Walking on Volcanic Domes in the Salton Sea Area: Mar 2020

Updated: Mar 7


The more I explore the Salton Sea area, the more interested I become in this strange and exotic location. For a primer on the Salton Sea, be sure to check out the main blog by clicking Salton Sea.


Today, we headed to Obsidian Butte which is part of the Salton Butte complex. The five Salton buttes are lava domes formed from viscous magma that rose from an 820 foot wide (estimated) volcanic vent located along the southeastern edge of the Salton Sea. The highly viscous magma was too thick to flow very far and piled high around the vent. Obsidian Butte formed as a result of this lava flow. Estimated to be a 2000 to 3000-year-old, this volcanic dome consists of pumice and black obsidian.

Obsidian Butte on Salton Sea shore in California 

We followed the dirt road from the base of the butte toward the shoreline. The butte has been extensively quarried, to the point that it has lost most of its original appearance. However, piles of rock debris and outcroppings of obsidian are everywhere.

Walking the Obsidian Butte trail on Salton Sea shore in California 

Once we entered the area surrounding the butte, the obsidian flow seemed to go on forever. The butte was formed by effusive eruptions, a type of volcanic eruption in which lava steadily flows out of a volcano/volcanic vent onto the grounds (versus explosive eruptions like Mount Saint Helens).

Obsidian flow around the butte in Salton Sea area 

What is obsidian? Obsidian is an igneous rock that forms when slow moving lava cools so rapidly that atoms are unable to arrange themselves into a crystalline structure.

Obsidian is an igneous rock that forms when slow moving lava cools rapidly. Obsidian Butte Salton Sea area
Obsidian is an igneous rock that forms when slow moving lava cools rapidly. Obsidian Butte Salton Sea area

We climbed over a bunch of the flow before making our ways onto the shoreline.

Obsidian flow in Obsidian Butte in the Salton Sea area

Some small pieces of obsidian we found resembled volcanic glass with a smooth dark appearance while others had a more banded appearance.

Obsidian rocks from Salton Sea area in California
Banded obsidian rock sample from Salton Sea area

On the beach were huge outcroppings with salt and sediment crusts from the once higher water levels of the lake.

Obsidian flow runs all the way to the Salton Sea shoreline

Until recently, the Salton Buttes were thought to have erupted 30,000 years ago, but new data concludes the most recent volcanic activity occurred between 2000-3000 years ago, making them the youngest volcanoes in California. Since USGS considers any volcanic eruption less than 10,000 years old as an 'active volcanic area' the California Volcano Observatory investigates and monitors the Salton Buttes.

Huge piles of obsidian flow along the at the Salton Sea area

Obsidian Butte and the other Salton Buttes (North Red Hill, South Red Hill, Mullet Island and Rock Hill) are located above the boundary between the Pacific Plate and the North American Plate. Deep underground, the plates are moving away from each other forming a spreading center. As the plates spread, magma from deep in the earth wells up to fill in the gap that was created. This large body of magma was most likely the source of the effusive eruptions. Today, the area is tapped by geothermal power plants in the area and is referred to as the Salton Sea Geothermal Field.

Steam rising from Salton Sea Geothermal plant along Salton Sea

The lava source beneath the Salton Sea heats brine 1.0-1.5 miles beneath the earth's surface to 680°F. This superheated brine is the source for the geothermal plants, which are considered to have one of the largest geothermal potentials in the world. These plants produce enough energy to power up to 325,000 homes.

Steam rising from Salton Sea Geothermal plant along Salton Sea

A field of small mud volcanoes or mud domes are located near the Salton Buttes. The mud produced by these volcanoes is formed as hot water, heated deep below the Earth's surface. It then mixes with subterranean mineral deposits and creates the mud slurry. This slurry is forced upwards through a geological fault or fissure. The temperature of any given active mud volcano generally remains fairly steady and is much lower than the typical temperatures found in igneous volcanoes. Mud volcano temperatures can range from near 36-212 °F. Unfortunately, the area surrounding the field was marked with 'No Trespassing' signs so we weren't able to get any closer.

Mud domes are located near the Salton Buttes along Salton Sea shoreline

I'm definitely going to plan a second trip to the buttes. Once again, the more I learn about the Salton Sea area the more excited I become to plan future visits.

Salton Sea beach along Obsidian Butte

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