PLUS, short for Probing the Lithosphere Under Samoa, is an ICDP project that proposes drilling a 2,500-meter borehole on the Samoan island of Savai‘i. The goal is to recover a long, continuous rock record from beneath Samoa’s volcanoes to test how this hotspot works compared with the Hawaiian model. By studying the lithosphere, scientists hope to answer why Samoan lavas often carry continental signatures, why tholeiitic magma is rare in Samoa’s shield stage, and whether plate flexure near the Tonga trench helps produce large volumes of rejuvenated lava. The drill core would also shed light on how mantle plumes interact with surrounding tectonics, deepen our understanding of deep biosphere and hydrothermal systems at depth, and inform geothermal resource potential. The proposed site is at coordinates around 13.625°S, 172.454°W on Samoa, and the project received workshop approval in 2024.