Week 3 - Neoproterozoic "Snowball Earth" Flashcards
What period is referred to as the ‘Snowball Earth’?
Neoproterozoic (Cryogenian) glaciations
This refers to a series of severe glaciations that may have covered much of the Earth in ice.
What are the key climatic conditions for Snowball Earth?
Reduced greenhouse effect, increased albedo, ice cap growth
These conditions led to a global-scale glaciation.
What geological evidence supports the occurrence of Snowball Earth?
Diamictites, cap carbonates, glacial sediments in tropical latitudes
These features suggest extensive glaciation during the Neoproterozoic.
What are the two main phases of glaciation during the Snowball Earth events?
Sturtian (c. 720 to 660 Ma) and Marinoan (c. 650 to 635 Ma)
These phases are characterized by significant global cooling.
Fill in the blank: The geological period encompassing the Snowball Earth events is called the _______.
Cryogenian
What geological event coincided with the Sturtian and Marinoan glaciations?
Break-up of the supercontinent Rodinia
The fragmentation of Rodinia occurred prior to the assembly of Pangea.
What is the significance of cap carbonates in relation to Snowball Earth?
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.
True or False: The Snowball Earth hypothesis suggests that all of Earth’s surface was frozen over.
True
What is one proposed mechanism for the initiation of Snowball Earth?
Loss of greenhouse gases and decreased solar output
The reduced greenhouse effect led to global cooling and glaciation.
What role did albedo play during Snowball Earth?
Increased reflectivity leading to lower temperatures
As ice and snow cover expanded, less sunlight was absorbed, further cooling the planet.
What were the average global temperatures during Snowball Earth?
As low as -50°C
The extreme cold was driven by the albedo effect and limited weathering processes.
Fill in the blank: The process of de-glaciation after Snowball Earth was triggered by rising _______ concentrations.
CO2
What is one major criticism of the Snowball Earth hypothesis?
Difficulty in explaining survival of complex life
Critics argue the extreme conditions would have made survival and evolution of multicellular life challenging.
What alternative model suggests that glaciations occurred locally due to tectonic movements?
Zipper Rift Earth
This model posits that rifting allowed localized glaciation rather than global freezing.
What is the ‘Slushball Earth’ hypothesis?
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.
What marks the beginning of the Ediacaran Period?
End of the Marinoan glaciation
The Ediacaran is characterized by the appearance of complex multicellular life.
Fill in the blank: The Ediacaran fossils were first discovered in the _______ Hills in South Australia.
Ediacara
What types of organisms are represented in the Ediacaran fossil record?
Complex multicellular organisms
These fossils show a variety of shapes and forms, indicating early biodiversity.
What is one challenge in comparing Ediacaran fossils to modern organisms?
Difficulty in determining their habitats and modes of life
Ediacaran fossils do not have clear modern analogs, complicating their classification.
What significant finds in the 1950s provided evidence of fossils older than the Cambrian?
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.
What do Ediacaran fossils represent?
The first forms of complex, multicellular organisms
Ediacaran fossils exhibit a variety of shapes and forms, indicating significant biological diversity.
How are Ediacaran organisms typically categorized?
Morphological groups such as discs, bags, and quilted forms
These categories help in understanding the diverse structures of Ediacaran life forms.
What major transition occurred at the end of the Ediacaran period?
The invention of mineralized hard parts
This development allowed organisms to better protect themselves from predation and improve their feeding mechanisms.
What are Small Shelly Fossils (SSF)?
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.
What term describes the rapid increase in the number of preserved fossils during the Cambrian Period?
Cambrian Explosion
This event marks a significant diversification of life and the emergence of complex organisms.
What hypothesis explains the complexity of evolutionary adaptations during the Cambrian?
Evolutionary arms race
This concept describes the dynamic interaction between predators and prey leading to rapid advancements in biological structures and behaviors.
What environmental changes aided the evolutionary adaptations in the Cambrian?
Increase in free oxygen and availability of Ca and P in seawater
These changes were crucial for the development of large, mobile predators and the formation of shells.
True or False: Ediacaran organisms were predominantly hard-bodied.
False
Ediacaran organisms were generally soft-bodied, which contributed to preservation biases.
Fill in the blank: The Cambrian period is characterized by a phase of _______ experimentation.
morphological
This experimentation led to a wide variety of body plans and structures in early life forms.
Which UK regions primarily contain Neoproterozoic rocks?
Wales, England, Northern Ireland, and Scotland.
What is the Dalradian Supergroup known for?
It features a remarkable stratigraphy with the oldest rocks in the Grampian Group and the youngest in the Southern Highland Group.
What are diamictite deposits and what do they signify?
Diamictite deposits contain poorly sorted material and indicate glacial conditions during the Neoproterozoic.
What is the significance of ice-rafted debris (IRD) in Neoproterozoic studies?
It highlights the role of icebergs in transporting clasts to marine sediments, reflecting climatic and geological conditions.
How did carbon isotope ratios behave during glacial deposits in the Neoproterozoic?
They were found to drop, indicating a complex relationship between climate and biogeochemical cycles.
What does the Snowball Earth hypothesis propose?
It suggests that the planet experienced two major glaciation events during the Neoproterozoic, leading to global ice cover.
What are cap carbonates, and how do they form?
Cap carbonates are large carbonate deposits that form after glaciation due to interactions between high CO₂ levels and alkaline-rich oceans.
How did rising oxygen levels impact life at the end of the Ediacaran?
They enabled higher metabolic rates, supporting the emergence of more complex marine organisms
