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Glacier Peak, Washington, in the prime of summer when much of the s...
July 22, 2004

Glacier Peak, WA, in prime of summer when much of snow has melted

Glacier Peak, Washington, in the prime of summer when much of the snow has melted from its flanks.

Glacier Peak, Washington simplified hazards map
December 31, 1905

Glacier Peak, WA simplified hazards map

Glacier Peak, Washington simplified hazards map showing potential impact area for ground-based hazards during a volcanic event.

Stratified 275-m (900-ft) thick mid-Holocene pyroclastic flow and l...

Stratified 275-m (900-ft) thick mid-Holocene pyroclastic flow and l...

Visible relief in the hillside exposure is about 800-900 ft. Dusty assemblage deposit occurred approximately between 5100 and 5500 yr B.P. Magma volume of >5 km3, which is a lot for what was probably one eruptive stage. The source lava dome is gone, apparently having disintegrated entirely during extrusion and subsequent glacial interaction. Beige rocks in the

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Dusty Creek drainage experiences regular lahars. Gamma Ridge Format...

Dusty Creek drainage experiences regular lahars. Gamma Ridge Format...

Non-volcanic peaks of the North Cascades lie in the background. Dusty Creek drainage experiences regular lahars. Gamma Ridge Formation are hydrothermally altered rocks on left ridge. Loose pyroclastic fill deposits cap right ridge; Eastern view, Glacier Peak, Washington.

Exposed rock ridges are thick Pleistocene lava flows that were conf...

Exposed rock ridges are thick Pleistocene lava flows that were conf...

Exposed rock ridges are thick Pleistocene lava flows that were confined between large glaciers. Glacier Peak, Washington, view north.

Geologists examining ash layers associated with the Dusty assemblag...

Geologists examining ash layers associated with the Dusty assemblag...

The orange layer just below geologist's hiking pole is the Mazama ash (about 7700 ybp). Below that are glacial deposits. Above the Mazama is about a meter consisting mostly of fine-grained tephras from Glacier Peak, capped by soil and plants. That the tephras sit directly on top of the Mazama indicates that "Dusty" eruptions commenced about 7,000 years ago. The fine grain

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Ice-chilled lava columns at the end of a Glacier Peak lava flow, Wa...

Ice-chilled lava columns at the end of a Glacier Peak lava flow, WA.

Impressive columns like these form along the margins of ice-confined lava flows but usually are eroded off the sides due to continued glacial movement after an eruption ceases. Columns are better preserved at the ends of the flows (this photo) where they are protected somewhat from the ice. The columns have irregular orientations due to the irregularly shaped ends of the

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Glacier Peak volcano, Washington reflected in pond below the Whitec...

Glacier Peak volcano, WA reflected in pond below the Whitechuck Gla...

Glacier Peak volcano, Washington reflected in pond below the Whitechuck Glacier, view from the south in late summer.