Structure of the Earth and the Rock Cycle. Lithosphere composed of minerals Definition of “Mineral” ? Definition of “Mineral” ?

Structure of the Structure of the Earth and Earth and

the Rock Cyclethe Rock Cycle

LithosphereLithosphere composed of composed of mineralsminerals

Definition of “Definition of “Mineral” ?Mineral” ?

SilicateSilicate minerals minerals

92% of crust92% of crust

silicon and oxygensilicon and oxygen

A A rockrock is a natural solid substance is a natural solid substance made up of mineralsmade up of minerals

rocks classified by rocks classified by origin : 3 typesorigin : 3 types

Types of RocksTypes of Rocks

1. IGNEOUS1. IGNEOUS molten rock that has cooled and solidifiedmolten rock that has cooled and solidified

molten rock is molten rock is magmamagma or or lavalava

a) INTRUSIVEa) INTRUSIVE cools below surface; big crystals; coarsecools below surface; big crystals; coarse

b) EXTRUSIVEb) EXTRUSIVE cools at surface; finecools at surface; fine

Fine-textured extrusive Coarse-textured intrusive

Glassy; rapid cooling

Basalt with vesiclesBasalt with vesicles

extrusive

intrusive

Mafic and felsic igneous Mafic and felsic igneous rockrock

FelsicFelsic: mostly felsic minerals : mostly felsic minerals High in feldspar and silicate mineralsHigh in feldspar and silicate minerals LighterLighter Less denseLess dense

MaficMafic: mostly mafic minerals : mostly mafic minerals High in magnesium and iron High in magnesium and iron DarkerDarker DenserDenser

UltramaficUltramafic: all mafic minerals: all mafic minerals

2. SEDIMENTARY2. SEDIMENTARY

made up of sediments that have been made up of sediments that have been compacted and cemented.compacted and cemented.

sedimentssediments: all solid particles transported : all solid particles transported by water, ice, wind, gravityby water, ice, wind, gravity

mud, sand, shells, debris, dust, rock fragmentsmud, sand, shells, debris, dust, rock fragments

mudstone, sandstone, limestone, mudstone, sandstone, limestone, conglomerate, shaleconglomerate, shale

accumulate in accumulate in stratastrata (layers) (layers)

mudstonemudstone

sandstonesandstone

limestonelimestone

conglomerateconglomerate

stratastrata

3. METAMORPHIC3. METAMORPHIC

altered from original rock by heat, altered from original rock by heat, pressure or chemical activitypressure or chemical activity

began as igneous, sedimentary, or began as igneous, sedimentary, or metamorphic rockmetamorphic rock

shale --> slateshale --> slate slate --> schistslate --> schist granite --> gneissgranite --> gneiss limestone --> marblelimestone --> marble

gneiss schistgneiss schist

slateslate

Rock CycleRock Cycle

Structure of EarthStructure of Earth

CoreCore

MantleMantle

CrustCrust

CoreCore InnerInner

5150 – 6370 km (below surface)5150 – 6370 km (below surface) Solid ironSolid iron 5400 – 9000 degrees F5400 – 9000 degrees F

OuterOuter 2900 – 5150 km2900 – 5150 km Molten ironMolten iron

CoreCore

MantleMantle

CrustCrust

Lower mantleLower mantle

UpperUpper

UppermostUppermost

Lower mantleLower mantle very dense; iron very dense; iron

and magnesiumand magnesium 670 – 2900 km670 – 2900 km

Upper mantleUpper mantle rigid at lower endrigid at lower end ““plastic” toward plastic” toward

crust: crust: asthenosphereasthenosphere

250 -670 km250 -670 km

Uppermost mantleUppermost mantle RigidRigid ““Moho” to 70 kmMoho” to 70 km

““Moho”Moho” Mohorovičić discontinuityMohorovičić discontinuity Boundary between crust and mantleBoundary between crust and mantle Change in seismic waves hereChange in seismic waves here

CoreCore

MantleMantle

CrustCrust

CrustCrust continentalcontinental : 25 miles thick : 25 miles thick

Lower mafic; upper felsic (granite)Lower mafic; upper felsic (granite) Less denseLess dense

oceanicoceanic: 5-6 miles thick: 5-6 miles thick Mafic (basalt)Mafic (basalt) More denseMore dense

LithosphereLithosphere = uppermost mantle and = uppermost mantle and crustcrust RigidRigid ultramaficultramafic

Lithosphere is divided into large Lithosphere is divided into large platesplates

rigidrigid plates “float” on the plates “float” on the plastic plastic asthenosphere, just deep enough to asthenosphere, just deep enough to support their own weight:support their own weight:

IsostasyIsostasy

Isostatic adjustmentIsostatic adjustment of crust: of crust:

add weight (sediment, glacial ice): crust add weight (sediment, glacial ice): crust will sinkwill sink

remove weight (erosion, glacial ice remove weight (erosion, glacial ice melts): crust will reboundmelts): crust will rebound

ice

Crust sank

Crust

rebound

Duluth

Northeast

“drowned “ St. Louis River