Module 3

Question 1

List the 4 most common elements in the bulk Earth

Answer 1

Fe, O, Mg, Si

Question 2

Briefly describe how the solar system was formed, which types of elements ended, up in rocky and gaseous planets

condensation, accretion, element distribution

Answer 2

Solar system formed:
-giant molecular cloud
-gets denser -> gravitational collapse
-collisions produces heat
-High T. Sun, start fusion, H-burning

condensation:
-Centre of solar system was very hot, edges cold
-Hot nebular gases
-cool and solidify into solid grains of dust
-Solar wind drives volatiles to outer solar system

accretion:
-Dust grains join to become planets
-Produces planetesimals
-Planetesimals attract each other
-growth of planetary embryos
-Collisions between planetary embryos

-Volatiles stay gaseous longer (get further from sun), refractory solidify near sun

Rocky planets -> small amounts of volatiles
Gas giants -> rocky/icy core, high amounts of volatiles

Question 3

Name the four most common types of meteorites and which parts of the Earth they are similar to

Answer 3

Carbonaceous chondrites:
-pre-planetary solar nebula composition
-reflects first solids formed in the protoplanetary disk

Achondrites:
-Fragments of differentiated
asteroids/planets
-Many are similar to igneous rocks
found on Earth

stony iron meterorites
-equal amount of Fe-Ni alloy and silicate minerals
-edge of core/mantle of differentiated
asteroids
-similar to earth core/mantle boundary

iron meteorites
-Fe-Ni alloy
-core of differentiated asteroids
-similar to the core of earth

Question 4

Describe the four Goldschmidt classifications of elements, where they are on the periodic table (generally), the kinds of bonds they form and where they are concentrated in the Earth

Answer 4

chalcophiles
-cu-loving
-bond with s, form sulphides
-Cu-S, between sidero and litho
right side of table
-both core and crust/mantle depending on how metallic (dense) they are

lithophiles
-bond with si and o, form silicates and oxides
-alkali, halogens, lanthanides, left side of table
-crust, mantle

atmophiles
-gas loving
-form gas and liquid
-volatiles, noble gases
-atmosphere

siderophiles
-fe-loving (form native metals)
-middle transition metals
-dissolve in liquid Fe and sink to core
-core

Question 5

Explain how the current chemical composition of the atmosphere developed

Answer 5

Started off high in H and He from sun

volcanic outgassing
evolution of oxygenic photosynthesis,
biogeochemical cycles
weathering
sedimentation

Has changed through time: gained N2 and O2; lost CO2 and CH4

Question 6

What are the 3 kinds of dissolved ions in water?

What is the relationship between residence time and mixing time

Answer 6

Conservative
-Constant concentration in water column relative to salinity

Recycled
-concentration increases with deeper water depth
-Organisms take up nutrients in surface waters, die and sink, nutrients back to deep waters

3. Scavenged (e.g. Pb, Mn)
   -concentration decreases with deeper water depth
   -Adsorb to surfaces of solid particles and sink into sediments

Residence time:
-time a single atom/molecule remains in reservoir of interest

conservative
residence time&raquo_space; ocean water mixing time (1000 yr)

recycled or scavenged
residence time &laquo_space;mixing time