77 Matching Annotations
  1. Apr 2017
    1. With Oblique there will come some strike slip- just like we found in lab!

    2. These were a handful of terrains but were sliced up instead of dozens of different terrains

    3. Orogenic Collapse- struggle and slumps due to gravity

    4. Instead of scraping stuff off the floor the floor scrapes stuff onto the wedges "cleaning" itself up- what the backstop image means on accretion wedge page

    1. Most of western US is due to extension of faults.

    2. Rifts reveal how the faults are detaching from one another they can be reconstructed.

    3. ophiolite- means ocean floor rocks" it's a general term

    4. Fast Moving ridges aren't as dramatic in their look because they move so fast. Slow rifts have more of the typical ridge shape but they move slower

  2. Mar 2017

    1. The equations aren't as important to remember as the concepts

    2. When i wrote Rhyolitic i mean Rheologic

    3. strength does depend on the composition. but it alternates between strong and weak composed materials. The Lithsopheric plates the crust is the piece if the mantle. to understand the role of the crust because of it's olivines composition. this is why in Rhyolitic layering the continental crust lithospheric mantle an then the asthenosphere which the olivine gets hot enough to become viscous.

      Lithosphere is both crust some mantle and the asthenosphere .

      the Crust is the scum of the earth as in it has very little to do with plate tectonics.

      Nearly all of the earth deforms viciously one where or another yes plate activity can cause earthquakes but it is mostly driven by two undeformable plates walking into one another rather than two plates deforming on to one another

    4. we can use equations to show it's not linear it's "Solid rhyolitic."

      think of this line on plastic flow stresses as an extrapolation of the Mohr diagrams, though instead of success vs failure it's viscous versus elastic.

      the earth does not outright prefer viscous behavior it it just easier for the earth to behave viscously. always takes the lowest values.

      Near the surface fracturing dominates,

      going down the behavior becomes more and more viscous less and less fracturing until we reach new material which while the first material is viscous but the second would fracture at that temp. moving down again the temp the second material is viscous at the third will still fracture

      see diagrams on Composite Strength Curves

    5. Recovering from a distortion can take 1000's of years there is still uplifting in Canada from the compression caused by the ice sheets

    6. Elasticity is recoverable Viscosity is not recoverable permanently deformed

    7. time matters greatly with in respect to weather or not the behavior is elastic or viscous. How can you have earthquakes and yet also be vicous?

      Time is the ones that govern behavior.

      fast short windows will still produce earthquakes even at high temperatures

      in longer time-spans the earth can begin to have more viscous processes.

      Elasticity dominates in short time scales and viscosity dominates in the long term

    8. yield stress- ductile behavior

    9. Giving the rock enough time it takes less stress to deform the rick. doing the deformation fast does more stress

    10. AT high temperatures the rock becomes easier and easier to deform.

    1. Drawing out the outcrop - will always look like rick rack not an xmas tree shape.

    1. See confusing terminology page

    2. much easier to deform in the b=plastic manner- higher temperature.... these are NEW concepts and that is okay.

      some straining mechanisms are faster than others.

  3. Feb 2017
    1. R is gas constant

      on Governing equations ( Flow Laws ) of plasticity

    2. Diagram on Stress Analysis: Paleopiezometry grain size in micometers not millimeters

    3. This is all generated by stress, not mineral reaction,. This just means there's a restructuring not a reformation

    4. Dislocation creep- Glide ( Strain) climb ( Strain rate)

      Microstructures: Twinning (low T) Recovery (mid T) Recrystalization ( high T)

      See Crystal Plasticity and Microstructures

    1. Diagram on Finite Strain Compilation page is called a Flynn Diagram

    2. Visually assessing the strain- initially spherical objects : the measurements are in the rocks already yay!

      But most often the objects were not spherical to begin with... We can use quantitative methods around counting how packed the rocks are in what direction gives light to the type of strain experienced.

      Fossils are somewhat helpful, the angles in objects like fossils are quite useful for determining strain between the gales between the objects

    3. This representation of strain in 2d and 3d shapes we assume that volumes does not change! It may change but from modeling we assume static volume but should consider the aspect of a changing volume physically not so much mathematically.

    4. Rosetta outcrops- they tell us the geologic strain history of the area

    5. See Vorticity page and particle paths page for formulas for kinematic vorticity.

    6. Computer card circle to ellipsoid distortion demonstration shows they new x y principal strain angles( Still perpendicular to each other)

      The block never turns, but it looks like it rotates- this is internal roation strain distorntion, this can be tracked and is the physical tracker for the ammount of strain the material experienced based on how much distortion happened

    7. angles are one way we track distortion in materials, finding the angle between principal strain and material lines.

      One you have the principal angles and the length changes the who strain profile of the material can be assessed

    8. Heterogeneous strain- the strain on the object differs, so the shape is different from every angle. on a regional scale the closer you move in the more homogeneous the strain gets the further out the more heterogeneous

    9. this page wil see itselfon the next exam the components of deformation

    1. Think about the stresses and that can break the rock up. once the rock is broken it turns towards friction more often than making new faults on top of faults. you can calculate out how heaxy a rock is- take a block and give it a large arbitrary area and normal force equals force divided by area. ratio of stress.

      The rock will break at the point you'd psuh it or soyou'd think.

      Class demo- Sliding a soda can is relatively easily. first thought was that faults were gravity driven but gravity cannot do the work. Okay then how does a rock slide uphill without breaking the rock?? adding liquid nitrogen decreased the friction greatly. but that cannot be done with rocks.

      the Air wanted to get out and pushed the can/rock up and it was extremely easy when the air was trying to escape, but the air represents a fluid pressure. A fluid pressure gives the rock a big cushion so that the frictional coefficent/ fluid pressure reduces the necessary forces needed to move the rock. Fluid pressure woks in all directions, will affect all the stresses so the fluid pressure decreases the force needed . The friction coefficient is unchanged but the rock "Feels lighter" because the air underneath it makes it feel lighter.

      Water makes it harder for rocks to slide actually not easier. In nature you will find rock at faults an rock being transformed.

      maybe the interface rock could help us solve the equation.

      Lubricant scenario- thin layer of material with a low friction properties that helps move the rock greases the skids, clay does it serpentine olvivine does it.

      One other really important realization- friction and greasing help with movement but thrust belts don't look like stacked rocks. loook a thrust wedges. blocks push together and forms wedge geometry. like when ypu plow snow. The geometry of the wedge changes . Cannot make very steep wedges gravity acts upon it wanting to pull the high side of the wedge down or the low side of the wedge up. there's a certain angle that nature likes a certain agle due to gravitational restrictions.

      This angle is the critical taper angle and thrust belts are not big blocks but eroded wedges. Thrust belts when they move, they still realease a lot of energy, it's not hard for the mto move it still releases a lot of energy.

      Mining materials- to the faults they can trap the precious materials.

    2. Changing fault character with depth, Breccia, Cataclasite, Mylonite and melts/ pseudotachylyte around all.

    3. Friction Melts-

      Pseudotachylyte- metamorphic rock that has igneous like melted blobs crazy smooth and an environment that can melt rocks is very full of friction- like giant earthquakes. or impact craters.

    4. Calaclasite and Gouge, rocks of the fault zones. Tectonic Breccia, sharp edges and sedimentary Breccia, usually rounded.

      Cataclasite- broken up rock, brittle fault, gouge breccia Mylonite- seen an enormous part of deformation, the rock doesn't loose deformation See Fault Rock Classification for the different fault rck classes. Types of MYlonites. won't be asked for specific types yet but it's an important rock type.

  4. Jan 2017
    1. None of these processes are scale dependent. the stress is the same on the small scale as it is on the large scale. Looking at size of faults they follows a trend- the larger the fault, the more displacement and vice versa. The displacement can be found as a function of fault length.

      The lab work can be scaled up to the field. There's a rosetta outcrop that helps us understand the size of the bed.

    2. Fault Bends- Thrust Ramps and Flats Andersonian Faulting- everything is in the same layers beforehand. IF afault was generated they rock is split between a layer the sayer will likely make ramp flat geology alternating ramp and flat parts through a section.

      Nature doesn't like to generate holes it will avoid making then because they won't stay open.

      Klippe- erosion took away all the stuff surrounding it the fault is the same as the far away thrust trace but erosion washed away the faulting in-between

      Nothing has perfect geology- most displacement is on the horizontal surface, a twist in the rock one way will create a hole or graben if twisted the other way this is a "releasing vent"

      Fault zones occur- once a fault is generated new faults and more new faults will occur, but it follows the rule of the conjugate around the fault.

      Fault Terminations- there are many ways a fault can terminate but the faults have t stop somewhere eventually. The faults must stop or change orientation they cannot go on forever.

    3. Normal faults require environments where rocks are pulled apart- think ocean ridge segments .Reverse faults are a little shorter, places where you'd think convergence occurs, subduction zones.

      Italy-pulling apart = normal faultsf happening

      entire area characterized by normal fault systems- detachtment systems

      Reverse Fault- Thrust system

      Lot of Germany is a normal faulting system- horst and graben sections.

      Low angle normal faults cause smooth hills between the tilted hanging wall blocks f normal faults these are not explained by Anderson theory of stress.

      The mountains of new Zealand exist because the lateral fault slipping weren't the most efficient so they caused mountains.

    4. Where there's 1 fault there's usually more- san andreas fault is a fault ZONE there are 3-4 active faults.

      Anastamosing faults- braiding faults that have moving parts in between may evolve like a braided river. The deeper in the earth the rck isn't broken up it's shear its rubbing against one another but pressure keeps the rock from breaking apart.

      See Fault Types page for fault types depictions. Dip slip- follows the dip when it breaks Stike slip- parallel to the stirke Right lateral- dextral Left lateral- sinistral comes from witches being left handed and sinister... yay.

    1. unloading relaxation of the joints causes a sheeting effect, this is only because there in no stress to press the rock together.

      Columnar joints- now the stresses are from shrinkage. hot basalt flow cools and crystallizes, solids take less volume than the liquid basalt. shrinks in the horizontal direction and that's hoe columnar joints are formed. closest in nature to rock circles.

      Joitns terminate when they reach the edge of the layer, when the joints try to line up and link together. Nature likes to crystallize deposits within the joints and when the joints fill up they become veins.

    2. Rocks of different elasticities under the given distortion rocks wit different degrees of elasticity will have different degrees of distortion between the two rock types.

      Jointing is the overcoming of a structure's elasticity.

      Don't worry about the shear modulus ( G).

    3. How do the joints "Talk to each other". Think on the springs, a grip of springs. 1 spring breaks and the whole area distorts around it. the more springs break and the more distortion present in the joint the joint gets larger and so does the stress shadow. As the joint gets bigger and bigger and so does the stress shadow. a thinly bedded rock will have more joints because small joins small stress shadow small spacing and thickly bedded rock will have bigger joints bigger stress shadows more space between joints. The spacing of joints is a function of how thickly bedded the rock it. Oil company do not like jointed rocks their oil leaks out

    4. Joints try and go in the direction of the principal stress. they have sort of feather-y pattern, french word for feather is plume . The energy moves away from the crack. these joints tell you about the capabilities of the ground water.

    1. Fuild Pressure- the friction coefficient pushes the mohr circle toward the failure envelope and break the rock easier that way. the introduction of the water pressure is what causes the shift of the friction coefficient. This is quite powerful. This increases failure rates and these failures can cause earthquakes and even land slides. it's the pressure that causes both of these events that water plays a role in. this was always known but only became financially attractive in recent years.

      the distance of sigma 1 minus the fuild pressure is the fluid pressure constant

    2. The magnitude of the earthquake can help predict what time of fault is involved. Reverse faults have the highest magnitude Strike sllip less so and Normal Faults the least magnitude earthquake correlation.

    3. Once a faulti s made it is easier to slide than create a new rock even though the stress conditions are met for more failures. In most environments, at faults there will be more fictional activity over more new faults being formed. Red line- fault formation Blue lines- sliding created coefficent of friction

    4. No longer the fault has to be made. from the columb failure to the firction failure is that there is no cohersion coefficient

    5. Frictionial sliding refers to the movement on a preexisting surface when shear surface exceeds sliding resistance.

      Frictional force is function of normal force. Frictional force is independent of the area of contact and independent of material used- weight of the block is dependent. whys is that?

      There is roughness to every surface which anchor the surface in the asperities. ifthe block is heavier ore areas will touch and increase how anchored the object is to the surface.

      A scaled up pool ball has higher topographical area than our own planet does if pool ball was size of earth.

      Table with legs on carpet= contact points sliding along a surface

    6. Anderson's theory of Faulting explains some of the faults found in nature but fails to find all types of fault and fault system.

      Parabolic failure envelope again as it gets into negative stresses.

      At high stresses( opposite of tensile stresses) plastic deformation occurs at high normal stress, shear stress would be independent here. if the differential stress is known you can start to form a composite failure envelope in which the 5 fault types occur at different differential stresses

    7. The 30/60 fracturing starts to break down as sigma three gets smaller and smaller and even gets negative. There's a value that goes from linear to the parabolic this is the Mohr portion ( dotted line). The failure envelope becomes parabolic in the negative space the straighter section is the Coulomb failure criterion (Solid red line). The coulomb line is consistent and would be infinite but rock conditions will change before it goes to infinity.

    8. IF you look at the stresses the shear stresses gets bigger to 45 degrees then gets smaller after 45 degrees. So why doesn't it follow the angle with seemingly the most stress. See Page: Why 30 degrees instead of 45 degrees Fracture Angle with sigma 1 Nature wants the minimum normal stress possible with the maximum shear stress possible and at 45 degrees we aren't in that sweet spot were the normal stress is as relatively small as possible and the shear spot is as relatively high as can been and this is at about 60 degrees this is why the faults will crack in the same orientation in nature.

    9. The relationship between the shear stresses vs the normal stresses will determine the type of fracture seen and it is called the composite failure envelope- KNOW THIS PAGE

      Coulomb failure criterion: shear stress = Cohesion + The multiplication between the normal stress and mu is the coefficient of internal friction.


      sigma 1- sigma3= sigma failure..... There is a straight line between the failure point of shear stress and the difference between sigma 3 and sigma 1.

      There's failure points of larger differences will be of the same angle... in the diagram it;s about 60 degrees. this is the coefficient of internal friction or mu.

      IF you generate a fault is always 30 degrees to sigma 1 and 60 degrees to sigma 3

    10. 1) The holes will come together and decreasing the volume getting a bight tighter ( elastic component) 2) After the elastic component, the stress orientation will promote cracks at a certain orientation and close cracks at perpendicular orientations ( there''s a crackle pop as the cracks are forming) and can form together.<br> 3) As the cracks grown and grow they eventually break completely with one big audible pop. ( if a rock breaks and no one is around to hear it....) 4) once the rock truly fails... we will get to that on monday But this is why earthquakes keep happening n existing faults, hwy do the hard work to make faults over and over again when you have an already failed structure (A Fault)

      Make materials with as few craks as possible ( Cast iron is one hunk of iron one "Crystal") if there are cracks there is no getting around them but a crackless object is incredibly strong

    11. See Crack Modes Slide for examples and modes of cracking.

      Shear cracks are NOT faults, the rotate into mode 1 orientation ("Wing cracks")

    12. Some cracks are more likely to happen than others, in extension, perpendicular to the force applied is where it will break first ( boof is the breaking sound apparently) in engineering it is most often extension. Geologists work in compression. What happens when you're pushing the original cracks together makes cracks in the vertical orientation will appear as the cracks in the horizontal orientation close.

      How do we know? Milk in glass bottles- glass in refillable bottles but they would break easily and someone wondered why? so they discovered there were microcracks and would make the bottles break easier- not all glass is created equal.


    14. The deformation of the eleastic band is generated by the ammount of stress applied and the elasticity of the material- how easily it reforms

      Rocks are A LOT LESS elastic than rubber bands. without elasticity within rocks we wouldn't have seismology.

      Rocks have a certain elasticity and there's this a pradox about the strength of rocks that are somewhat elastic see above note on tensile failure for explanation.

    15. The stresses build up around the discontinuity or hole and that can be concentrated on the edges is the shape has a an elliptical shape. The more elongated the crack to more stress is concentrated at the edges of crack. The total stress was the same but because of the discontinuity the bonds at the edges of the crack saw too much stress and with this the geologic stresses of 100 see total stresses of 1000 in those sports which would mean the paradox we had is essentially solved. stresses at the tips of cracks will continually keep multiply and continue cracking until... no more airplane wings. The concentration is caused by the loss of the stress the crack or hole could have handled if were whole. Nature keeps propagating the cracks so while t the hole may keep getting bigger the force the stresses likely will not get more intense.

      Wednesday we will se how this works with compression

    16. Rocks can only handle so much elastic distortion before permanent deformation, ( failure occurs). but it takes thousands of MPa to break . The theoretical strength of a rock is in the 1000's of MPa but the actual tensile strength is in the 10's of MPa. This came form that the rock was assumed that the atorms were all evenly placed and spaced but there are flaws in the system that impact the elasticity of the object. we couldn't break aperfect bond but thankfully rocks aren't perfect

    17. playing with rubber bands to show elasticity and failure. Breaking is simply going beyond the elastic capabilities of an object and causing a failure. Elasticity is the prime element when understanding brittle behavior. Earthquake seismology is all elasticity questions.

      What is elasticity? A distortion of the object in of which the distortion will revert to the original shape when the forces stop acting upon it. the distortion of the object is a function of how much stress being applied on an object.

      The More stress applied=the more strength exerted


    18. Once you have a fault, it's about motion of the fault. Before a fualt it's the making of a fault. There are fault specific rocks. WE will look at how a fault evolves.

    19. Shear stress is a function of normal stress. (frictional regime) Shear stress is a function of temperature and strain rate (Plastic regime).

    20. Pressure and Temperature increase with depth into the earth

    1. We have little infor on stress and earth, execpt where we are constantly measuring in boreholes, and the earth is very big but stresses on the earth are measured in very small windows. When you drill a deep hole the bore hole will get distorted by non isotropic stresses as it presses differently from directions.

      Pressure on water- the earth will start to crack if the water pressure exceeds that of the earth. We have some tools to measure stresses ut we heavily rely on theory but thankfully the theories work well as a predictor.

      Fault/plane solutions- exspression of stress on ap lane and that plain reacting to that stress. WE do not have enough information to correlate the stress directly on the earthquake magnitude. You would think big earthquake= big stress but we cannot make a numerical correlation as of yet.

      KTB borehole, they made the hole because the Russians wanted a big hole and the got to about 12 km deep. in Russia it's very highschool esque. the germans were peeved and said they could dig as deep of a hole as the russians. They went 9km deep and then the drill was too hot... when they were done they started testing for stresses within the earth.

      They found that for every kilmeter in the earths crust isotropic lithostatic pressure increases by 27MPa 1Kbar ever 3.3 Km...

      instead isotropic differential stress is smaller increasing to a few hundred MPa until dropping at Frictional Plastic Transition

    2. volume changei s due to isotropic mean stress, the same stress is coming from all angles

      Non isotropic (deviatoric stresses) are what change the shape under pressure

    3. Hydrostatic/ Lithostatic pressure- same pressure in all directions. in water it's compression the same and in space it's expanding the same. sigma 1=sigma 2=sigma 3 and no shear stresses if it is all equal.

    4. Normal and Shear stress Relationships place a block of clay or wax between wood and stress until fracture. to calculate the value it is the use of principal forces in relation to normal force.

      See Page 12 of LEct 2 for composition of sigma values.

      If you have the inputs it's plug and chug.

      [sigma 1 -sigma 3 ]= differential stress ( diameter of circle) Shear stress is 1/2 differential stress (Radius of circle)

    5. For each plane in a 3D object there is one normal stress and two shear stresses per plane and in 3D there are 3 planes so there will be 9 different stresses over the object and 6 will be distinct (3 will be s the same it they weren't the same the block would be spinning).

      Now we're talking about an infinite number of planes... yayy... infinite number of planes always connect in a point. Shrink cube to a point: a) two dimension : Stress ellipse b) three dimensions: stress ellipsoid. Ellipsoid axes are called principal stresses the longest (Sigma 1), the shortest( Sigma 3), the perpendicular to the longest (Sigma 2). with this you can solve all stress planes.

    6. Normal Stress = Normal force / area Normal Force decreases from finite value to zero while area increases to infinite. Shear stress+ Shear Force/area Shear force increases from 0 to finite value while area increases faster to infinity.

    7. We will use Trig. we could use tensile algebra but we just want to use it not know how the math works.

    8. Stress or Pressure = force/area = (m.a)/Area<br> 1 bar= 1.15^5 Pa .1 Mpa (Atmospheric conditions) 1kbar (Geologic conditions) = 100 Mpa MEMORIZE THE UNITS OF STRESS AND THEIR CONVERSIONS IT WILL BE ON TEST.

    9. What is Stress? are force and stress the same? Not for us it's rather tricky to say they're the "same" like it can be said elsewhere. Stress = Force/ Area if either changes the overall stress changes ( area will change more often than force) like saran wrap it seems to stretch forever until you stab it with a sharp object this is because the area of force applied changes ( big to small). Normal stress is perpendicular to the plane in 2D planes and shear stress is acting along the 2D plane, parallel. These are sometimes called "tractions" this is matrix algebra stuff. The pole is the normal stress and one along the earth that cause earthquakes are the shear stress. The area of the plane is important.

    10. The interaction of forces on objects is Newtonian but in our case when the force is applied the objects are changing shape within themselves. Newtonian only discusses the in between. While we will talk in terms of forces it is really continuum but we talk like it's Newtonian.