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EAS 205 > Snowball Earth > Flashcards

Snowball Earth Flashcards

1
Q

What was the name of the first supercontinent?

A

Rodinia

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2
Q

What were the names of the 3 glaciations in chronological order?

A
  1. Sturtian
  2. Marionan
  3. Gaskiers
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3
Q

Summarize the events of snowball earth.

A
  1. rodinia at equator breaks up
  2. chemical weathering at equator b/c warm and wet
  3. reduce atmospheric CO2
  4. fall in global temperatures
  5. ice from poles begins to encapsulate the earth
  6. albedo effect increasingly reflects sunlight and continues to lower global temperature
  7. snowball earth (completely encapsulated in ice)
  8. volcanoes and plate tectonics continue –> CO2 released
  9. rise in global temperature
  10. induced melting
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4
Q

What is the evidence for snowball earth?

A
  1. glacial features/deposits
  2. cap-carbonates
  3. limestone formation
  4. aragonite farms
  5. BIF resurgence
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5
Q

What are 2 glacial features?

A

tillites and dropstones

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6
Q

What are tillites?

A

glacial deposits, originally deposited on land

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7
Q

What are dropstones?

A

glacial deposits, originally deposited in the sea

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8
Q

Where are cap carbonates found?

A

directly on top of glacial debris

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9
Q

How are cap carbonates formed?

A

intense greenhouse climate after snowball earth –> enhanced landscape erosion/weathering by glacier –> increased alkalinity and carbonate precipitation –> rapid deposition of finely-laminated carbonate rocks (cap carbonates)

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10
Q

What do cap carbonates tell us about temperature? Explain.

A

cap carbonates tell us that temperatures abruptly switch from glacial conditions to tropical environments. this is because cap carbonates are found directly on top of glacial deposits due to being deposited as sea levels rose abruptly.

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11
Q

Where are tubestone stromatolites found?

A

cap carbonates

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12
Q

What are stromatolites and how are they formed?

A

fossilized microbial mats; form when microbes were covered in sediment

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13
Q

tubestone stromatolite (cap carbonate stromatolites are often very thin. What does this tell us about the events and conditions under which they formed?

A

must have formed very quickly in shallow water because they were buried super flat

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14
Q

What is a unique feature associated with cap carbonates?

A

aragonite fans

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15
Q

What are aragonite fans?

A

large blade-like crystals of calcium carbonate that grow perpendicular to the ancient seafloor

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16
Q

How did global freezing contribute to the resurgence of BIFs?

A

global freezing –> water stagnation –> build up dissolved iron because submarine volcanism continued with no gas exchange with atmosphere –> ice melted –> dissolved iron oxidized –> BIF suites formed

17
Q

Since snowball earth was basically inhabitable, how did species survive?

A
  • in polynya
  • within/under ice caps
  • in cryoconite
  • black smokers
18
Q

What is a polynya?

A

pockets of open water near the coast where strong winds push ice offshore

19
Q

What lake in Antarctica is found 4 km under the surface of the ice today?

A

Lake Vostok

20
Q

Can photosynthesis take place under ice?

A

yes, photosynthesis can take place under ice up to 100 meters thick

21
Q

What is a cryoconite?

A

powdery windblown dust made of combo of small rocks, soot, and bacteria found in ice/snow/glaciers

22
Q

How do cryoconites allow life to survive in glaciers?

A

dark colour absorbs solar radiation, melting snow/ice beneath the deposit –> cryoconite holes formed

23
Q

When did marine planktonic cyanobacteria evolve?

A

towards end of proterozoic eon and in the cretaceous period

24
Q

What is the oldest physical evidence of animals? What famous formation in china has this evidence?

A

metazoan embryos; Doushantou formation in China

25
Q

What are Ediacaran fauna?

A

soft-bodied marine animals that were preserved as casts, molds, and impressions

26
Q

When did Ediacaran fauna go extinct?

A

Cambrian explosion

27
Q

Which member of the Ediacaran fauna survived?

A

primitive worm

28
Q

What is the name of the UNESCO World Heritage Site in Newfoundland where you can find Ediacaran fossils?

A

Mistaken Point Ecological Reserve

29
Q

What is the oldest evidence of a shell bearing organism? What was its shape? What was the shell made of?

A

Cloudina; tubular shape; calcium carbonate

30
Q

What does the existence of shelly fauna imply about the time period that they began to flourish?

A

shells act as protection, so there must have been some kind of predator

31
Q

What are trace fossils and what do they imply?

A

fossilized tracks and burrows of early organisms; implies that there are organisms LARGE enough to leave tracks in this time period

32
Q

Was there evidence of animals before snowball earth?

A

no

EAS 205 (16 decks)

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