Scientist Explains What Water Pooling in Kilauea's Volcanic Crater Means

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This is Kilauea, one of Hawaii's most active volcanoes.

In 2018, it erupted and destroyed around 700 homes

and forced thousands to evacuate.

Since then, a lava lake that had been boiling

at the volcano's summit has been replaced

with something exceedingly rare, water.

So, how did all this happen, and what does this all mean

for Hawaiians living near the volcano?

To learn more, we spoke with a scientist at the USGS.

My name is Don Swanson.

I'm a geologist with the Hawaiian Volcano Observatory

of the US Geological Survey.

I'm retired, but I've been working

on volcanoes for my entire career.

So, most of us have heard of Kilauea,

but maybe walk us through some basics about the volcano

and what been happening in the past month or so.

Well, it was erupting almost continuously for decades

until last summer when a barrier that

had been keeping magma from getting

beyond that point failed somehow.

And so magma was then able to travel down the rift zone,

and the largest lava flow during recorded history

was erupted farther away from the summit,

destroying more than 700 homes and creating a lot of havoc.

The lava lake at the summit,

which had been present for 10 years,

began to drop down very rapidly.

And eventually, the entire summit collapsed,

the caldera collapsed, up to 500 meters, a little more,

and was quite quiet until July 25th

when we saw the first visual change

of the volcano in a year, and that was the appearance

of this green water pond in the bottom of the crater.

And that's the interest that we currently have.

So do we have a good idea yet

whether this is water that is just rainfall sitting

at the surface or whether this is water

that may be bubbling up from deeper in the ground?

That's a really good question,

and we don't know the definite answer for that yet.

But what we think it is is water

that is slowly infilling from below,

rising up into the low part in the crater.

There still remains the possibility

that it's rainfall that is directly feeding the pond,

but we don't think that's true

because the rate of rise of the pond, the rate of growth,

has been pretty steady, slow and steady now

since it was first recognized, and that's more consistent

with slowly rising water table than with rainfall.

So if it were just water sitting on top from the rain,

but perhaps, more likely, if it is bubbling up from below,

how would the implications be different

for maybe future eruptions of the volcano?

Well, if there's just a puddle of water on the surface,

then any future eruption probably

wouldn't be affected by the water at all.

It would just be so small.

But the problem comes in if the water

is deep, much deeper than just on that we can see

but going down maybe several tens of meters

into the hot conduit that feeds magma.

Then there are two possibilities.

If magma rises very slowly up through the water,

it's simply going to evaporate the water

and erupt as a lava flow, and that's the normal kind

of eruption at Kilauea.

But the problem comes in if the magma

is rising very rapidly, like it's starting one

of these big fire fountains that are so famous in Hawaii.

If the magma is rising very rapidly

or already starting to form a fountain

and then it encounters water,

then it transfers heat to the water very quickly,

the water boils, generates steam,

which helps to power the eruption,

and then we can have a real explosion manufactured

by both the gas that's in the magma

and the steam that's derived from the heated groundwater.

So in order to get an explosion like that,

we need to have really thick water body,

several tens of meters, probably, and rapidly rising magma.

But we're pretty sure that such eruptions have happened

in the past; we find evidence for that.

But we don't think they would be nearly

as large as some big boom that's going

to affect people in distant areas.

It would be something that would likely be confined

to the summit of the volcano and only a portion

of the summit, in fact.

So explosion, possibility; big explosion, probably not.

Walk us through what we're looking at here

as far as the geology is concerned and how that might play

into the way that this water's forming.

This all has to do with the level

that the water table is at Kilauea.

Below the water table, rocks are saturated with water

because they're quite permeable, they have fractures running

through them, and we know from measurements,

direct measurements, that the water table is at an elevation

that's about 70 meters higher than the bottom of the crater

where the pond is starting to form.

So there's quite a head there,

and so we think that the water

is rising back up into the crater

after having been displaced during the collapse last summer.

In theory, this level could continue

to rise up another 70 meters or so to the level

of the water table that we've been measuring.

Whether it will ever reach that height is,

of course we don't know.

So there are easier sciences to do

in this world than studying volcanoes.

Can you walk us through how you go

about studying the volcano from here

while still staying safe?

We're able to remotely watch what's happening from webcams

that have been installed on the rim of the caldera.

We can also go to the rim and make visual observations,

which we do on a daily basis now,

and make measurements to the surface

of the pond using a laser range finder.

I take a lot of photographs and videos and so forth.

And one of the most important things that we can do now

is to get a sample of the water in that pond.

Now that isn't the easiest thing in the world to do,

and we're considering two different options:

one, dangling a bucket from a long line from a helicopter

or using a drone to get the sample.

But if we can get a water sample,

then we will be able to tell a lot

about the chemistry of the gases

that is coming up through the water,

and also we'll be able to date the water.

And this can tell us whether the water

is coming from groundwater, as we think it is,

or if it's coming directly from rainwater

that's falling into the crater.

So this is the most important item on our agenda now

that we just hope that we can get permission

from the national park to do this sampling.

This is fundamentally a different kind of volcano

than what you would see more explosive types,

like Mount St. Helens.

The people of Hawaii are not in danger

of a catastrophic explosion,

but there's something unique going on here.

For the last 2,500 years, Kilauea has been

in an explosive mode more than half the time,

believe it or not.

But we've been lulled into thinking

that it's just a docile volcano

because the last 200 years since researchers have been here,

it's been acting that way.

But at some point in the future,

maybe the near future, it will return to an explosive phase.

But these explosions are not, in general,

as large as a Mount St. Helens

or at other big, explosive volcanoes.

They are smaller because the magma

is less viscous, fluid, and doesn't have as much gas in it.

And also, at Kilauea, everything that's happening

is deep in a hole in the volcano,

and large populations don't live right adjacent

to the summit of the volcano where the explosions occur.

Now there are people living there, don't get me wrong.

There are a few thousand people there,

but it's not like in Auckland, New Zealand

or someplace where you can have 100 populations at risk.

And also, the wind here for big explosions,

the ash can get up into the jet stream,

and the jet stream typically blows

toward the east and the southeast,

which is a very sparsely populated part of the island.

So for all those reasons, although Kilauea erupts frequently

and, in fact, I called Kilauea an explosive volcano,

its explosions are not as large

and probably will not have as much impact

on society as with something like Mount St. Helens.

How might this volcano, what's happening right now

to the volcano, help scientists figure out,

know more about the specific volcano

but also apply those findings, perhaps,

to other volcanoes around the world?

The generalization is always imperfect

because each volcano is a bit different.

But we will watch the rate of rise

of the water in the crater, and that will be something

that's probably never been done before,

watch the birth of a water lake in a caldera

from probably the groundwater, not from rainfall.

And then, whatever happens next regarding an eruption,

it will be able to observe and evaluate

what impact, if any, the water had on that eruption.

And that will certainly be of great interest to volcanoes

around the world that have water associated with it.

Even though, comparatively,

little is happening now at Kilauea,

it's still an exceedingly exciting time to be at the volcano

because there's so much uncertainty as to what might happen.

Following last summer's events, we really don't know

how the volcano is going to recover now,

if it's going to return to the way it was

before last summer, and I think most people assume

that's going to happen, or is it going to revert

into a period of more explosive activity

like we know that has happened in the past

after there's been a caldera collapse?

That's my feeling.

Are we gonna return to the way it was in the near past,

or are we gonna return to the way it was in the far past?

That's the big question.

Thank you very much for joining us.

You're welcome.

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