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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 hour ago
River Mountains Loop Trail

Fyi......Trail news.
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Construction For Red Rock Canyon Multi-Use Paved Trail Will Start In 2025 At The Earliest - LVSportsBiz

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ADVERTISEMENT ADVERTISEMENT By Alan Snel, LVSportsBiz.com Publisher/Writer Shovels will start moving dirt in 2025 for Phase 1 of the much-needed
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River Mountains Loop Trail
3 weeks ago
River Mountains Loop Trail
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We consider the HRT the mother of the River Mountains Loop Trail. Full development of the HRT to Boulder City was a precursor to RMLT planning and development. This included opening of tunnel #5 which had been closed for years. ... See MoreSee Less

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i ride my bike that would be so much fun.

River Mountains Loop Trail
4 months ago
River Mountains Loop Trail

Anyone know what all the helicopter activity is off McCullough Hill Trail on back side of Black Mountain??? ... See MoreSee Less

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They're doing water main construction. I live near there and was notified about the project.

Probably dropping construction materials to one of those mega mansions in the hill

Looks like a recovery or a rescue. Its been happening for a couple of hours.

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