Hi and welcome to Volcano Awareness Month
with the Hawaiian Volcano Observatory.
My name is Carolyn Parcheta,
and I'll be giving the first presentation in the month
on behalf of the entire geology staff at HVO.
Today, we're going to talk about the two eruptions we had
in 2021, which follows a two and a quarter year quiescence
at the volcano of no eruptive activity.
So let's jump right in.
This is going to be a 10 minute style talk.
This is not a 45 minute in-detailed science talk
but more just going to highlight the geology changes
that have happened over the past year.
If you want to hear about the seismic, gas,
or deformation parts of the eruptive history
of the past year, please come back every Tuesday this month
and those parts of the story
will have their own video to share.
There's some excellent information there
so please do come back every week.
What we'd first like to talk about or start with is 2020.
We had a water lake and the big question on our mind
was what's going to happen when magma returns
and lava reaches the surface because lava and water
are known to interact very violently
and cause major explosions.
And as you can see in the video,
we ended up not having a major explosion.
And there's a lot of steam
when the lava first starts erupting.
So why is that?
It was certainly a concern of ours that this was a potential
outcome when lava reached the surface again.
But what happened is that if you look in the infrared image
on the left, this is one of the first images
of the first fissure opening and lava was already
pouring down around the old Halema'uma'u floor
and into the water lake and that ended up boiling off
the water lake within 60 to 90 minutes.
During that time, this fissure propagated
across the old floor that is down-dropped.
And then there was a vent on the north side
that also opened up and this block,
this old floor of the crater,
became covered within the first day of the eruption.
Now even though we didn't see violent explosions
that were very large, we did see a few minor steam
and ash bursts from the eastern end of the lava lake,
over here, after it had replaced the water lake.
There was still some gas that could come through
and rip crust off the lava lake
and produced small amounts of ash.
We did see one of these plumes go over the road
but it didn't have any extra material
that wasn't already being produced by the fountains
when we checked the road for the deposit.
Now this video shows the north fissure
after the lava lake has significantly filled up
and the Halem'uma'u floor block is gone.
We're going to see something
really interesting in this video.
As the lava lake continues to rise it's going to shut down
the north vent and drown the fountain out
and the western vent, which is higher in elevation,
becomes more active and becomes the dominant vent
for the rest of the eruption.
Now, in this video you're also going to see that lava
had started to go back into the north vent,
you can tell by the convection pattern.
Now that daylight is breaking on this video,
you can see that the material coming in from the west
is actually pushing material up on the eastern side
and causing a reverse convection.
So as this video loops a second time
I'll point that out again and you can see that.
What's also interesting is that this island raft
as it approaches the northern vent,
that's also around the time that vent shut down.
And once the vent shuts down, it stops approaching
the northern wall and it backs off and goes back
into the center of the lake, which is really interesting.
These floating islands are not unique to this eruption.
Dr. Jaggar saw them when he first started HVO
in the lava lakes that he used to watch.
So here again you can see lava flowing into the north vent
briefly draining back down and then now you can see,
there's kind of a line here where material is coming
from the eastern wall towards the center of the crater
and also from the western wall from the vent.
And so we have kind of a upwelling convection
on the east side.
This is what's called a passive lava lake
where material flows in from the outside
and then it has nowhere to go so the material
as its molten and remains fluid, can convect around
and that's what all these different
plate patterns are showing us.
Now we have a few still image panels
showing that island raft moving
because it's kind of hard to see in the video.
This is the initial raft from the first day of the eruption.
And as the next couple of days progress,
it moves significantly north in the lake
towards that north vent.
When the vent shut down on the 26th it did back off
back into the center of the lake.
As the west vent started feeding more material,
we think that material helped push the raft
towards the west vent over here.
In early January, it did actually get really close
to the crater wall and then it backed off
and this ultimately did a 90 degree turn.
So this area of two peaks on the north side of the raft
in this December 30 image ended up facing the west vent
by the middle of January.
This is the total deposit eruption map
for the December 20 eruption.
It lasted until May 26 and when the total depth
of 226 meters or 740 feet.
The deepest part of the lake is right here in the center
in this brown color on the west side.
The total area here outlined in blue
is 45,000 square meters which is 111 acres.
If we were to cut this map in half,
we would have a cross section from west to east,
where this dashed line is the old pre-2018
Halema'uma'u crater floor and caldera floor.
The white line is the down-dropped block area
and this lower section is the old Halema'ma'u crater,
or what was left of it.
And then in here we've drawn this orange line
to show how much of the crater got filled
by this December 20 to May 26 eruption.
It's a total of 40 million cubic meters
which is about 10 and a half billion gallons of lava.
The peak effusion rate was 110 cubic meters per second,
which is 29,000 gallons per second.
And that's what these two plots here
on the bottom are showing us:
the total volume and then the eruption rate dying off.
Most of the higher eruption rates we saw
in the first three weeks and by day 20,
it had tapered off to a more consistent three to five
cubic meters per second every day for several months.
So this plot only shows
the first two months of the eruption.
We had a few months of quiescence
and then again on September 29th,
we had another fissure open up in Halema'uma'u crater.
It started off with this north-south oriented fissure
right in the middle of the lake right on the east side
of that main raft that is now rotated 90 degrees.
And we ended up getting another fissure on this west side
very shortly after this video ends.
It was above the western vent of the previous eruption
but basically in the same area.
As you watch this video, you can see the lava overtops
the old lake surface and some of these islands
that were previously formed get buried.
What was interesting is that through October
those rose up and so there's a buoyancy issue going on here
that was very interesting to document
and we're still trying to understand more about it.
Another interesting thing that we observed in October
and November and even now in December
is the surface of the lava lake has a slant to it,
which is a little interesting.
So, fluids usually make a very flat surface
and this is fluid rock.
But if you are standing here as the observer,
this is an image we would typically show
at our staff meeting showing all the measurements we make.
A lot of our updates come out giving an average number
or a single number, but in this particular image
it really highlights how much the lake is slanted,
the lake surface is slanted.
From the observer's view they measured the lava
being 327 meters below them on the eastern end of the lake,
but in the center of the lake
it was seven meters closer to them.
So higher in elevation.
And then at near the vent it was 313 meters
so another seven meters higher.
So there's a 14 meter, which is roughly 50 feet, 49 feet,
of difference elevation difference between the west end
of the lake and the east end of the lake.
That distance is about seven tenths of a mile
or 1.1 kilometers.
And that's a pretty big elevation gap.
So this is what we call dynamic ponding
where the material and the viscosity and the yield strength
of the lava basically pools up here.
It is very much similar to how if you pour syrup on a plate
or your pancakes it makes a blob first
and has to spread out.
And so at the end of the first eruption,
we did see the lava lake kind of correct itself.
The east end rose up and the west end sunk down a little bit
because all of this is fluid
under that solid crust that we see.
And that will probably happen again
whenever this eruption ends, but at the moment
there's anywhere from an eight to 10 to 14 meter difference
in the east and west elevations.
We're going to zoom into the far right part
of that former photo and this is another down-dropped block
that recently had some overflow
start to flow on to it on November 15.
And again the western vent area here on this left image
is in this photo, about 10 meters higher
than where the overflows are happening.
So there's a bit of a hydraulic or magmastatic head
if you will, that will help ooze this lava out as the crust
continues to rise above the level of this block.
It'll be a while before this one gets buried.
This is a very large block and is also inclined
so it won't be as easy to bury as the one
that got buried the first night of the first eruption.
In summary, the current eruption, which is still ongoing,
has already erupted almost the same amount of volume:
38 million cubic meters as opposed to 40.
So it's another 10 and a half billion gallons of lava
into Halema'uma'u crater.
It's added an additional 60 meters of depth,
which is just under 200 feet
and the surface area has expanded by 52 acres.
The peak effusion was 129 cubic meters per second
and that equates to 34,000 gallons per second
on the first day of the eruption.
That has also tapered off to an average of one to five
cubic meters per second for most of the eruption.
So here's that plot.
This is showing the effusion rate dropping.
In both cases, it dropped within the first 20 days
and maintained a low steady state.
And the orange line here is a 2020 eruption.
The red line is the 2021 eruption from September
showing the volume accumulation and again,
this is only showing the first two months of the eruption.
The 2021 obviously goes on for longer.
In the map here you can see the outline in red
of the current eruption and the current lake surface
and in blue you can see the end of May/early June outline
of the first eruption's lava lake surface
and so the difference between these two lines
is that 56 acres that was added to the surface area.
Sometimes these numbers are hard to comprehend
and my colleagues at the USGS did a fantastic job
making a visual that helps you understand
what all these numbers mean.
They compared the Empire State Building to our lava lake
right here at Kīlauea's summit in Halema'uma'u crater.
If you were to place the Empire State Building
at the bottom of the crater, you can see here
where the water lake would have risen to on that building.
This next orange plane between it and the top one
is where the first lava lake ended,
in terms of the first 40 million cubic meters.
And now we have another lava lake surface here
that is actually a little outdated, this is from October 5,
but it shows just how much more volume
has already been added with this eruption.
It's actually, the overflows are right here,
so this is actually several meters higher
than what this picture depicts.
But this is an excellent graphic to help comprehend
the sheer volume of lava that has been erupted this year.
Now the current activity.
If you'd like to see it, you probably can
but it's in kind of this on-again,
off-again quasi-steady state.
Previously, it was steady state but low level but constant.
Now we've noticed that with the tilt,
and the deflation-inflation events, it seems to turn off
and come back on and this lasts a day or two.
This line is kind of arbitrarily drawn across the DI events
but essentially at the bottom of the DI event
the lava seems to go away for a day or two
and then inflation will start
and then we'll see lava come back as the inflation recovers
and the pressure recovers.
It doesn't happen on some of these smaller ones
but it has happened on these three bigger ones
that the red line crosses.
As I was making this PowerPoint presentation
to share with you guys today, you can see we had started
a deflation and by the time I ended up recording
this presentation the lava was already gone.
It'll probably be gone for a day or two
and then if inflation starts again, it should come back
in a day or two and we're expecting to see this pattern
for a little bit, but one of these could be the last time
we see lava until the next eruption.
Just stay tuned and if inflation comes back
then lava should come back as well for now.
Alright, with that, I will say thank you very much.
It's been a pleasure to share the first Tuesday
of Volcano Awareness Month with you all
and if you have questions
please email us at askhvo@usgs.gov.
Please come back for other future talks
by the other disciplines because they will be covering
these same events but from their perspective
of seismicity, gas, and deformation.
Alright, have a great one everyone.