EAR 110 3rd Edition Lecture 16Outline of Previous Lecture:I. ReviewII. Rock CleavageIII. Rock FabricsIV. Metamorphism of Sedimentary RocksV. Metamorphism of Igneous RocksVI. Causes of MetamorphismVII. Types of MetamorphismVIII. Processes During MetamorphismOutline of Current Lecture:I. Geologic Principles to determine relative age of rocksII. Typical landscape formation processIII. Determining age of landscapesIV. UnconformitiesChapter 9: Geologic TimeI. Geologic Principles used to determine relative age of rocksa. Uniformitariamism – the present is the key to the pastb. Principle of original horizontality – sedimentary layers or lava flows were originally deposited horizontallyc. Law of lateral continuity – deposits extend laterally until they pinch out and run out of materiald. Law of superposition – if deposits are undisturbed, the oldest is on the bottom and the youngest is on the tope. Law of inclusions – any piece of rock that becomes incorporated into a newly forming rock is older than the new rockf. Law of cross cutting relations –any feature that cross cuts a sedimentary body of rock is younger i. Can include rivers – the river is younger than the rocks it is flowing acrossg. These ideas were first discussed by Nicolas Steno in mid 1600’sII. Typical landscape formation processa. Pre-existing rock covered by seab. Sea deposits layer of sedimentc. Environment changes, depositing more rockd. Deposition stopse. Area eroded by rivers etc. after upliftf. Continued erosionIII. Determining age of landscapesa. Landscape surface (soil) younger than rocks on which it formsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b. Lava flows younger than soil/rock on which is flows overc. Most river terraces formed before erosion down to present leveld. Surface with well develop soil is older than one that is less developedIV. Unconformitiesa. Represent missing timeb. 3 typesi. Angular unconformity: sediment deposited on top of eroded surface (tilted layers)ii. Nonconformity – nonlayered rock uplifted and eroded; erosion surface buried bysedimentiii. Disconformity – deposition of horizontal layers; weathering erodes surface, eroded surface covered by later