Exam 3 - Geol 101 - pt 1

• Principles of relative dating; Be able to explain each and use these to determine relative ages

  • stratigraphy: principles used to determine relative ages

    • original horizontality: rocks are deposited horizontally

    • superposition: undisturbed rocks; oldest are on bottom, youngest on top; prior to any folding

    • cross-cutting relationships: features that cut across rocks are younger than the rocks

    • inclusions: rock fragments contained within another rock are older than the rock they are in

• Absolute dating and isotopes; Be sure you can calculate the age of a rock if given the percentage of parent and daughter elements.

  • the more radioactive the element, the more unstable

  • isotope: form of an element that has the same number of protons but different number of neutrons

  • atomic number: number of protons in the nucleus

    • Understand the concept of a half life

      • amount of time needed for ½ of the atoms of the parent to decay to the daughter

        • 1 half life: 50% parent, 50% daughter

• types of unconformities

  • define unconformity: surface representing a period of time where deposition stopped and erosion occurred

    • disconformity: surface between two parallel sedimentary layers

    • angular conformity: surface between two non parallel sedimentary layers

    • nonconformity: surface between horizontal rocks of any kind

• Fossils and the conditions that favor fossilization. Also know what makes a good index fossil.

  • define fossils: evidence of past life,

    • body fossils: bones, teeth, shells, leaves, petrified wood

    • trace fossils: tracks, coprolites, burrows

  • conditions for fossilization

    • hard parts, low- energy environment, buried quickly, sedimentary rocks are needed

  • good fossil index

    • organisms succeed one another in a definite and determinable orders

• Geologic time scale: know this!  You will be given a partially completed time scale and asked to fill in the correct time periods for the missing sections.

  • phanerozoic: cenozoic (quaternary, neogen, paleogene), mesozoic (cretaceous, jurassic, triassic), Paleozoic (peppermind patty makes donuts, sometimes on christmas)(permian, pennsylvanian, Mississippian, devonian, silurian, ordovician, cambrian), Precambrian 

Chapter 11 – Rock Deformation

• Strike and dip define the orientation of planar rock bodies.  Be able to draw strike and dip map symbols.

  • review labs

• Brittle vs ductile deformation

  • brittle deformation: fracture with movement on either side; faults

  • Ductile deformation: consists of two limbs and an axis; folds

• Types of stress:

  • extension: stretching and thinning. associated with a divergent boundary

  • compression: squeezing, shortening and thickening. associated with a convergent boundary

  • shear: sliding, shifting, lateral shifting. associated iwth a transform boundary

• Faults:

  • Dip-slip: can only be found in cross-section view

  • strike-slip faults: can only be viewed in map(top) view

• Dip slip faults

  • normal: hanging wall is down, foot wall is up

  • reverse: are squished, causing the hanging wall to be up

• Strike-slip faults; Be able to identify each

  • strike slip faults are horizontal movement. associated with transform plate boundaries

    • left-lateral: have to look left to find other side

    • right-lateral: have to look right to find other side

• Folds; Be able to sketch each in cross section view.  Also be able to use block diagrams (like in lab 10) to show anticlines and synclines in map and cross section view.  Use age relationships between rock units to determine if a fold is an anticline or syncline.

  • Anticlines: oldest rocks are in center. Rocks will dip away from the center of the fold in map view

  • Synclines: youngest are in center. rocks will drip toward the center in map view

  • Monoclines: one ilmb, formed by compression