the volcanoes of Iceland owe their existence to the mantle plume underlying the convergent-plate boundary on which they sit. b. rifting above a plume produced flood basalts such as the Columbia River Plateau of Washington and Oregon and the Deccan Plateau of India. c. the Ring of Fire bordering much of the Pacific Ocean is a long chain of transform plate-boundary volcanoes. d. active volcanoes in East Africa and extinct volcanoes of the Basin and Range Province of Nevada are the result of plate convergence.