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You are here: Home / Geology of the River Mountains

Geology of the River Mountains

River Mountain Loop Trail

Volcanoes?

This phrase will certainly get the attention of many, particularly those who are not familiar with the geology of the River Mountains. This certainly explains why they are so rugged!

The River Mountains are composed of tilted and faulted mid-Miocene (15 to 12 million years old) andesite and dacite lava flows. Two volcanoes, the source of most of the lava, have been identified in the River Mountains. *

Strato Volcano

Volcano cross-section

Stratovolcano cross section – USGS file photo

The first, located just north of Boulder city, is a stratovolcano surrounded by numerous domes. Stratovolcanoes are cone-shaped features composed of lava flows interbedded with abundant agglomerate and breccia that formed from explosive eruptions. The surrounding domes formed by the eruption of very sticky lava such as dacite, which erupted to the surface but did not flow. Lava formed a low spine or a dome that quickly crumbled to a ring of debris about the dome.

Volcano with lava flow.

This could have been River Mountains 14-million years ago. The birth of a mountain range.

Shield Volcano

The second volcano, located in the northern part of the River Mountains, is a shield volcano – a broad volcano composed of basaltic and andesitic lavas similar to those erupting today on the island of Hawaii.

Both volcanos have been tilted, cut by numerous faults, and broken into numerous parts producing a jigsaw pattern of rocks that is now very difficult to recognize.

The photo below is of a cinder cone just a mile north and east of the River Mountains and can be seen from the trail between mile-marker 12 and mile-marker 14. Locally it is called “Lava Butte.”

Volcanic cinder cone, Henderson, NV.

Lave Butte, a volcanic cinder cone just north of the River Mountain Loop Trail.

* Reference material from Nevada Bureau of Mines and Geology Special Publication #16, “Geologic tours in the Las Vegas area.”

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River Mountains Loop Trail
1 week ago
River Mountains Loop Trail
Good morning  Las Vegas!!!

Good morning Las Vegas!!! ... See MoreSee Less

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My fave and I ride it every time I visit Vegas.. ❤️‍🔥

Any updates on the path damage from the rains? Thanks!

Awesome trail/path!!!

River Mountains Loop Trail
3 weeks ago
River Mountains Loop Trail

ALERT: YESTERDAYS HEAVY RAINS HAS DAMAGED TRAIL IN MORE PLACE THAN WE CAN LIST. BEWARE , BE SAFE, BE PATIENT IT WILL TAKE TIME TO FIX AND CLEAN, ... See MoreSee Less

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Special Thanks to the Guy with the Shovel cleaning up the Trail. You made it safe for many that rode the trail today..

Please call for volunteers if needed to help clean and/or repair.

The trail I somewhere under that mudd

Yesterday 8-6. Worse on the other side of tunnels.

Just a Little Muddy today..

Yesterday 8-6

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River Mountains Loop Trail
2 months ago
River Mountains Loop Trail

🌳 We are proud to announce City of Henderson Parks and Recreation Department has received a Finalist Award in the 2022 National Gold Medal for excellence in Park and Recreation Management. 🏆 Congratulations team!🎉 ... See MoreSee Less

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