THE GEOMORPHIC EVOLUTION OF SHALLOW-SOURCED METHANE PRODUCED MUD VOLCANOES: LAKE POWELL, HITE UTAH

Mud volcanoes are typically viewed as positive landforms. At Hite, Utah shallow-sourced mud volcanoes are developing on the modern delta plain formed as the Colorado River enters Lake Powell. These features display a complex evolution that has not been documented from either modern or ancient mud volcanoes. Hence this work adds to the understanding of the geomorphic variability of short-lived mud volcanoes from initial activity to dormancy unrecognized in modern and ancient settings.

The mud volcanoes reflect two distribution patterns across the delta plain: linear, along slump failure planes and random, elsewhere. Mud volcanoes, developing nearest to the Colorado River, display a linear trend with caldera elongation parallel to the river. The river incision related to falling lake levels causes slope failure and creates a planar conduit for sediment and gas expulsion at vents. Farther from the river, larger mud volcano fields develop randomly with greater vent density.

These mud volcanoes display various stages of landform evolution, beginning as positive features then collapse to caldera-like forms. The initial form is a blistering phase, breaching the surface and leading to typical mud volcano landforms. The positive form actively erupts mud and gas from single or multiple clustered vents. After a period of eruption, the landform undergoes collapse and the positive inverts to a negative, caldera-like form that can then be either active or dormant. Active, collapsed forms can expel gas, up to 95% methane or potentially resurge to create another mud volcano in the confines of the caldera. As these conduits fill with sediment or gas pressure drops, the mud volcano becomes dormant.

These documented modern geomorphic changes in mud volcanoes illustrate the growth history of shallow-sourced, fluid escape features, from initial landform through dormancy that can potentially be recognized in the rock record.