Post by Catsmate on Oct 28, 2016 9:50:06 GMT
Some notes from a scenario I'm working on about what the Earth was like long ago that might be useful for gaming. Specifically on how easy it'd be to walk around without dying.
Periods in the Earth's past are broken down into Superaeons, Eons, Eras, Periods, Epochs and Ages. Currently were in the Subatlantic Age of the Holocene Epoch of the Quaternary Period of the Cenozoic Era of the Phanerozoic Eon of an unnamed supereon. More on the subject here.
The Phanerozoic eon dates back about 570 million years before the present (MYBP). During most of this period a human could walk around the planet pretty much as in more recent history. There is plenty of solid land, and it's cool. The atmosphere contains plentiful oxygen, and few dangerous gases except in areas of active vulcanism. There's bio-compatible plant and animal life if you're feeling hungry, though that worlks both ways...
Early in the Phanerozoic (say the Silurian period, 443MYBP) the land would be rather barren with relatively simple (though probably extensive) flora and few land animals (lots of spider analogues however; not a good spot for arachnophobes, though they were probably not poisonous). The landmasses would also be very different from the current continents; the supercontinent Gondwana covered much of the southern hemisphere, from the equator down. There were lots of island chains and few mountains.
Temperatures would be warm and pretty stable, though the period probably had a number of small ice ages.
Late in this period the Earth became far warmer through greenhouse heating; atmospheric carbon dioxide levels reached 0.45% (more than ten times the current level) and the succeeding period, the Devonian, was much hotter averaging 30°C with no polar ice masses.
Really early in the Phanerozoic the only life would be simple multicellular creatures; a stranded traveller should bring some advanced technology or learn to farm algae.
Before the Phanerozoic was the Proterozoic eon, stretching from 2500MYBP to 542. During this period the Earth underwent frequent and violent changes. Most significant of these (to humans anyway) was the Oxygen Revolution. Exactly how and when this happened are still not agreed on (and an interesting area for field study) but atmospheric oxygen seems to have reached its present levels during the Cambrian period (~550-490MYBP); there are competing theories that postulate that it may have happened somewhat earlier or later.
Before this the Earth's atmosphere is unbreathable by humans; before about 1,800MYBP there wasn't enough atmospheric oxygen to rust free iron in seawater. Back to 2,500MYBP atmospheric oxygen was around 0.1%, arising from cyanobacteria. The majority of the atmosphere was a mix of ammonia, methane, water, carbon dioxide (the majority) hydrogen and hydrogen sulphide; all quite toxic and rapidly incapacitating. Bring good protective equipment (the temperature averages 40°C) and don't rely on the local food being edible (the biochemistry is broadly similar to that of current life but with some oddities likely).
Further back, into the Archaean eon, things get more complex. The boundary between Archaean and Proterozoic is conventionally given as 2500 or 2600MYBP; actually it's rather fuzzy (a hundred million years worth of fuzziness). The boundary is defined principally by a gradual shift in tectonics; from a generally mobile and fluid crust and lithosphere to a more rigid one. During this eon, and back to ~3800MYBP, typical seawater temperatures are 70°C or higher. We have no real data on land conditions but they were probably similar.
The only known life is bacterial; THE cyanobacteria, which produce small amounts of oxygen, archaebacteria (which adapted to live in extreme environments) and the ancestral, primitive, forms of the eubacteria of modern times.
Atmospheric oxygen is minuscule, barely detectable. A time (or space) traveller would need very heavy insulation to survive. In fact Earth orbit would probably be easier and safer.
Back further is is the Hadean eon; extending from the formation of the Earth (~4600MYBP). Surface temperatures average about 230°C with very high atmospheric pressure (mostly carbon dioxide). It's not quite as bad as the present day surface of Venus but is similar.
Periods in the Earth's past are broken down into Superaeons, Eons, Eras, Periods, Epochs and Ages. Currently were in the Subatlantic Age of the Holocene Epoch of the Quaternary Period of the Cenozoic Era of the Phanerozoic Eon of an unnamed supereon. More on the subject here.
The Phanerozoic eon dates back about 570 million years before the present (MYBP). During most of this period a human could walk around the planet pretty much as in more recent history. There is plenty of solid land, and it's cool. The atmosphere contains plentiful oxygen, and few dangerous gases except in areas of active vulcanism. There's bio-compatible plant and animal life if you're feeling hungry, though that worlks both ways...
Early in the Phanerozoic (say the Silurian period, 443MYBP) the land would be rather barren with relatively simple (though probably extensive) flora and few land animals (lots of spider analogues however; not a good spot for arachnophobes, though they were probably not poisonous). The landmasses would also be very different from the current continents; the supercontinent Gondwana covered much of the southern hemisphere, from the equator down. There were lots of island chains and few mountains.
Temperatures would be warm and pretty stable, though the period probably had a number of small ice ages.
Late in this period the Earth became far warmer through greenhouse heating; atmospheric carbon dioxide levels reached 0.45% (more than ten times the current level) and the succeeding period, the Devonian, was much hotter averaging 30°C with no polar ice masses.
Really early in the Phanerozoic the only life would be simple multicellular creatures; a stranded traveller should bring some advanced technology or learn to farm algae.
Before the Phanerozoic was the Proterozoic eon, stretching from 2500MYBP to 542. During this period the Earth underwent frequent and violent changes. Most significant of these (to humans anyway) was the Oxygen Revolution. Exactly how and when this happened are still not agreed on (and an interesting area for field study) but atmospheric oxygen seems to have reached its present levels during the Cambrian period (~550-490MYBP); there are competing theories that postulate that it may have happened somewhat earlier or later.
Before this the Earth's atmosphere is unbreathable by humans; before about 1,800MYBP there wasn't enough atmospheric oxygen to rust free iron in seawater. Back to 2,500MYBP atmospheric oxygen was around 0.1%, arising from cyanobacteria. The majority of the atmosphere was a mix of ammonia, methane, water, carbon dioxide (the majority) hydrogen and hydrogen sulphide; all quite toxic and rapidly incapacitating. Bring good protective equipment (the temperature averages 40°C) and don't rely on the local food being edible (the biochemistry is broadly similar to that of current life but with some oddities likely).
- Of course there might have been life back then. Even intelligent life. The subsequent geologic upheavals could have erased all traces.
- And there's also the possibility that that oxygen excreting cyanobacteria wasn't just a natural evolutionary product.
Further back, into the Archaean eon, things get more complex. The boundary between Archaean and Proterozoic is conventionally given as 2500 or 2600MYBP; actually it's rather fuzzy (a hundred million years worth of fuzziness). The boundary is defined principally by a gradual shift in tectonics; from a generally mobile and fluid crust and lithosphere to a more rigid one. During this eon, and back to ~3800MYBP, typical seawater temperatures are 70°C or higher. We have no real data on land conditions but they were probably similar.
The only known life is bacterial; THE cyanobacteria, which produce small amounts of oxygen, archaebacteria (which adapted to live in extreme environments) and the ancestral, primitive, forms of the eubacteria of modern times.
Atmospheric oxygen is minuscule, barely detectable. A time (or space) traveller would need very heavy insulation to survive. In fact Earth orbit would probably be easier and safer.
Back further is is the Hadean eon; extending from the formation of the Earth (~4600MYBP). Surface temperatures average about 230°C with very high atmospheric pressure (mostly carbon dioxide). It's not quite as bad as the present day surface of Venus but is similar.
