Mount Haddington formed during the Miocene and Pliocene epochs and it has had subglacial eruptions which formed tuyas (a distinct, flat-topped, steep-sided hill when lava erupts through glaciers or ice sheets) but recent eruptions produced tuff cones on its slopes.
Haddington formed along the Larsen Rift dominantly during the Miocene and Pliocene epochs but more recent eruptions have produced tuff cones on its slopes. It is 60 km (37 mi) wide and has had numerous subglacial eruptions throughout its history, forming many tuyas. A tuya is a type of distinctive, flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet. 
