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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
15 hours ago
River Mountains Loop Trail
Hi All,

The RTC, Southern Nevada Bike Coalition and Trek bikes are hosting a bike safety/maintenance class this Sunday at their Henderson store (formerly McGhies)

Hi All,

The RTC, Southern Nevada Bike Coalition and Trek bikes are hosting a bike safety/maintenance class this Sunday at their Henderson store (formerly McGhies)
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River Mountains Loop Trail
2 weeks ago
River Mountains Loop Trail
Do you know what section of the trail this is?

Do you know what section of the trail this is? ... See MoreSee Less

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When I rode it and it was 95⁰ outside, I called it "F-ing with Death"

Isn’t this behind that water treatment plant??

Fun, depending on which way you’re riding!

It’s the part that’s about 1 mile behind my house!!!! I ride it every weekend! 😂

yes, that section with the hills is by the rest stop at river mountain water treatment

I have been away from Vegas for 10 YEARS and the only part of the trail I can picture in my mind are those 3 sisters. Not what I called them then

Glad they finally put the warning for wildlife lookout. There's a drinker there and a few times near miss for bighorn sheep while coming down that hill

Before the 3 sisters

no shade at all. smh 🤦‍♂️

Yes

After the Casino

The whoop section!

Sweet rest stop.

Rolly 🤣

Nice place to separate your shoulder at… 😂

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River Mountains Loop Trail
3 weeks ago
River Mountains Loop Trail
The Rage Triathalon will be held this Saturday morning April 30th at Boulder Beach/Hemenway Harbor. Expect increased traffic near the trail especially near Boulder Beach. The bike and foot race will not be using the trail for their event.

The Rage Triathalon will be held this Saturday morning April 30th at Boulder Beach/Hemenway Harbor. Expect increased traffic near the trail especially near Boulder Beach. The bike and foot race will not be using the trail for their event. ... See MoreSee Less

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