The San Francisco Volcanic Field in northern Arizona (shown above) is one of several late Cenozoic volcanic fields located along the
southern margin of the Colorado Plateau.
Volcanic activity began about 6 million years ago in
the western portion of this field and continued intermittently, culminating in
the eastern portion of the field approximately 900 years ago with the eruption
of Sunset Crater Volcano (pictured left). There are on the order of 600 volcanic vents in the area.
My work focuses on volcanoes and lava flows located in the eastern portion of the field, including Sunset Crater Volcano and the lava flows at Wupatki National Monument. I am geochemically evaluating cinder cones and lava flows with the goal of creating a volcanic history of the region and determining the source of the melt.
My work focuses on volcanoes and lava flows located in the eastern portion of the field, including Sunset Crater Volcano and the lava flows at Wupatki National Monument. I am geochemically evaluating cinder cones and lava flows with the goal of creating a volcanic history of the region and determining the source of the melt.
The fumarole deposit to the left, located on the summit of Sunset Crater Volcano, was deposited as hot gasses and steam escaped from the volcano during the waning stages of eruption less than 1000 years ago; just yesterday in geologic time
This is me sampling the Grand Falls lava flow. This flow, a mere 20,000 years old has long been attributed to the eruption of Merriam Crater. Geochemical evidence collected in this study suggests that another volcanic vent, The Sproul, was responsible for this eruption.
Hanson, S.L. (2009) Evaluation of Potential Source Vents for the Grand Falls Lava Flow, San Francisco Volcanic Field, Northern Arizona. GSA Abstracts with Programs. v. 41, no.7, p. 644.
Hanson, S.L. (2009) Evaluation of Potential Source Vents for the Grand Falls Lava Flow, San Francisco Volcanic Field, Northern Arizona. GSA Abstracts with Programs. v. 41, no.7, p. 644.
The Grand Falls lava flow effused eastward and plunged into the Little Colorado River channel forming a lava dam that created an upstream lake. The lake has since filled with sediment and the river cut an new channel across the sediment filled lake, around the toe of the flow, and now cascades into the pre-dam channel at Grand Falls.
The river only flows intermittently, usually during the Spring snow melt and in late summer during the monsoonal rains. For the remainder of the year, the falls are dry.
Perhaps the most unique feature of this waterfall is the color of the water. Much of the upstream flow meanders across the deep red Triassic Moenkopi Formation. Eroded sediment from this formation is carried downstream by the river giving the river a reddish-brown color. For this reason, the falls are often called the "Chocolate Falls."
The river only flows intermittently, usually during the Spring snow melt and in late summer during the monsoonal rains. For the remainder of the year, the falls are dry.
Perhaps the most unique feature of this waterfall is the color of the water. Much of the upstream flow meanders across the deep red Triassic Moenkopi Formation. Eroded sediment from this formation is carried downstream by the river giving the river a reddish-brown color. For this reason, the falls are often called the "Chocolate Falls."