Iliamna volcano

stratovolcano 3053 m / 10,016 ft
Cook Inlet (SW Alaska), 60.03°N / -153.09°W
Current status: normal or dormant (1 out of 5)
Last update: 7 Mar 2013
The summit of Iliamna volcano with active fumaroles (photo: Tina Neal, Alaska Volcano Observatory / USGS)
The summit of Iliamna volcano with active fumaroles (photo: Tina Neal, Alaska Volcano Observatory / USGS)

Iliamna volcano is a large stratovolcano on the western side of the Cook Inlet, in Lake Clark National Park 220 km SW of Anchorage or 100 km NW of Homer.
There are several uncertain reports about activity in the past 250 years, but the only confirmed known historical eruptions were small to moderate explosive eruptions in 1876, 1867, and between 778 and 1879. A larger eruption with pyroclastic flows was dated by radiocarbon method and occurred between 300 and 140 years ago, but was not observed. Most of the sparse eruption reports from Iliamna are probably referring to strong activity of fumaroles located east and SE of the summit.

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Typical eruption style: explosive
Iliamna volcano eruptions: 1953(?), 1952(?), 1933(?), 1876, 1867, 1843(?), 1793(?), 1778-79, 1768(?)
radiocarbon-dated: 1650 ?, 450 BC ?, 2050 BC ?, 5050 BC ?

Latest nearby earthquakes

TimeMag. / DepthDistance/Location
Mon, 21 Jun 2021 (GMT) (5 earthquakes)
21 Jun 2021 22:04:21 GMT
1.9

105 km
28 km (17 mi)
56 Km WNW of Ninilchik, Alaska
21 Jun 2021 14:53:08 GMT
1.5

97 km
40 km (25 mi)
Southern Alaska
21 Jun 2021 13:39:52 GMT
1.3

121 km
13 km (8.1 mi)
42 Km WNW of Ninilchik, Alaska
21 Jun 2021 11:20:47 GMT
1.4

88 km
50 km (31 mi)
34 Km WNW of Ninilchik, Alaska
21 Jun 2021 07:36:01 GMT
2.5

95 km
24 km (15 mi)
61 Km WNW of Ninilchik, Alaska

Background

Iliamna volcano has no distinct summit crater, but forms a flat top joined on the south by a 5 km long ridge with the prominent flank lava domes of North and South Twin Peaks. Another important flank vent is the Johnson Glacier dome on the NE flank.
Steep headwalls on the southern and eastern flanks expose an inaccessible cross-section of the volcano.
Several major glaciers radiate from its summit; the 4 largest together contain an estimated volume of 15 cubic km of ice.
Eruptions producing pyroclastic flows have been dated at as recent as about 300 and 140 years ago (into the historical period), and elevated seismicity accompanying dike emplacement beneath the volcano was recorded in 1996.

1996-97 earthquake swarms
During 1996-97, dike intrusions under the volcano caused several shallow earthquake swarms, but no eruption. ...more

1987 steam plume
On the morning of 19 March 1987 at 8am, several pilots observed an unusually large steam plume rising about 1000-1100 m above the summit of Iliamna. The plume originated from an area on the upper S flank vent, but did not contain visible ash.
The event is not counted as an eruption, but a period of exceptionally strong degassing from active fumaroles.

1978 steam eruption
A brief steam eruption occurred on 7 November 1978 between 10 and 13 h local time, producing puffs of steam, ejected every 1-5 minutes, that rose an estimated 3 km above the summit. No ash was visible in the steam puffs. No unusual seismic activity was recorded.

See also: Sentinel hub | Landsat 8
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Locatioin map of Iliamna volcano (source: Alaska Volcano Observatory / Alaska Division of Geological & Geophysical Surveys)
Locatioin map of Iliamna volcano (source: Alaska Volcano Observatory / Alaska Division of Geological & Geophysical Surveys)
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