GEO_103_Exam_3_Key

Name: Version #1 GEO 103 – Semester Exam #3 (each question is worth 1 point out of a possible 25 points) 1) Together, the Hadean, Archean and Proterozoic eons encompass about _____ percent of Earth's history. Precambrian rocks are mainly located ______ A. 90; in continental cratons B. 50; along the outer margins of the continental crust, near the ocean C. 10; in continental cratons D. 90; under the ocean in the Earth’s oceanic crust 2) From the list below, select the reason that Archean rocks are so difficult to interpret. A. They are highly altered by metamorphism and complexly deformed B. They are typically buried deep beneath younger rocks C. They contain few fossils, and those that are present are of little use in stratigraphy D. All of the above 3) The origin of Earth's Moon was the result of: A. Vaporization of rock from the Earth’s early magma ocean into space B. Accretion of a swarm of asteroids that were captured by the Earth’s gravity C. The impact of a Mars-sized planet into the Earth shortly after Earth's accretion 4) The Earth's early atmosphere and hydrosphere was derived from: A. Degassing of Earth's interior by volcanic emissions B. Comets and asteroids that impacted the Earth’s surface, delivering water and other elements C. Gases from the solar nebula that were captured by the Earth during accretion D. All of the above contributed, though “A” is thought to have been the biggest source 5) All of the items below represent valuable sources of information about the Hadean Eon on Earth, except for_____ A. Meteorites B. Samples from the Moon and other moons and planets in the Solar System C. Hadean-aged zircon grains that are found in Archean-aged sedimentary rocks D. Abundant Hadean sedimentary rocks that are found in all of the Earth’s cratons 6) The Archean Crust of the Earth, which is found in the Earth’s continental cratons, is characterized by microcontinents made of: A. Gneiss complexes, composed of metamorphosed igneous and sedimentary rocks B. Granite complexes, which are younger metamorphosed igneous rocks C. Greenstone belts , which are made up of oceanic crust and deep-water marine sediments D. All of the above, with gneisses forming the nucleus of Archean microcontinents, greenstone belts accreted to the margins of the gneiss complexes, and granite complexes representing younger rocks that intrude into the gneiss complexes

2 7) There is general scientific consensus that plate tectonic processes in the Hadean and Archean Eons operated the same way as they have during the Proterozoic and Phanerozoic Eons: A. True B. False 8) Which of the following is NOT a correct statement about the composition of the Archean atmosphere? A. The atmosphere of the Archean was dominated by CO 2 derived from volcanic degassing B. The atmosphere of the Archean had an extremely low O 2 concentration because oxygenic photosynthesic metabolisms had not emerged yet C. The atmosphere of the Archean had an O 2 concentration similar to the modern atmosphere because the high flux of ultraviolet light from the young Sun was able to efficiently decompose water vapor to form O 2 gas D. The N 2 concentration of the Archean atmosphere was lower than today b/c the abundant CO 2 in the atmosphere was not yet being efficiently stored in carbonate rocks 9) The earliest forms of life on Earth were most likely: A. A species of bacteria or archaea, which probably performed non-oxygenic photosynthesis or chemosynthesis for their metabolism B. Single-celled eukaryotes that consumed algae C. Cyanobacteria (aka blue-green algae), which performed oxygenic photosynthesis D. Trilobites 10) It is likely that the organ responsible for photosynthesis within single-celled eukaryotes, which is called a chloroplast, was originally formed by: A. A chance mutation of eukaryotic DNA that gave it an evolutionary advantage B. Endosymbiosis, in which a single-celled cyanobacteria was engulfed by a eukaryote, which was not digested and provided energy to the eukaryotic cell C. The origin of chloroplasts is not understood by evolutionary biologists 11) In Neoproterozoic rocks about 570 million years old, evidence of multicellular animal life called the Ediacara fauna consists mainly of: A. The imprints of soft-bodied organisms B. Trace fossils, called “ Treptichnus pedum ”, left behind by the earliest form of burrowing organisms C. Large, complex skeletons of early vertebrates D. Mammoths and saber-toothed tigers 12) The Great Oxidation Event, which occurred between about 2.3-1.8 billion years was caused by: A. The extinction the cyanobacteria and the rise of eukaryotes B. The effects of a massive lava eruption, which oxidized organic matter in swamp lands C. The buildup of significant oxygen in the atmosphere and oceans as a result of abundant oxygenic photosynthetic life forms

4 19) The fish group that went on to become the ancestor of all terrestrial vertebrates was the_____ A. Ray-finned fishes B. Lobe-finned fishes C. Acanthodians D. Placoderms 20) The key evolutionary adaptation that first allowed plants to move out of marine environments and live above water is: A. Stems with vascular tubes and tissues B. Spores C. Seeds D. Flowers 21) What effect did the widespread colonization of the land by plant life have on the Earth’s surface environment in the Middle Paleozoic? A. Enabled early amphibians to live part of their lives on land b/c they had access to shade and plant matter that they could eat B. Changed the shape and movement patterns of river systems by providing stable banks for rivers to flow in C. Caused widespread glaciation in the late Devonian as a result of the removal of CO 2 from the atmosphere by photosynthesis, storage of sedimentary organic matter in widespread swamps, and the accelerated rate of chemical weathering of rocks D. All of the above 22) Below is an idealized cross-section through the Silurian Thornton Reef deposit found in Illinois, USA. Based on the structure shown below, what direction were the dominant wind and ocean currents moving? A. From left to right, towards the part of the reef system where the highest-standing ridge is located B. From right to left, towards the part of the reef system where the lower-standing ridge is located C. In and out of the page, across the lagoon deposits in the middle of the reef system

5 23) __________ are a group of animals that were attached to the seafloor and captured food with their waving arms as it came floating by. They expanded to their greatest diversity during Early Carboniferous and make up a significant fossil component of Carboniferous limestone deposits A. Crinoids B. Brachiopods C. Bryozoans D. Fusulinids 24) Which of the following is NOT a factor related to the mass extinction events that occurred towards the end of the Permian? A. Changes in ocean circulation patterns caused by global warming that caused large portions of the deep ocean to turn anoxic B. Global-scale glaciation and loss of shallow marine habitats due to sea level fall C. The eruption of massive quantities of lava from the Siberian Traps, and the burning of coal swamps by the lava, both of which released CO 2 into the atmosphere and caused climate warming 25) In the mid-Carboniferous, Gondwana and Euramerica collided to form the supercontinent ______, which completed the final phase in the construction of the ______ mountains in eastern and southern North America A. Pangaea, Appalachian-Ouachita B. Rodinia, Ural C. Nuna, Guadalupe D. Pangaea, Cordilleran