GEOL 1040 1st EditionFinal Exam Study Guide Lectures: 13 - 26Lecture 13 (February 16)Where do most magmas originate and how are they melted?- Magmas originate in the mantle and are derived by three processes of partial melting: Decompression melting- Decrease in pressure due to stretching of lithosphere- Rifting= extension- Found at Mid Ocean ridges- As the plate stretches out, the idle area is thinner with less pressure. Flux melting- Adding volatiles- Happens at convergent boundaries and subduction zones- Adds H20 and CO2 to change melting point of the mantle Increase in temperature- Hot Spots- Plumes- In Hawaii, yellow stone, Iceland : Confirmed Hot Spot- The increase in temperature from the hot materials melts the rock- why the gradient curve (blue line) bends sharply at about 100 km deptho The gradient curve bends sharply because this is where the mantle meets the core. You go from a silicate to a liquid metal. The liquid metal is denserso pressure increases. o As Temperature increases,solids turn to liquids becausethey heat up. As Pressureincreases, meltingtemperatures go up and liquids become solids. The deeper in the Earth, the morepressure there isLecture 14 (February 18)o what has to happen to any pre-existing rock in order to produce a sedimentary rock? exposure of the rock at the surface ofthe Earth Weathering and erosion  deposition of sediments  lithification into rock. o What are some common environments wheresediments are being deposited today? Braided rivers- Fluvial process: sedimentsbeing distributed by streamsand rivers Sand dunes Wet lands (organic sediments) Beaches Shore lines of tidal flatsLecture 15 (February 20)o What is the fundamental difference between sediment?o Answer: you can scoop up sediment with a shovel but you must use a hammer tosample sedimentary rocko What is the difference between physical and chemical weathering?o Physical weathering: the physical breaking apart of rocks that are exposed to the environment. There are four major causes of physical weathering Near surface fracturing- due to uplift, exposure, and gravity Frost and mineral wedging- Water and salt crystals go in a fracture and expand Thermal Expansion- Heat expands rock from sun or fire and they may crack Biological activity- Roots growing crack the rock up, animals burrowingo Chemical weathering: Includes several types of chemical reactions that affect a rock by breaking down minerals, causing new minerals to form, or by removing soluble material from the rock.  Dissolutions- Some minerals dissolve in weakly acidic water. This changes composition- Oxidationo Some minerals are unstable when exposed to Earth’s atmosphereo Hydrolysis Reaction of water and mineralso Biological Reaction Decaying organic material produce acids that attackrocks. o What are clastic sediments and what controls the shape, size and sorting of clasts? Clasts: loose fragments of rocks and minerals Shape, Size, and Sorting:- Clasts near the source are normally large, angular, and poorly sorted- As they travel, they get broken down further, rough edges get smoothed out, and the erosion source separates the material by size which makes it better sorted. Factors that may help this include: Steepness of slope, strength of current, sediment supply, and agents of transport. o Clastic sediments (loose material) is turned into rock by the process called lithfication. The two primary processes are cementation and compaction. Know the difference between these two processes and what types of cement are common.o Compaction: as sediments beneath more sediments or materials, increasing pressure pushes clasts together. This forces out water and causes semiments to lose as much as 40% of their volume. Loose sediments become more dense and more compactedo Cementation: After compaction, adjacent clasts do not fit together perfectly. The pore spaces are commonly filled with water containing dissolved materials. This material can precipitate to form minerals that act as a natural cement that holds pieces of sediment together. 4 types of cements that are common:-Calcite-Silica-Clay minerals-Iron oxideso What is the difference between conglomerate and breccia? o Conglomerate: Rounded pebbles, cobbles, or boulders with sand and other fine sediments between large clastso Breccia: Angular clasts that is poorly sorted.What are some examples of non-clastic rocks and how do they form?o Mostly, non-clastic rocks are formed when minerals dissolved in water precipitate (crystallize) out by processes of evaporation (e.g., halite/salt deposits) or when critters use them for their shells (e.g., limestone and chert). The textbook includes peat as non-clastic sedimentary rocks (not true) but coal is.o Coal: peat that has been buried, compacted and heatedo Limestone:  forms from the calcium carbonate remains of animalso Chert:o The accumulation and compaction of tiny silica-rich plankton shells that fall to the ocean bottom . Lecture 16(February 23)Sedimentary structures, which include ripple marks, cross-bedding, mudcracks and fossils, can be used to interpret the sedimentary environment in which they formed long ago. o Cross blending Sediments are deposited in layers, form cross-beds Currents carries sediments, then deposits them- Deserts (wind current)- Shorelines (waves)- Rivers (water)o Ripple Marks Caused by water washing in and out- Beacho Mud Cracks Environments where mud-rich sediments dry out- Lakes that dry outo Fossils Buried and preserve Trace fossils preserved- Fossilized evidence of existence. o Dinosaur foot printso Ancient Shrimp burrowsLecture 17 (February 25)What has to happen to any rock type for it to become a metamorphic rock? o Basically, it has to been buried or shoved down into the Earth (e.g., by subduction) and heated (i.e. hotter down deeper or against rising magma)Definition of metamorphism o The mineralogical and structural changes of solid rock in response to changes in environmental conditions, especially depthWhat are the three agents of metamorphism?o Heato Contact Metamorphism: Heat comes from contact with magmao Geothermal Gradient: Heat comes from increased temperatures with deptho Pressureo Confining: All directions evenlyo Differential: not even, side with least amount of pressure causes folitation Fluidso Volatiles, H20Lecture 18 (February 27)Metamorphic rocks are subdivided based on