Question
As a retired person I'm involved in a activity known as Earthcaching. This is partly sponsored by the Geological Society of America and involves traveling to different geological features and answering some basic questions. One of these features I was directed to was just east of the Yuma Proving ground and the questions related to volcanic activity, this feature is located at 33.108983 -114.310528. My question for you is this hill the remnants of a cinder cone volcano as it's represented to be? I've not had any formal geology training but have completed several of these Earthcaches and what is represented as a volcano appears to me as a highly eroded mesa. I would appreciate if you could confirm or deny this location is volcanic in nature, thanks!
Answer
Hi Thomas,
Well it is certainly conical, but conical shape does not a cinder cone make. I copied the description for that area from our 1:1,000,000 scale map and pasted it below.
I don't believe this hill is or was a cinder cone. The rock debris certainly looks like basaltic rubble, but more likely to be associated with lava flows. Mike
Middle Miocene to Oligocene Volcanic Rocks (11-38 Ma)
Lava, tuff, fine-grained intrusive rock, and diverse pyroclastic rocks. These compositionally variable volcanic rocks include basalt, andesite, dacite, and rhyolite. Thick felsic volcanic sequences form prominent cliffs and range fronts in the Black (Mohave County), Superstition, Kofa, Eagletail, Galiuro, and Chiricahua Mountains. This unit includes regionally extensive ash-flow tuffs, such as the Peach Springs tuff of northwestern Arizona and the Apache Leap tuff east of Phoenix. Most volcanic rocks are 20-30 Ma in southeastern Arizona and 15 to 25 Ma in central and western Arizona, but this unit includes some late Eocene rocks near the New Mexico border in east-central Arizona.