A breakfast inquiry

Now that science has determined why Guinness bubbles trend downwards, perhaps they can answer this one:

Why does the top half of a pancake look so markedly different from the bottom half of the pancake? Is it solely because the bottom starts its life cycle with the bubbles on it, or are there other factors at play (ie. boundary conditions on the "halfway" point in the cross section which is uncooked for the top side and partly cooked for the bottom side).

Those with insights please add to the comments.