional environments (along contact between ocean and land) 3.Continental environments (on land-terrestrial)
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marine depositional environment
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Continental shelf - shallow water (0-200m) -sand &gravel -waves and currents Continental slope - deeper ocean (200m-1400m) 3. Continental rise (1400-3200m)-turbidity currents Abyssal plain - deepest ocean (>3200m) - oozes, fine grain sediments/clay The deep ocean floor (studied by "Alvin" sub. vehicle) Nearly flat Water depths of 3 - 5 km + (2 - 3 mi. & deeper) Covered by very fine-grained sediment and shells of microscopic organisms -------------Clay & Oozes Volcanic ash Foraminifera (calcareous) Radiolarians (siliceous) Diatoms (siliceous)
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transitional depositional environments
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Environments at or near the transition between the land and the sea. Deltas Beaches and barrier Islands Lagoons Tidal flats Estuaries
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deltas
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Rivers move across coastal areas - hundreds of kilometers of shifting
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beaches and barrier islands
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Shoreline deposits -Ocean and lakes Exposed to wave energy Dominated by sand Marine fauna (organisms) A few km or less in width but may be more than 100 km long Separated from the mainland by a lagoon (or salt marsh) May be associated with tidal flat deposits and ripple marks/flooding
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lagoons
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Bodies of water on the landward side of barrier islands Protected from the pounding of the ocean waves by barrier islands Contain finer sediment than the beaches (usually silt and clay) Lagoons are also present behind reefs, or in the center of atolls.
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tidal flats
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Nearly flat, low relief areas that border lagoons, shorelines, and estuaries Periodically flooded and exposed by tides (usually twice each day) May be cut by meandering tidal channels May be marshy, muddy, sandy or mixed sediment types (terrigenous or carbonate) Laminations and ripples are common Sediments are intensely burrowed Stromatolites (Algal mats) may be present (if conditions are appropriate)
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estuaries
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Mouth of a river drowned by the sea Brackish water (mixture of fresh and salt) May trap large volumes of sediment Sand, silt, and clay may be deposited depending on energy level Many estuaries formed due to sea level rise as glaciers melted at end of last Ice Age Some formed due to tectonic subsidence, allowing sea water to migrate upstream
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continental environments
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Rivers or fluvial environments Alluvial fans - mountains flash floods Lakes (or lacustrine environments) Glacial environments - Ice Eolian environments - Wind
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fluvial environments
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Braided and meandering river and stream systems River channels, bars, levees, and floodplains are "subenvironments" Channel deposits are coarse, rounded gravel, and sand. Bars are sand or gravel. Levees are fine sand or silt. Floodplains are covered by silt and clay.
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alluvial fans
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Fan-shaped deposits at base of mountains. Most common in arid and semi-arid regions with rapid erosion. Sediment is coarse, poorly- sorted gravel and sand.
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lakes/ lacustrine environments
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Filled with terrigenous, carbonate, or evaporitic sediments Sediments are typically fine grained but may be coarse near the edges
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ice/ glacial environments
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Sediment is eroded, transported, and deposited by ice (glaciers) Glacial deposits called "till" contain large volumes of unsorted mixtures of boulders, gravel, sand and clay
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eolian environments
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Wind is the agent Dominated by sand and silt-cross-bedding & dunes Common in many desert regions
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color of sedimentary rocks
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Black and dark gray "coloration" in sedimentary rocks generally indicates the presence of: organic carbon and/or iron. Organic carbon in sedimentary rocks requires "anoxic" environmental conditions.
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texture interpretation of sedimentary rocks
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Texture = size, shape, sorting, and arrangement of grains in a sedimentary rock. The texture of a sedimentary rock can provide clues to the depositional environment. Fine-grained textures typically indicate deposition in quiet water. In general, it takes higher energy to transport larger grains.
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grain size- sedimentary
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Sedimentary grains are categorized according to size using the Wentworth Scale.
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wentworth scale
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gravel: greater than 2 mm sand: 1/6-2 mm silt: 1/256- 1/16 mm clay: less than 1/256 mm
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conglomerates
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have rounded clasts. If the particles are angular, the rock is a breccia
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sedimentary structures
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Larger features which form during (or shortly after) deposition of the sediment, but before "lithification". Stratification (= layering or bedding) is the most obvious feature of sedimentary rocks. The layers (or beds or strata) are visible because of differences in the color, texture, or composition of adjacent beds.
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graded bedding
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The grain size in a graded bed is coarser at the bottom and finer at the top. Graded bedding results when a sediment-laden current (such as a turbidity current) begins to slow down.
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cross-bedding or cross- stratification
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An arrangement of beds or laminations in which one set of layers is inclined relative to the others - planar or trough x-beds.
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ripple marks
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Undulations of the sediment surface produced as wind or water moves across sand. Symmetric ripple marks are produced by waves Asymmetric ripples form in unidirectional currents (such as in streams or rivers).
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mud cracks
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A polygonal pattern of cracks produced on the surface of mud as it dries.
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scour marks
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Depressions or erosional features formed as a current flows across a bed of sand.
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determining up direction
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Because rocks can be overturned (folded) by tectonic forces. Examine sedimentary structures to determine "up direction". Graded beds Cross beds Mudcracks Scour marks Symmetrical ripples Stromatolites Burrows Tracks
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4 major types of sandstone
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Quartz sandstone - dominated by quartz Arkose ss - 25% or more feldspar Graywacke ss - about 30% dark fine-grained matrix Lithic sandstone - quartz, muscovite, chert, and rock fragments. Less than 15% matrix.
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lithostratigraphic unit
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A body of sedimentary, extrusive igneous, metasedimentary, or metavolcanic rock distinguished on the basis of lithologic characteristics (texture, color, composition, etc.) and stratigraphic position. The smallest lithostratigraphic rock unit is the bed.
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formations
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Lithologically homogeneous & mappable Distinct and different from rock units above and below. Traceable from exposure to exposure, and of sufficient thickness to be mappable Named for a geographic locality where well exposed.
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members
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Subdivisions within formations
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group
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A set of similar or related formations
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facies
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-The sedimentary characteristics of a particular rock unit & -which we can be use to interpret the depositional environment. Every depositional environment puts a distinctive imprint on the sediment, making a particular facies.
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facies change
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Each depositional environment grades laterally into other depositional environments.
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transgression.
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A sea level rise. produces a "fining-upward" (deepening-upward) sequence of facies. Finer-grained (deeper water) facies overlie coarser-grained (shallower water) facies. Sometimes called an onlap sequence.
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onlap sequence
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Sedimentation during a transgression produces an
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offlap sequence
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Sedimentation during a transgression produces an
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correlation
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The branch of geology that deals with the correlation of rock units from one area to another is known as stratigraphy.
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lithostratigraphic correlation
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Matching up rock units on the basis of lithology and stratigraphic position. Demonstration of lithostratigraphic correlation from one exposure to another.
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biostratigraphic correlation
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up rock units on the basis of fossils they contain.
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chronostratigraphic correlation
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Matching up rock units on the basis of age equivalence, as determined by radioactive dating methods or fossils.
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types of nonconformities
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Angular unconformity Nonconformity Disconformity
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geotools
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Various ways in which the distribution of rocks can be depicted: Geologic columns Stratigraphic cross-sections Structural cross-sections Geologic maps Paleogeographic maps Isopach maps Lithofacies maps
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stratigraphic cross-sections
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They correlate geologic columns from different locations to show how rock units change in thickness, lithology, and fossil content in a given area. q
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structural cross- sections
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They show the timing of tilting, folding, and faulting of rock units. Tops and bottoms of rock units are plotted by elevation. Folds and faults are depicted clearly.
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geologic maps
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Geologic maps show the distribution of various layers and types of rocks in an area. Map symbols indicate structural features (folds, faults, etc.) and formation names.
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paleographic maps
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Interpretive maps which depict the geography of an area at some time in the past.
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isopach
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Isopach maps show the thickness of formations or other units in an area.
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lithofacies maps
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They show the distribution of lithofacies that existed at a given time over an area.
