The state of California has several volcanoes which are classified as active.
Of these, the most recent volcanic eruption occured from Lassen Peak in 1917.
However, Lassen Peak is not the only volcano within california which could erupt in the
near future.
In northern california, there is a volcanic field in a heavily populated area.
The volcano I am referring to is the Clear Lake Volcano.
Although this volcano is currently dormant, it is still geologically active.
At some point in the future, this area will produce another eruption.
This video will discuss this unique volcanic field, and mention what its future hazards
are.
For this video, we are defining a dormant volcano as any volcano or volcanic field which
has not erupted in the last 10,000 years, but is likely to erupt again at some point
in the future.
The Clear Lake volcano is a volcanic field which can be found in the central-northwestern
portion of the state.
Specifically, it can be found 90 miles north of San Francisco.
The clear lake volcanic field is named after the large freshwater lake called clear lake.
Despite its appearance from satellite, this lake was NOT formed from a caldera collapse.
This volcanic field exists due to an ancient triple junction related to the san andreas
fault.
It contains cinder cones, lava domes, and maars.
The Clear Lake Volcanics erupted during four periods of time beginning at about 2.1 million
years ago.
Most of these eruptions took place to the south, east, or southeast of the large clear
lake.
The oldest eruptive period lasted for about 800,000 years, and largely deposited dark
colored basalt over a vast area.
During this period, the area which is now Wilbur Hot Springs and the gold and mercury
ores at the McLaughlin mine formed.
The second eruptive period began 1.1 million years ago and lasted for 300,000 years.
This eruptive period featured eruptions of lower temperature lavas which produced rhyolite
and dacite rock.
One of these eruptions created Mount Hannah, which may have been formed in as little as
100 years (5,000 years is a more likely estimate).
The third eruptive period began 650,000 years ago and continued until 300,000 years ago.
Compared to the previous periods, this serious of eruptions took place northwest of other
lava flows.
One of the largest series of eruptions formed the highest point in the volcanic field, Mount
Konocti.
It climbs to slightly over 4300 feet above sea level.
The last eruptive period took place from 100,000 to 11,000 years ago.
These eruptions features a mixture of basalt, basaltic andesite, and andesite, which is
different than the two previous periods.
One of the features which formed during this period was little borax lake.
This lake was the result of an explosive eruption which is called a phreatic eruption.
Phreatic eruptions occur when rock heated from nearby magma causedes water in the volcano
to flash to steam and explode.
This style of eruption does not produce lava, but is still rather dangerous.
Between 60,000 and 11,000 years ago, this volcano erupted about once every 1800 years.
As of 2021, the clear lake volcanic field has not erupted in a little over 11,000 years.
A future eruption is eventually certain, but it may take several more thousand years before
a new eruption occurs.
Beneath the volcano, there is still a magma chamber which is about 4 miles or 7 kilometers
beneath the surface.
If a future eruption was to occur, it could erupt in a number of ways.
The most likely future eruption style is a phreatic eruption which does not involve erupted
magma, much like what formed little borax lake.
This eruption style is explosive, but is considered to be a relatively small type of volcanic
eruption.
Although the clear lake volcano is dormant, the US geological survey assigned the volcano
a high risk rating.
Why?
Simply put, the region is still geologically active, and about 50,000 people live within
3 miles of this volcanic field.
Additionally, the size of the magma chamber that feeds this region is very large, and
contains more than 330 cubic miles or 1400 cubic kilometers of lava.
I hope that you enjoyed this video.
If you would like to request a specific topic, please leave a comment below.