If you have ever driven on interstate 40 in California, odds are that you have passed through
a volcanic field which erupted quite recently. 32 miles east of Barstow is a prominent black lava
flow which crossed both sides of the highway. This lava originated from a vent 10 miles away,
from what is called Pisgah Crater. This cinder cone volcano was only the latest in a series of
several vents to form in the Lavic Lake Volcanic field. Although this field is dormant, it could
erupt once again. This video will discuss this volcano, and mention what its future hazards are.
The Lavic Lake volcanic field exists in a section of California where the crust is
slowly spreading apart. This area is part of an area called the basin and range province,
which contains numerous lengthy faults. One of these faults, called the Lavic Lake fault, likely
offered the path of least resistance as lava at depth traveled upwards and onto the surface.
We aren't exactly sure when the first eruption occurred, but we do know that it occurred less
than 100,000 years ago. To date these young lava flows, we need to identify charred or
preserved organic material buried by lava flows. However, since the early volcano erupted in a
sparsely vegetated desert, nothing sufficient has been found to determine an exact age.
This first eruption was moderately explosive, and began with a series of small explosions.
Once the magma breached the surface, it formed a several hundred foot tall lava fountain.
This lava then fell near the vent which ejected it, and began travelling downhill to the east.
The lava which erupted had a very low viscosity, and moved at 5 to 10 miles per hour downhill.
This subsequently cooled as a dark black volcanic rock called basalt. As intermittent explosions
continued, it deposited ash which fell close to the erupting vent, thus forming a volcanic feature
called a cinder cone. After 4 square miles was covered with lava, the eruption ended. As lava
drained away, it caused the existing cone to collapse, forming a crescent shaped rim.
About 20,000 years later, lava once again reached the surface but this time
12 miles east of the previous eruption. Over the course of this eruption,
another cinder cone was built to a height of 250 feet tall above the surrounding landscape.
This eruption occurred in a series of moderately sloped hill, so lava first filled the valleys
between the hills, then flowed downhill to the north. Over the course of an eruption
that lasted many months, lava flowed up to 7 miles away, and created a flat black volcanic plateau.
The third eruption occurred adjacent to the Lavic Lake fault just to the south of the first
eruption. Over the course of this eruption, a darker colored basaltic lava overlaid the previous
lava flow to the north. After this eruption ended, faults moved the area by several hundred feet,
forming a very prominent fault scarp. This fault is the same one that produced the
magnitude 7.1 hector mine earthquake in 1999. The most recent eruption from this volcano
occurred 22,500 years ago, and produced the most famous feature in the overall volcanic field.
Initially, the lava which erupted onto the surface flowed outwards in all directions.
Over time, a 300 foot tall cinder cone called Pisgah crater was created by moderate volumes
of ash during minor explosive activity. Some of this lava traveled 10 miles to the northwest,
crossing what is now highway 40. However, lava also went in other directions,
as it was carried by a series of lava tubes. In total, four different eruptions occurred from this
cinder cone, and they may have been separated by thousands of years. After the eruption had ended,
lava solidified and drained away within the lava tubes. This created the largest
concentration of caves in southern California, many of which are more than 1000 feet in length.
Overall, this easily accessible volcanic field has covered 30 square miles with lava in the last
100,000 years. Although this field will erupt again, the odds of this occurring each year are
quite low at about 1 in 35,000. In the event of a new eruption, it would take place somewhere
adjacent to the existing volcanic features in the map I have shown on screen. Although a few
inches of ash would be deposited in a several mile radius, the eruption would most likely not result
in a high level of destruction due to the lack of structures in the area. The main threats would be
long distance lava flows, which could over time travel more than 15 miles from an erupting vent.
I hope that you enjoyed this video! If you would like to request a specific topic, please leave
a comment below! Additionally, if you wish to support this channel, consider becoming a patreon.