Lava Onion? Lava flow - peeling back the layers.

Lava flows are one of the coolest (or maybe hottest!) features about volcanoes, but what would a lava flow look like if you could peel away the surface and take a peek underneath? For lava flows that cool slowly, you might see spectacular columns. Find out more in the November 2023 update from the USGS Yellowstone Volcano Observatory. 

Sheepeater Cliff is named for a band of the Shoshone tribe that lived in the Yellowstone area year-round and subsisted off of bighorn sheep. 

The cliff is a great example of columnar jointing in a basaltic lava flow. We can learn a lot about the cooling history of the flow and the cooling surface that the flow was up against by taking a closer look.

The first thing we learn is that this lava flow cooled very slowly. When lava cools slowly, it contracts. The contraction forms columns that have somewhat hexagonal shapes when you view them from above.

Another thing we learn is that the cooling surface was horizontal. The cooling surface is always perpendicular to the direction of the columns. In some places, you can see horizontal rather than vertical columns if a lava flow or ash flow cooled against a canyon wall or maybe even the side of a glacier.

Columnar jointing is observed in many places in Yellowstone, near Tower Junction, in the walls of the Yellowstone River Canyon, and Obsidian Cliff. Examples of columns outside the Park are found at Devils Tower, Wyoming, Devils Postpile, California, in the Columbia River Gorge of Oregon and Washington, the Giant's Causeway in Ireland, and many places in Italy. In Iceland, there's a place where columnar joints actually form the floor of a church because the hexagonal pattern resembles a tiled floor.

That’s the story of Sheepeater Cliff. Now, let’s look at recent seismic, deformation, and geyser activity in Yellowstone.

During the month of October 2023, the University of Utah Seismograph Stations, which monitors and operates the Yellowstone seismic network, located 113 earthquakes. Deformation trends continue as with previous months. At the end of October, snow on GPS antennas showed up in the data but is not related to ground deformation. Steamboat Geyser had one water eruption on October 8. Yellowstone Volcano remains at normal, background levels of activity.

For questions, email yvowebteam@usgs.gov

Read Caldera Chronicles https://www.usgs.gov/volcanoes/yellowstone/caldera-chronicles

Visit Yellowstone Volcano Observatory website https://www.usgs.gov/volcanoes/yellowstone