GEOL 1425 1nd Edition Lecture 4 Outline of Last Lecture I. Earth System Part 2II. Global Scale of the Climate SystemIII. Greenhouse gasesIV. Convection currents Outline of Current Lecture I. Warm-up question discussionII. Start of Plate TectonicsIII. Plate tectonic theoriesIV. Concept 1V. History of Plate tectonicsVI. Concept 2VII. Convergent plate boundaryVIII. Concept 3Current LectureI. Warm-up questions:Q1. Was the great oxygenation event a good or bad thing for life on Earth?Over billions of years, stromatolites have produced lots of oxygen creating iron formations in water and on land. Free oxygen reacted with atmospheric methane with catastrophic results—all of this oxygen poisoned the anaerobic bacteria. Though at this point the results were on the bacterial level, this is known as possibly the greatest mass extinction period of Earth’s history. Q2. With the GOE the free oxygen reacted with the atmospheric methane (a greenhouse gas) reducing its concentration. What would be the result of this?Less methane is probably responsible for triggering Huronian Glaciation—possibly the largest “snowball earth”, a crisis!Q3. How does mountain building change the climate?These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.The structure of mountains forces air to rise. Then water is condensed, it rains on the windward side and there are dry and desert-like conditions on the opposite side. This is called the rain shadow effect. EX- Atacama Desert of northern Chile is the world’s second largest desert region and lies in the rain shadow of Chile’s coast range which squeezes out moisture from the atmosphere. II. Start of Plate Tectonicsa. Plates embedded in the Lithosphere are moving around causing continental drif. This is the process of mountain building! b. Plate tectonics: plates moving around. Mountain building, where volcanoes and earthquakes erupt, and different rock formations can all be explained by plate tectonics. III. Plate tectonic theories and theoristsa. The first idea of plate tectonics (which wasn’t completely correct), said that the lithosphere was made of a series of platesb. New theory: created 40-50 years ago post World War II where much of the oceanseabed was mapped and when many new ideas came together.c. One new theory—“Contraction Theory”—the surface of the Earth contracted andwas thought to have shrunk (a good visual is of a plum drying up and turning intoa prune). Problem with this theory was that the dates of the land did not come together (the mountain tops should all be the same height/date but they are not)d. Orteilus thought that Africa and South America were once attached and torn away from each other by earthquakes and floods… that continents were once joined!e. “Jigsaw puzzle” – rocks and other geological evidence suggest that Earth may have once been a supercontinent because when we put the continents together their coastlines all seem to match up. We call this once-supercontinent “Pangaea”. f. Wegener is an un-sung hero of this theory! He was a meteorologist, so other geologists thought “what is he doing in geology? He doesn’t know what he’s talking about, he’s a meteorologist!” BUT he was correct!i. Wegener showed that the continents really were at one point stuck together, but he didn’t have a good explanation as to why they aren’t still together. We do now have proof though: matching rock assemblages, mountain belts, and Norway and Greenland have similar rocks!g. Mesosaurus- fossils that have showed up on separate continents. If the continents weren’t at some point formed, how did this happen? h. Other examples that proof a supercontinent: i. Distribution of plants and animalsii. Glosopteris leaves found in fossil beds across continentsiii. Glacial deposits of same age in Africa found in India, South America, and Antarctica indicating that they were all from the same traveling glacier. Scientists have matched a circle of glacier deposits across continents. i. Dark matter/dark energy: we know nothing about it except that it [probably] exists. Speculated by expansion of the universe and other things but no one has seen it or knows what it is. Like dark matter, it is speculated that the continents were once together but not for sure true.j. Arthur Holmes- father of radiometric dating. He proposed that there are convection currents within Earth causing the plates to move. This was a pretty good idea!IV. Concept 1: The continents aren’t static—they move! The original continental drift idea was wrong and Wegener was right. This change in ideas is referred to as Paradigm Shif.V. History of Plate tectonicsa. The plate tectonics theories really hit off after WWII with seafloor mapping! b. Weird structures at the bottom of the seafloor were identified—a giant rift in the Atlantic ocean and other cracked structuresc. A map of the Atlantic Ocean seafloor was made d. A new question that came up—when new crust forms, where does the old crust go? This is the seafloor spreading hypothesis. Seafloor is recycled in areas of volcanic and earthquake activityVI. Concept 2: There are plate boundaries and activities happen at those boundaries!VII. Convergent plate boundarya. Deepest part of ocean is in Marianas Trench, where there is a crazy amount of pressure at the bottom. We are still trying to discover how life down there can even survive under so much pressure!b. 3 types of convergent plate boundaries: Ocean-ocean (results in chain of volcanoes), ocean-continent (results in mountain ranges), and continent-continent (crumpling collisions result).VIII. Concept 3: Mountain ranges and earthquakes form along plate