Image 1 of 1
Oregon, southeast, consolidated lava cliff in Leslie Gulch. Geological formations in Leslie Gulch of southeast Oregon are unique and striking. They are often similar in appearance when compared to the color and texture of the eroded sandstone regions of the southwest. However, the Leslie Gulch geology is quite different. The impressive patterns, shapes and forms are consolidated volcanic ash from a series of eruptions around 15.5 million years ago. Fine ash and rock fragments from the eruptions fell back into the volcano and left deposits up to 1,000 feet thick. About 100,000 years later, this substance was buried with deposits from other volcanic eruptions nearby. Since then gradual erosion has left some of the harder material behind creating what we see today as towering cliffs, arches, honeycomb like features and other unique textures and forms. These remarkable characteristics have lead geologists to call it the Leslie Gulch Tuff to distinguish it from other landscapes formed by ancient volcanic activity.