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Advanced structure of the Earth By Doba D. Jackson, Ph.D. Associate Professor of Chemistry & Biochemistry Huntingdon College Slide 2 Outline of Lecture 1 Part I: Matter & Matter changes Natural Science-Physical Science Physical & Chemical Properties Elements of Nature Temperature, Pressure Physical States of Matter Part II: Origin of the Universe and matter Big Bang (video) Formation of atoms, elements Formation of galaxies, our solar system Slide 3 Outline of Lecture 1 Part III: Structure & Components of Earth Earths Core Earths Mantle Earths Crust Lithosphere Asthenosphere Rock Cycle (Sedimentary, Metamorphic, Igneous) Plate Tectonic Theory (intro) Geologic Time (intro) Slide 4 Plate Tectonic theory Plate tectonic theory states that the lithosphere is divided into rigid plates that diverge, converge, or slide past each other as they move over the asthenosphere. Slide 5 Plate Tectonic theory The movements of the plates and the interactions of plates along their boundaries cause volcanic eruptions, earthquakes, the formation of mountain ranges and ocean basins, and recycling of rock material. Slide 6 The Rock Cycle What is a rock? A rock is an aggregate of minerals. GraniteLimestone Conglomerate Slate Gneiss Quartzite Slide 7 The Rock Cycle Slide 8 What are the characteristics of each of the three major rock groups? Igneous rocks result from the crystallization of magma or the consolidation of volcanic ejecta. Slide 9 The Rock Cycle Sedimentary rocks are typically deposited in layers formed by the: consolidation of rock fragments precipitation of mineral matter from solution compaction of plant or animal remains Slide 10 The Rock Cycle Metamorphic Rocks- that result from the alteration of other rocks; Metamorphic rocks usually form beneath Earths surface, by Heat Pressure Chemically active fluids. Slide 11 The Rock Cycle connects the internal and external processes of the earth Slide 12 Plate Tectonic theory Plate tectonic theory states that the lithosphere is divided into rigid plates that diverge, converge, or slide past each other as they move over the asthenosphere. Slide 13 Plate interaction is a major factor that determines when, where and what kind of rock develops. Plate Tectonics? Slide 14 Geological Time Slide 15 Radioactive Decay Example 0 C 6 14 N 7 + -N is the number of radioactive atoms per minute per gram Carbon -N 0 is the initial number of radioactive atoms per and per gram Carbon -k is the decay constant for carbon -t is the age of the sample NtNt N0N0 Ln = -kt Equation: Half-life 14 C is 5730 years ParentDaughter Slide 16 Radioactive Decay Example 0 C 6 14 N 7 + -N is the number of radioactive atoms per minute per gram Carbon -N 0 is the initial number of radioactive atoms per and per gram Carbon -k is the decay constant for carbon -t is the age of the sample NtNt N0N0 Ln = -kt Equation: Half-life 14 C is 5730 years ParentDaughter Slide 17 Radioactive Dating Methods ParentDaughterHalf-lifeSamples Used 147 Sm 143 Nd106 billion yearsRocks 87 Rb 87 Sr50 billion yearsRocks 238 U 206 Pb4.47 billion yearsRocks 40 K 40 Ar1.3 billion yearsRocks 235 U 207 Pb704 million yearsRocks 234 U 230 Th80,000 yearsRocks 235 U 231 Pa34,300 yearsRocks 14 C 14 N5,730 yearsOrganic Fossils 3H3H 3 He12.3 yearsOrganic Fossils Slide 18 Geological Time Eon- Time periods around.5 to 1 billion years. Era- Time periods between 100 million and 500 million years. These occur within Eons. Periods- Time periods between 10 million and 100 million years. Ages- Slide 19 Slide 20 No Slide 21 Early Evidence for Plate Tectonics: Continental Drift Hypothesis The idea that continents have moved in the past is not new and goes back to the first maps, in which one could see that the east coast of South America looks like it fits into the west coast of Africa. Pangaea Slide 22 Supporting evidence for a Continental Drift 1)Continental Fit- Outlines of coasts closely approximate each other. 2) Fossil Evidence- Similar extinct plant and animal fossils on different continents. 3) Glacial Evidence- Similar leftover tills in rocks on different continents. 4) Rock layers sequences in different ages. Slide 23 Scientists responsible for Continental Drift hypothesis Abraham Ortelius (1596)- developed the first map and theorized that continents drifted across oceans to their present positions. Edward Suess (1885)- First to propose that continents were connected based on fossil evidence. Named southern continents as Gonwana. Alfred Wegener (1915)- credited for the continental drift hypothesis. (Named supercontinent Pangaea) Harry Hess (1962)- revised the continental drift theory into the Plate Tectonic theory. Slide 24 Abraham Ortelius developed the first map of the world Ortelius was a world renown English geographer in his day. He spent his life making regional and continental maps. Through lots of partnerships, and traveling, he was able to develop the first maps of the world. Latin: Theater of the WorldHe suggested after publishing his 33 rd map of the world: The Americas may had originally been joined together but later drifted away by earthquakes and floods in 1578 Slide 25 Edward Suess was the first to provided fossil evidence for the continental drift hypothesis Edward Suess 1831-1914 Glossopteris flora- The fossil flora that succeeds the Permian glacial deposits of South Africa, Australia, South America, and Antarctica. It grew in a cold, wet climates. Plants with elongate, tongueshaped leaves dominated the southern flora. Slide 26 Austrian Geologist Edward Suess proposed the southern continents were once connected and used the term Gondwana Slide 27 Alfred Wegener noted similarities of rock sequences for southern continents Slide 28 Glacial Striations as evidence for continents drifting Glacial striations are scratches or gouges cut into bedrock by glacial (ice) abrasion. Glacial striations form when ice picks up small rock fragments. When the ice forms or melts on rock, picks up small pieces of rock or sand and it scratches the surface of the rock as it moves across it. Glacial striations are usually multiple, straight, and parallel lines. Slide 29 Glacial Striations in bedrock found in South America, India, South Africa and Australia Arrows on each picture represent the direction of melting of the ice The directions of the glacial striations indicate that the southern continents were closer together at the south pole. Notice Indias presence Slide 30 Setback in the Continental Drift Theory None of the scientist could reasonably explain How could the continents drift? Continental Shelf- region off the ocean boundary where the seafloor is shadow. Mapping of seafloors found no evidence of continents drifting on liquid water. Slide 31 Paleomagnetism studies of the 1950s revived the debate - Electrical currents in the (liquid Iron) outer core probably generate Earth's magnetic field. The lines of magnetic field surrounding Earth resemble those of a bar magnet. Where and how is Earths magnetic field generated? Slide 32 Paleomagnetism Rocks North South Paleomagnetism is the reminant magnetism of ancient rocks. Lodestone, Magnetite, Maghemite- iron containing mineral rocks with magnetic properties (Fe 3 O 4 ). Ancient rocks showed a different orientation of its magnetic field. Slide 33 Paleomagnetic data can be used to construct the positions of early continents Rocks analyzed during the same time period gave different positions of their magnetic poles. Scientists assume the position of the magnetic pole has not changes over millions of years, but the position of the continents have changed. Slide 34 Paleomagnetic data can be used to construct the positions of early continents Rocks analyzed during the same time period gave different positions of their magnetic poles. Scientists assume the position of the magnetic pole has not changes over millions of years, but the position of the continents have changed. Slide 35 Discovery and mapping of the Mid-Atlantic Ridge Slide 36 Paleomagnetic studies revealed the existance of Earths magnetic field reversals Slide 37 Paleomagnetic studies revealed the existence of Earths magnetic field reversals in lava flows Slide 38 Henry Hess proposed the theory of Seafloor Spreading in 1962 What is the theory of seafloor spreading? He suggested that the seafloor separates at oceanic ridges, where new crust is formed by upwelling magma. As the magma cools, the newly formed oceanic crust moves laterally away from the ridge. Slide 39 How was the theory of seafloor spreading confirmed? Slide 40 Slide 41 Another confirmation of Seafloor Spreading theory is the age of rocks on ocean floor Sea floor spreading is confirmed by the ages of fossils in sediments overlying oceanic crust radiometric dating of rocks on oceanic islands and floors. Red- present to 48 mya Yellow- 48-68 mya Green 68-155 mya Blue- 155-180 mya Slide 42 Model for How Seafloor Spreading Occurs Slide 43 Plate Tectonics: A Unifying Theory Overwhelming evidence in support of plate tectonics led to its rapid acceptance and elaboration since the early 1970's. The theory is widely accepted because it explains so many geologic phenomena. Plate Tectonic Theory encompasses the Seafloor Spreading Theory with thye existance of Earthquakes and Volcanism. For these reasons, it is known as a unifying theory. Slide 44 What are the main tenets of Plate Tectonic Theory? Slide 45 The Three Types of Plate Boundaries Divergent Plate Boundaries- Spreading ridges that occur where new lithosphere is forming and older lithosphere is separating away. Convergent Plate Boundaries- Boundary where older crust is destroyed and recycled to keep the surface area of the earth the same. Transform Plate Boundaries- (or Transform faults)- Changes one type of motion between plates to another type of motion. Slide 46 History of Divergent Boundaries Divergent boundaries form when rising magma beneath a continent pushes crust up to form mountains, faults, valleys and volcanic activity As more continental crust is broken, valleys form with volcanic activity. Slide 47 History of Divergent Boundaries -As more continental crust is broken, valleys form with volcanic activity. -(East African Rift Valley) -Continued spreading splits apart the continent and a seaway develops (Red Sea) Slide 48 History of Divergent Boundaries -Continued spreading splits apart the continent and a seaway develops (Red Sea) -Continued spreading, a oceanic ridge system develops (Mid-Atlantic Ridge) Slide 49 East African Rift Valley may be the future Diverging plate boundary Slide 50 Red Sea may be the next Mid- Atlantic Ridge system Slide 51 The Three Types of Convergent Plate Boundaries Convergent boundaries are places where two plates collide and one plate is subducted into the asthenosphere. Oceanic-oceanic boundary is where two oceanic plates collide, one ocean plate will subduct beneath the margin of the other plate. Oceanic-continental boundary is where an oceanic plate and a continental plate collide, the oceanic plate will subduct. Continental-continental boundary occurs when two continents collide Slide 52 Oceanic-Oceanic Convergent boundaries One oceanic plate is subducted beneath the other and a volcanic island arc forms on the non-subducted plate An oceanic trench forms parallel to the volcanic island arc where the subduction is taking place. The volcanoes result from rising magma produced by the partial melting of the subducting plate. Slide 53 Oceanic-Continental Convergent Boundary An oceanic plate and a continental plate converge, with the denser oceanic plate being subducted under the continental plate. Just as with an oceanic-oceanic boundary, a chain of volcanoes forms on the nonsubducted plate. Slide 54 Continental-Continental Plate Boundaries Two continents converge and the ocean floor separating them is subducted, resulting in a collision between the two continents. Neither plate will subduct. When the two continents collide, they are welded together to form an interior mountain chain along a zone marking the former site of subduction. Slide 55 Transform Plate Boundaries Transform boundaries (also Transform Faults) are boundaries along which plates slide laterally past each other, which change one type of motion between plates into another type of motion. Slide 56 Types of Plate Boundaries Slide 57 Introduction to Chapter 3 What is a mineral? A mineral is Naturally Inorganic Crystalline solid Characteristic physical properties Specific chemical composition. Slide 58 Matter, Atoms, Elements, and Bonding What are the atomic number and atomic mass of an atom? The number of protons in an atoms nucleus determines its atomic number, whereas an atoms atomic mass number is the total number of protons and neutrons in the nucleus. Slide 59 Matter, Atoms, Elements, and Bonding Chemical bonding Atoms are joined to one another by forces known as bonding. Atoms of different elements which are bonded to one another form compounds. Slide 60 Types of Chemical Bonds Ionic Bonds Ionic bonds form when ions with opposite electrical charges attract one another Slide 61 Types of Chemical Bonding Covalent Bonds Covalent bonds atoms share electrons. Slide 62 Native Elements vs Minerals By definition native elements are made up of only one chemical element, such as: Gold (Ag) Silver (Ag) Aluminum (Al) Copper (Cu) Diamond (pure C) Slide 63 Elements of the Earths Crust Why are there so few common minerals? Even though there are 92 naturally occurring elements, only 8 of them are very common in Earths crust. Most common minerals are made up of oxygen, silicon, and one or more other elements.