Geography 1111 Lecture 22 Notes
Geography 1111 Lecture 22 Notes GEOG 1111
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This 4 page Class Notes was uploaded by Bridget Notetaker on Tuesday October 4, 2016. The Class Notes belongs to GEOG 1111 at University of Georgia taught by Hopkins in Fall 2016. Since its upload, it has received 16 views. For similar materials see Intro to Physical Geography in Geography at University of Georgia.
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Date Created: 10/04/16
Geography 1111 Lecture 22 Notes Info to know: The age of the oldest rocks: 4 billion years old The oldest sea floor: 200 million The beginning and ending of each of the eras o 520- 250 o 250- 65 o 65- current Tertiary (2 million) and quaternary (currently in) The top two epoch’s Geologic Time Scale: a method or depiction of the Earth’s age and geologic history using both a sequence of rock strata (their relative age) and their absolute ages o It is thus both a relative time scale and an absolute time scale and is governed by uniformitarianism o It assumes superposition, the idea that younger rocks and sediments are near the top of a formation, and older material is near the bottom o Absolute ages are determined by methods such as radioactive isotope dating Geologic Cycle: the vast cycling of material that occurs in and on the lithosphere, encompassing the hydrologic, tectonic, and rock cycles o The building up and wearing down of landforms involving various processes and events o 3 components: Hydrologic cycle which is the movement of water (H2O) through all 4 of Earth’s spheres Evaporation, Condensation, Precipitation, etc. Tectonic cycle: the movement of water (H2O) through all 4 of Earth’s spheres; evaporation, condensation, precipitation, etc. Rock cycle: refers to the formation of the three basic types of rock, igneous, sedimentary, and metamorphic Rock Cycle: ***know the diagram of the rock cycle*** o Mineral is a combination of elements that forms an inorganic, natural compound which has specific qualities, such as a unique crystalline structure, hardness, etc. Ex: Silicates, based on silicon (Si); Carbonates, carbon (C) These together make-up 90% of all minerals 3000 minerals, only about 10-20 make up 90% of the crust o Rock is an assemblage of minerals bound together, usually 2 to 5 different minerals Thousands of rock types, but all are classified into one of the three basic rock categories: igneous, sedimentary, or metamorphic The interactions/interrelationships between the processes which form the different rock types can be expressed by the Rock Cycle Igneous Process and Rocks: o Igneous Rocks are formed by the Crystallization of magma/lava, the solidifying of molten material either below or above the surface o The material may cool fast forming a fine-grained structure (extrusive igneous rocks) or cool slowly forming a coarse- grained structure (intrusive igneous rocks) o Two basic types of igneous rock: 1. Intrusive Igneous rocks are those which form below the surface, within the crust, as the magma cools and crystallizes before it reaches the surface The masses of rock formed in this process are generally known as plutons Ex: granite, rhyolite; Stone Mountain is composed of granit 2. Extrusive Igneous rocks are those which form on the surface, on the crust or as new crust as the magma cools and crystallizes after it reaches the surface The ocean floor is primarily composed of basaltic igneous rock Ex: lava or basalt, volcanic ash, obsidian, pumice Sedimentary Process and Rocks: o Sedimentary rocks are formed by a two-step process in which existing material (rocks) are first weathered/eroded down into smaller pieces of the original rock called sediments (dirt, sand at a beach, mud in a river, etc.) These are often then transported and deposited some distance from the location of the original rock The second step involves these sediments being “put back together” in the process of Lithification to form new rocks Lithification: is a process of cementation, compaction and hardening of sediments to new rock o Ex: Material is deposited on a lake bottom, inland sea, etc. and then has more material deposited on top, then more and so on The material, layers at the bottom come under greater pressure and get “squeezed” back together into a hard mass of new rock 2 main types of Sedimentary rock: 1. Clastic sedimentary rock forms from bits and pieces of former rocks that are/were visible pieces, such as the sand at the beach, or mud on a lake bottom, or soil material Ex: shale, siltstone, claystone, etc. 2. Non-Clastic sedimentary rock forms from the minerals dissolved in solution (water) which were deposited as a solid after evaporation of the water The material is various salts and other minerals originally dissolved in a river, lake or ocean Ex: limestone, coal, salts, chalk, gypsum Metamorphic Process and Rocks: o The rearrangement of rock crystals in an existing rock is the process of Metamorphism This can be accomplished by either physical and/or chemical change, and is often done under high pressure (dynamic metamorphism) and/or high temperature (contact metamorphism) situations o The new material/rock is usually more compact, denser, than the original material and thus harder Contact metamorphism: is the rearrangement of crystals brought about when magma comes in contact with the adjacent rock, and slightly (but not completely) melts it o This causes the crystals to move and rearrange Dynamic metamorphism: is when the rearrangement of crystals in a rock is brought about by it coming under high pressure and thus compacted or squeezed together o This occurs at convergent plate boundaries 2 main types of Metamorphic rock: 1. Foliated Metamorphic rock: is formed when minerals/crystals of the same chemical composition within the original rock form distinct bands or striations after metamorphism The like minerals are essentially drawn together into more homogeneous groups Ex: gneiss, slate, schist 2. Non-Foliated Metamorphic rock: exhibits a more homogenous mixture of the crystals after rearrangement and few, if any, striations It often forms from more homogenous rock (few different minerals) Ex: quartzite, marble, greenstones