Planet Earth (lecture)

Earth’s layers

1. crust

2. mantle

3. outer core (liquid)

4. inner corse (solid)

Lithosphere

rigid, cool earth outer layer that forms tectonic plates

asthenosphere

warmer, weaker, ductile (soft) mantle rock that flows slowly over geologic time

mantel convection

circular heat pateern that causes tectonic plates to move

tectonic plates

underneath continents/ocean basins, lots of geological activity, builds mountains, form ocean basins, drive continents across the globe

divergent (plate boundary)

plates move apart

convergent (plate boundary)

plates collide

transform (plate boundary)

plates slide past each other

minerals

naturally occurring, solid, crystalline (atoms in perfect order), specific composition

electrons

occupy orbitals around nucleus

outer (valence) electrons

decide how atoms bond, full outer parking lot = stable, happy atom

covalent bond

atoms share a pair of electrons

ionic bond

electrons are transferred

metallic bond

electrons frow freely (sea of electrons)

Crystalline

atoms in an orderly pattern

glass (amorphous)

no structure, randomized atoms

halite’s structure

sodium and chloride alternate in a cubic lattice, look like crystalline structure

crystal shape

ion size/charge control shape and appearance, tight packing = different structures

polymorph

same chem, different structure (diamond/graphite)

• conditions pick the structure (pressure/temperature)

mineral formation

• form from cooling (melts, precipitation, or metamorphosis

• as magma cools, atoms bond and crystals grow outwards

precipitation

dissolved water leaves behind ions that form minerals (rock salt)

metamorphism

heat/pressure reshuffle atomic structure, new minerals grow

color

light not absorbed, impurities shift it wildly

streak

rub on tile, powder color tells more truth

luster

shine, how light bounces off

moh’s hardness scale

levels 1-10, 1 being the softest

crystal habit

like a plants shape reflecting how it grew

cleavage

splits in mineral, 90 degree planes along minerals natural growth

fractures

irregular breaks, no planes

acid test

reveals calcite

magnet test

reveals magnetite

salty taste

halite

silicates

most common mineral in crust/mantel

1. feldspar

2. mica

3. quartz

4. amphibole

silicate tetrahedron

4 o’s surround silicone molecule

shield volcano

wide, low angle, cone shaped, less violent erruptions

strato

classic volcano, symmetrical (mt. fuji)

caldera volcano

• giant volcanic depressions with massive craters

• form when a magma chamber empties and roof collapses (yellowstone)

pyroclastic flows

deadly super heated cloud of volcanic ash and gas

lahars

volcanic hazard, fast moving mixtures of water, volcanic ash, and rock

igneous rocks

rocks that solidify from melts (magma/lava)

intrusive rocks

cools slowly deeply in earth

extrusive

cools rapidly at the surface

phaneritic

large, coarse crystals

aphanitic

finer crystals

porphyritic

combo of fine + large crystals

glassy texture

extreme rapid cooling of lava (obsidian)

Silica amounts

• melt chemistry depends on amount of silica/oxides

1. felsic (light)

2. intermediate

3. mafic

4. ultramafic

Higher silica

higher viscosity

hotter temperature

lower viscosity

Magma density & buoyancy

upward driving force that causes molten rock (magma) to rise through the Earth’s crust because it’s less dense than the solid surrounding rocks

sedimentary rocks

made of pieces or chemical/biological parts of other rocks

weathering (sedimentary cycle)

rocks are broken down at or near Earth’s surface by physical or chemical processes

erosion (sedimentary cycle)

weathered material removed from original location by natural forces such as wind, water, ice, or gravity

transport (sedimentary cycle)

sediment is carried from one place to another by natural forces

deposition

sediment settles out of transport and is deposited in layers

lithification

compaction/cementation turn the sediment into sedimentary rock

physical weathering

• mechanical, freezing water causes frost wedging, results in cracks

• growing roots force roots apart (root wedging)

chemical weathering

dissolving fluid removes certain minerals, transforms the composition of the sediment

transport - angular rock

large (coarse grained) and sharper (angular) = less distance

transport - rounded rock

smaller (fined grained) = farther distance

clastic

cemented fragments from already existing rocks

non clastic

minerals precipitated from solution (chemical)

biogenic

accumulated organic remains/skeletons/shells

breccia

coarse grains, sharp, angular clasts

conglomerate

coarse grains, rounded clasts

coal

made from carbonate and decayed plant matter

metamorphic rocks

formed by altering existing rocks

____, pressure, and ___ create new minerals and new textures without melting

heat, fluid

foliated rocks

have minerals that are banded (in lines)

non foliated rocks

rock crystals not aligned

prolith

the original rock before metamorphism

recrystallization

the same mineral/chemistry/crystals but new texture/grain size

phase change

same mineral/chem, but crystal structure changes

prograde

when temperature/pressure increase and change the rock

retrograde

temperature/pressure decrease and change the rock

index minerals

• appear within a specific pressure/temperature

• easy way to tell how much metamorphism occurred in the field

regional metamorphism

large scale metamorphism caused by high temp/pressure

• related to mountain building

• where foliated rocks come from

contact metamorphism

localized, caused by heat from magma baking surrounding rocks

• high temp, low pressure

• non-foliated rocks

shock

impacts briefly generate extreme pressure (bomb, meteor, etc.)

• results in significant deformation of rock