You probably noticed that the ages of the volcanoes do not always decrease linearly toward the present location of the hotspot. Explain in 1-2 sentences why you think this is the case.
There is a gradual decline of volcanic age form the continental to the oceanic. As some of the volcanoes get eroded away.
Explanation:
The hotspot volcanoes are transported by plate movements as they move away form the mantel plumes the hotspot volcanism decreases. Then eventually the hotspots become extinct.
Thus on the basis of age the youngest are near the places active tectonism where the magma is directly ground underneath the ground surface.