. "Tofua Caldera"@en . "Tofua Caldera, in Tonga, is the summit caldera of a steep-sided composite cone that forms Tofua Island. Tofua Island is in Tonga's Ha'apai island group. Pre-caldera activity is recorded by a sequence of pyroclastic deposits and lavas constituting the older cone, followed on the northern part of the island by froth lavas or welded and unwelded ignimbrite."@en . "515.0"^^ . "515.0"^^ . . . . "2004Z"^^ .