ABSTRACT
BACKGROUND: THE EMERGENCE OF FEATHERED DINOSAURS, BIRDS, AND FLOWERING PLANTS During the Cretaceous Period the Earth was warmer than at any other time in its history – atmospheric CO2 was high and the greenhouse effect led to warm, dry climates. Polar ice caps melted and the rise in sea level flooded large areas of the continents with shallow seas. At the end of the early Cretaceous intense volcanic activity, particularly at mid-ocean ridges, lifted ocean floors and sea levels rose even further. The volcanic activity released more CO2, further exacerbating the greenhouse effect. Atmospheric oxygen levels were also continually rising during the late Jurassic and throughout the whole of the Cretaceous to a peak of around 35%, which is higher than at any other time of the Earth’s history apart from the late Carboniferous.
