Geology midterm-- from my notes

Minerals

naturally ocurring combination of specific elements arranged in a particular lattice structure

Rocks

may be made up of a few minerals

Igneous rock formation

from magma either cooled slowly underground or quickly after volcanic eruption

Sedimentary rock formation

weathered products of other rocks accumulated at surface then buried by other sediments

Metamorphic rock formation

either igneous or sedimentary heated and squeezed so that new minerals form

plate tectonics

the concept that the earth’s crust and upper mantle is divided into a number of plates that move independetly on the surface and interact at their boundaries

The earth’s interior

core, mantle, crust

Core

interior, metallic, mostly iron. outer core is liquid, inner is under so much pressure that it is solid

Mantle

most of the mantle surrounding outer core is solid but can flow freely. outer mantle is rigid. Made up of iron and magnesium silicate minerals

Crust

granite on continents, basalt beneath oceans. Rigid

Lithosphere

the crust and the outermost rigid mantle, divided into 20 plates that move in different directions on the Earth’s surface

Geothermal gradient

rate of increase of temperature with depth

Convection

in the mantle, caused by heat coninuously flowing outward, transfer of heat from core to mantle

What drive movement of tectonic plates

Convection at places where current moves upward, new lithosphere forms at ocean ridges and plates diverge

Where two plates converged, flow in mantle moves downward and one plate will be subducted back into the mantle

Age of earth

4.5 Billion years, 4.57 GA

Big bang theory

that the universe started with a giant explosion approximately 13.77 billion years ago

a sudden expansion of matter, energy, space from a signle point

Cosmic microwave background

light from 375,000 years after the big bang. We can “see” concentrated light from the formation of stars and planets

how we know universe is expanding

red shift and doppler effect

The red shift

increase in wavelength when source of light is moving away from observer, tells us galaxies are moving away from us

Doppler effect

so, we know what elements our sun is made up of because they absorb light from a certain part of wavelength, so we can compare other star’s light and see how the wavelength are red-shifted

Formation of planets

stars create new atoms by fusing them under heat and pressure

heaver planets need larger stars because they take more energy

solar system

star and planets surrounding it

nebula

a concentration of gases

First stage for new solar system

When nebulae collapsee, gravity and static electrcity draw particles together

Second stage for new solar system

The materials at the center of the collapsed nebula form a star, dust and gas settle into a disc and rotate around that star

Protoplanetary disc

a rotating cloud of dust and gas surround a young star

3 categories of planet

Terrestrial, Jovian, Ice Giant

Terrestrial planet

rocky mantle and crust and metallic core

dominated by silicates and metals

solidified at high temperatures

Jovian/Gas Giant

consist primarily of hydrogen and helium

Ice giant

made of gases heavier than hydrogen and helium such as oxygen carbon and nitrogen

Frost line

the boundary beyond which volatile components (water, carbon dioxide, methane) are frozen

Inner part of protoplanetary disc was too hot for anything but metals and rock, and outer disc was cool enough for ice

Accretion

process by which solid celestial bodies are added to existing bodies during collisions

If too fast, both will smash and scatter

Farthest from sun— more material to accumulate, so larger planet

First planets collect minerals, when bigger they keep gasses in their gravity

Reasons why earth was hot in its first 2 billion years

heat from thermal energy already contained in objects accreted into earth

from collisions, some energy became heat

as earth grew, so did gravitational pull and compression heated earth

heat melted silicate minerals and metals. The denser metal sunk and became core

Why earth was bombarded by objects from outer space

because of irregularities in orbit from Jupiter/Saturn

A planet named Theia hit earth to form the moon (the debris coalesced in around 10 years)

Giant impact hypothesis

A Mars-sized protoplanet named Theia struck the early, forming Earth (proto-Earth) at an angle

How the atmosphere devloped

volcanos helped by releasing water vapor and Co2

earth’s atmosphere didn’t have O2, until life began

Photo-synthetic organisms used abundant Co2 and released O2 as a byproduct

Habitable zone

region around a star considered suitable for life-giving planet

Possibility of other “Earth”

would have to be a terrestrial planet, around our size, and in a star’s habitable zone

What kinds of things does relief tell you?

Density, dynamics of internal earth, surficial processes, info about where the rock was formed by seeing type of rock and fossils

Crossbeds

inclined layers of sediment within a larger rock or deposit that form at an angle to the main horizontal bedding planes

Erg

a sand sea

Shape of earth

oblate elypsoid

Circumfrerence of the earth

40,075.02 km

Geocentric model

believed everything orbited us

Retrograde planetary motion

people saw the planets in the night sky stop rotating and turn back

they explained it with epicycles

but, as technology advanced, our observations could only be described by more and more complex epicycles

Heliocentric model

From Copernicus

now explains the planets “going back and forth” because we are orbiting at different velocities

Heretical, Copernicus was punished by Church

Phases of venus

Galileo tracked venus’ retrograde motion and explained why it got brighter and darker, like phases of our own moon

this could only be explained by us both rotating around something else

Moons of Jupiter

Galileo said the moons proved that we’re not the only celestial body that things orbit

Planetary motion

Heliocentric and elyptical model, so sometimes closer/farther from sun

Closer to sun, move faster

Period it takes direct proportionality to distance

Leon Foucault’s pendulum

evidence that the earth underneath it is rotating

Solar system

8 planets

earth is 4.543 Ga

Age of solar system

4.6 billion years old

Age of milky way

13.6 billion years old

Age of universe

13.8 billion years old

Spectral absorption lines from sun

when sunlight passes prism and we record the spectrum of light, there are gaps

this gives us info on material the light has traveled through

so this can tell us what any planet is made of

Big bang nucleosynthesis

around 380,00 years post big bang

the universe cools down enough to make H and He atoms, begins to emit light

Cosmic microwave background

maps distribution of temp during nucleosynthesis

shows subtle differences in temperature representing denser concentrations of mass, which will begin to form stars

Star nucleosynthesis

200-500 million after Big Bang

Stellar reactions

make elements up to iron

Supernova explosion

source of heavier elements

Seismology

the study of vibrations within Earth (could be caused by earthquakes, tidal effects, or extraterrestrial impacts)

Body waves

seismic wave that travels through earth (P-waves or S-waves)

P-wave

a seismic body wave characterized by deformation of the rock in the same direction that the wave is propagating (compressional vibration)

fastest traveling waves, compress the material in front of it

S-wave

a seismic body wave characterized by deformation of the rock transverse to the direction that the wave is propagating (shear wave)

the motion is perpendicular to the direction of movement

Seismic waves movement effected by

both kinds of wave travel faster in mantle than crust because it is denser

seismic waves are slowed by down phases of rock such as melting

Mohorovicic discontinuity

boundary between crust and mantle

waves curve out toward surface (toward lower density material)

because of the gradual density increase with depth

Core-mantle boundary

s-waves stop at the CMB

p-waves that travel through the core are refracted away from the surface

S-wave shadow zones

where seismometers cant detect them in the core

can tell us about size of a planet’s core

Earths temperature

increases with depth, as does the rate of increase

Mantle convection

we know it convects because temperature gradient is much greater in lithosphere than main mantle

so, heat from depth is being brought up

as mantle from core heats, it becomes lighter than what is above it and bouyancy floats it up

Over time, planet cores cool and convection ceases

Why is the center of the earth hot?

1. friction of particles from gravitational force + planet formation

2. radioactivity of decaying isotopes in mantle

Earth’s magnetic field

motion of iron from inner core convected out to outer core generates a magnetic field

North and south poles

aligned with axis of rotation

Magnetic force

flows into northern hemisphere and out of southern hemisphere

force is vertical at poles, everywhere else different angles, at equator its horizontal

Generation of magnetic field

convective movement of liquid iron in outer core

Isostasy

the equilibrium between a block of crust floating on the underlaying plastic mantle

when mass is added to crust, it pushes down into the mantle. When crust erodes, the crust rebounds and mantle flows back

Similarly, crust and mantle rebound after glacier melt

Oceanic crust, being heavier than continental floats lower on the mantle

Dust

small amalgamations of heavier elements

Ice contains frozen blobs of volatile elements

The nebula that formed our sun

it was probably around 10 light years across and had a mass a 1000x the suns mass

Collapse of our nebula and making of sun

a localized event caused the process of collapse. Nebula began spin and gravitational collapse

Three processes responsible for disc shape of what will become a planetary system

1. gravitational attraction

2. angular momentum (spin) increases as mass concentrated in center

3. centrifugal force (perpendicular to axis) pushed outward

T-tauri stars

energy produced rom gravitational collapse of protostar and accretion of new material from nebular disc

Solar winds

streams of charged particles escape the sun’s gravitational field

Chondrules

dust material visible to naked eye, made up up dust/grain aggregates

Carbonaceous chondrites

considered most primative meteorites

can be used to discover age of solar system

Elemental abundances in the solar system

strong correlation between chondrites and our sun. THis shows we all started with the same stuff

Planetesimals

inner part volatile poor, outer volatile rich

Grand track theory

as Jupiter and Saturn formed they migrated toward the sun, distributed material away from Mars, and distributed the material that would’ve been another planet is now just an asteroid belt

they stabilized past the frost line

Outer gaseous giant planets

exist beyond the frost line

lack solid surface

volatile rich (similar to constituents of original nebula)

low temperature solidficiation

Asteroid belt

smaller remaining planetesimals never swept into space into a planet

Earth was once a magma ocean

we radiate heat and outer part cools into a shell

Development of volatile gas atmosphere on terrestrial planets

some came from asteroids, some emitted by volcanoes

atmospehre modified by organisms

Kuiper belt

orbits beyond Neptune, includes Pluto

Cause of earthquake

rupture and subsequent displacing of rocks beneath earth’s surface

Rupture

breaking of rocks subject to stress, typically resulting in earthquake

How does rupture work?

Stress deforms rock. Rock ruptures. The two sides slide apart

Elastic deformation

the deformation of material from which it can fully recover if stress is removed

Rupture surface

the area over which rock rupture takes place during quake

Magnitude of earthquake

depends on rupture surface area and average amount of displacement (sliding)

Rupture origin

one point and spreads out, amount of displacement varies across the area

Aftershocks

earthquake shown to be caused by other earthquake