The Ksi Sii Aks (formerly Tseax River) is a tributary of the Nass River in northwestern British Columbia, Canada.[3][5] It is most notable as the namesake of Tseax Cone, a volcano within its basin that was responsible for an eruption in the 17th century that killed 2,000 Nisga'a people. Prior to the eruption, the Nisga'a name for this river was Ksi Gimwits'ax.[3] Buried by the eruption, it eventually resurfaced. The Nisga'a recognized it as the same stream but renamed it Ksi Sii Aks: sii aks means "new body of water".[3]

Ksi Sii Aks
The river Ksi Sii Aks.
Mouth of Ksi Sii Aks
Location
Country	Canada
Province	British Columbia
District	Cassiar Land District
Physical characteristics
Source	Nass Ranges
• location	Hazelton Mountains
• coordinates	54°59′13″N 128°55′15″W[1]
• elevation	1,310 m (4,300 ft)[2]
Mouth	Nass River
• coordinates	55°13′20″N 129°6′24″W[3]
• elevation	29 m (95 ft)[2]
Length	45 km (28 mi)[4]

As prescribed by terms of the Nisga'a Treaty, the Tseax River is now officially named the Ksi Sii Aks.

Ksi Sii Aks flows about 45 km (28 mi) north to the Nass River.[4] From its source near Sand Lake the river flows through Sand Lake,[6] Gainor Lake,[7] and Lava Lake.[8] It collects many tributary streams, the largest of which are Poupard Creek,[9] May Creek,[10] Alder Creek,[11] Crater Creek,[12] Auk Creek,[13] and Gitzyon Creek.[14]

References