Term | Definition |
principle of uniformitarianism | processes happening now happened before; large changes require a long time |
principle of original horizontality | sediment deposited horizontally; tilted rocks deformed by tectonics |
principle of superposition | younger formations on top |
principle of lateral continuity | form in lateral sheets; erosion dissects once continuous layers |
principle of cross-cutting relations | younger features cut older features |
principle of inclusions | inclusions always older than enclosing material; must be present to be included |
principle of fossil succession | index fossils determine time range |
disconformity | erosion, lack of deposition |
angular unconformity | relationship is angular |
non-conformity | sedimentary deposited on top of eroded igneous or metamorphic rocks |
relative dating | based on order of formation; younger or older |
absolute dating | actual number of years |
Hadean Eon | first; formation of Earth, molten core goes to center, oceans formed, meteorites |
Archean Eon | second; continents, lithosphere formed, meteorites stop, rock record survives, mats of cyanobacteria |
Proterozoic Eon | third; multi-cellular vertebrates appear |
Phanerozoic Eon | fourth; Permian extinction @ beginning; hard-shelled organisms (better records), Pangaea rifts apart |
Mesozoic Era/Jurassic and Triassic Period | Subduction sutures terrenes onto continent, collision build up Rockies, feathered birds, ancestors of mammals |
Mesozoic Era/Cretaceous Period | seas flood continents, modern fish, flowers |
K-T boundary event | Cretaceous-Tertiary, meteorite impacts, blots out sun -stops photosynthesis; evidence: plankton-free clay, iridium rich clay, micro tektites, buried crater visible |
geologic column order | eon - era - period - epoch |
classification of mass-movements | type of material, rate of movement, nature of mass, immediate surrondings |
slides | rotational/slump: concave; translational: whole block slides down |
falls | one chunk drops |
flows | debri flows: muddy, granular, lahar-style; creep: air freezes, grains pulled out, air warms, grains pulled down |
factors of slope stability (8) | water (adds weight, lubricates); steepen slope; remove base/top; add material to top (pipes, adds water); remove vegetation; tilted bedding planes; composition of slope; preexisting weaknesses |
base level | level below which stream cannot erode |
discharge | cfs |
bedload | sediment being transported |
gradient | slope |
sinuosity | curviness |
too much discharge | increase sinuosity, decrease gradient - lower discharge
meandering stream |
too much sediment | decrease sinuosity, braided stream |