Exam 2- Earth System Sciences
Chapter 6: Metamorphism
∙ Metamorphism- means to “change form”
∙ Solid-state change (no melt involved)
o Agents against metamorphism:
Chemically active (HOT)
∙ Key thing = a new metamorphic rock is stable and in equilibrium in its new environment of higher heat & pressure (often deep within the earth)
∙ Major categories of metamorphism:
o 1) Contact (therma) metamorphism- metamorphic aureole o 2) Dynamic (pressure) metamorphism
o 3) Dynamo-Thermal (regional) metamorphism
Gneiss (High grade
Schist Metamorphic Rocks)
∙ Regional Dynamo Thermal Metamorphism
o Banded gneiss (felsic, mafic bands often folded)
∙ Regional Dynamo- Thermal metamorphism
o Amphibolite (dark layers & “pods”, “hornblende rich”)
∙ PARA GNEISS- sedimentary rock
∙ ORTHO GNEISS- igneous rock Don't forget about the age old question of What is covariance?
∙ Schist= individual mica minerals that are visible to the naked eye.
∙ Contact metamorphism- thermal metamorphic limestone (marble)
o Contact or thermal metamorphism
∙ Pressure metamorphism causes:
o 1) Metamorphism or deep burial ~~~~ p lithostatic= pgz
o 2) Tectonic pressures
Z- (thickness in earth, the depth below the surface) G- (Gravity within the earth
P- (2,700 kg/m3)
∙ P= density of continental crust
∙ High pressure metamorphism causes atoms to move closer together
o Low pressure atomic spaces
Chapter 7: Mountain Building and Geological Structures
∙ Crags, Cracks & Crumples
o Mountain building & geological structure
∙ Mountain Belt: orogens If you want to learn more check out Patriarchy means what?
∙ Orogeny: process of mountain belt formation
∙ Deformation: process during which rocks bend/break/or flow ∙ Geologic structures: features produced by deform, joints, faults, folds and foliations
∙ Displacement: Change in location
o Occurs when a block of rock moves from one location to another
∙ Rotation: a change in orientation
o Occurs when a body of rock undergoes tilting
∙ Distortion: change in shape
o When a body of rock changes shape, development of a fold represents one type of distortion.
∙ Strain: Change in shape/volume, stretching
o A measure of the amount of distortion during deformation ∙ Strain: Sheer
o Transforms the cube into a parallelogram and changes angular relationships
∙ Brittle Deformation:
o Process which a material cracks or fractures, creating joints or faults in rocks
∙ Plastic Deformation:
o Process by which objects change shape without visibility breaking creating folds in rocks
∙ Deformation Factors:
o Temperature: heat makes materials softer & more prone to plastic deformation Don't forget about the age old question of How do you know how full a cylinder is?
o Pressure: greater pressures causes rocks to behave more like plastic Don't forget about the age old question of What are compensatory behaviors?
o Deformation Rate: sudden changes make materials more prone to brittle deformation, whereas slower change allows more plastic deformation
∙ Stress compression:
o Takes place when an object is squeezed
∙ Stress tension:
o When the opposite ends of an object are pulled in opposite directions.
∙ Stress: sheer
o Develop when one surface of an object slides relative to the other surface.
∙ Stress: pressure
o Occurs when an object feels the same stress in all sides. ∙ Faults: surfaces of slip
o Dip Slip
o Hanging wall: block above fault lie
o Footwall: block below fault line. Don't forget about the age old question of What is the lederberg and tatum experiment?
Types of Faults;
o Fault Scarps: a small step or offset on the ground surface where one side of a fault has moved vertically with respect to the other
o Slicken slides: a smoothly polished surface cause by frictional movement between rocks along two sides of a fault Don't forget about the age old question of How do fungi defend itself against bacteria and also infect plants?
o Slip lineation’s: linear groves on fault surfaces
o Folds: a curve in the shape of a rock later
o Anticline: arch, limbs dip away from hinge, big oil and gas exportation
o Syncline: looks like trough, limbs dip toward hinge o Recumbent fold: has two horizontal axial plane
o Monoclines: looks like stair step, usually draped over a fault block
o Plunging Folds: occurs where the hinge of the fold is tilted relative to the surface
o Domes: dome shape of an overturned bowl.
Chapter 8: Earthquakes
o Seismic Waves:
o Body waves:
P waves: compressional
S waves: shear
o Surface Waves:
R waves: vertical undulations
L waves: back & forth movement
o Mw: moment magnitude: provides consistent scale for comparing earthquakes
o Seismic belts: mark plate boundaries
o Reverse faults
o Thrust faults
How do earthquakes cause damage?
o Sediment liquefaction
o Ground shake/displacement
o Liquid sand layer causes the ground to crack and sand volcano’s to erupt.
WORLDS LARGEST EARTHQUAKE:
o With an instrumentally documented magnitude occurred on May 22nd, 1960 near Valdivia, in Southern Chile.
o Magnitude 9.5 by USGS
o Referred to as the “Great Chilean Earthquake” & the “1960 Valdivia Earthquake”
Earthquakes at plate boundaries:
o Divergent-boundary seismicity
o Convergent-boundary seismicity
o Transform-boundary seismicity on continents
Chapter 9: Deep Time
o Deep time: How do we age natural disasters?
o James Hutlon: lived during Age of Enlightenment in the 1700’s, Europe
o Physical processes we observe today also operated in the past & were responsible for the formation of geological features we see in outcrops
o Geological time (changes) occurs over long periods of time.
Modern view of geological process/time change: o Punctuated Equilibrium
Earth age based on dating estimates (~4.6 BYO =
o Absolute (radiometric) Dating of Mineral & Rocks: o Mostly used for dating: Igneous & metamorphic rocks o Minerals contain radioactive isotopes
o Isotopes: atoms that have the same atomic number but different mass numbers.
o 1) Decay Rate- unique for each isotope
o 2) Half-lite- function of decay rate
o Radiometric Geochronology:
o This system works because of High Heat, which causes parents to separate from daughters during heat/melting & radioactive clocks are reset to 0 at the time of cooling (“block temperature”)
o Rate of decay: n/N
o n- # of atoms that decay in a given time
o N- total # of atoms
o Geological Time Scale: name of Eons (youngest at top) o Phanerozoic- “visible life” (542 Ma to present time) o Proterozoic- “before life” (2.5 to .542 Ga)
o Archean- “ancient” (3.8 to 2.5 Ga)
o Hadean- “hell” (4.6 to ~4.0 Ga)
∙ Fossils & Eudution
o Fossils important for understanding “deep time”/construct geological time-scale.
Fossils mean ‘dug up’ in Latin
∙ What it takes to become a fossil:
o 1) Hard parts: shelly exoskeleton
o 2) Minimal Post- morten transport (usually by scavenging organisms)
o 3) Rapid Burial in subsiding sedimentary basins
o 4) Diagenic alteration after burial that does not chemically destroy the remains
o 5) Uplift, erosion & exposure to the elements