Week 3 - Neoproterozoic "Snowball Earth"

Question 1

What period is referred to as the ‘Snowball Earth’?

Answer 1

Neoproterozoic (Cryogenian) glaciations

This refers to a series of severe glaciations that may have covered much of the Earth in ice.

Question 2

What are the key climatic conditions for Snowball Earth?

Answer 2

Reduced greenhouse effect, increased albedo, ice cap growth

These conditions led to a global-scale glaciation.

Question 3

What geological evidence supports the occurrence of Snowball Earth?

Answer 3

Diamictites, cap carbonates, glacial sediments in tropical latitudes

These features suggest extensive glaciation during the Neoproterozoic.

Question 4

What are the two main phases of glaciation during the Snowball Earth events?

Answer 4

Sturtian (c. 720 to 660 Ma) and Marinoan (c. 650 to 635 Ma)

These phases are characterized by significant global cooling.

Question 5

Fill in the blank: The geological period encompassing the Snowball Earth events is called the _______.

Answer 5

Cryogenian

Question 6

What geological event coincided with the Sturtian and Marinoan glaciations?

Answer 6

Break-up of the supercontinent Rodinia

The fragmentation of Rodinia occurred prior to the assembly of Pangea.

Question 7

What is the significance of cap carbonates in relation to Snowball Earth?

Answer 7

They indicate post-glacial conditions and changing water depths

Cap carbonates are associated with glacial deposits and reflect a transition from glacial to warmer conditions.

Question 8

True or False: The Snowball Earth hypothesis suggests that all of Earth’s surface was frozen over.

Answer 8

True

Question 9

What is one proposed mechanism for the initiation of Snowball Earth?

Answer 9

Loss of greenhouse gases and decreased solar output

The reduced greenhouse effect led to global cooling and glaciation.

Question 10

What role did albedo play during Snowball Earth?

Answer 10

Increased reflectivity leading to lower temperatures

As ice and snow cover expanded, less sunlight was absorbed, further cooling the planet.

Question 11

What were the average global temperatures during Snowball Earth?

Answer 11

As low as -50°C

The extreme cold was driven by the albedo effect and limited weathering processes.

Question 12

Fill in the blank: The process of de-glaciation after Snowball Earth was triggered by rising _______ concentrations.

Answer 12

CO2

Question 13

What is one major criticism of the Snowball Earth hypothesis?

Answer 13

Difficulty in explaining survival of complex life

Critics argue the extreme conditions would have made survival and evolution of multicellular life challenging.

Question 14

What alternative model suggests that glaciations occurred locally due to tectonic movements?

Answer 14

Zipper Rift Earth

This model posits that rifting allowed localized glaciation rather than global freezing.

Question 15

What is the ‘Slushball Earth’ hypothesis?

Answer 15

Earth did not freeze entirely; some liquid water refuges existed

This model suggests that life could have survived in pockets of liquid water during glaciation.

Question 16

What marks the beginning of the Ediacaran Period?

Answer 16

End of the Marinoan glaciation

The Ediacaran is characterized by the appearance of complex multicellular life.

Question 17

Fill in the blank: The Ediacaran fossils were first discovered in the _______ Hills in South Australia.

Answer 17

Ediacara

Question 18

What types of organisms are represented in the Ediacaran fossil record?

Answer 18

Complex multicellular organisms

These fossils show a variety of shapes and forms, indicating early biodiversity.

Question 19

What is one challenge in comparing Ediacaran fossils to modern organisms?

Answer 19

Difficulty in determining their habitats and modes of life

Ediacaran fossils do not have clear modern analogs, complicating their classification.

Question 20

What significant finds in the 1950s provided evidence of fossils older than the Cambrian?

Answer 20

Charnia from the Charnwood Forest near Leicester

Charnia is one of the earliest known Ediacaran fossils, indicating the presence of complex life forms before the Cambrian period.

Question 21

What do Ediacaran fossils represent?

Answer 21

The first forms of complex, multicellular organisms

Ediacaran fossils exhibit a variety of shapes and forms, indicating significant biological diversity.

Question 22

How are Ediacaran organisms typically categorized?

Answer 22

Morphological groups such as discs, bags, and quilted forms

These categories help in understanding the diverse structures of Ediacaran life forms.

Question 23

What major transition occurred at the end of the Ediacaran period?

Answer 23

The invention of mineralized hard parts

This development allowed organisms to better protect themselves from predation and improve their feeding mechanisms.

Question 24

What are Small Shelly Fossils (SSF)?

Answer 24

Organisms showing mineralized hard parts from the late Ediacaran

SSFs reflect an important evolutionary phase where life forms began utilizing minerals to modify their body plans.

Question 25

What term describes the rapid increase in the number of preserved fossils during the Cambrian Period?

Answer 25

Cambrian Explosion ## Footnote This event marks a significant diversification of life and the emergence of complex organisms.

Question 26

What hypothesis explains the complexity of evolutionary adaptations during the Cambrian?

Answer 26

Evolutionary arms race ## Footnote This concept describes the dynamic interaction between predators and prey leading to rapid advancements in biological structures and behaviors.

Question 27

What environmental changes aided the evolutionary adaptations in the Cambrian?

Answer 27

Increase in free oxygen and availability of Ca and P in seawater ## Footnote These changes were crucial for the development of large, mobile predators and the formation of shells.

Question 28

True or False: Ediacaran organisms were predominantly hard-bodied.

Answer 28

False ## Footnote Ediacaran organisms were generally soft-bodied, which contributed to preservation biases.

Question 29

Fill in the blank: The Cambrian period is characterized by a phase of _______ experimentation.

Answer 29

morphological ## Footnote This experimentation led to a wide variety of body plans and structures in early life forms.

Question 30

Which UK regions primarily contain Neoproterozoic rocks?

Answer 30

Wales, England, Northern Ireland, and Scotland.

Question 31

What is the Dalradian Supergroup known for?

Answer 31

It features a remarkable stratigraphy with the oldest rocks in the Grampian Group and the youngest in the Southern Highland Group.

Question 32

What are diamictite deposits and what do they signify?

Answer 32

Diamictite deposits contain poorly sorted material and indicate glacial conditions during the Neoproterozoic.

Question 33

What is the significance of ice-rafted debris (IRD) in Neoproterozoic studies?

Answer 33

It highlights the role of icebergs in transporting clasts to marine sediments, reflecting climatic and geological conditions.

Question 34

How did carbon isotope ratios behave during glacial deposits in the Neoproterozoic?

Answer 34

They were found to drop, indicating a complex relationship between climate and biogeochemical cycles.

Question 35

What does the Snowball Earth hypothesis propose?

Answer 35

It suggests that the planet experienced two major glaciation events during the Neoproterozoic, leading to global ice cover.

Question 36

What are cap carbonates, and how do they form?

Answer 36

Cap carbonates are large carbonate deposits that form after glaciation due to interactions between high CO₂ levels and alkaline-rich oceans.

Question 37

How did rising oxygen levels impact life at the end of the Ediacaran?

Answer 37

They enabled higher metabolic rates, supporting the emergence of more complex marine organisms