geology exam 1

kill me

geology

the science that pursues an understanding of planet earth

how did the universe form?

big bang theory

how did our galaxies and solar systems form?

nebular theory

how did earth form?

as the planetesimals formed earth, the planet was super-hot it was melting iron and nickel in the middle. metals sank it the center of earth as it cooled. molten rock rose to the top forming a crust and separated earth into three parts, the atmosphere started due to volcanic gases, as the planet cooled entirely oceans developed and atmosphere adapted to oxygen. 

how did earth compositionally evolve?

characterized by volcanic gases and lack of stable atmosphere, as it cooled the metals separated, the outer layer formed the crust while the heavier one formed the core, and the light one formed the mantle. the movement of tectonic plates has formed continents, mountains, etc. volcanic gases heavily contributed to the production of the early atmosphere.

big bang theory

where/how the universe began 15 million years ago, components of the solar system formed by essentially the same time out of the same material

doppler effect 

a phenomenon in geology that describes how the frequency of waves changes due to the relative motion between an observer and the source of the wave.

what two theories are used for the question, what next?

steady state and oscillation

steady state

ever expanding universe, getting colder and colder 

oscillation

the energy from the big bang will eventually crunch the earth

nebular theory

condensing gases and other materials in space to form stars, planets, etc. 

how far back can we calculate from the big bang theory

1 × 10-45 seconds after

nebula

composed of mainly of hydrogen and helium, it begins to rotate and contract, becomes pro planetary disk

nebular theory steps

1) pro-planeteral disk forms, 2) proto sun forms, 3) planetesimals form, 4) planets form 

earths three layers

mantle, crust, and core

crust

earth’s thin, rocky, outer layer, lower density

mantle 

middle section, thickest layer, high density 

core

composed of iron and nickel, inner core is solid, outer core is liquid.

lithosphere

rigid outer layer of earth, consists of the crust and upper mantle

asthenosphere

soft weak layer below lithosphere

transition zone

zone marked by sharp increase in density below the asthenosphere

lower mantle

strong, very hot rocks subjected to gradual flow because of transition zone

outer core

liquid layer of the core 

inner core 

solid inner ball of the core 

oceanic crust

thinner crust, composed of basalt and gabbaro

continental crust

thicker than oceanic crust, composed of granite

evidence for structure of earth’s interior

density of earth vs density of crust, meteorite composition, sampling by volcanic activity, earth’s magnetic field, earthquakes 

earth is made up of mostly

iron, oxygen, silicon, and magnesium

earth’s crust is made up of mostly

oxygen and silicon

meteorites

leftovers from formation of solar system, different types include stony, iron, and stony iron 

chondrites

building blocks for planet earth

what do meteorites tell us about earth’s interior

that part of earth is composed of iron

types of seismic waves

p waves and s waves

p waves

compressional/primary waves, CAN go through liquids= smaller shadow zone, FASTER, imagine as a slinky  

s waves 

shear/secondary waves, CANNOT go through liquids= HUGE shadow zone, SLOWER, imagine as a string

earth’s magnetic fields

protects us from the sun’s radiation and it gives us the right temperatures and amount of pressure to have bodies of water.

what causes earth’s magnetic fields?

movement of molten iron in the earth’s outer core, motion creates electric currents due to the convection currents

earthquakes are also called

seismicity

low velocity zone

when the p/s waves hit the asthenosphere and drop in velocity

core mantle boundary

where solid and liquid meet, depending on where the focus is and if it reflects/refracts (if the refracts it makes a shadow zone) 

reflection/refraction

depends on the layer below.

who discovered the moho

andrija mohorovicic in 1919

moho

is the crust mantle boundary, when a focus goes through the crust it moves slow, but going through the mantle it moves fast

reflection 

waves bounce back after hitting a boundary 

refraction 

bending the wave as it passes into a different medium 

alfred wagner 

proposed the continental drift hypothesis in 1915, suggested the supercontinent pangaea, however his theory was not accepted

pangaea

supercontinent that existed over 200 million years ago, “drifted” apart to current continental configuration. 

wagner’s evidence for pangaea

1) fit of continents, 2) glacial records, 3) paleoclimate (rock records) 4) fossil records, 5) deformation and mountain belts 

fit of continents

wagner drew out how each continent fit together and proved the supercontinent

paleoclimate

how different ecosystems/climates appeared in the same places that used to fit together as continents 

fossil evidence 

different organisms appeared in the same areas as the paleoclimate, fossils of these organisms and their similarities prove this

matching geology and mountain belts

mountain belts that appear in separated continents would have been together in the supercontinent

why was wagner’s theory not accepted

his inability to prove continental drift. he thought it was a gravitational force from the sun and moon, also proposed that the continents broke through ocean crust like icebreakers

plate tectonics theory

the theory explains the movement of earth’s lithosphere which is divided into plates that float on the asthenosphere which leads to phenomena like earthquakes, volcanic activity, and mountain formations

sea floor topography 

allowed geologists to identify mid ocean ridges, fractures, and deep trenches 

sediment accumulation

showed geologists that thickness of sediments increases with increasing distance from the ridge crust. as you get further away from the ridge crust, the sediment gets older.

magnetic north 

direction in which earth’s magnetic field points

geographic north

considered to be “true” north

dipoles during melting temperatures

change orientation rapidly, so the flowing lava cannot have permanent magnetization. NO NET MAGNETIZATION

dipoles during cooling temperatures

dipoles align with earth’s magnetic field, so they lock into a permanent orientation.

paleomagnetism

allows geologists to examine how earth’s magnetic field was during the time of different rock layers by where the paleomagnetic dipole was pointing- how wagner’s theory was PROVED 

magnetic reversals

overtime, magnetic field reverses and rotates

sea floor spreading

new crust being made in ridges and it is moving continents.

types of plate tectonics

convergent, transform, and divergent

divergent plate boundary

moves away from each other, makes mid ocean ridges

convergent plate boundary

plates moving towards each other, older layer subducts into the lithosphere, has a trench, forms mountains/volcanoes, earthquakes 

transform plate boundary 

sliding past each other, neither converging or diverging/ production/destruction of the lithosphere 

mid ocean ridges =

new crust!!! 

continental rifting

 diverging plate motions produce forces that thin the lithosphere and promote upwelling in the mantle, eventually forms a rift valley that turns into a mid ocean ridge

ocean-continent convergence 

fault belt, trench, volcanic arc, accretionary prism, subduction, mountain ranges

ocean continent collision example 

cascade range in pnw 

ocean ocean convergence

subducting lithosphere, trench, volcanic island arc

ocean ocean convergence example

mariana trench

continent continent convergence

trench, NO volcanoes, earthquakes, deep crust, big mountains, lithosphere DETACHES and SINKS

continent continent convergence example

himalaya mountains

transform faults

produces a zig zag plate margin of a spreading center, can be found in mid-Atlantic ridge, no mountains, no magma, earthquakes, no trench

what country is still actively moving

india, moving northward in active collision

examples of transform plate boundary

san andreas fault

what was believed to be the driving factor of plate tectonics

mantle convection

what was the actual driving factor of plate tectonics 

ridge push and slab pull

ridge push

asthenosphere upwells and gravity makes it want to sink back down = causes an outpush

slab pull

plastic sinks down the asthenosphere 

how is plate motion measured

dates of the ocean floor from hundreds of locations gathered by ocean drilling ships combined with paleomagnetism + GPS (global positioning system) uses satellites to track motion. 

minerals 

building blocks for rocks, naturally occurring, solid, formed geologically, crystalline structure, definite chemical composition. and mostly inorganic. 

biogenic minerals 

special case of mineral due to them being formed by a living organism 

synthetic minerals

humans can recreate natural processes to make mineral equivalents

mineral vs glass

minerals have ordered SiO2 while glass has disordered SiO2

crystal

a single, continuous piece of crystalline solid, typically bonded by flat surfaces

atom 

smallest part of matter that cannot be chemically split 

protons

charge of +1

neutrons

charge of 0

electrons

charge of -1

atomic number 

number of protons in the nucleus of an atom 

element 

a group of the same kind of atoms, organized on periodic table so those with similar properties line up 

why do atoms bond 

to gain a full valence electron shell, octet rule 

ionic bonding

atoms gain or lose electrons to form ions, ionic bond is the attraction of oppositely charged ions to one another 

what is the most common type of bonding for minerals

ionic bonding, 90% of minerals use it 

covalent bonding

electrons are shared between

metallic bonding

special case of covalent bonding, neighboring atoms share electrons

weak types of bonds

hydrogen and van der waals