Sentences with phrase «ago oxygen content»
250 — 300 million years ago oxygen content rose to up to 25 percent, and this led to the development of some enormous insects.
https://www.sciencedaily.com/ Not exact matches
Only during the second marked increase in atmospheric oxygen content 600 million years ago did the deep ocean become fully oxidised, which allowed the oceanic crust to gain the «fingerprint» of high uranium - 238.
This is the big question after a Danish / Swedish / French research team, led by University of Southern Denmark, has shown that the oxygen content 2.1 billion years ago was probably the same as when life exploded 500 million years ago.
So because the Earth was much warmer many millions of years ago and the Earth's climate has naturally changed due to asteroid impact, volcanic eruptions, changes in the solar flux, the emergence of plants which produced ~ 20 % oxygen content in the air and which in turn allowed animals to evolve, there's just no way that 7 billion humans can cause any problem at all.