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sustainable earth 1/19

Terms in this set (36)

mya
million years ago
bya
billion years ago
either the universe has always existed, or
there was a definite start
evidence for expanding universe
astronomers in 1920s noticed that galaixies are moving away from us
-no matter which direction
-more distant galaxies are moving away faster
how did they know that the galaxies were moving away?
the light waves reaching us were red shifted
-light wave stretched
--the opposite (moving towards us) would be blue shifted
--like doppler effect but with light waves
the big bang
the singularity, that if the universe is expanding, at some point in the past, it must have been closer together
when was the big bang they think?
14bya
the singularity is
very hot, infinitely dense
steps of big bang,,?
ENERGY -> mass (protons and electrons) -> stable atoms start combining via nuclear fusion (He) -> nebulae (clouds of gas H and He) -> galaxies and stars form due to gravity -> expanding and cooling
gravity
force of attraction between two masses
Fg = G[(m1*m2)/r^2]
-stronger for larger masses close together
atom
basic unit of matter
-a nucleus orbited by electrons
-smallest unit of a substance that still has the same chemical properties
nuclear fusion
nucleus of one atom collides and merges with another, forming a new, heavier element
isotopes
atoms of the same element but have a different mass, aka number of neutrons
where do elements come from?
all of the H and most of the He came from the big bang
-the rest are from fusion processes and they came from exploding stars (needs massive energy to create)
remnant light from the Big Bang
cosmic microwave background radiation is thought to be residue energy from the Big Bang
-faint, uniform "glow" coming from all directions, have been traveling since the beginning of the universe, when its density first got low enough for light to escape
terrestrial planets
small, rocky, metallic (iron and sulfur)
gas/ice giants
large, mainly gas and volatiles
-water, CO2, methane, ammonia
formation of the solar system
clouds of gas began to contract and slowly rotate, atoms stick together becoming molecules, then ice and dust
-rotation causes flattening into a disk, dense bulb at the center becomes hot enough for nuclear fusion and becomes a star
-volatiles in the inner disk evaporate and drift outwards and freeze
rings of planetesimals are
the building blocks of planets, rings of dust and ice form as particles clump and bind together, larger ones form planetesimals
how do planetesimals grow?
by attracting surrounding objects (accretion), clearing their orbits and becoming planets
accretion
produces heat and tidal forces that create heat also making it liquidy and creating a spherical shape instead of weird clumps
differentiation of formation of planets causes
hot core surrounded by mantle
earth composition
35% iron
30% oxygen
15% silicon
13% magnesium
the earth's crust's composition is
different than the whole earth, lighter elements are found more at the top
desnity is
mass per unit volume
inside of the earth
crust, upper mantle, lower mantle, outer core, inner core
how do we measure inside of the earth? like how deep?
gravity measures with satellites
magnetic measurements
seismic wave measurements, shock waves from earthquakes like ultrasound - diff speeds of waves going thru diff materials
Crust
is chemically different from the mantle
continental crust
35-40km thick
-less dense
oceanic crust
7-10km thick
-more dense
Moho
the boundary between the crust and the mantle
Mantle
is solid, deformable, mostly peridotite
-is heated from below, cooled from above
-movement like a lava lamp
-convection
the core
the outer core is liquid
the inner core is solid
-mostly iron, some nickel, oxygen, sulfur, silicon
-inner core hotter but higher pressure
-outer core makes magnetic field
plasticity (deformability)
the difference between the crust and the mantle is chemical
-shallow mantle is brittle, deep mantle is ductile
divided into
the Lithosphere (upper mantle and crust)
the Asthenosphere (lower mantle)
plate tectonics
that the lithosphere is made up of plates; movement is driven by lateral density differences (also mantle convection they think)
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