EVSC20004 Lecture Notes - Lecture 1: Cyanobacteria, Cambrian Explosion, Permafrost
21 Jun 2018
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Lecture 1: Evolution of the ‘Blue Planet’
Our blue planet is made up of 97.5% saltwater and 2.5% freshwater.
Freshwater is 0.3% lakes and river storage, 30.8% groundwater, including soil
moisture, swamp water and permafrost, and 68.9% glaciers and permanent snow
cover.
The ocean and its species didn’t just ‘appear’, it evolved:
Timeline of the formation of the ocean and evolution of its species:
4200 mya- Oceans formed
3600 mya- first known life
2500 mya- Oxygen levels start to rise in atmosphere
800 mya- water cycle reaches steady state
570 mya- ‘Cambrian explosion’
The planet was originally uninhabitable- full of lava, no water etc. There were volcanoes that
erupted, one of them erupting steam which lead to thousands of years of constant rain
made up half of earth’s water). The other half was because of comets filled with water
bombarding the Earth. Cyanobacteria thrived and allowed for the evolution of species,
plants etc., and oxygen levels begin to rise (due to photosynthesis).
In addition to the evolution of our oceans, so did our equipment and technology for
oceanic expeditions/discoveries evolution of the scuba diving gear and submarines,
as well as boats.
Major physical properties and processes:
1) Heat capacity: The ability of the planet to regulate heat
2) Temperature
3) Salinity
4) Density
5) Light: Concerning the wavelengths that penetrate the ocean
6) Flow: Tides, waves
7) Dissolved oxygen: Also heavily affected by photosynthesis
*Thermocline, halocline and pycnocline= area of surface where rapid change of temperature, salinity
and density occur.
*Temperature and salinity both vary spatially (countries closer to the equator have warmer waters)
as well as with depth (the deeper in the water, the colder the temperatures).
The deeper you are in the oceans, the colder, saltier, denser, more nutrient-rich it is, the
and less oxygen there is.
Colder because less exposure to the sun. Warm water is less dense than cold water
Saltier because freshwater sources (such as icecaps) dilute surface water more than
deeper water. Saltiness is also dependent on temperature
Denser because of temperatures and salinity changes
More nutrient rich because nutrients settle naturally on the seabed rather than
disperse equally throughout the water; also, because it is harder for sea creatures to
access and so there’s more of it.
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