Climate Change Over Geologic Time Flashcards
Continental Drift
the very gradual movement, assembly and rifting of the crustal plates + their associated continents
- the movement of tectonic plates cause continents to move in a “supercontinent cycle” - or a periodic aggregation and dispersal (moving together + breaking apart) over 300-500 MYs
- when continents collide, the result is fewer + larger continents
Supercontient
result when all or most continents assemble together; two major supercontinents
1. Rodinia
2. Pangea
Rodinia
a Precambrian (Proterozoic Eon) supercontinent that assembled ~1.2 BYA and broke up ~750 MYA
- located near the equator
- its breakup end-Proterozoic is thought to have contributed to climatic conditions that facilitated the rapid evolution of early multicellular life
Pangea
Earth’s most recent supercontinent; ~335 MYA in late-Paleozoic and broke up ~200 MYA during early Mesozoic
- located near the equator
- dramatically affected the evolution of life
- prior to Pangea, smaller continents near the equator had wet/swampy conditions that favored massive lycophyte forests + amphibians
- the assembly of Pangea resulted in increasingly arid conditions that favored gymnosperms + amniotes
Snowball Earth
evidence from geology, the oxygenation of the atmosphere, and tectonic plate movement models prove that Earth was covered with glacial ice sometime preceding 600 MYA during the PROTEROZOIC. What caused it was this process in these steps:
1. continents located near the equator
2. excessive oxygen production
3. reduction of greenhouse gases
Snowball Earth: Continent Location
CONTINENTS LOCATED PRIMARILY NEAR THE EQUATOR
- land near the equator reflects sunlight more effectively than open ocean, which maximizes the ALBEDO EFFECT (cooling due to reflected sunlight)
- while oceans absorb rather than reflect heat, land at the equator reflects light and heat, preventing surface temperature from increasing
- RODINIA was located at the equator during Snowball Earth
Snowball Earth: Excessive Oxygen Production
As RODINIA broke up, its separation created coastal environments with excess availability of mineral runoff into the oceans
- Cyanobacteria flourished in the oceans as a result - producing excess oxygen that was used by reactions in the ocean with iron
- formed banded iron formations, indicating that oxygen was present in the oceans and reacting with dissolved iron to form ion oxides, which sank to the ocean floor
Snowball Earth: Greenhouse Gases
once iron + other reactants, like organic carbon, depleted in the ocean, the excess oxygen eventually accumulated in the atmosphere where it reacted with the GG methane to form CO2
- the subsequent reduction in methane would have reduced the ability of the planet to retain the reflected light + heat, allowing the surface to cool
Oxygenation of the Atmosphere
- no other planet in the solar system has an oxygenic atmosphere
- O2 is highly reactive + quickly consumed by oxidation reactions
- oxygenic photosynthesis by cyanobacteria, green plants, and protists replenishes the O2 consumed by respiration and other oxidative processes
- Evolution of oxygenic photosynthesis changed the plants atmosphere over BYA, and caused radical changes in the evolution of life on earth
Oxygenic Atmosphere + History of Life
- Prior to the evolution of oxygenic photosynthesis in early cyanobacteria during late-Archaean, the early Earth had NO O2 GAS and all life was anaerobic
- Early-Proterozoic, early cyanobacteria produced O2 gas as a byproduct of photosynthesis, which was abosrbed in the oceans and seabed rock to form banded iron rock formations. OXYGEN DISSOVLED IN WATER CAUSES MASS EXTINCTION OF MANY ANAEROBIC ORGANISMS (Oxygen Catastrophe) AND ALLOWS EVOLUTION OF AEROBIC METABOLISM, enabling the evolution of the First Eukaryotes
- Mid-Proterozoic, O2 starts to leave the oceans into the atmosphere, is absorbed by land, and forms the ozone layer. The first multicellular eukaryotes evolve
- Late-Proterozoic, O2 sinks become saturated + gas accumulates, facilitating the Phanerozoic Cambrian Explosion
Temperature + Sea Level
The Earth has experienced large swings in global temperature, from Snowball Earth in the Proterozoic to fluctuation between hothouse + intermittent glaciation in the Phanerozoic
- multiple factors caused these large swings including solar output, extreme volcanic activity, meteors, and greenhouse gases
- CO2 levels are currently the highest in the last 14 million years
Biological Innovations
- in most cases, biological innovations appear BEFORE the environment changes to select for that innovation
- if these innovations provide an adaptive advantage, changes in the environment will then select for those innovations, causing them to become more common/dominant
- EX: Oxygen Revolution, Paleozoic Drying
The Oxygen Revolution
- high levels of oxygen in the atmosphere resulted in the extinction of many anaerobic bacteria and the evolution of aerobic organisms which use oxygen to respire
- the availability of oxygen allowed larger + more complex aerobic life to evolve cumulating in the Cambrian Explosion
Drying of the Earth (Paleozoic)
Early-Paleozoic era; the earth was very wet, resulting in the proliferation of seedless plants + early amphibious tetrapods. As Earth became drier late-Paleozoic ~ early-Mesozoic, organisms with traits that allowed them to survive in drier environments were more likely to survive and reproduce than organisms without
- seed plants were able to reproduce + spread without water assistance dominated the drier land
- amniotic tetrapods used impermeable membranes to keep water inside their eggs + bodies, allowing them to dominant drier environments in the Mesozoic
Anthropocene Epoch
named for the outside influence humans are having on Earth’s climate + ecology; it is noted for human driven climate change, which can be understood through:
- drivers of global CC
- evidence of current and past global CC
- documented results of CC
