ERS120H5 Study Guide - Final Guide: Solar Irradiance, Porosity, Clastic Rock
Document Summary
Principles:: crosslcutting!relationships:!any!feature!which!cuts!across!other!rocks!or!features!must!be! younger!and!the!feature!that!has!been!cut!is!older, ex:!if!an!igneous!dike!cuts!across!a!sequence!of!sedimentary!bed,!the!beds!must!be! older!than!the!dike, ex2:!if!a!fault!cuts!across!and!displaces!layers!of!sedimentary!rock,!then!the!fault!must! be!younger!than!the!layers! !any!piece!of! rock! (inclusion/xenolith)!included!within!another!rock!must!be!older!than!the!rock!in!which!it!is! incorporated: ex:!if!a!layer!of!sediment!deposited!on!an!igneous!layer!includes!pebbles!of!the!igneous! rock,!then!the!sedimentary!layer!must!be!younger, ex2:!if!an!igneous!intrusion!contains!fragments!of!another!rock,!the!fragments!must!be! older!than!the!intrusion, superposition:!the!oldest!layer!is!at!the!bottom!and!the!youngest!layer!is!at!the!top, a!layer!of!sediment!can"t!accumulate!unless!there!is!already!a!substrate!on!which!it!can! collect, unconformities:!any!unconformity!is!a!rock!interface!which!represents!a!gap!in!the!geologic! record,!like!pages!missing!from!a!book. , original!horizontality:!sedimentary!layers! (and!lava!flows)!are!usually!originally!laid!down! horizontally. Fossil&succession:: a!particular!assemblage!of!fossil!species!can!be!found!only!in!a!limited!interval!of!strata,!and!not! above!or!below!a!certain!interval, once!a!fossil!species!disappears!at!a!horizon!in!a!sequence!of!strata,!it!never!reappears!higher!in! the!sequence! !extinction!is!forever, we!can!define!the!range!of!specific!fossils!in!the!sequence,!meaning!the!interval!in!the!sequence! in!which!the!fossils!occur, sequence!contains!a!definable!succession!of!fossils, the!range!in!which!a!particular!species!occurs!may!overlap!with!the!range!of!other! species, once!a!species!vanishes,!it!doesn"t!reappear!higher!in!the!sequence! Isotopes!=!different!versions!of!an!element!with!the!same!atomic!number!but!different!atomic! weight!have!same!protons!but!different!neutrons. : radioactive!isotopes!=!unstable,!they!undergo!radioactive!decay!converting!them!into!a! different!element, parent!isotope!=!isotope!that!undergoes!decay, daughter!isotope!=!the!decay!product, halfllife!=!the!time!it!takes!for!half!a!group!of!parent!isotopes!to!decay, for!a!given!decay!reaction,!the!halfllife!is!a!constant! Figure!16. 5: elevation!of!groundwater(gravity)!+!pressure!within!the!water!can!provide!energy!to!cause!the! water!to!flow, potential!energy!driving!this!flow!=!hydraulic&head, groundwater!flows!from!locations!where!water!table!is!higher!to!locations!where!the! water!table!is!lower, groundwater!flows!along!concavelup!curved!paths! !regions!where!water!table!is!high! (below!a! hill)!to!regions!where!water!table!is!low! (below!a!valley)! If!the!level!lies!above!the!ground!surface,!the!well!is!a!flowing!artesian!well!and!water! actively!fountains!out!of!the!ground: occur!in!special!situations!where!a!confined!aquifer!lies!beneath!a!sloping!aquitard, water!enters!a!tilted,!confined!aquifer!that!intersects!the!ground!in!the!hills!of!a!highlelevation! recharge!area, pressure!in!the!confined!aquifer!can!push!water!up!the!well! !potentiometric!surface! lies!above!the!ground! Groundwater&flowing&to&form&springs: ground!surface!intersects!the!water!table!in!a!discharge!area! !typically!occur!in!valley!floors! where!they!may!add!water!to!lakes!or!streams, flowing!groundwater!collides!with!a!steep,!impermeable!barrier,!and!pressure!pushes!it!up!to! the!ground!along!the!barrier, perched!water!table!intersects!the!surface!of!a!hill, downwardlpercolating!water!runs!into!a!relatively!impermeable!layer!and!migrates!along!the! top!surface!of!the!layer!to!a!hillslope, network!of!interconnected!fractures!channels!groundwater!to!the!surface!of!a!hill, artesian!springs!can!form!if!ground!surface!intersects!a!natural!fracture! (joint)!that!taps!a! confined!aquifer!in!which!the!pressure!is!sufficient!to!drive!the!water!to!the!surface! !forming!clouds!to!drop!rain/snow!on! oceans/lands: water!on!land!can!be!held!by!glacial!ice!or!in!surface!water! (surfacelwater!reservoir), some!flow!back!to!the!ocean,!evaporates!into!the!air,!sink!into!the!ground, water!sinking!into!the!ground!to!remain!temporarily!on!surface!of!soil!grains, some!water!sinks!deeper!to!be!trapped!as!groundwater, groundwater!fills!holes/crack!between!grains!of!rock!or!sediment! (subsurface!=!water!reservoir), some!bubbled!back!to!ground!surface!!!lakes,!rivers,!streams! (springs), some!flow!all!the!way!back!to!the!coast!and!reaches!the!sea! Materials&transported: bed!load, consists!of!larger!particles! !sand,!pebbles,!cobbles, bounces!or!rolls!along!the!stream!floor, movement!involves!saltation,!a!process!during!which!grains!on!the!channel!floor!get! knocked!into!the!water!column!momentarily,!follow!a!curved!trajectory!downstream,! and!gradually!sink!into!the!bed!again,!where!they!strike!other!grains!and!knock!them! into!the!water!column, suspended!load, consists!of!tiny!solid!grains! !silt!or!clay!size! Streams!carry!abundant!course!sediment!during!floods!but!can"t!carry! this!sediment!during!normal!flow: during!normal!flow,!sediment!settles!out!and!the!channel!becomes! choked!with!sediment, as!a!result,!the!stream!divides!into!numerous!strands!weaving!back! and!forth!between!elongate!mounds!or!bars!of!gravel!and!sand, a!river!channel!that!winds!back!and!forth! Forms!where!running!water!travels!over!a!broad!floodplain!underlain! with!a!soft!substrate,!in!a!region!where!the!river!has!a!very!gentle! gradient: development!of!meanders!increases!the!volume!of!the!stream!by! increasing!its!length, natural!variations!in!water!depth!cause!fastlmoving!current! to!swing!back!and!forth, water!erodes!side!of!stream!more!effectively!where!it!flows! faster!=!begins!to!cut!away!faster!on!outer!arc!of!the!curve, each!curve!begins!to!migrate!sideways!and!grow!more! pronounced!until!it!becomes!a!meander! Formation&of&oxbow&lake:: meanders!evolve!because!erosion!occurs!faster!on!the!outer!bank!of!a!curve,!and!deposition! takes!place!on!the!inner!curve, on!the!inside!edge,!water!slows!down!so!that!its!competence!decreases!and!sediment! accumulates!in!a!wedgelshaped!deposit!=!point&bar, continued!erosion!=!meander!may!curve!more!than!180!degrees, cut!bank!at!meander"s!entrance!approaches!cut!bank!at!its!end,!leaving!a!meander!neck, erosion!eats!at!a!meander!neck,!a!cutloff!develops, meander!that!has!been!cut!off!=!oxbow&lake!if!it!remains!filled!with!water, abandoned&meander!if!it!dries!out! Shape!depends!on!many!factors: bird"s!foot!shape!=!strength!of!the!river!current!exceeds!that!of!ocean!currents,! sediment!can!be!carried!far!offshore, triangle!shape!=!ocean!currents!are!strong!and!redistribute!sediment!in!bars!running! parallel!to!the!shore, no!delta!=!waves!and!currents!are!strong!enough!to!remove!sediment!as!fast!as!it! arrives! Lobe&switching:: existence!of!several!toes!=!main!course!of!the!river!in!the!delta!has!shifted!on!several!occasions, shifts!occur!when!a!delta!builds!so!far!into!the!sea!that!the!slope!of!the!stream!becomes! too!gentle!to!allow!the!river!to!flow, river!overflows!a!natural!levee!uplstream!and!begins!to!flow!in!a!new!direction! ! avulsion, ex:!lobes!of!the!mississippi!delta, can!be!induced!by!floods! !spilling!out!on!to!a!different!direction!where!lobes!of!sediment!can! be!deposited, also!induced!when!the!river"s!own!flow!is!so!slow! !finds!another!path!to!form!another! sediment!deposit, lobes!=!areas!of!sediment!deposit! Snow& &ice: three!conditions!must!be!met!for!a!glacier!to!form, local!climate!must!be!cold! (winter!snow!doesn"t!entirely!melt!during!the!summer), must!be!sufficient!snowfall!for!a!large!amount!to!accumulate, slope!of!the!surface!on!which!the!snow!accumulates!must!be!gentle!enough!that!the! snow!doesn"t!slide!away!in!avalanches/snow!doesn"t!blow!away, young!snow!progressively!buries!older!snow, hexagonal!crystals!of!snow!don"t!
