ERS120H5 Study Guide - Final Guide: Active Fault, Malaysian Ringgit, Cyanobacteria
Document Summary
Formation!of!solar!system:: a!nebula!forms!from!hydrogen,!helium!and!helium!left!over!from!big!bang, nebula!condenses!into!a!swirling!disc,!with!a!central!ball!surrounded!by!rings, ball!at!centre!grows!dense!and!hot!enough!for!fusion! !becomes!the!sun, in!the!rings,!dust!particles!collide!and!stick!together,!forming!planetesimals, planetesimals!grow!into!the!protogearth;!interior!heats!up!and!becomes!soft, gravity!reshapes!protogearth!into!a!sphere;!interior!differentiates!into!a!core!and! mantle, soon!after!earth!forms,!a!small!planet!collides!with!it! !blasts!debris!forming!a!ring! around!earth, the!moon!forms!from!the!ring!of!debris, atmosphere!develops!from!volcanic!gases;!when!the!earth!becomes!cool!enough,! moisture!condenses!and!rains!to!create!the!oceans. Shaping!of!earth! !sphere: when!a!protoplanet!gets!big!enough,!gravity!can!change!its!shape, rock!composing!a!small!planetesimal!is!initially!cool!and!strong, once!the!planetesimal!reaches!a!critical!size! (1000!km),!interior!becomes!warm!and!soft! enough!to!flow!in!response!to!gravity, protrusions!pulled!inward!toward!the!centre, spherical!shape!is!formed, gravity!is!nearly!the!same!at!all!points!on!its!surface, shape!is!supported!because!mass!is!evenly!distributed!around!the!centre!in!a!sphere! Mantle: mafic!and!felsic, oxygen!=!most!abundant!element, entirely!of!peridotite, mantle!rock!can!be!soft!enough!to!flow! (100g150! km)! S%waves:!causes!particles!of!material!to!move!back!and!forth!perpendicular!to!the!direction!in! which!the!wave!itself!moves: s!waves!don"t!travel!through!liquid, ability!to!travel!through!a!certain!material!and!the!velocity!at!which!it!travels! depend!on!the!character!of!the!material, particles!in!liquids!aren"t!close!enough!to!support!the!movement!of!particles! moving!perpendicular!to!the!direction!the!wave!is!moving! Relatively!ductile! (easily!deformed): lithosphere!is!thin,!cool!and!hard, asthenosphere!is!hot!and!weak, lithosphere!can!be!broken!into!large!fragments!called!plates, plates! float !on!the!asthenosphere, plates!move!around!and!interact!with!each!other! Evidence!for!continental!drift:: fit%of%the%continents:!part!of!eastern!south!america!can!fit!into!southgwestern!africa, matching%rock%units:!found!common!group!of!rocks!on!eastern!part!of!south!america! and!south!western!africa, matching%mountain%belts:!if!the!atlantic!didn"t!exist,!paleozoic!mountain!belts!on!both! coasts!would!be!adjacent, fossils:!occur!on!multiple!continents;!hard!to!explain!if!continents!were!always! separated!by!oceans, matching%paleoclimate%belts:!distribution!of!late!paleozoic!coal,!sandgdune!deposits!and! salt!deposits!could!define!climate!belts!on!pangaea, glaciations:!studying!age!of!glacial!till!deposits! !determined!that!a!variety!of! continents!had!glaciers!at!the!same!time! Topography: midgocean!ridges! !bathymetry!on!one!side!of!the!axis!is!nearly!a!mirror!image!of! bathymetry!on!the!other!side, deepgocean!trenches! !border!volcanic!arcs,!curving!chains!of!active!volcanoes, fracture!zones! !ocean!floor!is!diced!up!by!narrow!bands!of!vertical!cracks!and!brokeng up!rock, layer!of!sediment!becomes!progressively!thicker!away!from!the!midgocean!ridge!axis! Formation!of!magnetic!stripes!on!sea!floor: magnetic!reversals:!there!is!an!alternating!normal!and!reversed!polarity!in!rock!layers, reversed:!south!magnetic!pole!lies!near!the!north!geographic!pole!and!vice!versa, may!be!result!of!changes!in!circulation!patterns!in!the!outer!core, positive!anomalies!form!when!seagfloor!rock!has!the!same!polarity!as!the!present! magnetic!field, negative!anomalies!form!when!seagfloor!rock!has!polarity!that!is!opposite!to!the! present!field! Evolution!of!sea!floor: ridge:!rocks!=!young,!sediment!=!thin, away!from!ridge:!rocks!=!older,!sediment!=!thicker, youngest!rocks! (at!the!crest)!have!presentgday,!normal!magnetism, stripes!of!rocks!parallel!to!the!crest!alternate!in!magnetism! (normalgreversedgnormal,! etc! Evolution!of!a!divergent!boundary: rifting!causes!the!continent!to!crack!and!break!apart;!new!midgocean!ridge!forms!and! seagfloor!spreading!begins, as!continents!pull!apart,!magma!rises!from!the!mantle!into!a!magma!chamber, some!magma!along!the!sides!of!the!magma!chamber!cools!to!form!gabbro, gabbro!moves!away!from!the!magma!chamber, new!magma!rises!to!keep!volume!of!magma!constant, some!magma!rises!to!fill! !vertical!cracks!above!the!magma!chamber,!solidifying!to!form! dikes: dikes! (verticle)!break!in!half!as!seagfloor!spreading!continues!and!move!to!the! side, new!magma!rises!to!fill!the!crack!and!create!new!dikes, some!magma!makes!it!to!the!surface!and!extrudes!as!basalt!pillows! !forms!the!top!of! the!seagfloor!crust! Continental!transform!fault:!north!americagpacific!in!the!us: actively!slipping!segment!of!a!fracture!zone!between!two!ridge!segments, one!plate!slides!sideways!past!another, no!new!plate!forms!and!no!plate!is!consumed, earthquakes!occur!on!segment!of!a!fracture!zone!that!lies!between!the!two!ridge! segments, very!young!oceanic!crust, high!elevation;!wide!and!decreases!moving!away!from!the!ridge! Hot!spots:!hawaiian!islands: volcanoes!that!exist!as!isolated!points!and!are!not!a!consequence!of!movement!at!a! plate!boundary, heat!source!for!hot!spots!=!mantle!plume! !very!hot!rock!rising!up!through!the! mantle!to!the!base!of!the!lithosphere, hotgspot!track!forms!when!overlying!plate!moves!over!a!fixed!plume, movement!of!plates!slowly!carries!the!volcano!off!the!top!of!the!plume! ! becomes!extinct! Driving!mechanisms of plate tectonics: mantle convection: when mantle rocks near the radioactive core are heated, they become less dense than the cooler, upper mantle rocks.
