Geology of the National Parks

GeoMations and GeoClips


There is one GeoMation and there are four GeoClips available for your viewing in this unit. Hopefully, you'll find this helpful in understanding Unit 5 just a little bit better.



We can measure the uplift of mountains, which may occur slowly, or suddenly in earthquakes, and we can watch volcanoes erupt. But overall, nature tears down mountains about as rapidly as they form, and we can watch and measure the tearing-down, too. The slow disappearance of names from old tombstones, the hubcap-rattling holes in late-winter city streets, and the maintenance budget for university buildings all attest to the effects of nature on human-made things. Here, Dave Witmer takes you to Bryce Canyon, one of the many, many places where you can see nature removing natural things.

Erosion at Bryce Canyon National Park

Geologists observe the wear-and-tear of nature on human-made and natural things, gaining clues to help understand how mountains are torn down. When climbing the sheer cliffs of Zion National Park into the mysterious crevice of Hidden Canyon, the intrepid hiker clings to a rather precarious-looking chain to avoid falling into the stream-carved potholes just beside the trail, and on down to the Virgin River, in the Canyon a hair-raising drop below. In these two clips, Dave Witmer and Dr. Anandakrishnan show how rocks are worn away, a little at a time, and what this has to do with south-Indian cuisine. You might begin thinking about what this wearing-away of rocks has to do with the Virgin River in the Canyon far below.

Chain of Events / Zion National Park

Pothole Grinding / Zion National Park

Rocks and soil on hillsides really do slide down, whether rapidly or slowly, in big chunks or small ones. When a river erodes downward to make cliffs in the riverbank, or when a volcanic eruption or an earthquake makes a cliff, rocks fall or creep or slump or are washed off the steep slope, smoothing it over time. Here, Dr. Alley shows this for a tiny "canyon" in the bottom of the truly Grand Canyon.

Making a Sand Canyon / Grand Canyon National Park

Want to see more?

Enrichment: More movies for you to enjoy—and these two won't be on a quiz. Erosion has carved fantastic forms from rocks, and weathering is important in loosening pieces to be transported away. Here, National Park Service Ranger Jan Stock and the CAUSE students explore weathering in Bryce National Park, and then Dr. Richard Alley explains changes at Delicate Arch in Arches National Park.

Bryce Windows and the Freeze/Thaw Cycle, (Transcript)

Forming Arches (Transcript)

Here are some optional animations you might also want to explore! (No, these won't be on the quiz!)

Soil Erosion
(An extensive collection of animations on this subject)

Mass Wasting/Landslide Animations
(An extensive collection of animations on this subject)