If you have ever driven through Santa Clara or Diamond Valley in Utah, you have likely passed
through the black lava flows of a recent volcano. The volcano in question is called Santa Clara,
which had produced two recent eruptions. Its lava flows contain an abundance of caves and
lava tubes, along with other recent volcanic features. Although this volcano is dormant,
it could erupt once again in the future, threatening nearby cities. This video covers
the recent eruptions from this volcano, and states the general hazard which it poses in the future.
The Santa Clara volcanic field in southwestern Utah contains dozens of volcanic vents which
have erupted over its history, which cover an area of 617 square miles. Some of these
vents are quite recent, while others are older and have very high levels of erosion.
The reason why this volcanic field exists is due to stretching of the crust in this
section of western Utah. This stretching has created thin zones in the crust which allows
magma to travel upwards and erupt onto the surface. Since this magma originated
directly from the mantle, it largely erupted as a dark black volcanic rock called basalt.
The Santa Clara volcanic field began forming 2.5 million years ago, as magma first reached the
surface 4 miles north northwest of the town of Washington. This first eruption began with the
creation of three distinct cinder cones. These cinder cones intermittently ejected bombs of
lava in small explosions, but primarily ejected lava in an effusive flow of lava. This lava then
flowed downhill for 6 and a quarter miles. The lava was deposited on top of sedimentary rock,
creating a beautiful contrast between white limestone and black basalt.
Since this eruption ended, large segments of rock have been eroded, creating unusual
features such as this hill called t bone hill. Over the next several million years, intermittent
eruptions occurred which once again created more cinder cones along with flows of lava.
One of these eruptions 1.23 million years ago is quite notable as saint george airport is now built
on top of it. When the eruption occurred, the plateau which the airport is built on did not
exist and instead was one of the many valleys in the local landscape. This valley funneled the rock
into creating an elongated shape, representing an ancient dry wash. After the eruption ended,
the weaker sedimentary rock around the volcanic rock eroded. Since basalt is much harder than
limestone or sandstone, it remained thus creating the beautiful plateaus. This change
in topography is called an inverted valley. Over time, the numerous eruptions began to
slowly trend in a northward direction. For example, the well defined cinder
cone south of the town of Veyo formed 690,000 years ago, which today is 700
feet taller than the surrounding landscape. However, the most famous eruption in the Santa
Clara field occurred 27,000 years ago. This eruption began with a series of explosions, as
lava first breached the surface. As lava continued to pour outwards, small explosions deposited ash
around the erupting vent. This formed a 250 foot tall cinder cone and adjacent spatter cone west
of the town of Diamond Valley. Over the course of this several month long eruption, a large
quantity of lava flowed downhill via a series of valleys. Eventually, this lava reached what is
now the town of Santa Clara, which was 7 miles away. This eruption deposited a prominent layer
of black volcanic rock which today is the site of numerous lava tubes and even a golf course.
The most recent eruption occurred 4000 feet to the north of the prior eruption. This eruption
formed a much younger looking cinder cone called the diamond valley cone. Although
we aren't sure how old this volcano is, it could very well have erupted in the last 10,000 years.
If this was the case, the Santa Clara volcanic field would be classified as active. However,
based on the level of erosion around this vent, I estimate its age at about 15,000 years old.
Since then, no additional eruptions have occurred. Overall, the Santa Clara volcanic field is a
dormant volcanic field which is unlikely to erupt in the near future, but will awaken once again in
the more distant future. Such an eruption could occur anywhere in the volcanic field,
including in highly populated areas such as Saint George and Santa Clara. The main hazard from such
an eruption would be a slow moving lava flow. The odds of a future eruption occurring is quite low,
at about 1 in 40,000 each year. I hope that you enjoyed this video!
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