Lecture: Oct. 1st, 6th, and 8th
Lecture: Oct. 1st, 6th, and 8th 11883 - GEO 105 - 01
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This 9 page Class Notes was uploaded by Andrea on Monday October 12, 2015. The Class Notes belongs to 11883 - GEO 105 - 01 at Grand Valley State University taught by Tara Ann Kneeshaw in Fall 2015. Since its upload, it has received 63 views. For similar materials see Living with the Great Lakes in Geology at Grand Valley State University.
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Date Created: 10/12/15
Living with the Great Lakes Notes from class on October 1st 2015 The MidContinental Rift o 11 billion years ago 0 As the crust spread apart magma rose to the surface and cooled 0 We do not have complete evidence of breakinglava because overtime erosion has erased things 0 This happened repeatedly Erupting layer upon layer of lava on surface 0 In time between flows sediments were deposited on these layers 0 Weathering as well created over time I Clastic Sandstone fragments I Chemical evaporation of seawatermaterial Precipitation 0 Rifting abruptly stopped 1 billion years ago Why 0 Heat source went away found another path of least resistance up to the surface 0 How do we know rifting occurred 0 As it s crystallizingcooling rocks become very dense o Lava rises with convention system under the Earth then as it reaches the surface it cools and fails I These layers caused depressions in the layers over time piled up one on top of another 0 Create Rift Valley 0 Sediments fill on top of one another like stacked bowls 0 ex Lake Superior I What happens when tectonic plate move the sediments I Lake Superior Syncline o The pressure from the plates cause the depression underneath the surface to bow Squeezing it until it has nowhere else to go but up and out Creating an uplift 0 Ex Isle Royale and the Keweenaw Peninsula are two side of a syncline where the pressure brought layers up to the sunace 0 Top Hat Review question 0 What happened during the midcontinental rift I The crust spread apart and basaltic magma rose to the surface and cooled Lake Shore Traps o The exposed layers of the Lake Superior Syncline have weather over time to create a pattern in the rocks that undenNater looks like pieces ofjagged rock out in the water 0 As they ve been weathering and eroding it creates a stair step pattern and each step is a different flow I The stairlike resemblance comes from the way basalt cools which creates joints in the rock 0 Visible Lake Shore Traps can be seen at Eagle Harbor in the UP 0 And these traps are also a main contributor to many shipwrecks in Lake Superior 0 Today not many of these traps remain They have erodedwashed away Paleozoic Era The basement of Michigan ex Pictured Rocks 0 Rock Types 0 lgnenous and Metamorphic rocks found largely in the UP 0 Sedimentary rocks dominate the Michigan Basin in the LP I These rocks are 500 million years old 0 Michigan Basin 0 Distinct difference between Precambrian and Paleozoic rocks I Most rocks are buried deep in the surface Can t see those 0 Lower Peninsula Both chemical and evaporite I Limestones I Sandstones I Shale 0 Time Scale Moving up from Precambrian I Paleozoic ancient life fossils Rapid expansions of life 0 7 periods in the Paleozoic Era o Permian etc look on BB lecture slides o From 570245 MYA million years ago 0 Turtles alligators sharks gt survived all the mass ex nc ons 0 Nothing from the Mesozoic Era dinosaurs I Rock Types 0 Dolomite exactly like limestone Both calcium carbonate But limestone neutralizes acid easier and dolomite has to be ground to a powder in order to o Limestone From when you evaporate sea water ground water Lots of calcium 0 Sandstone Different sizes whatever color the sediments are collected will be the color of sandstone or multiple 0 Shale Claymudslide particles Basically hardened mud 0 Coal All organic material Not exactly rock but fossilized plants Evaporites o Halite rock salt 0 Gypsum calcium and sulfate Main ingredient in drywall o Anhydrite Another version of gypsum o Familiarize with names 0 Understand how these are important economically Basin 0 47 carbonates 0 Calcium carbonates limestone and dolomite o 23 sandstones 0 Sand grains Drinking water Holds lots of water 0 18 shale o Muddried o 12 evaporites o Gypsum Most have been mined out I ex Grand Rapids Gypsum Mine Living with the Great Lakes Notes from class on October 6th 2015 The Cambrian 0 Mountain that had formed in the UP region during the Precambrian were worn down allowing a shallow sea to lap over Michigan 0 The sandstone we have came from the beaches by the sea made during this time I ex Pictured Rocks 0 Different layers in the rock show wave lapping Built during this time 0 North American continent was closer to the equator tropical climate I Earliest lifeforms marine invertebrates clams snails 0 Also trilobites all shapes and sizes 0 brachiopods fairly common The Ordovician 0 Warm tropical environment still Persisted over a of Michigan 0 Positioned over equator still 0 More diverse tropical marine life I Still trilo and brachio in addition to o Crinoids Sea lillies o Corals o Crinoids Can be found along L Michigan shores Stems disc shape and are more common Finding the head of one is rare I Living crinoids are referred to as sea lilies 0 Because of their colorful flowerlike appearance The Silurian 0 Warm and tropical still Shallow sea 0 Water in the middle of the sea was deep creating a very isolated basin and resulting in a very salty sea Hypersaline Poor circulation Coral reefs are around the edges of the sea LOTS forming Evaporation of the water continued and layers of salt and gypsum were deposited in shallow areas 0 ex ln gypsum mines you can create tunnel through these thick layers 0 Huge coral reefs began to form from all the coral 0 Life near these still include coral crinoids trilo brachio clams snails and new I Bryozoans Sea moss I Cephalopods Modern squids o The Basin 0 Michigan Formation I Perfect ring of gypsum underneath the basin I Calcium and sulfate Gypsum Soft I Down 80ft to find evidence of the ring The Devonian 0 Still warm still tropical etc o More species still 0 Trilo snails brachio cepha crinoids in addition to I Phacops type of fish Early amour covering body Like a turtle shell I Hexagonaria coral Creates Petosky Stones The Carboniferous o Mississippian 0 Change Warm shallow sea starting to withdraw for the first time Last time we were covered by sea water I lsolated the basin from the salt water Big deposit of Mississippian aged rocks 0 ex Limestone o Fossils now of sea life Crinoids clams coral blastoids coral o Pennsylvanian known for it s coal 0 Tidal flat mud clay shale Giant swamp land 0 Plants start growing 0 Fossils are now of plants from this era not creatures I ex Ferns 0 So much plant material started forming huge amounts of coal I Formation of coal Nonrenewable resource 0 Takes time 0 Organic material decomposes is buried and given very little oxygen Suffocate o 7 ft or more of compacted plant life to get 1 foot of bituminous coal I When in water plankton decomposes and drops to the bottom where there is no oxygen oil The Permian last period of the Paleozoic o No rocks or fossils from the Permian 0 Why I A glacier came and wiped it all away 0 Erosion was happening faster than deposition Rest of the World Records from other parts of the world 0 Mesozoic 0 Big things Mammals I Turtles dinosaurs basically giant lizards o Pangea was in the known position 0 Ended with mass extinction A reset button I 90 of marine species gone I 70 of terrestrial species died 0 Only known mass extinction of insects Took 30 million years to recover Leads to present day 0 Why did it happen Combination of things to equal a catastrophes Eruptions Pangea breaking methane Asteroids Methane filling the air Living with the Great Lakes Notes from class on October 8th 2015 TopHat Review The rocks in the center of a basin are o The youngest rocks in a basin TopHat Review The gap in the rock record in Michigan is due o Erosion faster than deposition Skipping the Mesozoic and parts of the Cenozoic Paleogene and Neogene The Michigan Basin 0 Unique about the GL region is that we have a basin shape 0 Nearly circular pattern of sedimentary starts with a nearly uniform structural dip toward the center I Nesting bowls outside oldest amp inside youngest o How deep is the basin I Isolines represents the same depth on a map Show the bowl and depth I Deepest point in the basin deepest point in the bowl 0 Gladwin MI 16000 ft 3 miles 0 Importance of Rocks Economy 0 Mining metals copper iron gold silver I Other important deposits gypsum salt limestone slate coal 0 Limestone carbonate rock Paleozoic constant 0 Uppermost bedrock in MI big part of lower UP and upper LP 0 Industrial quality clean and pure Northeastern lower peninsula and up I Shipping convenient coastal mining on shores 0 Close to the water success 0 Port Calcite largest limestone quarry 0 Number of quarries have decreased I Only 3 left that are still really active 0 Port Dolomite o Cedarville Michigan both dolomite and limestone o 34 million net tons per year 0 Port Inland o Gulliver MI high calcite carbonate limestone and dolomite o 34 million tons per year 0 Port Calcite Largest limestone quarry 0 Rogers City MI Presque Isle high calcium carbonate limestone produces o What is limestone used for I When heated in some cases and or combined with salt is used for making many products 0 ex paper glass paint soap textiles baking powder pharmaceuticals Michigan Basin greatest area of rock salt in the world 0 Basis of major chemical and plasterboard drywall industries in Michigan 0 The formation of basins and arches restricted circulation of water in the sea 0 The basin was filling up as the basin was subsiding sinking down I Allows reefs to build up on the sideedges Salt cycle Evaporation Formation I 600 meters of gypsum and salt in the basin I One bed of salt nearly 150 meter thick o It would take a column of seawater nearly 250 km 820000 ft deep to form a layer of 150 km thick I Deposition of immense volume of salt took 1520 million years and ended 390 million years ago Salt Industry Michigan led nation in salt production 0 Between 19051958 give or take 4 years 0 Present still have salt but other places are easier to mine No economical 0 Two methods to extract salt I Water pumped down to make salt water then pumped to surface to let evaporate I OR I Underground mining of rock salt soft o Began early 20th century under the city of Detroit Since 1890 s Michigan s chemical industry has made thousands of products based on chemical compounds found in or near salt brine o Bromine pools calcium chloride and magnesium o Wyandotte Chemical Company 0 Dow Chemical Company Gypsum o Began in 1840 s nearunder Grand Rapids MI 0 1861 aboveground mining in Alabaster MI 0 By 1970 s Michigan gypsum was valued at 10 million annually I ex plaster drywall building materials 0 Mined most of it out Clay and Shale Mining 0 Clay is main material in bricks I Ml million tons of bricks I Comes from two sources 0 Clay sediments laid down in glacial ancient lakes 0 Shale and bedrock 0 Spread out throughout the state
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