Most oceanographers have assumed that the iron needed to fertilize infrequent plankton blooms in the high-nutrient, low-chlorophyll regions of the world’s oceans comes almost entirely from wind-blown dust. Earth scientists have now shown that in at least one of three major HNLCs around the globe, the Subarctic North Pacific, the key source of iron is not dust but the volcanic continental margins. Understanding the origins, transport mechanisms, and fate of naturally occurring iron in high-nutrient, low-chlorophyll surface waters is important in calculating climate change.