WALPASS: Walvis Ridge Passive-Source Seismic Experiment The Etendeka continental flood-basalt province in northern Namibia, linked by the Walvis Ridge to the Tristan da Cunha hotspot, has a great importance in global plate tectonic concepts, and is an ideal place to understand the roll of the plume-lithosphere interaction during break-up of the Southern Atlantic Ocean. We propose to operate an amphibian passive-source seismic network at the position, where the Walvis Ridge intersects with the continental margin of northern Namibia. The broadband seismic network will be composed of 23 three-component land stations and 12 ocean-bottom stations, and will be operated for 1-1.5 years. This configuration of stations will allow us to map the lithospheric and deeper upper mantle structure in the ocean-continent transition beneath the passive continental margin of northern Namibia and to find seismic anomalies related to the postulated hotspot track from the continent to the ocean along the Walvis Ridge. The acquired data can also be used to study the velocity anomaly in the lowermost mantle caused by the Africa super plume.