California is host to a number of large active volcanoes such as Mammoth Mountain and Mount
Shasta.
However, towards the northern part of the state, there are a large group of lava fields
which few are aware of.
These lava fields stretch between Lassen Peak to the south and Medicine Lake to the north,
and contain 6 different volcanoes.
Although none of these volcanoes have erupted in the last 10,000 years, they have each produced
eruptions recent enough to create black lava flows visible from satellite.
Of these volcanoes, the most notable is called Tumble Buttes, as it produced a series of
several hundred foot high andesite lava flows.
These lava flows originated from a chain of 11 cinder cones, which form a straight line.
Although this volcanic complex has not erupted for a long time, it will eventually erupt
again.
The Tumble Buttes volcanic complex is located within the northeast section of California.
Specifically, this volcano is only 10 miles north of the Lassen Peak volcanic complex.
Just like Lassen Peak to the south, the Tumble Buttes volcanic complex is considered to be
part of the Cascade Mountain range.
The reason why this volcano exists is due to the collision of the Juan de Fuca plate
underneath the North American plate offshore of California.
The melted crust from this collision then migrated upwards, before erupting on the surface
and forming a chain of volcanoes.
The Tumble Buttes volcanic complex is one of the most recent fields to form within the
state.
It began forming only 75,000 years ago, when magma erupted onto the surface via a zone
of subduction in the crust, which forms a straight line northward of Lassen Peak.
When this magma erupted onto the surface, it began forming aa lava flows out of a gray
rock typed called basaltic andesite.
Typically, this type of lava is only seen at stratovolcanoes, so this was quite unusual.
As this lava flow advanced to the southwest, intermittent explosions of ash began.
Much of the ash settled back near the erupting vent, thus building a 100 foot tall cinder
cone.
By the time this eruption had ended, a small 6000 foot long lava flow had overlaid part
of a pine forest.
The next sequence of eruptions along this volcanic chain formed two small cinder cones
50,000 years ago.
These cinder cones erupted an even more viscous type of lava called andesite.
Instead of creating a'a' lava flows, several hundred foot tall andesite flows slowly crept
across the landscape.
The most active and long term eruption occurred 35,000 years ago, which resulted in the creation
of 7 different cinder cones during a single eruptive series.
The most notable of the cinder cones formed during this time period is called Bear Wallow
Butte.
This butte output a mass of andesite lava which reached an impressive 500 feet thick
adjacent to the erupting cinder cone.
Today, the lava flows from this eruption only have small amounts of vegetation.
The most recent eruption in this volcanic complex occurred 12,500 years ago at a vent
2.5 miles to the north.
From this vent emerged a blocky andesite lava flow, which slowly built up over the surrounding
landscape.
As the eruption continued, the newly erupted lava eventually was unable to move beyond
the vicinity of the cinder cone due to the mass of newly solidified volcanic rock.
However, this lava later became channeled into a single direction, thus creating a series
of southward facing lava tubes.
Today, the collapsed remnants of one of these lava tubes is easily visible.
The eruption which had just occurred formed the lava flow referred to as the Devil's Rock
Garden.
When this volcanic chain erupts again, it won't pose much of a hazard to anyone due
to the remoteness of the area.
The next eruption will occur somewhere along the already existing volcanic chain, potentially
even partially overlapping an already present cinder cone.
The main hazard from such an eruption would be its several hundred foot tall blocky lava
flows.
These lava flows would advance across all terrain, although generally in a downhill
direction.
In total, areas up to 4 miles away from an erupting vent would be put at risk.
Additionally, large amounts of carbon dioxide gas would be emitted, so an extended evacuation
radius would be necessary.
Overall, the odds of the Tumble Buttes producing another eruption are about 1 in 18,000 each
year.
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