Source of sediments

Question 1

Hvordan spiller fysisk erosion og kemisk forvitring ind på hinanden?

Answer 1

Frisk overflade skabt af erosion = større potentiale for forvitring

Forvitring svækker sten = lettere at erodere

Question 2

6 kontroller på sediment og opløst materiale

Answer 2

Temperatur
* Varmere klima -> højere temp., mere nedbør, mere vegetation -> mere kemisk forvitring -> fjerner CO2 fra atmosfæren -> reduktion af det varmere klima (= koldere)

Nedbør = runoff (-> vand til forvitring og letter erosion)

Sæsonbestemt nedbør

Surhed af nedbør

Gennemsnitlig højde af drænbassinet (virker på erosions-rater).

Vegetation (stærk indflydelse på erosionshastigheder)

Question 3

Hvordan er forvitringen og erosionen af silikate mineraler?

Answer 3

Inkongruent (= proportion of elements in solution differs from the proportion in the former mineral(s))

The weathering of silicate minerals is yielding other solid products in addition to dissolved ones.

Silicate rock -(weathering; incongruent reaction)-> ions + clay minerals

Silicate rock -(erosion; incongruent reaction)-> grains + clay minerals = siliclastic sediments

Carbonate rock -(weathering, congruent reaction)-> ions

Question 4

Hvilken struktur følger mud-grade sedimenter?

Answer 4

Lagdelt

Silica sheet, alumina sheet …
Silica sheet, alumina sheet, silica sheet, K+-ioner …
Silica sheet, alumina sheet, silica sheet, H2O-molekyler …

Question 5

Silicate weathering

Answer 5

2CO2 + CaSiO3 + H2O ➙ Ca^2+ + 2HCO3^- + SiO2

Question 6

Carbonate precipitation

Answer 6

Ca^2+ + 2HCO3^- ➙ CO2 + CaCO3 + H2O

Question 7

Net effect (dvs. silicate weathering + carbonate precipitation)

Answer 7

Consumes 1 CO2

2CO2 + CaSiO3 + H2O ➙ CaCO3 + SiO2+ H2O + CO2

Question 8

Jordens termostat ift. sten og CO2 (og knapt så meget ift. temperatur)

Answer 8

1. Volcanoes spew CO2 into the atmosphere
2. CO2 keeps Earth warm via greenhouse effect
3. Warmth helps seawater evaporate, forming rain
4. Rain contains CO2 so is slightly acidic and dissolves minerals from the rocks into the water
5. Dissolved carbon-containing minerals wash into rivers and into the sea
6. Minerals precipitate out to form new carbon-containing rocks
7. Rocks are eventually subjected into the mantle, where the CO2 is released
8. CO2 returns to the atmosphere through volcanoes

Question 9

Hvad fortæller sphericity om grains?

Answer 9

Low sphericity = aflange
High sphericity = runde

Very angular = close to the source
Well rounded = long transport time

Question 10

Hvad fortæller sorting af grains?

Answer 10

Very poorly sorted = close to the source
Very well sorted = far from the source

Question 11

Hvad er Sorby-Princippet?

Answer 11

At kalksten (limestone) er hovedsageligt biogene sedimenter = over 90% af karbonaterne er biologiske

Carbonate sediments are born, not made!

Question 12

Hvad er de tre mest almindelige carbonat-grupper?

Answer 12

Calcite group
- Calcite
- Magnesite
- Siderite
- Rhodochrosite

Dolomite group
- Dolomite
- Ankerite
- Kutnohorite

Aragonite group
- Aragonite
- Witherite
- Strontianite

Question 13

Er havvand bare “koncentreret” flodvand?

Answer 13

Nej, fordi der er forskellige proportioner af ioner.
Havvand er afledt af både fordampning og kemisk/biologisk differentiering af flodvand.

Question 14

Koncentration af havvand ved fordampning

Answer 14

1/2 vand = Calcit (CaCO3)
1/3 vand = Gips (CaSO4)
1/10 vand = Halit (NaCl)
1/20 vand = K- og Mg-salte

Question 15

VIGTIGT: Hvad er Henrys lov?

Answer 15

[CO2] = K0 x fCO2
hvor fCO2 er ‘fugacity’ af gasformig CO2 ≈ pCO2 (partial pressure)

Carbon dioxide dissolved in water produces carbonic acid.

CO2(g) ⬌ [CO2] ; K0
hvor K0 er en T- og salinitets-afhængig opløselighedskoefficient

Opløselighed af CO2 FALDER med STIGENDE T°.

Question 16

VIGTIGT: Hvad er reaktionen for, at kulsyre opløses i bicarbonat- og carbonationer?

Answer 16

CO2 + H2O ⬌ H2CO3 (carbonic acid) ; K0
H2CO3 ⬌ H^+ + HCO3^- (bicarbonate ion) ; K1 HCO3^- ⬌ H^+ + CO3^2- (carbonate ion) ; K2

CO2 + H2O <-(ligevægt, K1)-> HCO3^- + H^+ <-(ligevægt, K2)-> CO3^2- + 2H^+

Question 17

Hvad betyder DIC?

Answer 17

Dissolved Inorganic Carbon

Question 18

I hvilken form er størstedelen af den opløste CO2?

Answer 18

HCO3^- og ikke CO2

Question 19

Carbonate saturation state

Answer 19

Ω_CaCO3 = [Ca^2+] * [CO3^2-] / K_CaCO3

hvor K_CaCO3 = støkiometrisk opløselighedsprodukt af den passende polymorf af CaCO3

Omega > 1: precipitation
Omega < 1: dissolution

You favour the precipitation of aragonite in the areas around the equator, and you favour the dissolution of aragonite at the Poles.
Temperature plays a role; see Henry’s Law.

More CO2 = more acidic water (low pH) = dissolves carbonates.

Question 20

Hvad er ooids?

Answer 20

Partly of nonbiogenic origin

Formed in super saturated waters (high temp., low CO2, high carbonate (CaCO3))

Question 21

Hvad er micrite?

Answer 21

Carbonate mud

Composed of silt- or clay-sized particles.

Looks like yoghurt

Question 22

Hvor dannes evaporitter?

Answer 22

Hvor der er mere fordampning end nedbør

Question 23

Hvilke 4 sedimentære bassiner findes, og hvordan dannes de?

Answer 23

Foreland basins – craton side of collisional mountain belt
- Weight of the mountain belt pushes down on the crust’s surface

Rift basins – divergent [pull-apart] plate boundaries (Som Vosges)
- Downward slip on faults produces narrow troughs

Intracontinental basins – interiors far from margins
- The basin forms in the interior of a continent, perhaps over an old rift

Passive margin basins – non-plate-boundary continental edge
- Subsidence occurs over thinned crust at the edge of an ocean basin

Question 24

Hvad kan man sige om et sedimentært bassin?

Answer 24

Et hul, der bliver fyldt med sedimenter på samme tid, som det bliver dannet (= vandret overflade)

Question 25

Hvad er depositional environments?

Answer 25

Locations where sediments accumulate. They differ in…
- Energy regime.
- Sediment delivery, transport, and depositional conditions
- Chemical, physical, and biological characteristics

Environments range from terrestrial to marine