geology final exam

geocentricism

earth at the center of the universe and the sun revolved around it

heliocentrism

sun at the center of the universe and the earth revolved around it

the big bang

universe was formed by a massive outward explosion of all matter and space from single infinitesimally small point

how do we know the big bang occurred?

expansion of the universe, cosmic background waves, abundance of light elements

redshift

increase in wavelength of light (relative to the sun) coming from distant stars

microwave radiation

uniform, black body thermal radiation from uncoupled photons

how much helium and hydrogen ended up in the universe after the big bang?

74% and 24%

the milky way

barred spiral galaxy with relatively loosely wound arms

what’s at the center of the milky way?

a black hole

order of planets from closest to farthest from the sun

mercury, venus, earth, mars, jupiter, saturn, uranus, neptune

which are smaller? terrestrial or gas giant planets?

terrestrial

about how many moons are in the solar system?

290

nebular hypothesis

our solar system formed about 4.6 billion years ago from a massive, rotating cloud of gas and dust

what caused the cloud of gas and dust to collapse?

gravity

accretion

accumulation of particles into a massive object by gravitationally attracting more matter

planetary differentiation

a young planetoid separates into layers based on density and composition

elemental abundance in earth from highest to lowest

iron > oxygen > silicon > magnesium

earths interior is composed of what three layers?

core, mantle, crust

what does earth’s core consist of?

iron and nickel (metallic)

earths mantle makes up what percentage of earths volume?

84%

what does earths mantle consist of?

iron and magnesium (silicates)

texture of earths mantle

predominantly solid but has plasticity

what does earths crust consist of?

solid silicate minerals

which is more dense? continental or oceanic crust?

oceanic

how thick is earths continental crust?

35 km

what is continental crust made of?

a heterogenous mixture of rocks (similar to granite)

how thick is oceanic crust?

5-12 km

what is oceanic crust made of?

a homogeneous mixture of rocks (similar to basalt)

order of earths interior from outermost layer to inner layer

lithosphere > asthenosphere > mesosphere > outer core > inner core

lithosphere

crust and the top most portion of the mantle

texture of asthenosphere

solid but has plastic behavior

mesosphere

lower mantle

texture of outer core

liquid

texture of inner core

solid

compositional layers of the earth

continental crust, oceanic crust, mantle, core

mechanical layers of the earth

lithosphere, asthenosphere, mesosphere, outer core, inner core

what distorts earths magnetic field?

solar wind

charged particles of the solar wind are trapped by what?

van allen belts

plate tectonics theory

the earths lithosphere is separated into plates that move over the asthenosphere

evidence of continental drift

fit of continents, locations of ancient glaciations, fossils, matching geological units

why did wegener propose the theory of continental drift?

he observed that continents, particularly south america and africa, fit together like puzzle pieces, indicating they were once joined in a supercontinent named Pangea

paleomagnetism

inclination and declination changes in a layered succession of lavas can preserve the history of tectonic plates moving a continent

does a compass point to true north or magnetic north?

magnetic

declination

angle between true north (map north) and magnetic north (compass north)

why didn’t alfred wegener gain the support of the scientific community for his hypothesis of continental drift during his lifetime?

he couldn’t describe a mechanism that explained why or how continents moved

which of the following was NOT evidence supporting the theory of continental drift?

observations of seafloor earthquakes

true or false? marie tharp’s work was instrumental in proving plate tectonic theory

true

where does the heat come from in plate tectonics?

radioactive decay from the core

tectonic plate

massive, irregularly shaped slab of solid rock, composed of continental and oceanic lithosphere

divergent plate boundary

plates moving away from each other

what forms from a divergent plate boundary?

new crust

convergent plate boundary

plates moving towards each other

what forms from convergent plate boundaries?

mountains

subduction occurs during which plate boundary?

convergent

transform plate boundary

plates sliding against each other

which plate boundary has no real creation or destruction of the plates?

transform boundary

plate tectonics is primarily driven by what?

mantle convection

continental rift

tectonic forces stretch , thin, and break a continental plate apart

what is a continental rift filled with?

sediment and water

what is a primary cause of mountain building?

continent to continent plate boundaries

how does subduction occur?

denser oceanic crust slides under the less dense continental crust

where do earthquakes and stratovolcanoes most commonly occur?

ocean-continent boundary

wadati benioff zone

zone of earthquakes that trace the path of a subducting tectonic plate as it sinks into the mantle

ring of fire

path along the pacific ocean home to 75% of earths active volcanoes and 90% of its earthquakes

slip n slide

a transform boundary where two tectonic plates slide horizontally past one another

hotspots

volcanically active areas fed by underlying mantle plumes. create volcanoes such as the hawaiian islands as the crust moves over the magma source

characteristics of a mineral

naturally occurring, inorganic, solid at room temperature, defined chemical composition, regular crystal structure

mineral

an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes

polymorph

same composition, different structure

what makes up minerals?

atoms and elements

are most minerals compounds of more than one element?

yes

ionic bonds

transfer of electrons between a metal and non metal

covalent bonds

sharing of electrons between non metals

characteristics of ionic bonds

solid at room temperature, extremely strong, dissolves easily in water

characteristics of covalent bonds

strong in water, a liquid or gas at room temperature, can be all the same element

precipitation from liquid

a mineral grows out of a liquid

crystallization from magma

ionic bonds are broken due to heat and move freely in molten magma. the magma cools and the crystals reform and deep in the earth, pressure overcomes heat, the bonds form again, reforming crystals.

bowens reaction series

specific minerals are formed at specific temperatures as magma is cooled

precipitation from organism

organism takes ions and precipitates the minerals out to make body parts

solid state diffusion

movement of atoms/ions through a solid to arrange in a new structure

what is solid state diffusion caused by?

high pressures and temperatures

mineral identifiers

luster, color, streak, hardness, crystal habitat, cleavage and fracture, special properties

why isn’t color always a reliable way to identify minerals?

impurities

streak

the color of a powdered mineral

do streaks vary?

no

crystal habit

shape of crystals determined by chemical structure of atoms

can some minerals be found with multiple crystal habits?

yes

euhedral

perfectly formed

subhedral

partially formed

anhedral

lack recognizable faces

cleavage

fractures in the crystal due to weakness in the atomic structure of the molecule

luster

how the mineral looks

how do silicate minerals form?

silicon and oxygen atoms combine to form a silica tetrahedron structure. these link together as the magma cools and crystallize into solid minerals.

minerals in the olivine family are determined by what?

the relative amount of iron or magnesium in their formula

what is the most abundant mineral in the shallow mantle?

olivine

isolated tetrahedra

tetrahedra don’t share any oxygen atoms with each other. held together by ionic bonds with other cations

paired tetrahedra

two tetrahedra share a single oxygen atom, forming a “bowtie” shape

examples of isolated tetrahedra

olivine, garnet

ring tetrahedra

tetrahedra linked together to form closed rings, usually in groups of 3-6. each tetrahedra shares two of its oxygen atoms

examples of ring tetrahedra

tourmaline, emerald