A pyroclastic rock deposit formed by one or more ground-hugging flows of hot volcanic fragments and particles, essentially synonymous with pyroclastic-flow deposit, ash-flow tuff, flood tuff, or welded tuff. When coined by the New Zealand geologist P. Marshall in 1935, the term “ignimbrite” referred only to flows with emplacement temperatures high enough to cause the fragments forming the deposit to become adhered together or welded; this restriction no longer applies, and the term now includes any pyroclastic-flow deposit, welded or not.