ch 4 – Geology – Flashcards
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fossil
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preserved remains or traces of organisms
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sedimentary rock
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made of hardened sediment
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mold
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hollow area in sediment shaped like an organism
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cast
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solid copy of the organism
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petrified fossils
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are fossils in which minerals replace all or an organism
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carbon film
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an extremely thin coating of carbon on rock
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trace fossils
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evidence of activities of ancient organisms
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paleontologists
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Scientists who study fossils
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scientific theory
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A well-tested concept that explains a wide range of observations.
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evolution
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gradual change in living things over long periods of time
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extinct
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no longer exists on earth
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relative age
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The age of a rock compared to the ages of rock layers
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absolute age
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the age of a rock given as the number of years since the rock formed
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law of superposition
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to determine the ages of sedimentary rock layers
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extrusion
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lava thats hardens the surface
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intrusion
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The magma that cools and hardens into igneous rock
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fault
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break in earth's crust
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unconformity
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when new rock layers meet old rock layers
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index fossils
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help geologists match rock layers. A fossil must be widely distributed and must represent an organism that existed only briefly.
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how do geologists determine the relative age of rocks?
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extrusion intrusion igneous rock faults
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how are index fossils useful to geologists
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they can tell the relative ages of rocks
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geologic time scale
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A record of the geologic events and life forms in Earth's history
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era
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3 divisions of time between the precambrian period and the present
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period
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Eras are divided into geologic time called periods
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comet
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A ball of ice and dust that orbits the sun
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continetal drift
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continents moving very slowly over earth's surface because of forces inside earth
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invertbrate
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An animal without a backbone
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vertebrate
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An animal with a backbone
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amphibian
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animal living on both land and water
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reptile
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Animals that have dry, scaly skin and lay eggs with tough leathery shells.
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mass extinction
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event in which many types of living things become extinct at the same time
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mammal
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warm blooded vertebrate that feeds its young milk
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quaternary period
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the period humans live in
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jurassic period
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the period dinosaurs live in
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ice ages
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happened during the quaternary period
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cenozoic era
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started when dinosaurs became extinct
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How do fossils form?
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Most fossils forms when living things die and are buried by sediments.
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What are the different kinds of fossils?
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1. Molds and 2. casts 3. Petrified fossils 4. Carbon films 5. Trace fossils
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What is a fossil record?
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Provides evidence to support the theory of evolution.
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What does the fossil record tell about organisms and environments of the past?
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Provides evidence about the history of life and past environments on Earth. Also shows that different groups of organisms have changed over time.
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What are the three ways in which remains of an organism can be preserved with little change?
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Tar, Amber and ice.
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Which parts of an organism are most likely to be preserved as fossils?
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Hard parts of an organism like bones, shells, teeth, seed, and woody stems are the most likely to form fossils.
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Why?
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Because the soft parts often decay quickly or are eaten by animals.
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How does a carbon film fossil form?
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When sediment buries an organism some of the parts evaporate or become gases leaving carbon behind. Eventually only a thin film of carbon remains.
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How are petrified fossils similar to preserved remains?
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Well, both fossils and preserved remains retain the shape and form of the remains.
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How are the petrified fossils different from preserved remains?
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fossils do not actually retain the matter that made up the remains, instead, bones and tissues (usually just bones) have been replaced with stone.
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What two things do scientists learn from a fossil record?
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1. Picture of Earth's past environments 2. Changes to Earth's surface.
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Why do sedimentary rocks have layers?
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Younger rocks superpose older rocks as years go by forming layers in sedimentary rocks.
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An extrusion crosses an intrusion. Which layer is older?
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Since intrusion forms the surface over which the extrusion happens - intrusion is older than extrusion.
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Why is the geologic time scale used to show Earth's history?
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Because the time span of Earth's past is so great.
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What are the different units of the geological time scale?
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1. Precambrian 2. Paleozoic 3. Mesozoic 4. Cenozoic 5. Present
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What era does the Jurassic period belong to?
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Mesozoic
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What information did the geologists use in developing the geologic time scale?
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Rock layers and fossils world wide initially. Then radioactive dating helped determine the absolute age of the time divisions.
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Which major division of geologic time was the longest?
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Precambrian
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When did the longest period begin?
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4.6 billion years ago
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When did it end
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544 million years ago
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When did earth form?
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Roughly 4.6 billion years ago
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How did Earth's physical features develop during precambrian age?
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Atmosphere, oceans and continents began to form during the first 100 million years
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What forced caused the materials that formed Earth to come together?
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Gravity
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How did volcanic eruptions and comets change earl Earth?
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Volcanic eruptions released carbondioxide, water vapor and other gases from earth's interior. Comets collided with earth and released other gases.
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What caused water erosion to begin on Earth's surface?
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The cooling of earth's surface condensed the water vapor to form rain, The rainwater caused water erosion.
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What do scientists think were the first organisms to evolve on earth?
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Single celled organisms that are today called bacteria.
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What were the major events in the Paleozoic era?
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1. The cambrian explosion 2. Vertebrates arise 3. Life reaches land 4. The carboniferous period 5. Mass extinction 6. The supercontinent panagea
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What were the major events of the mesozoic era?
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1. The triassic period 2. The jurassic period 3. The cretaceous period 4. Another mass extinction
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What were the major events of the Cenozoic era?
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1. The tertiary period 2. The quaternary period
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What was Panagaea?
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During the permean period earth's continents moved together to form a great landmass, or supercontinent, called panagaea.
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What major groups of organisms developed during the Mesozoic era?
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1. Reptiles 2. Mammals 3. Fish 4. Insects 5. Conifers 6. Flowering plants
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How did Earth's climate change during the Quarternary period?
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Earth's climate cooled causing a series of ice ages. Then it started to warm causing the ice to melt except in Greenland and Antartica.
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What are the periods of the Paleozoic era?
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1. Cambrian 2,. Ordovician 3. Silurian 4. Devonian 5. Carboniferous 6. Permian
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How did the organisms change during the first Paleozoic era?
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Great explosion of invertebrates occurs in the seas. They appear with hard shells.
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What event do scientists think may have caused the mass extinction at the end of the Paleozoic era?
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scientists do not know but think the climate change caused the mass extinction
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Which group of animals was dominant in the Mesozoic era?
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Dinosaurs
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How was their small size helpful to the mammals in the Mesozoic era?
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Helped them to survive the mass extinction
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What term do scientists apply to the Cenozoic era?
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Age of the mammals
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What conditions allowed so many different kinds of mammals to evolve during the Cenozoic era?
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Climate was generally mild and warm.
