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The Valley of Ten Thousand Smokes is a valley within Katmai National Park and Preserve in Alaska which is filled with ash flow from the eruption of Novarupta on June 6-June 8, 1912. Following the eruption there were thousands of fumaroles venting steam from the ash. Robert F. Griggs, who explored the volcano's aftermath for the National Geographic Society in 1916, gave the valley its name. Griggs wrote: "The whole valley as far as the eye could reach was full of hundreds, no thousands—literally, tens of thousands—of smokes curling up from its fissured floor."
The 1912 eruption was the largest (most voluminous) eruption in the 20th century (erupting about 13 cubic km of material). Novarupta generated as many as 14 major earthquakes, with magnitudes between M6 and M7 (release of this much energy is virtually unprecedented during volcanic eruptions), and over 100 earthquakes greater than M5. Following the eruption, the summit of Mount Katmai subsided (collapsed) about 1200 m, forming the central caldera.
Katmai is a stratovolcano, being formed of alternating layers of lava flows and pyroclastic rocks. The mere presence of pyroclastic materials indicates that Katmai eruptions are explosive, as is further evidenced by the subsidence of the summit to form the central caldera and the extraordinarily energetic earthquakes accompanying the 1912 eruption.
Canyon cut in ash by River Lethe
The ash filled valley covers a 40 square mile (104 km²) area and is up to 700 feet (210 m) deep. In places deep canyons have been cut by the River Lethe, allowing one to view the ash flow strata. Since the ash has cooled, most of the fumaroles are now extinct and the valley is no longer filled with smoke, but it retains its name. The signs of volcanic activity are still visible on nearby hills. Katmai's most recent eruption was in 1927, but there have been non-eruptive events as recent as 2003. The Alaska Volcano Observatory still monitors Katmai's activity as part of the Katmai Cluster, where there are 5 active stratovolcanos within 15 km of Katmai.
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