Hwniindi K'eLt'aeni

Language: Ahtna
Meaning: Upstream from The One (K’elt’aeni)

Volcanic Province: Wrangell Volcanic Arc
Location: Ahtna Nenn’ / East-Central Alaska, USA - 62.213°N, 144.13°W

Type: Shield Volcano
Age: Estimated to 900,000 years
Last Known Eruption: Estimated to about 320,000 ago

Mount Sanford is a massive, deeply dissected shield volcano capped by a broad, glacier-covered dome. It ranks among the highest Quaternary volcanoes in the United States and towers over the Copper River basin. Its flanks are incised by large cirques carved by glacial erosion, most pronounced on the southwest and southeast sides.

The south face is widely regarded as the steepest major mountain face in North America, rising approximately 8,000 feet in one mile. Despite its heavy ice cover, geological evidence suggests the upper portion of the volcano is relatively young—possibly Holocene in age—and was built atop older, coalescing andesitic shield volcanoes. These ancestral volcanic centers, located to the south, northwest, and north-northwest of the modern summit, began forming roughly 900,000 years ago.

Geologic records document a major mid-Pleistocene rhyolitic lava flow, dating to approximately 600,000–500,000 years ago, that erupted from a vent on the northeast flank and traveled more than 18 kilometers. This single lava flow is locally more than 1,000 feet thick. The most recent radiometrically dated volcanic activity occurred about 320,000 years ago, when basaltic lava flows erupted from a rift zone along the northeast flank.

Most of Mount Sanford is covered by perennial icefields above 8,000 feet. These icefields feed multiple alpine glaciers, including Sanford Glacier, which originates in the large cirque at the base of the south face. This glacier transports vast amounts of debris generated by constant rockfall and erosion of the steep southern wall.