DESCRIPTION:
Jordan Craters, Oregon

Location: Oregon
Latitude: 43.1 N
Longitude: 117.4 W
Height: 1,200 to 1,400 meters
Type: Volcanic Field
Remarks: Erupted in 2 main phases less than 30,000 years ago.

The Jordan Craters volcanic field is located on the Owyhee-Oregon Plateau at the southeastern end of a series of young basalt fields extending from near Bend, Oregon, through Diamond Craters in south-central Oregon. The Jordan Craters field, as defined here, is limited to the northernmost and youngest portion of a larger (250 square kilometers) Quaternary alkaline basalt field that has three major north-south aligned vents following surficial and inferred expressions of regional Basin and Range faulting. Fluid pahoehoe basalt flows emanated from each of these sources, with pyroclastic activity confined to small scatter cones and to a larger crater-cone complex (Coffeepot Crater) at the northernmost edge of the Jordan Craters portion of this field. This entire Quaternary alkaline basalt field is part of a larger field (nearly 800 square kilometers) that includes Pleistocene and Pliocene olivine tholeiite to transitional basalt flows and vents. ...

Jordan Craters is highlighted because of its well-preserved vents and striking flow features. The area is dominated by a 75-square-kilometer olivine basalt lava-flow field which originated from Coffeepot Crater, the main eruptive center. Near the vent, the flow surfaces are highly vesiculated shelly pahoehoe, and grade to massive, tube-fed ropy pahoehoe in the distal regions. Coffeepot Crater is a heart-shaped tephra cone constructed of numerous overlapping lobes of alternating densely to weakly welded scoriaceous lapilli and bombs. The walls of the crater show good evidence for a fluctuating lava pond which appears to have broken through and rafted away portions of the northeastern and southeastern crater walls. Backflow of the lava pond into the conduit is indicated by pahoehoe crust on the present crater floor. Additional material was vented from a series of S45degreeW trending spatter cones. A two stage eruptive history is suggested:

1. initial strombolian tephra cone and spatter cone-building eruptions, and
2. minor fire-fountaining, creation of a lava pond, voluminous outflows of lava, and small-volume phreatomagmatic activity.

The Jordan Craters lava flow field is mineralogically and chemically homogeneous, whereas proximal tephra and flow deposits exhibit significant chemical heterogeneity which correlates with the eruptive history. Also noteworthy are the many excellent examples of basalt flow and eruption features, including ropy and shelly pahoehoe surfaces, lava channels, lava blisters, pressure ridges and squeeze-ups, pit craters, lava-tube skylights, vertically striated internal crater walls, and re-fused cobbles of rhyolitic country rock. Additionally, the southeasterly flowing lava altered ancestral drainage patterns, giving rise to a natural dam and the formation of two small lakes (Upper and Lower Cow Lakes).

The Jordan Craters field is located on a high plateau approximately 200 kilometers southwest of Boise, Idaho. Access to Coffeepot Crater is best achieved by following US 95 north out of Jordan Valley, Oregon. The southern edge of the lava flow field is reached by traveling west out of Jordan Valley.

Return to:
[Jordan Craters Menu] ...
[Oregon Volcanoes and Volcanics Menu] ...