DESCRIPTION:
Indian Heaven Volcanic Field

During the past one million years, numerous volcanic vents were active throughout south-central Washington, from Vancouver to Goldendale. Most were probably active for relatively short times ranging from days to tens of years. Unlike Mount Adams, which has erupted repeatedly for hundreds of thousands of years, these vents typically did not erupt more than once. Rather, each erupting vent built a separate, small volcano, and over time a field of numerous overlapping volcanoes was created. Clusters of these vents define the Mount Adams, Indian Heaven, and Simcoe Mountains volcanic fields. In addition, the Goat Rocks volcanic center lies 30 kilometers (18 miles) north of Mount Adams. The Mount Adams and Indian Heaven fields have been the most active recently; the Simcoe field and the Goat Rocks center have not erupted for hundreds of thousands of years.

The Indian Heaven volcanic field, midway between Mount St. Helens and Mount Adams, is a Quaternary center, chiefly of basalt. ... About 60 eruptive centers lie on the 30-kilometer-long, N10degreesEast-trending, Indian Heaven fissure zone. The 600 square kilometer field has a volume of about 100 cubic kilometers and forms the western part of a 2000-square-kilometer Quaternary basalt field in the southern Washington Cascades, including the King Mountain fissure zone along which Mount Adams was built.

All lava flows at Indian Heaven have normal magnetic polarity and so are assumed to be younger than about 0.73 million years, consistent with their morphology and geomorphic relations. ... The youngest eruption produced Big Lava Bed about 8,200 carbon-14 years B.P. (before present).

The field is dominated by small shield volcanoes surmounted by cinder and spatter cones. Subglacial vents occur on the northwest flank of the field. The overall shape of the field is that of a north-south elongate shield, with basal diameters of 30 kilometers and 10-15 kilometers, whose center rises about 1 kilometer above its base. Hammond (1984) noted that most of the flows erupted from the center of the field. Hence Indian Heaven can be interpreted as a large, complex shield volcano, fed by a central reservoir, that supports numerous flank vents. ...

Swanson, et.al., 1989 -- Indian Heaven Volcanic Field

The Indian Heaven volcanic field is midway between Mount St. Helens and Mount Adams, its principal feature is a 30 kilometer long, N10degreesEast-trending linear zone of coalescing, polygenetic shield volcanoes, cinder cones, and flows, with a volume of 100 cubic kilometers. The shield volcanoes, which form the backbone of the volcanic field, are from north to south: Sawtooth Mountain (1,632 meters in height), Bird Mountain (1,739 meters), Lemei Rock (1,806 meters), East Crater (1,614 meters), Gifford Peak (1,636 meters), Berry Mountain 1,523 meters), and Red Mountain (1,513 meters). Most of these cones are deeply glaciated, but a few retain characteristic shield morphology.

Of the 48 eruptive units in the field, monogenetic cinder cones account for 67 percent, polygenetic shields compose 29 percent, and tuyas and mobergs form 4 percent. Cinder cones have basal diameters ranging from 305 to 1,600 meters, and volumes from 0.9 to 185 cubic meters. Shield volcanoes range from 1.3 to 9.5 kilometers in basal width, with volumes of 60 cubic meters to 11.8 cubic meters. Mobergs at Crazy Hills grew within glacial ice, but never reached the surface. They are made of pillow lavas and palagonitized hyaloclastic breccia. The mobergs cover 21 square kilometers and have a volume of 1.7 cubic kilometers. Lone Butte tuya is an isolated volcano that grew through a glacier and rose above its surface. Its bottom part is similar to the mobergs but its upper part is made of surge deposits, air-fall scoria, and subaerial lava flows. The tuya has 1,027 meters of relief, covers more than 2.5 square kilometers, and has a volume of 0.3 cubic kilometers. About half of the volume has been removed by more recent glaciation.

Basalt to mafic andesite lava flows range from 0.4 to 24 meters in thickness, whereas andesite flows are up to 90 meters thick. Individual flows extend up to 46 kilometers in length, have areas to 116 square kilometers, and volumes to 1.2 cubic kilometers. Most flows less than 150,000 years of age contain extensive lava tubes, making the Indian Heaven Volcanic Field and important speleological area.

Lava flow units are separated stratigraphically into two main groups. The older group has been extensively eroded during the Hayden Creek Glaciation, around 250 to 150 thousand years ago. A younger group ranges in age between Hayden Creek Glaciation and Evans Creek Glaciation (approximately 25 to 15 thousand years ago). The youngest unit is Big Lava Bed, dated by radiocarbon at 8,150 years B.P. (uncorrected). The oldest lavas are believed to be less than 730,000 years old due to their relative freshness and normal magnetic polarity. If the entire field formed since 730,000 years ago, the average eruption rate would be 375 cubic meters /d. If the last eruption was Big Lava Bed (volume 0.88 cubic kilometers) the field is overdue for another eruption.

The center of the field lies around 60 kilometers east of Vancouver, Washington, and around 35 kilometers north of the Columbia River, in the Gifford Pinchot National Forest.

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