[1] They are found near Oamaru, South Island New Zealand,[1] and are small Surtseyan volcanoes that erupted originally on a submerged continental shelf.

The field has an area on land of about 890 square kilometres (340 sq mi).

[1] There are probably Southern Pacific Ocean subsurface components from sonar studies but these have not yet been characterised by core sampling.

The presence of six overlapping Surtseyan volcanoes at one site, Cape Wanbrow, is an example of this complexity.

[7] This is acknowledged in the first comprehensive geology review of Oamaru district that uses extensively the term "Deborah limestone" with respect to sedimentary strata in relationship to the volcanics.