L1-3 earth and space Flashcards
Origin of hydrogen
Process: big bang
Location: expanding universe
Origin of helium
Process: proton - proton chain
Location: “main sequence” stars during 90% of their lives
Origin of carbon nitrogen and oxygen
Process: CNO cycle
Location: depleted H leads to temp rises and He gains the ability to merge in “main sequence” stars
Origin of extra carbon
Process: triple alpha process
Location: once H becomes depleted in “main sequence” stars
Origin of elements up to iron
Process: not given
Location: the death of large stars
Origin of elements between iron and bismuth
Process: s-process (the slow addition of neutrons
Location: supergiant stars
Origin of neutron rich elements eg uranium and thorium
Process: r-process (the rapid addition of neutrons)
Location: supernovae
Origin of Sun
A gravitational collapse which resulted in a spinning hot gas nebula.
Most matter collapses into sun and fusion begins.
Origin of planets
Remainder of nebula which collapsed to form sun cools and begins to separate according to condensation temperature
Describe two kinds of planets and how they form
Rocky planets: metals and silicates condense at high temperatures meaning they predominantly form closer to the sun. Accretion then occurs through collisions.
Gas and ice planets: volatiles only condense at low temperatures so volatile rich planets form further out from the sun. Accretion then occurs through collisions.
Evidence for the formation of the galaxy
Observation of other stars
Meteorites - chondrites (combinations of metals silicates and volatiles) and achondritic and iron (remains of planetoids)
Structure, density and composition of earths interior
Crust: thin outer layer. predominantly made up of Na-Ca-Al silicates. 3.3 g/cm3
Mantle: 2d = 50%, 3d = 84%. predominantly made up of Mg-Fe silicates. 4.4 g/cm3
Outer core: 2d = 66.66% of core, 3d = 16% collectively. 12 g/cm3 collectively.
Inner core: 2d = 33.33% of core, 3d = 16% collectively. 12g/cm3 collectively.
Earth as a whole: 5.5 g/cm3
Principal sources of information about earths interior
Seismic waves: p waves travel faster and velocity is distorted by moving through different states while s waves travel slower and cannot travel through liquids. therefore, we know that the outer core is liquid
Meteorites:
Chondrites - most abundant, metal and volatile rich, oldest objects in solar system “starting stuff”
Achondrites - metal and volatile poor, younger then chondrites, silicates from the mantle of planetoids, some from mars and the moon, post differentiation part of mantle
Iron meteorites - metal rich samples of core of planetoids
Acceleration due to gravity: acceleration can be used to calculate mass and mass / volume = density. this means that we figure out the approximate relative densities of layers
Formation of earths interior
Earths interior was molten so material was separated according to density.
Fe-Ni metal as the densest sunk to core
Mg-Fe silicate was layered on top of this
Na-Ca-Al was layered on top of that
Thickness, composition, age and density of oceanic and continental crust
Thickness
Continental crust - 25-60 km ave. 35 km
Oceanic crust - 5-10 km ave. 7 km
Composition
Continental crust - Sedimentary, metamorphic and rhyolites or granites
Oceanic crust - basalt with a sedimentary cover
Age
Continental crust - all of earths history
Oceanic crust - 200 ma
Density
Continental crust - 2.7 g/cm3
Oceanic crust - 3 g/cm3
Differences between lithosphere asthenosphere and crust mantle
Lithosphere-asthenosphere: deformation behavior is what delineates the two - the lithosphere will crack where as the asthenosphere is malleable. the relationship is NOT defined by composition
Crust-mantle: composition delineates the two - mantle is mainly Mg-Fe silicates while the crust is Na-Ca-Al silicate based
Basic plate tectonic boundaries and how they operate
Divergent boundary: spreading, often mid ocean ridges but can occur continentally as well
Convergent boundary:
Subduction - one plate subducts under the other. causes volcanic belts. occurs with plates of different densities
Collision - both plates collide pushing each other up. causes mountains. occurs when plates are similar densities
Transform boundary: plates move from side to side
Principal sources of energy that drive Earth processes
Convection traction: convection currents pulling the plates with them
Slab pull: subducting plates pull down
Ridge push: ridges push out
