I need to focus. I need to stop looking at the hepcat, stop contemplating Daggett, stop filling in the Os in my lecture notes, and stop reading the ingredients on my snacks.
I need to stop watching this Spongebob ep called "Procrastination".
I should also stop reading and responding on LJ.
I did every single thing that Spongebob did to procrastinate, except call my best friend, because he's not home yet.
Doodydoodydoodydoody. Binky boo, minky boodle. Drip drop. Goochie. Butter?
Structural geology is not tectonics, and it's not rock mechanics. Those things are different. It's all about deformation and structures. Tectonic structures are caused by the movement of the lithospheric plates. Nontectonic structures are not caused by lithospheric plate movement. Nontectonic sedimentary structures include bedding, graded bedding, load casts, mud cracks, sole marks, flute casts, rain imprints, tracks, etc. Nontectonic igneous structures include cracks and vesicles, amygdules, pillow structures, and contact metamorphism. These things can help tell the younging direction of the outcrop. Unconformities are breaks in the stratigraphic sequence of the rocks. A disconformity is an erosional surface betwween sedimentary rocks in the same plane. A nonconformity is an erosional surface between igneous rocks and sedimentary rocks. An angular unconformity is when the sedimentary rocks below lie at an angle to the overlying bedding.
Stress is what causes rocks to go all bendy or break. If the stress is primarily in the vertical direction, then you'll get a normal fault (when the rocks go to break.) If the major stress is in a horizontal direction, and the minor stress is in a vertical direction, you'll get an oblique strike slip fault. If the major stress is in a horizontal direction, and the minor stress is in the perpendicular horizontal direction, you get a strike slip fault. According to some guy named Anderson, anyway. A Mohr circle for stress uses the mean stress as the center of the circle, and the major and minor stresses as the x-intercepts (in a cartesian plane). The radius of the circle is max-min/2. The angle between the fault plane and the major stress is 2theta. Theta is the angle of inclination of the fault plane. Alpha is the angle of the stress normal to the plane, from vertical. The angle between minor stress and the plane is 2alpha. Phi is the angle of the envelope from horizontal. Things plotting in the negative x area are experiencing tensional stress, whereas things plotting to the positive x area are experiencing compressional stress. Shear stress is the y component of the intersection of the plane with the circle.
Strain has to do with deformation related to stress. The kinds of deformations include dilational, translational, distortional, and rotational. Strain indicators include.. lots of things. Deformed fossils and oolites. Bookshelf sliding, fringe shadows, trail of inclusions, and rotated phenocrysts. Homogenous strain is when things that were parallel before remain parallel, inhomogenous strain is when they don't. The strain ellipsoid is.. a ... well, there's 3 kinds. Triaxial, when none of the x,y,z values are equal; prolate, when the greatest stress is horizontal and the other two dimensions are equal; and oblate, where the greatest stress is vertical and the other two dimensions are equal. Strain ellipses show the direction of major and minor strains. Or something. Not too clear on those things. The ellipsoids show up on a flinn diagram as such: on a line y=x, the ellipsoid will be triaxial. As one moves closer to the y axis, the ellipsoid will become more prolate (cigar). As one moves toward the x axis, the ellipsoid will be more oblate (pancake). I don't really understand it.
Fractures and faults. Faults come in a few types. Oblique strike slip faults have both a strike slip component and a dip slip component. Add these vectors and you get a net component. The angle between strike slip component and net slip is the rake. Separation is apparent displacement. Dip separation includes Heave (the horizontal distance) and Throw (the vertical distance). This is the opposite of what I would call it were I naming these components. Then of course there's normal faults, thrust faults, reverse faults (the only difference in reverse and thrust is the angle of the fault plane), and strike-slip faults. There's also grabens and horsts, both formed by normal faulting. Grabens are drop-downs, and horsts are upthrows. Strike slip faults there are two types: sinestral and dextral. There are three types of transform faults - ridge-ridge, ridge-arc, and arc-arc. Yes, we know what these are. Mmm-hmm. Joints and fractures associated with folding include a joints (parallel to the axial planar surface), b joints (perpendicular to the axial planar surface) and c joints, which are parallel to the bedding plane. In faulting, there are usually conjugate sets. One set will be dominant based on external factors, like composition, bedding planes, etc.
OK, defects of crystal lattice. Right. Planar defects (missing a layer or an extra layer); dislocation gliding, which is when some of the crystals move to one side or the other; twin gliding - forms twinned crystals based on flipping. Line defects: edge dislocation, when the edges don't match up where they should; screw dislocation, when it's like someone twisted the lattice around a screw. Or, when someone screwed the lattice HAHA. Controlling factors in deformation are: composition, temperature, pore pressure, texture, confining pressure, rate of strain, rate of stress increase, and anisotropy. The elastic-plastic stress-strain curve, including elastic limit and rupture point.
Is that all? I think there's more. I hope we don't have to know the atomic deformations, because I don't.
I can't believe you read the whole thing! That's my BORING class! I'm all :