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Frozen bubble plus level 1253/26/2023 The Atlantic and Pacific Ocean floors are swept clean and are replaced by fresh upwelled material roughly every 200≣00 million years ( 4). ![]() For example, measurements indicate that South America and Africa separated a mere 125 Mya ( 3) you could have walked directly east from New York to the Sahara Desert 155 Mya ( 4). Although this may seem to be very slow to us on the human timescale, it is not slow on Earths timescale. Recent measurements ( 2) show surface movements of 2≣0 cm/year or more. Evidence shows that fresh mantle material upwells at fractures in midocean, spreads to the continents, and then sinks back into the interior. Earths surfaceīecause the atmosphere is largely influenced by the characteristics of Earths surface, let us consider its history. We will also look into the composition of Earths atmosphere, but we will first discuss Earths surface and see how it affects the atmosphere. The third alternative seems to be the most reasonable, so let us pursue it. The atmosphere could have started at higher pressure and then decreased continuously through Earths life to ~4≥ bar ~100 Mya and down to 1 bar today (curve C).The pressure could have been ~4≥ bar from Earths beginning, 4600 Mya and ~65 Mya, it could have begun to come down to todays 1 bar (curve B).The pressure could have been at 1 bar throughout Earths earlier life, risen to 4≥ bar ~100 Mya (just at the time when the giant fliers needed it), and then returned to 1 bar (curve A).What was the air pressure for the 97% of Earths life before the age of dinosaurs? We have three possible alternatives, as shown in Figure 1. Three possible alternatives for the atmospheric pressure early in Earths lifetime, given that it was at ~5 bar, ~100 Mya. For example, how did the atmosphere get to that pressure 100≦5 million years ago (Mya)? What was the pressure before that? And how did it drop down to todays 1 bar? Although we have no definite answers to these questions, let us put forth reasonable possible explanations.įigure 1. If this is so, it raises several interesting questions. Earths atmosphere before the age of dinosaursĪn earlier article in Chemical Innovation ( 1) showed that if you believe that biologys mouse-to-elephant curve also applies to the flying creatures of the past, and if you also trust aerodynamic theory (which applies equally to flying insects, birds, and airplanes), then the giant flying creatures of the dinosaur age could only fly if the atmospheric pressure was much higher than it is now: at least 3.7≥.0 bar.
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