(light upbeat music)
My name is Kendra Lynn,
and I'm a new research geologist
at the Hawaiian Volcano Observatory.
My research focuses on using
the chemistry of rocks and minerals
to better understand
how, when, and why
Hawaiian volcanoes erupt.
For Volcano Awareness Month,
I wanted to talk about
my favorite mineral, olivine.
It's actually very common
in Hawaiian rocks.
So anytime that you're out on a hike,
and you look at a lava
and you see these little green minerals,
that is the mineral olivine.
Now, olivine is one of
the most common minerals
on our planet.
In fact, we think that most
of the interior of the Earth
is made of this mineral,
but it's also very common
in Hawaiian lavas
and using olivine,
I can learn a lot about the magma history.
Where it moved,
how it was stored,
and what happened to this magma
before it erupted at the surface.
Another cool thing I like about olivine
is that if anybody
has a birthday in August,
the birthstone for August
is called Peridot.
Peridot is the gem-quality
variety of the mineral olivine.
So all you August birthdays out there,
this is your mineral.
Olivine is a relatively simple mineral.
It's primarily composed
of iron and magnesium atoms,
and we can measure these compositions
in the minerals using a variety
of different techniques.
So part of my job is to be out
in the field collecting samples,
but perhaps the bigger part of my job
is to be in the lab.
We can look at these minerals
using a scanning electron microscope
and that actually tells us a lot.
We can infer how hot the magma was,
so we can get temperature
with this iron and magnesium measurement,
and changes in these
iron and magnesium contents
also tell us a lot about time.
So we can actually look at changes
in the chemistry to think about
how long the magmas
were sitting inside the volcano.
When we measure the composition of olivine,
we are often working
with our partners at
the University of Hawai'i at Hilo.
They have a scanning electron microscope,
and we can take our samples
and use that instrument to map
all the different elements that are present.
Most of the time we try
to study phenocrysts,
which is just a geologic term
for a crystal that's typically
greater than a half a millimeter in size.
And these phenocrysts,
which are kind of larger minerals,
those are primarily only olivine.
So after we go out into the field
and we collect a sample,
we usually bring back a bag
that's sort of a mixture of
fragments of older rocks,
some fresh lava,
or we call it juvenile material,
and then in this bag
are also olivine crystals.
Using the microscope,
we can search through this mixture of material
and pick out the olivine crystals
that we can then study.
And ultimately, after we pick our crystals,
we will polish them and mount them
so that we can put them in instruments.
And this is one example
of an olivine mount.
These are Keanakako'i olivine,
and they're mounted in a metal disc
that's then been coated with gold.
And so each one of these
little shiny surfaces that you see,
each one is an individual olivine crystal
and we've cut them in half
and prepared them for the instrument.
One of the techniques
that I'm really excited to apply
in Hawaiian volcanoes research
is called diffusion, diffusion chronometry.
Each individual crystal
is like a little stopwatch.
It's a time capsule of information
and if we know how to read
the chemistry correctly,
we can get at how long the magmas
were inside the volcano
before they erupted.
This map is one example
of what a Kilauea olivine
looks like when you measure it
with an electron microprobe.
We're looking at the distribution
of iron in this olivine crystal
and you can see based
on the color changes
that there's more iron
in parts of the crystal compared to others.
And there's kind of a gradient between them.
In this case,
I would make a measurement
between the core of this crystal and its rim,
and use that information
to think about the timescales
of this magma storage process.
These olivine crystals
from Kilauea's December 2020 eruption
have forsterite zoning,
shown as dark gray cores
with light gray rims
in these scanning electron microscope images.
Most December 2020 olivine crystals
have modeled diffusion times
of about 60 days or less.
This suggests that the crystals,
which originally grew deeper
inside the volcano,
moved up to a few kilometers
or less than two miles
below the ground surface
about 60 days before they erupted.
At that time,
in late October of 2020,
HVO detected the first set
of earthquake swarms
during the period of unrest
leading to the eruption.
These olivine crystals show
that the earthquakes were due
to magma intruding shallowly
underneath Kilauea summit.
There are also some zoned olivine crystals
from the September 2021 eruption
that are being modeled right now
to calculate the timescales
from these most recent crystal clocks.
Using diffusion in olivine
is actually a really
important tool for us
because it helps us to understand
eruptions that occurred prior
to any scientific monitoring.
So we know that Kilauea
is very dynamic volcano
with lots of effusive eruptions
that characterize sort of our historical past,
but before that Kilauea
was actually quite an explosive volcano
during the period we call the Keanakako'i Tephra.
Most of these eruptions,
especially the Keanakako'i Tephra
and other prehistoric explosive periods,
they occurred prior
to the arrival of Western visitors
to the Hawaiian Islands
and not many are recorded
in native Hawaiian oral tradition.
And so we have very little
scientific monitoring data
and we have very little
observational data
that tells us what
these eruptions were like.
We're hoping that we can use
the mineral chemistry
to fill in the gaps of this knowledge,
so that we can have a better understanding
of what was going on
at the volcano during these times.
As an example,
what olivine is telling us
about Keanakako'i is that
the plumbing system,
the magma reservoirs beneath the surface,
was actually very different
at Kilauea during this explosive time
compared to the modern effusive period.
From the timescales modeling,
we know that magmas during Keanakako'i
were coming in from deep
into the shallow parts of the system
and mixing with other stored magmas.
Now these mixing events
were occurring anywhere
from a few weeks to a few months
prior to each eruption.
And so using this information,
we're getting a better understanding
of how the volcano evolved over
this 300-year period
of mostly explosive eruptions.
We want to keep looking
at these prehistoric eruptions
to learn as much as we can about them.
We also want to apply diffusion chronometry
on Mauna Loa eruptions.
And we can also use these techniques
on Hualalai and other volcanoes in Hawaii.
Overall, we hope to get a better understanding
of how these volcanoes evolved
long-term over hundreds,
maybe thousands of years.
Having a better understanding
of how Hawaiian volcanoes
have evolved over centuries
and thousands of years,
gives us a better idea
of what future hazards might be
if the volcanoes start to erupt
in this different explosive style.
(light upbeat music)