San Felipe, Baja, Mexico  
This Joe has Two Volcanoes

The Enchanted Islands emerge from the Sea of Cortez just off the coastline of Baja between Puerocitos and Gonzaga Bay. These are small islands with Isla San Luis reported as being the largest at less than four square miles. Do not let the size or the fact that it is named for a Saint fool you because this island provides a home for two volcanoes. Scientists believe that this volcano has erupted within the past 500 years. That is a very short period of time for a volcano, something on the order of a heartbeat.

I have been going to this area for many years and found that all of the beaches from Puertocitos south are littered with pumice mostly a very light red in color but some a light gray. I had read of an annual pumice release, didn’t much believe the annual part so I started to search the www and found the information that I wanted at Once you begin a web search it is amazing what can be found and the inane matches can be either frustrating or amusing. This site details work done by Dr. Brian Hausback of the University of California Sacramento, Dr. Hausback has allowed me the use of the information providing that I give credit. The site also has photos along with some awesome spectral images taken from satellite. The photos are copyrighted fortunately I have many of my own except the ones taken and transmitted from space.

A Wealth of ObsidianCurrent activity suggests that this volcano is likely building for another explosion. The active gas vent and the fact that this island is rising at a rate faster than anything else in the area point toward a future eruption. The gas vent is reported to be on the north side of the island but I don’t know exactly where it is located. It is rare that an island of this size has two volcanoes even more astounding they are different types. One is a cinder cone and the other a lava flow (it suddenly seems that Lava Soap should be named Pumice Soap). A telpha ring or cinder cone is formed as the material that has been exploded from within the earth settles back to earth. The entire south end of the island is cinders and that is reported as a massive amount.

The telpha ring has one side missing and is named Plaza de Toros. The lava flow has capped the highest part of the island with a dome of obsidian or natures glass. One word about obsidian, it cleaves sharper than man can sharpen anything and Indians native to North America have been using it for hundreds of years. A hike up to the obsidian dome will take you through a rookery of brown pelicans and sea gulls. Let your imagination run wild about the odor. Arriving at the flow I see pieces of obsidian much larger than anything that I have seen in Quartzsite which is billed as the world’s largest gem and mineral show. Ten miles from the island I have found many Apache Tears which are essentially obsidian raindrops

Still searching for the pumice release and now we know that Isla San Luis has active gas vents; does pumice come up with some of the gas releases? A fellow from the US who now lives at Punta Willard has observed the island calving. I am guessing that he saw this from shore and that would represent a large amount of pumice being released into the sea water. Running through small patches of this with the boat is fun and it cleans the bottom of the boat. When approaching from the open side of Plaza de Toros distinct layering is evident and looks very much like sedimentary layers. Closer observation reveals that these layers are all composed of cinders. On the island one can see many places where the cinders have collapsed leaving near vertical walls.

When the new road from Puertocitos to Gonzaga Bay was being built a very thick layer of black cinders was exposed between La Castillo and Nacho’s camp. These are a soft composition and scrape away very easily, now I believe that Isla San Luis is responsible. South of Gonzaga there is reported to be large deposits of cinders again spawned by our small but violent island. And speaking of violent what happened to the south side of our cinder cone? A blow out through the side, something like Mount Saint Helens on a smaller scale could have taken it away. My guess would be natural erosion from storms in the Sea of Cortez which would cause intermittent releases of pumice.

The cinder cone is very likely the more dangerous of the two volcanoes. The seagulls firmly believe that they own the Plaza de Toros and they do not hesitate to show their irritation at your presence. Once a friend and I started to walk across the lowest part of Plaza de Toros’ as we approached the center of the depression our footing became more and more soft. When we were sinking past our ankles on every step I succinctly declared “I ain’t going any farther”.

The island is like a magnet it continues to pull me ashore whenever I get close.

Note: This is the area that host’s the “Three Terrible Sisters”. The new road has done a good job of taming the sisters. The old road was much, much worse and I have a collection bent and broken suspension parts to offer as proof. Now I ride my ATV along the old road and reflect on how tough these hombres really were.

Ray Alexander
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