Feb 16, 2021 04:18 AM
(This post was last modified: Feb 16, 2021 04:20 AM by C C.)
https://www.science20.com/news_staff/why...ere-253139
EXCERPT: In the age of the dinosaurs, you could have walked from one pole to another. At that time, the continents were all joined together, forming the supercontinent Pangea. Yet they didn't. Though sauropodomorph dinosaurs first appeared in Argentina and Brazil about 230 million years ago, it took them 15,000,000 years to migrate to the northern hemisphere.
Even if a dinosaur herd walked only one mile per day, it would take less than 20 years to make the journey between South America and Greenland. [...] The answer may be CO2; 215 million years ago, though the temperature was not drastically higher, CO2 levels were 1,000% of what they are today - 4,000 parts per million. Over the next 3,000,000 years, the CO2 concentration halved, to about 2,000ppm.
[...] "We know that with higher CO2, the dry gets drier and the wet gets wetter," said Kent. 230 million years ago, the high CO2 conditions could have made the arid belts too dry to support the movements of large herbivores that need to eat a lot of vegetation to survive. The tropics, too, may have been locked into rainy, monsoon-like conditions that may not have been ideal for sauropodomorphs. There is little evidence they ventured forth from the temperate, mid-latitude habitats they were adapted to in Argentina and Brazil.
But when the CO2 levels dipped 215-212 million years ago, perhaps the tropical regions became more mild, and the arid regions became less dry. There may have been some passageways, such as along rivers and strings of lakes, that would have helped sustain the herbivores along the 6,500-mile journey to Greenland, where their fossils are now abundant. Back then, Greenland would have had a temperate climate... (MORE - details)
EXCERPT: In the age of the dinosaurs, you could have walked from one pole to another. At that time, the continents were all joined together, forming the supercontinent Pangea. Yet they didn't. Though sauropodomorph dinosaurs first appeared in Argentina and Brazil about 230 million years ago, it took them 15,000,000 years to migrate to the northern hemisphere.
Even if a dinosaur herd walked only one mile per day, it would take less than 20 years to make the journey between South America and Greenland. [...] The answer may be CO2; 215 million years ago, though the temperature was not drastically higher, CO2 levels were 1,000% of what they are today - 4,000 parts per million. Over the next 3,000,000 years, the CO2 concentration halved, to about 2,000ppm.
[...] "We know that with higher CO2, the dry gets drier and the wet gets wetter," said Kent. 230 million years ago, the high CO2 conditions could have made the arid belts too dry to support the movements of large herbivores that need to eat a lot of vegetation to survive. The tropics, too, may have been locked into rainy, monsoon-like conditions that may not have been ideal for sauropodomorphs. There is little evidence they ventured forth from the temperate, mid-latitude habitats they were adapted to in Argentina and Brazil.
But when the CO2 levels dipped 215-212 million years ago, perhaps the tropical regions became more mild, and the arid regions became less dry. There may have been some passageways, such as along rivers and strings of lakes, that would have helped sustain the herbivores along the 6,500-mile journey to Greenland, where their fossils are now abundant. Back then, Greenland would have had a temperate climate... (MORE - details)