GEOL 11 Module 1 Notes.pdf

Geol 11 Module 1 Notes: [Thanks for reading (and hopefully adding to, via Suggest Mode) my notes! Please turn off Print Layout while viewing, it separates the pages – Isabel] [These particular notes are still a WIP, will rework formatting in a bit :)] Definition of Geology: old definition: the s...

Geol 11 Module 1 Notes: [Thanks for reading (and hopefully adding to, via Suggest Mode) my notes! Please turn off Print Layout while viewing, it separates the pages – Isabel] [These particular notes are still a WIP, will rework formatting in a bit :)] Definition of Geology: old definition: the study of Earth new definition: the study of Earth and other bodies, their forms, and the composition processes they have undergone and are undergoing Geology as a Discipline issue of time ○ short vs long! nigh instant processes like earthquakes or volcanic eruptions vs continental drift or the formation of mountain ranges issue of scale ○ small vs large, rocks vs whole mountains ○ micro vs macro, invisible vs visible to naked eye ○ local vs regional, local = expanse visible to naked eye, regional = needs a map to see see complexity of replicating natural phenomena ○ difficult to replicate certain things, especially without computer simulations Branches of Geology physical geology – examines the visible/present, earth’s rocks and minerals, seeks to understand the processes driving change (most branches fall under this) ○ mineralogy – study of the chemistry, crystal structure and physical properties of the mineral constituents ○ petrology – study of rocks - igneous, metamorphic, and sedimentary - and the processes that form and transform them ○ structural geology – formations, manifestations and stuff ○ seismology – seismic waves, earthquakes ○ environmental geology – how geology affects the environment ○ engineering geology – application of geological knowledge to engineering problems ○ mining geology – study of geologic structures and particularly the modes of formation and occurrence of mineral deposits and their discovery  ○ petroleum geology – study of the geological processes that create crude oil and natural gas reservoirs ○ geomorphology – “form of the earth”, study of landforms and landform evolution, Earth's topographic features ○ planetary geology – on other planets! study of surface and interior processes on solid objects in the solar system historical geology ○ paleontology – history of life on earth, through fossils ○ stratigraphy – layers of earth (cake metaphor), description of rock successions and their interpretation in terms of a general time scale, provides a basis for historical geology ○ geochronology – “whole story of earth”, determining the age and history of Earth’s rocks and rock assemblages, determined by studying rock strata and fossils preserved within them Early Schools of Thought Catastrophism ○ Pioneered by Baron Georges Cuvier, 18th cent. ○ “Everything in earth was formed by a catastrophe” ○ Sudden worldwide catastrophes are agents of change ○ Popular among theologians since it’s consistent w/ biblical stuff (1650 James Ussher's 4004-year chronology) Uniformitarianism ○ pioneered by James Hutton “father of geology”, 1700 ○ Earth is continuously modified by geological processes that have always operated throughout time (at different rates) ○ the physical/chemical/biochemical laws of the present were the same laws that existed in the past — “the present is the key to the past” ○ popularized by Charles Lyell in “Principles of Geology” (lyell also inspired darwin) ○ acceptance of this theory also meant accepting earth was Old old, older than biblical estimates Lecture 2 – The Universe and the Earth Formation of the Universe and the Earth singularity — infinitely small region of space with 0 volume and no dimensions. it was the universe before the Big Bang. it simply Was. Big Bang – when the singularity suddenly expanded rapidly and became the universe (13.7 billion years ago) ○ today the diameter of the observable universe is estimated to be 28 billion parsecs, BUT the diameter of the universe is increasing 6.5 times faster than the speed of light in a vacuum – in short, we can’t catch up. we can’t ever fully observe the entire universe (nothing is faster than light) ○ the BBT was first proposed by Georges Lemaitre in 1931, but it wasn’t taken seriously until evidence was found later Big Bang Theory Evidence Cosmic Microwave Background Radiation (CMB) ○ remnants of the radiation from the very beginning of the Big Bang, now super stretched out to microwave radiation  Hubble’s Law / Redshift ○ “galaxies recede at speeds proportional to their distances from the observer” ○ as the universe expands, things that emit light get farther away from each other ○ as distance increases, the light is stretched/elongated – this stretches the wavelengths (and since light gets redder as wavelengths get longer…) it’s a red-shift ○ if the universe is expanding, it must have been smaller in the past ○ Edwin Hubble, in 1929, made the connection between the distance of a galaxy and its redshift (grounded on Vesto Slipher’s 1912 discovery of galaxies exhibiting motion) Abundance of Primordial Elements (H, He) ○ most of the matter in the universe is just H and He ○ H and He were created during the Big Bang mismo; everything else came after Our Solar System Nebular Hypothesis 1. rotating gas-dust cloud start contracting due to gravity 2. gas-dust cloud flattens into a protoplanetary disk 3. most of the matter is concentrated in the center, forming the sun (which accounts for 99% of the mass in our solar system) proposed by Immanuel Kant (yes THAT Kant, critique of pure reason Kant) and Pierre-Simon Laplace frost line – divides the solar system, separates the terrestrial planets from the jovian planets  ○ Terrestrial – within reach of solar winds, warmer, so planetesimals accrete silicate rocks and metals while the gases are blown away and also can’t condense much. ○ Jovian – lack solid surfaces, were formed from rock-ice, cold enough for lighter elements to condense Nucleosynthesis formation of new elements due to fusion in the sun and other stars (the sun is a 2nd/3rd generation star) when the iron core implodes, the star explodes in a supernova Earth Stuff The Iron Catastrophe EARTH’S CONDENSATION 1. Earth began to accrete from the nebular cloud’s planetesimals 2. As mass increased, gravitational force increased and earth started to compress into a smaller and denser body 3. The interior of the earth started to heat up (from collision heat, heat from solar radiation, and heat from radioactive elements) and melt. Since Fe was the heaviest common element, as Earth melted, the droplets of melted iron sank towards the core where they condensed 4. It started out slowly and then sped up to catastrophic proportions (hence the name) accretion > heating > differentiation the lighter elements float as the heavier elements (Fe, Ni) sink, creating the layers of the earth Formation of the Moon the moon was formed from collision with a Mars-sized planetesimal Formation of Earth’s Atmosphere Formed by heating/differentiation, just like the earth itself 1. 4.5 Ga – primordial gases are blown away by solar wind 2. 4.0 Ga – volcanic gases start to accumulate (H2O, CO, CO2, NH4, CH4) (+ HCl, HCN) alongside possible gases from comet impacts 3. ?? more accumulation of volcanic gases  4. 3.5 Ga onwards – cyanobacteria/blue-green algae start converting CO2 into O2 Lecture 3 – Earth Layers of the Earth Layers of the Earth – Chemical Composition Name Properties Crust - mostly iron and silicon - solid outer shell (variable thickness) - low density rock - 7-70 km thick - continental – 15-60 km - oceanic - 3–15 km - less than 1% of Earth’s mass and volume Mantle - composed of oxygen, silicon, magnesium, iron - high density rock - 83% of Earth’s volume - 68% of Earth’s mass Core - iron and nickel alloy (but mostly iron) - approx. 3500 km - 16% of Earth’s volume - 31% of Earth’s mass Layers of the Earth – Physical Composition Category Name Properties Crust Crust - 7-70 km thick (7km oceanic) - relatively thin, rocky outer skin - composed of continental and oceanic crust - continental – many rock types, generally older and less dense than oceanic - oceanic – mostly composed  of basalt, generally younger and denser than continental Entire Crust Lithosphere - 100 km thick and Uppermost - whole crust and uppermost mantle Mantle - Relatively cool and rigid - Earth’s outer shell Upper Mantle Asthenosphere - softer, comparatively weak (660 km) - top part has a little melting, enough to allow the lithosphere to move independently of the asthenosphere Lower Mantle Lower Mantle - 2240 km thick??? - solid, but hot and capable of very gradual flow Core Outer Core - 2260 km thick - liquid layer - movement of liquid iron generates Earth’s magnetic field Inner Core - 1216 km radius - solid (despite higher temperature) due to pressure Differentiation - the different layers of the Earth have different properties, due to: increase in temperature and pressure increase in temperature alone -> melting increase in pressure alone -> solidification Evidence for Layers Seismic waves ○ P waves (can penetrate both solid and liquid) ○ S waves (can only penetrate solids) Xenoliths (but not from meteorites!) ○ rocks that form in the mantle, solidifying as they go up Earth’s Size and Features Earth’s Size Equatorial circumference = 40,076 km Polar circumference = 40,008 km Eratosthenes measured the Earth’s circumference and got 41,000 km (computing the difference in shadow angles in different locations at the same time of year, then using the ratio and proportion to compute) Earth’s Features Continental features Oceanic features Theories of Isostasy Isostasy - “the state of balance that the lithosphere are thought to achieve when vertical forces remain unchanged” - basically… why do we have different levels of elevation? - NONE OF THE ABOVE can cover all the bases! Pratt’s Theory of Isostasy there are differences in density low density crust becomes mountains CRITICISM: the Himalayas are not less dense! Airy’s Theory of Isostasy the lithosphere is equally dense elevation comes from roots in the asthenosphere that push up the crust has some supporting data, but density isn’t constant Flexural Theory of Isostasy a combo of smaller theories over geologic time, load bends the asthenosphere, but it eventually recoils and adjusts, forming mountains (with load on top of asthenosphere) Lecture 4 – Plate Tectonics Continental Drift proposed by Alfred Wegener Pangaea > Laurasia & Gondwanaland Panthalassa – 1 sea Evidence continental jigsaw puzzle fit – Africa and South America fit if atlantic ocean is closed fossil match – fossils that couldn't have traveled (Mesosaurus, Lystrosaurus, glossopteris) rock type/geologic features – self-explanatory (appalachian-caledonian mountains) paleoclimate – (coal seams in northern hemisphere had tropical trees: bc northern hemisphere used to be in equator) (glacial till/striations in southern africa, south america, australia, india) Opposition: Wegener couldn't give a mechanism for continental movement hypotheses: tides/continents came through ocean Seafloor Spreading Harry Hess, early 1960s extensive mapping meant we found submarine volcanoes, mid-oceanic ridges, etc earth’s crust moving away from MOR (MORs produce new oceanic crust) (the closer, the younger) Extra Evidence paleomagnetism, polar wandering ○ curie point – temp. at which mineral's magnetic properties change ○ small magnetite minerals point to wherever north was at their birth: pointed DIFFERENTLY, showing that north was oriented differently when they were born magnetic reversals ○ shows differences in age (callback to MOR, ridge) hotspot volcanism ○ hotspots = localized hot regions below lithosphere (mantle plume)  ○ frame of reference for motion ○ age of volcanism (island) corresponds to time since it was on top of the hotspot seismicity, plate boundaries ○ deep earthquakes (>150km) indicate subducting slabs ○ shallow earthquakes indicate rifting regions Plate Tectonics Theory unifying theory of geology lithosphere is made of segments called tectonic plates plates are in constant motion Major plates: NA, SA, pacific, eurasian Plate boundaries – where movement is ○ divergent – constructive (new material); oceanic ridges, continental rifts ○ convergent – destructive (subduction); two plates form either arcs/mountain systems; form subduction zones when there's oceanic lithosphere involved, continental crust makes mountain ranges, orogenic (crumple + uplift) (basically squish) belts ○ transform — wala HJKFDHFJSDKL two plates colliding/grinding, but parallel motion; connects oceanic ridges; faultlines Mechanisms for Plate Motion ○ mantle convection: 2 layer convection – sa mantle, asthenosphere only, crust separate 1 layer – isahan lang, mantle directly moves crust ○ ridge push warm mantle pushes surface upwards, gravity driven ○ slab pull cold lithosphere slab is pulled down by density ○ mantle drag asthenosphere's velocity drags the plate along Philippine Tectonics volcanism (pacific ring of fire) ○ caused by subduction of East Ph Plate under the Ph belt earthquakes ○ everywhere except palawan bc palawan is outside/farther from convergent plate boundaries convergent boundaries  ○ oceanic/oceanic = Ph Mobile Belt (east) amd Ph Fault Zone (west?) ○ continental vs oceanic = palawan microcontinental block, suture zones plates: eurasian, ph moile belt, ph sea plate trenches: manila, negros, cotabato, sulu + east luzon trough, ph trench Lecture 5 – Minerals Definition “any naturaly occuring inorganic solid with orderly crystalline structure and well-defined chemical composition ○ naturally occurring – self-explanatory. lab-grown gems don't count! ○ homogeneous solid – solid within Earth's usual temperature range (so ice counts as a mineral, but liquid water isn't) ○ orderly crystalline structure – crystals have to have regular shape, crystal lattice (so obsidian doesn't count, since it's amorphous) polymorphous – chemical can crystallize in multiple configurations ○ well-defined chemical composition - chemical composition can vary but it has to be within specific and well-defined limits ○ generally inorganic – exception being CaCO4, calcium carbonate, aka calcite, sometimes counted as a mineral Mineraloids - naturally occurring inorganic solid WITHOUT orderly crystalline structure Rocks - loosely defined - any naturally occurring solid (including organic debris like coal, non-mineral matter) - can be aggregate of minerals or pieces of pre-existing rocks Properties of Minerals luster appearance or quality of light reflected from the surface if they look like metals, it's a metallic luster tarnished minerals exhibit submetallic luster most have nonmetallic luster ○ vitreous – glassy ○ dull/earthy  ○ pearly ○ silky – like satin cloth ○ greasy – like coated in oil diaphaneity / ability to transmit light basically opacity/transparency opaque/translucent/transparent color obvious not really diagnostic since colors can vary a lot idiochromatic mineral – mineral that only occurs in shades of a specific color (like malachite, azurite) allochromatic mineral – mineral that can have lots of diff. colors due to chemical substitutions/impurities (like fluorite) streak color of mineral in powdered form (using a streak plate) streak is usually consistent, unlike color can distinguish between metallic/nonmetallic luster ○ metallic minerals generally have dark streak, nonmetallic luster generally have light-colored streak not all minerals streak! Crystal Shape/Habit minerals generally have one common crystal shape, but some have two or more shape/form Individual – Strength Hardness measure of resistance to abrasion/scratching Mohs scale (relative ranking!) Tenacity mineral's resistance to breaking and deforming  brittle – shatter malleable – can be hammered into diff shapes sectile – can be cut into thin shavings elastic – will bend and snap back into original shape Cleavage tendency of mineral to break along planes of weak bonding related to habit not all minerals have cleavage: you can tell by the relatively smooth flat surface of the breakage when a mineral exhibits cleavage, it will break into pieces that all have the same geometry; don't confuse it with crystal shape! Fracture minerals with bonds equally strong in all directions (no cleavage) exhibit fracture when broken usually they are irregular BUT some are smooth and curved (conchoidal) some are splintery or fibrous Other Properties Density and Specific Gravity density is mass/volume, usually g/cm3 specific gravity is ratio of weight to weight of equal volume of water most common rock-forming minerals have specific gravity between 2-3 Other other properties feel smell magnetism double refraction fluorescence Mineral Composition (and other stuff) Common rock-forming minerals oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium Silicates most common type of mineral comprise 90% of Earth’s crust made from the basic building block, the silicon-oxygen tetrahedron (SiO4-), arranged in various ways Silicate Table: Olivine -> pyroxene -> amphibole -> mica -> feldspar -> quartz  As temperature increases, complexity decreases (olivine is the least complex, so we can say that it probably originates from a lower level than quartz) ○ this is because the lower you get, the hotter and more compressed the atoms are, so some chemicals that can be used for crystals are liquid and can’t crystallize olivine – island silicates / nesosilicates pyroxene – inosilicates amphibole/augite – inosilicates micas – sheet silicates/phyllosilicates (phyllo, like the dough used for baklava) feldspar – framework silicates / tectosilicates quartz – framework silicates / tectosilicates Other Silicate Factoids: feldspars (minerals under the feldspar umbrella, including orthoclase and plagioclase) are the most abundant silicate and the most abundant mineral in Earth’s crust quartz is the second most abundant silicate Non-Silicates self-explanatory; all the minerals that AREN’T silicates economically useful Carbonates [CO32-] ○ much simpler than the silicates structurally ○ calcite (CaCO3) – used for cement, lime, fertilizer ○ dolomite (CaMg(CO3)2) – cement, lime, also beaches haha Halides (from halogens) [F, Cl, Br, I] ○ halite (NaCl) – salt ○ fluorite (CaF2) – use ○ d in steelmaking, also very pretty ○ sylvite (KCl) – fertilizer Sulfates [SO4] ○ gypsum (CaSO4 plus some water) – used in plaster, dentistry, orthopedics ○ barite (BaSO4) – very like gypsum but also very toxic. Do NOT eat. heavy  Oxides [O] ○ hematite (Fe2O3) – iron ore (from Iron (II)) ○ magnetite (Fe3O4) – iron ore, magnetic (recall: paleomagnetism) Sulfides [S] ○ galena (PbS) – lead ore ○ pyrite (FeS2) – fool’s gold, also used for producing sulfuric acid ○ lots of ores for other metals also (copper, zinc, mercury) Native elements ○ Elements available in relatively pure form Copper, gold, diamond, etc Lecture 6 – Rock Cycle MOSTLY you just want to study the diagram here, but i’ll add some extra notes. Igneous rocks - formed as magma/lava cools and crystallizes (magma is molten rock, when it reaches the surface it’s called lava) - melting happens in subduction zones  - extrusive/volcanic – generally smaller crystals, solidify at surface - intrusive/plutonic – generally larger crystals, formed underground Sedimentary rocks - “most common” ??? “most common at earth’s surface” - Diagenesis = conversion of sediment into rock, via compaction (particles of sediment getting squeezed together) and cementation (crystals forming within the gaps of those particles, sticking them together) - deposits occur in layers Metamorphic rocks - Are still solid! change in temperature and pressure! - metamorphism influenced by heat, pressure, volatiles - heat – most important, heat makes minerals unstable and triggers chemical reactions - pressure – makes mineral grains closer together - confining pressure – equal in all directions - differential stress – where warping occurs, makes rock texture curvy: rocks are shortened in direction of greatest stress and elongated in direction perpendicular to said stress - volatiles/chemically active fluids – ion-rich fluids can act as catalysts to promote recrystallization, and speed up the chemical reactions (sir noted oceanic vents known as black smokers)