Middle Sister volcano's east face with shingled stacks of thin lava...

Middle Sister volcano's east face with shingled stacks of thin lava...

Detailed Description

The east face of Middle Sister is 350 m (1150 ft) high. Ice-sculpted pile of lavas at right, variously called "Black Hump," "Prouty Point," or "Step Sister," has 190 m of relief and consists of at least five flows. Hayden Glacier is below both summits; 25-m-thick cliff in front of right side of glacier is terminal lobe of fissure-fed andesitic scoria, spatter, and fountain-fed lava flow that drapes south flank of North Sister; dated at 21 ±6 ka, this flow (unit anh) is much younger than North Sister but about same age as Middle Sister and "Black Hump." Well-formed moraine in foreground was left by Hayden Glacier in Little Ice Age time.

Details

Image Dimensions: 3300 x 808

Source:


Hildreth et al., 2012