Scientists find the Earth’s largest, hottest volcano

Puhahonu, a shield volcano located in the central northern Pacific near Honolulu, is mostly submerged with only a third of its volume above sea level, forming the Gardner Pinnacles. It is twice the size of Mauna Loa, the former largest known volcano. Research using sonar and gravity mapping revealed that Puhahonu's size is due to abundant magma from a hot mantle spot. The high temperature of the magma is indicated by its high forsterite content. The volcano's massive weight caused the Earth's crust and mantle to buckle, submerging most of it underwater.

What is suggested about the temperature of the magma that created Pujahonu?

What geological feature caused the bulk of Pujahonu to sink under the sea?