Snowball Earth

Question 1

what time period was the snowball earth?

Answer 1

middle of neoproterozoic

Question 2

formation of neoproterozoic began at what event?

Answer 2

-formation of first supercontinent, Rodinia, at 1.2 bya

Question 3

Rodinia lasted for how long? and broke up when?

Answer 3

-450 million years
-750-630 mya

Question 4

what are the phases of ice advance during snowball earth episode?

Answer 4

-Sturtian glaciation (715-680 mya)
-Marionan glaciation (650-632 mya)
-Gaskiers glacation (less global evidence)

Question 5

why did global glaciations happen?

Answer 5

rodinia breaks up and landmasses was positioned in the middle and low latitudes

Question 6

what is declination?

Answer 6

measures the angular deviation between true and magnetic north

Question 7

what is inclination?

Answer 7

the direction of earth’s magnetic field lines

Question 8

magnetic lines run N-S and vary in dip with latitude. Effect on rock?

Answer 8

-magnetic materials in rock tells us magnetic north direction & magnetic latitude which tells us where rock was when it was magnetized

Question 9

polar wander curve (def.)

Answer 9

poles are stationary but continents wander w/ time; magnetized rocks on single continent appear to different pole positions

Question 10

chemical weathering effect on glaciation

Answer 10

-breakup of rondinia = increase landmass near water = increase rainfall = decrease CO2 in air = increase erosion/weathering
-decrease CO2 = fall in global temp

Question 11

effect of ice albedo on glaciation

Answer 11

-ice has high albedo = reflects solar energy back into space
-reduce global temp

Question 12

point of no-return for glacation

Answer 12

33 latitude north and south = cooling effect unstoppable -> equator froze over in a decade

Question 13

global temp at this point

Answer 13

-50C

Question 14

why are snowball earth short-lived?

Answer 14

volcanoes continued to release CO2 into atmosphere/ocean -> no weathering –> melting -> equator melting first (positive feedback)

Question 15

evidence of snowball earth

Answer 15

-glacial deposits (tillites/dropstones)
-cap carbonate
-banded iron formation

Question 16

how cap carbonate is formed?

Answer 16

-due to transient but intense greenhouse climate, rising sea levels
- increase weathering = increase alkalinity = increase carbonate precipitation on glacial debris

Question 17

cap carbonate indicates what about the environment at the time?

Answer 17

conditions changed from glacial to tropical quickly; ocean was oversaturation with carbonate despite ocean acidification

Question 18

what are tubestone stromatolite?

Answer 18

structure in cap carbonate; very thin and grow close together; growed in shallow water; indicated that water was precipitating carbonate quickly

Question 19

what are aragonite fans?

Answer 19

feature in cap carbonate; blade in CaCO3 = grow perpendicular to seafloor

Question 20

small BIF resurgence after snowball earth. why?

Answer 20

freezing of oceans = water stagnation = buildup of dissolved iron
ice melted. = ocean circulation starts = iron oxidized = BIF in oxic zones

Question 21

consequence of snowball earth on biosphere

Answer 21

-decline in microbial/macrofauna diversity

Question 22

place biosphere survived in snowball earth

Answer 22

-volcanic hot spring
-polynya = pockets of open H20 near coast
-under iceccaps ( photosynthesis happens hundreds of meters under ice, equator ice. = 10 m)
-cryoconite - dirty ice
-black smoker environments

Question 23

why does cyanobacteria blooms after glaciers melt?

Answer 23

outwash has phosphate, increase cyanobacteria = increase oxygen

Question 24

ediacaran fauna (def.)

Answer 24

appear in neoprote., bottom waters become oxic, sot-bodied marine animals

Question 25

fossil lagerstatten (def.)

Answer 25

lots of fossils

Question 26

other evidence of animals after glacitation

Answer 26

-shell bearing organisims (Cloudina)
-trace fossils
-burrowing