IEDA / DECADE Detail

Data from the Global Volcanism Program of the Smithsonian Institution

Details for: Okmok

The broad, 35-km-wide Okmok shield volcano is truncated by two spectacular, largely overlapping, 10-km-wide calderas. Both calderas at this dominantly basaltic volcano were formed by voluminous eruptions of dacitic tephra and pyroclastic flows during the Holocene, one about 8250 years ago and the other about 2400 years ago. Numerous satellitic pyroclastic cones and lava domes dot the floor of the caldera and the flanks of the volcano. Explosive eruptions and lava flows have originated from cones within the caldera in historical time. Photo by John Reeder (Alaska Division of Geological & Geophysical Surveys).

Volcano Number:	311290
Volcano Name:	Okmok
Country:	United States
Volcano Type:	Shield
Last Eruption:	2008 CE
Elevation:	1073m
Tectonic Setting:	Subduction zone / Intermediate crust (15-25 km)
Pop. within 5km:	0
Pop. within 10km:	0
Pop. within 30km:	0
Pop. within 100km:	4
Latitude:	53.43
Longitude:	-168.13

Eruption Data from the Global Volcanism Program of the Smithsonian Institution

Volcano Number	Volcano Name	Eruption Number	Activity Type	Explosivity Index Max	Explosivity Index Modifier	Activity Area	Start Evidence Method	Start Date	End Date
311290	Okmok	19833	Confirmed Eruption	4	P		Radiocarbon (uncorrected)	-6310
311290	Okmok	19834	Confirmed Eruption	6		Okmok II caldera	Radiocarbon (uncorrected)	-100
311290	Okmok	19835	Confirmed Eruption				Historical Observations	1805
311290	Okmok	19836	Confirmed Eruption	3		Cone E? or B?	Historical Observations	1817/3/1	1820
311290	Okmok	19837	Confirmed Eruption			Cone B?	Historical Observations	1824	1830
311290	Okmok	19839	Confirmed Eruption	2	?	Cone A?	Historical Observations	1878
311290	Okmok	19840	Confirmed Eruption	3		SW part of caldera (Cone A)	Historical Observations	1899
311290	Okmok	19841	Confirmed Eruption	2		Cone A?	Historical Observations	1931/3/21	1931/5/13
311290	Okmok	19842	Uncertain Eruption			SW part of caldera (Cone A)		1936
311290	Okmok	19843	Confirmed Eruption			SW part of caldera (Cone A)	Historical Observations	1938
311290	Okmok	19844	Confirmed Eruption	1		SW part of caldera (Cone A)	Historical Observations	1943
311290	Okmok	19845	Confirmed Eruption	2		SW part of caldera (Cone A)	Historical Observations	1945/6/4	1945
311290	Okmok	19846	Confirmed Eruption	3		SW part of caldera (Cone A)	Historical Observations	1958/8/14	1958/8/25
311290	Okmok	19847	Confirmed Eruption	3		SW part of caldera (Cone A)	Historical Observations	1960/10/15	1961/4/15
311290	Okmok	19848	Confirmed Eruption	3	?	SW part of caldera (Cone A)	Historical Observations	1981/3/24	1981/3/24
311290	Okmok	19849	Confirmed Eruption	2		SW part of caldera (Cone A)	Historical Observations	1983/7/8	1983/7/8
311290	Okmok	19850	Confirmed Eruption	2		SW part of caldera (Cone A)	Historical Observations	1986/11/18	1988/2/26
311290	Okmok	19851	Confirmed Eruption	3		SW part of caldera (Cone A)	Historical Observations	1997/2/11	1997/5/19
311290	Okmok	19852	Confirmed Eruption	4	?	NE caldera floor	Historical Observations	2008/7/12	2008/8/19

Emissions Data from the Global Volcanism Program of the Smithsonian Institution

Emission ID	SO2 Kilotons	Start Date	End Date
214	150	2008/07/12	2008/07/12

Data from the Earthchem Library

Title	Author	Release Date	DOI	Link
The emissions of CO2 and other volatiles from the world’s subaerial volcanoes The emissions of CO2 and other volatiles from the world’s subaerial volcanoes	Fischer, Tobias	2020-11-21	10.1594/IEDA/111445	Details
Field Report for the Collection of Mafic Tephra from the Aleutians Islands between Unimak and the Island of Four Mountains (Alaska, USA)	Plank, Terry	2020-06-23	10.26022/IEDA/111584	Details

Data from the Earthchem Portal

Sample ID	LINK	Method	Material	Rock Class	Rock Name	SiO₂ WT%	TiO₂ WT%	Al₂O₃ WT%	Fe₂O₃ WT%	Fe₂O₃ Total WT%	FeO WT%	MnO WT%	MgO WT%	CaO WT%	Na₂O WT%	K₂O WT%	P₂O₅ WT%	Total WT%	Ba PPM	Be PPM	Co PPM	Cr PPM	Cs PPM	Cu PPM	Dy PPM	Ga PPM	Nb PPM	Ni PPM	Pb PPM	Rb PPM	Sc PPM	Sr PPM	U PPM	V PPM	Y PPM	Zn PPM	Zr PPM	⁸⁷Sr / ⁸⁶Sr RATIO	¹⁴³Nd / ¹⁴⁴Nd RATIO	²⁰⁶Pb / ²⁰⁴Pb RATIO	²⁰⁷Pb / ²⁰⁴Pb RATIO	²⁰⁸Pb / ²⁰⁴Pb RATIO
87-20-04	DETAILS	DCPAES	Rock	Igneous Mafic Volcanic	Basalt	52.94	1.79	14.46		12.65		0.21	4.3	8.5	2.99	1.49	0.41	99.74	470			37		329				36			35	349		308	37	107	174
QCF1	DETAILS	DCPAES	Rock	Igneous Mafic Volcanic	Basalt	49.99	1.04	18.91		9.95		0.17	4.9	11.83	2.7	0.63	0.16	100	223			56		166				31			36	420		326	21	91	72
OK16	DETAILS	INAA	Rock	Igneous Mafic Volcanic	Tholeiite														549		20	9	2.57								31.1		1.9
OK16	DETAILS	EMP (EPMA)	Rock	Igneous Mafic Volcanic	Tholeiite	57.4	1.54	15.49	1.97		7.86	0.15	2.94	6.74	4.11	1.53	0.32	100
87-20-12	DETAILS	DCPAES	Rock	Igneous Mafic Volcanic	Basalt	56.93	1.51	16.26		10.03		0.2	2.85	6.49	3.89	1.59	0.36	100	496			14		48	6.78			14			25	352		195	32	105	157
87-10-07	DETAILS	DCPAES	Rock	Igneous Mafic Volcanic	Basalt	54.22	2.5	14.68		12.68		0.24	3.28	6.93	3.74	1.28	0.38	99.93	452			17		72				17			33	346		260	39	109	146
QCF5	DETAILS	DCPAES	Rock	Igneous Mafic Volcanic	Basalt	50.09	1	18.77		9.96		0.17	5.06	11.69	2.52	0.56	0.15	99.97	216			63		161				35			38	421		326	22	73	70
QCB8	DETAILS	DCPAES	Rock	Igneous Mafic Volcanic	Basalt	52.37	1.28	18.01		10.47		0.19	3.95	9.79	3.06	0.97	0.22	100	306			52		190				27			33	382		338	28	84	118
87-04-01	DETAILS	DCPAES	Rock	Igneous Mafic Volcanic	Basalt	56.7	1.44	16.05		10.38		0.19	2.97	6.71	3.79	1.49	0.31	100	477			18		79				13			26	342		243	35	97	166
87-08-08	DETAILS	DCPAES	Rock	Igneous Mafic Volcanic	Basalt	54.59	1.46	15.91		11.24		0.2	3.7	7.86	3.47	1.27	0.27	99.97	409			17		179	5.89			18			30	351		323	33	92	148
87-20-02A	DETAILS	DCPAES	Rock	Igneous Felsic Volcanic	Dacite	66.57	0.63	15.06		5.54		0.16	0.69	2.72	4.42	2.9	0.16	98.85	825			11		26				10			12	207		11	39	101	254
87-20-03	DETAILS	DCPAES	Rock	Igneous Felsic Volcanic	Dacite	66.04	0.6	14.84		5.54		0.15	0.62	2.58	4.46	3.15	0.16	98.14	809			9		33				14			12	203		13	37	98	242
QCF2	DETAILS	DCPAES	Rock	Igneous Mafic Volcanic	Basalt	50.47	0.95	18.5		9.61		0.17	5.83	11.59	2.57	0.55	0.15	100	202			81		163				44			36	403		310	20	73	68
ID-20	DETAILS	ICPMS	Rock	Igneous Unknown Volcanic	Not-given														119		37	64	0.21		2.46		0.95	21	2.41	3.56	40.4	388	0.17	295	15.3		38.3
ID-20	DETAILS	POES	Rock	Igneous Unknown Volcanic	Not-given															0.46
ID-20	DETAILS	XRF	Rock	Igneous Unknown Volcanic	Not-given														114.1			57		127.2		17.8	0.9145	26.2	1.493	3.428	38	374		290.9	14.24	70.4	34.95
QDF1	DETAILS	DCPAES	Rock	Igneous Mafic Volcanic	Basalt	50.05	0.92	17.89		9.75		0.17	6.08	11.29	2.51	0.54	0.15	99.35	193			109		148	3.15			41			39	383		308	20	69	74
QDF1	DETAILS	TIMS	Rock	Igneous Mafic Volcanic	Basalt																																			18.899	15.56	38.409
QDF1	DETAILS	TIMS_ID	Rock	Igneous Mafic Volcanic	Basalt																								6.18	10.57			0.53
QDF1	DETAILS	TIMS	Rock	Igneous Mafic Volcanic	Basalt																																	0.70333	0.513063
UM20	DETAILS	WET	Rock	Igneous Intermediate Volcanic	Andesite																								7.97				1.09
UM20	DETAILS	TIMS	Rock	Igneous Intermediate Volcanic	Andesite																																			18.831	15.569	38.374
UM20	DETAILS	XRF	Rock	Igneous Intermediate Volcanic	Andesite																									20.2		325
QCB14	DETAILS	DCPAES	Rock	Igneous Mafic Volcanic	Basalt	53.48	2.14	13.81		14.05		0.24	3.57	7.39	3.13	1.72	0.45	99.98	546			32		439	8.27			18			35	282		341	46	117	216
UM18	DETAILS	TIMS	Rock	Igneous Intermediate Volcanic	Andesite																																	0.70344		18.885	15.573	38.408

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Data from the SESAR Database

IGSN	Object Name	Object Type	Material	Field Name	Link
NHB0074B0	NMNH 117457-13 (PET)	Individual Sample	Rock>Igneous	Obsidian	Details
CAI00002G	47ABy3	Individual Sample	Rock>Igneous>Plutonic>Felsic		Details
CAI00002H	47ABy31	Individual Sample	Rock>Igneous>Plutonic>Felsic		Details

Data from the MaGa Database

Sorry. No data exist for this volcano in the MaGa database.