1.1 - Earth Functions as a System Flashcards
How do biology and physical processes interact so the Earth is said to function as a system?
Biological activities change physical processes
Physical environments constrain biological activities
Life has modified the planet and the planet has controlled life (co-evolution of life and Earth)
Case Study 1: Sediment transport from terrestrial surface to coastal and marine settings (braided and meandering rivers) (erosion/weathering produces sediment).
What is the hypothesis and test?
Hypothesis: it is not uniform through time and it changes after (and before) evolution of land vegetation
Test: Compare the proportion of ‘braided’ rivers vs ‘meandering’ rivers over time
What are the properties of meandering rivers?
High sinuosity Stable channels Fine sediment (suspended load) Constant flow Dense vegetation
What are the properties of braided rivers?
Low sinuosity Channel switching Coarse sediment (bed load) Episodic/variable flow Sparse vegetation
What is sinuosity?
The measure of deviation of a channel between 2 points from the shortest possible path
Case Study 1: Sediment transport from terrestrial surface to coastal and marine settings (braided and meandering rivers).
Who did the study?
Davies and Gibling (2010)
Case Study 1: Sediment transport from terrestrial surface to coastal and marine settings (braided and meandering rivers).
What were the geological time periods split into?
Cambrian (542mya): VS2
Ordovician (472 mya): VS2 change to VS3
Silurian (436mya): VS3 change to VS4
Devonian (416 and 398mya): change to VS5 and then to VS6
Case Study 1: Sediment transport from terrestrial surface to coastal and marine settings (braided and meandering rivers).
What are the results of the case study?
Cambrian, Ordovician and Silurian periods dominantly braided systems.
Devonian show more meandering systems.
Increase in proportion of mudrock in terrestrial systems over geological time (VS2 = 15% to VS6 = 90%+)
Case Study 1: Sediment transport from terrestrial surface to coastal and marine settings (braided and meandering rivers).
What % of rivers were braided in VS2-6?
VS2: 90%+ VS3: 100% VS4: 90% VS5: 30-35% VS6: 20-30%
Case Study 1: Sediment transport from terrestrial surface to coastal and marine settings (braided and meandering rivers).
What % of rivers were meandering?
VS2: 0% (mixed = 5%) VS3: 0% VS4: 0% (mixed = 10%) VS5: 25-30% VS6: 35-40%
Case Study 1: Sediment transport from terrestrial surface to coastal and marine settings (braided and meandering rivers).
What is the explanation offered for the results?
There is more mud once extensive vegetation evolves
More mud is produced because of chemical weathering effects of roots and more stored in terrestrial/coastal systems (not washed to sea)
Case Study 1: Sediment transport from terrestrial surface to coastal and marine settings (braided and meandering rivers).
What is the % of mudrock in each section?
VS2: 10-15% VS3: 35-40% VS4: 50% VS5: 80-85% VS6: 95%
What does VS stage stand for?
Vegetation Stage
What is the general trend for the VS?
earlier VS has more braided systems which progresses to more meandering and mixed systems (function of vegetation stablising landscape and preventing rapid channel switches) - mud increases steadily throughout time (produced from weathering, no longer being transported into oceans as it gets trapped due to vegetation)
Case Study 2: Occurence of Oxygen in Earth’s Atmosphere.
What are the 2 processes that produce oxygen?
Photochemical dissociation of water vapour
Oxygenic photosynthesis
