Ice and life Flashcards
What is the faint sun paradox?
the sun has gained considerable size and luminosity since earth formation (25-30% more warmth)
What is one proposed idea for why earth temp wasn’t below freezing at earth formation?
potentially due to high levels of ghgs but its said that lithosphere might not have been able to support the required levels
Beside higher ghg levels what might have been another reason for the absence of an early freeze?
low albedo due to the close proximity of continental land mass leaving lots of ocean (energy absorbing) surface to maintain temp
What was the first glaciation event?
Huronian 2.3 billion years ago
How has the maximum age of the Huronian been dated?
From lava s at the bottom of the sequence which can be radiometrically dated
How has the minimum age of the Huronian been dated?
An intrusion which runs through the rock sequence
How many glaciations were there in the Huronian event?
4 (3 in Canada and 1 in Africa)
When did the Neoproterozoic glaciations occur?
After the boring billion
What periods within the Neo-Proterozoic are focussed on for life and glaciation?
Cryogenian (colder period)
Ediacaran
What will modern glacial sediment look like?
Fine grain rock flour (produced by milling of rock) which holds a boulder matrix
Striated (scratches) and faceted (smoothed face)
What is an example of the global application of glacials (tillites)?
Australia has 2 distinctive tillites separated by a magnesium carbonate (dolomite)
The younger = Marinoan
Older = Sturtian
What can be noticed with the global distribution of the Marinoan and the Sturtian?
They pretty much cover all modern day continents in how they are distributed this is because when the land was in a supercontinent most land was glaciated around the equator at ocean level showing planet was cold
What is panglaciation?
glaciation at sea level at the equator
How many ice ages were in the Neoproterozoic era?
2 ice ages in the Cryogenian and 1 in the Ediacaran
What are the different models for Neoproterozoic (Cryogenian) glaciations?
Snowball earth
High-tilt earth
Slushball earth
Zipper-rift earth
