The answer is D. The Palaeozoic era was characterized by the supercontinent of Pannotia which was located at the current position where Chile is, 500 million years ago. There is evidence that shows that central Africa was once at the polar regions due to evidence of glaciers in its geological rocks. Due to tectonic movement, the Appalachians and the Ural Mountains were formed in the resulting Pangea supercontinent.
Convection currents occur in the MANTLE. The mantle is the second layer of the earth after the crust. The mantle is approximately 2900 km thick. Convection currents are triggered or fueled by the heat from the Earth's core.
The part of the mantle closest to the core gets heated. It then becomes less dense than the layers above so it rises. When this rising plume interacts with the crust it cools and becomes more dense than the layers below and so it sinks and this circular motion continues to form convection currents.
A) China 1.4 billion (India had 1.3 billion)
