The subglacial volcanoes can be identified according to type as tuyas (bigger edifices whose upper parts are covered by the products of subaerial eruptions), hyaloclastite ridges (also called tindars) which means elongated subvolcanic volcanic buildings of different sizes (most of them) and cone-like subglacial mounds (very rare). On the other hand, there are many hyaloclastite ridges, actually most of them consisting of mixtures of pillow lavas, hyaloclastite and lapilli tuff. There are also elongated pillow structures, called pillow tindars by Pedersen. Examples on Reykjanes peninsula are Sveifluháls, Núpshlíðarháls, Undirhlíðar, Helgafell (Hafnarfjörður) and Vífilsfell.