Snowball Earth
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University of Guelph *
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Course
2240
Subject
Geography
Date
Dec 6, 2023
Type
docx
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2
Uploaded by BaronFlamingoPerson819
Snowball Earth (BBC Horizon
) (due Nov 6 by 11:59pm)
https://www.dailymotion.com/video/xw5nro
Name and student ID___________ruitian chen
1145966____________
1.
What happened on Earth around 600 ma and what was the evidence discovered by
P. Hoffman and others in Namibia?
Around 600 million years ago, Namibia's terrain was submerged, evidenced by dropstones in
ancient seabeds. These large boulders, found within fine sediment, indicate glacier activity in
the tropics. P. Hoffman's team confirmed this by replicating dropstone formation in laboratory
simulations, supporting the theory of tropical glaciation during that period.
2.
What was the contribution of B. Harland?
List the reasons of why he failed to convince other
scientists?
B. Harland's significant contribution was his study of dropstones in the Arctic, leading him to
propose a global glaciation event 600 million years ago due to his findings of these rocks
worldwide. However, his theory faced skepticism because the perennially sunlit tropics were
believed to have remained warm, contradicting evidence from the last ice age. Additionally, the
concept of continental drift provided an alternative explanation for the widespread distribution of
dropstones, challenging Harland's glaciation hypothesis. This latter explanation gained wider
acceptance in the scientific community.
4.
Explain the Budyko paradox.
The Budyko Paradox, named after Mikhail Budyko, addresses the conundrum of ice age
initiation and progression. It hinges on the albedo effect, where ice, being light-colored, reflects
solar energy, leading to cooling. As ice spreads, more heat is reflected, not absorbed, amplifying
the cooling in a feedback loop. Budyko's formula suggests a critical threshold: when ice nears
the equator, the reduced heat absorption could trigger a runaway freeze, the "snowball earth,"
even in tropical regions. This paradoxical situation poses a theoretical limit where a nuclear
winter could push the Earth past its tipping point into an irreversible icy state, a stark contrast to
the current warm conditions maintained by dark oceanic and land surfaces that absorb solar
radiation.
5.
What was J. Kirschvink contribution?
How could Earth possibly get out of deep freeze?
Joseph Kirschvink's pivotal contribution was identifying the origin of dropstones in ancient
glacial deposits by tracing their magnetic direction, a process indicating a global freeze event,
known as Snowball Earth, around 600 million years ago. His research involved using a
magnetometer on rocks from Earth's warmest regions. Kirschvink posited that Earth escaped
this frozen state through geothermal heat sources like magma, which kept active beneath the
ice. The persistent volcanic activity emitted substantial greenhouse gases, such as CO2,
without the interference of rain to remove them. This accumulation of greenhouse gases
eventually triggered a warming effect, melting the ice and ending the Snowball Earth period.
6.
Describe the importance of cap carbonate rocks found in Namibia. How could they possibly
form (according to D. Schrag)?
Cap carbonate rocks in Namibia signify a transition from glacial conditions to a warmer
climate. Daniel Schrag proposes that they formed from prolonged rainfalls that followed ice melt,
which caused acid rain. This rain broke down rocks, releasing calcium to form these carbonate
layers.
7.
Why were the biologists (e.g. G.Narbonne) skeptical about the snowball idea?
Biologists like G. Narbonne doubted the complete snowball Earth hypothesis because ancient
cyanobacteria, which require sunlight to thrive, survived from 600 million years ago, indicating
persistent open waters and inconsistent ice coverage.
8.
What did C.McKay of NASA discover in Antarctica?
Chris McKay of NASA found that sunlight could penetrate thick Antarctic ice, supporting life
such as cyanobacteria and algae beneath. This suggests that even during Earth's "snowball"
phase, equatorial regions may have sustained life.
9.
What happened to life on Earth after the end of the snowball?
Post-snowball Earth saw surviving life flourish due to reduced competition, leading to the
evolution of complex multicellular organisms, as evidenced by fossil records.
10.
What are some of the remaining questions about the Snowball Earth?
Snowball Earth has happened a few times now, so what is the root cause of these events? Will
Snowball Earth happen again in the future?
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