PubTalk 04/2015—"Fearfully Grand" Eruptions: Lassen Peak, CA, 1914-17

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Title: A Sight "Fearfully Grand" Eruptions of Lassen Peak, California, 1914 to1917

  • A summary of the eruptions and their effects
  • Illustrated with historical photographs


Date Taken:

Length: 01:26:16

Location Taken: Menlo Park, CA, US


[ Music ]

Welcome to the U.S. Geological
Survey in another installment of

our monthly public lecture series.
It’s always a pleasure for me to

introduce the speakers and
to see all of you each month.

My name is Leslie Gordon, and as usual,
I always have announcements because

I want you to come back and listen to
us next month and the following month.

There’s something that’s not part of
our lecture series but that’s happening

in this room next week on Wednesday,
April 29th, at 6:30 in the evening.

The USGS is partnering with the
local Menlo Park Fire Department,

and there’s an event here for
local emergency response for

neighbor groups – CERT –
the Community Emergency

Response Teams – to be prepared
for events such as earthquakes.

So if you are at all interested
in learning how you and your family

can be more prepared,
be here in this room next week

on Wednesday the 29th
at 6:30 in the evening.

Next month’s lecture – I want to
call your attention – it’s not on

the last Thursday. I think it’s the
third Thursday. It’s May 21st.

It will be about the San Andreas Fault,
a lecture called Breaking Badly –

Forecasting California’s Earthquakes.
Morgan Page, a geophysicist

with the USGS in our Pasadena office,
will be traveling up here.

So please do join us next month to
learn about California’s earthquakes.

- What was that date again?
- May 21st.

And in case anyone didn’t notice,
there are fliers on the table in that corner

of the room – not only fliers for
next month’s talk, but there are

some handouts and fact sheets
relevant to tonight’s presentation

about Lassen Peak – its last eruption
and about the USGS California

Volcano Observatory and
how we monitor quakes.

Okay, so run back. Get those
before they all go away. [laughter]

I’m just poking fun.

- There’s a ringer in the audience.

- Okay, so enough about earthquakes.
Did you also know that

California is volcano country?
And in fact, volcanoes erupt

in California just about as frequently
as there are major large earthquakes

in the state. And a lot of people
forget that we have active volcanoes.

Well, just 100 years ago,
Lassen Peak erupted,

and that’s what we’re
going to be talking about tonight.

I do want to point out that there
are many, many events that are

scheduled within the next month,
within May, to commemorate

this centennial, not only
here in Menlo Park, but especially

in the Lassen
Volcanic National Park.

So if you’re not doing anything
on the Memorial Day weekend,

it will be a lovely
weekend to visit the park.

Come with us. Go on some hikes to
Sulphur Works and the devastated area,

and do join us as we –
and learn more about Lassen Peak.

So tonight’s speaker is Michael Clynne.
Michael is a geologist here

with the U.S. Geological Survey.
He’s been with us for 45 years.

He has degrees from UC-Santa Cruz
and San Jose State University.

He received his Ph.D.
at UC-Santa Cruz in 1993.

- 1993.
- Maybe – that wasn’t that long ago.

- 45 years?
- Not 45, actually.

Now that I think about it,
it’s less than 25.

Mike is what I call a
traditional field geologist.

He still goes out in the
field and looks at the rocks.

He’s not someone who
just sits in front of a computer

and does numerical modeling,
which a lot of folks do.

His specialty is young volcanic rocks,
especially in the Cascade Range,

including Lassen Volcanic
Center and Mount St. Helens.

So without further ado,
I’d like to introduce Mike Clynne,

who is going to speak about
a site fearfully grand – the eruptions

of Lassen Peak from 1914 to 1917.
Please welcome Mike Clynne.

[ Applause ]

- Well, thank you, Leslie,
for those kind words.

Next month, the National Park Service
will be celebrating the 100th anniversary

of the May 22nd eruption of
Lassen Peak, which was the last

in the continental United States before
Mount St. Helens erupted in 1980.

A variety of accounts
and interpretations of the eruptions

were published in the
years shortly after 1915.

Most have flaws for
a variety of reasons.

One was the lack of volcanology
experience of the scientists of the day.

Another was failure to recognize
critical evidence in the deposits.

And there was
considerable misinterpretation

of the photographs that
were available at the time.

This work on the 1915 eruptions
was done in the mid-1980s

with Robert Christiansen, who is
another geologist here in Menlo Park.

And he deserves considerable credit –
maybe more than half –

for the interpretations that
I’m going to talk about today.

We had the advantages
of modern volcanology –

understanding how volcanoes work,
analytical techniques – which are

much easier to do now
than they were 100 years ago,

and we had the photographic record –
a more complete photographic record

than the early geologists, and still
reasonably well-preserved deposits.

The total volume of this eruption was
on the order of 0.02 cubic kilometers –

a tiny eruption compared to
something like Mount St. Helens,

which was about
a cubic kilometer.

So 25 or 30 times smaller than the

Today the deposits are rapidly becoming
obscured by vegetation and erosion.

And this event was one that will not
be well-preserved in the geologic record.

So if you come back a million years
from now, it’s not one of the ones

that you’re going to be able to
see and record as part of the history

of the Lassen
Volcanic Center.

Well, Lassen Peak is part of the 
southernmost – it is the southernmost

active volcano in the Cascades.
It’s part of the Lassen Volcanic Center,

which is an area of volcanism
rather than a single volcano.

It’s located about

and about 100 kilometers
south of Mount Shasta.

Lassen Peak is not a typical
strata volcano like Mount Shasta.

It’s a volcanic dome,
albeit a big one –

about 2 cubic kilometers in volume,
and it’s one of the largest in the world.

It’s 27,000 years old and
had not had an eruption

since its 27,000-year-old
formation and 1914.

So the 1914-17 eruptions of
Lassen Peak were one of the first

to occur after photography became
readily available to amateurs.

Thus, it was well-documented
and popularized by northern –

the northern California media,
particularly the San Francisco Chronicle

and the Sacramento Bee, and
subsequently by the popular media.

Reporters were in competition
to get scoops to outdo each other,

thus much of what was
reported was sensationalized

and doesn’t bear the scrutiny
of the way news does today.

Benjamin Franklin Loomis
was a local businessman.

He was a Lassen Park supporter
and an amateur photographer.

He used an 8-by-10 view camera.
So he hauled this 8-by-10 camera

out to the field, which required
a lot of big lenses and a big tripod,

and he took his pictures
on glass plate negatives.

So they would haul a tent out
there to have a portable darkroom.

They’d take the glass plates out,
put the emulsion right on the plates

in the field, expose them
and then take the pictures,

and then take them
back home to be developed.

So it was a pretty arduous process
in those days, but he was successful

in doing this, and he has
a lot of good pictures.

Many photographers recorded Lassen
Peak eruptions, and there’s a number

of different compilations of photos
that you can find in archives today.

But Loomis left the most complete
and the best-documented record.

Many of his photographs were
published in a book called – his book

that he wrote – the Pictorial History
of Lassen Volcano, which has sold

so many copies in the 1920s and ’30s
that you can find it today on

Amazon for relatively inexpensive.
And it’s been reprinted many times

by the Park Service, so there’s lots
of more modern copies around too.

Most of Loomis’ pictures now reside
in the National Park Service archives.

But some have been lost,
and many were given away.

Several of Loomis’ photographs
were absolutely critical in our

understanding of the chronology
and processes of the 1915 eruptions.

So what happened?

The initial event of
the eruptance series occurred

on Memorial Day –
May the 30th, 1914.

Without any discernable warning,
there was an explosion at the

summit of Lassen Peak.
The explosion was viewed

from considerable distance –
Chester, 30 miles away, and in the

northern Hat Creek Valley,
also about 30 miles away –

and caused considerable
consternation among the residents.

Many people probably didn’t realize
that Lassen Peak was an active volcano.

No magma was ejected
in this explosion or any of

the explosions that occurred
over the next 11-1/2 months.

They were driven
by blasts of steam –

what we call phreatic
eruptions or phreatic activity.

Phreatic eruptions occur
when groundwater in the volcano

is heated under pressure to
temperatures higher than boiling.

And when it works its way to the
surface and encounters lower pressure,

it explodes – flashes to
steam and explodes.

Think of it like taking the lid off a
pressure cooker while it’s still hot.

You’re going to make
a mess in your kitchen.

The Loomis photograph –
this Loomis photograph was

taken from Manzanita Lake,
about 6 miles from Lassen Peak.

It shows a phreatic eruption that
occurred on June 14th, 1914.

There were no
earlier pictures from the

explosion that occurred
two weeks earlier.

This location was a popular spot
for people to come and watch –

to set up their cameras,
wait for something to happen,

and take pictures –
because it was safe.

Far enough away, and it had
a good view of the volcano.

One of the things that was –
that you can see in this picture here is

this ring at the bottom of the explosion.
This is a base surge, which is the part of

the explosion that comes out
at the base of the erupting column.

This was a phenomenon that
was not recognized at the time.

And until careful
observations of atomic bomb tests,

base surges in explosions
were not well-explained.

This slide shows six successive
views of the same explosion

that you saw in the previous slide,
which was this picture.

It starts in frame 1 with the
vertical-erupted – vertical-directed

eruption column
of steam and ash.

A few minutes later, this one was taken.
A few minutes later, this one was taken.

And then, in the fourth frame, a
second eruptive column is coming out.

All together, these six photos
show about 20 minutes of activity.

And the explosions sometimes
occurred in quick succession like this –

two, three, four, even 10 in a row.
But at other times over the next

for days or weeks at a time.

So they were intermittent.

The steam explosions blasted a
crater at the summit of Lassen Peak.

The crater was first observed
the first day after May 30th

when it was very small –
only about 20 feet in diameter.

There had been no crater previously
at the summit of Lassen Peak.

It had not had an eruption
in its 27,000-year-long history.

Loomis and a party of locals
climbed the volcano on June the 20th,

took these pictures.

Fortunately, it didn’t erupt
while they were there. [laughter]

And of course,
in today’s atmosphere,

or today’s bureaucracy,
nobody would be allowed to do that.

We’d be flying around
in helicopters watching it.

Note here – this is the
summit of Lassen Peak.

Note the cragginess
of that original outcrop.

And here you can see deposits of rock
and ash thrown out of the volcano,

and note how thin they are. This is a very
early picture in the history of the crater.

Well, the …

The phreatic eruption clouds consist
mostly of steam, but they also

contain ash – small sand-sized
particles of rock – derived from

pulverized rock that’s ground up in the
crater by the steam venting and blocks

of rock that are thrown out in the
eruptions but only travel a short distance.

These blocks peppered
the lookout at the summit

of Lassen Peak and eventually
completely destroyed it.

Here we see four successive
views of the lookout – prior to

May 30th, in October, about
five months after the eruption started,

and then in August of the next year.
By that time, it’s completely gone.

- I didn’t know they had –
on August 1915,

I didn’t know they had laptops then.

- It does look like …

- Apparently that’s not a computer.

But I can’t tell
you what it is.

Here’s another view of the
crater on October 12th, 1914.

You can see now
it’s much bigger.

You can see, in the wall of the crater
here, is the old rock of Lassen Peak –

that light-colored dacite
that forms Lassen Peak.

And you can see that
the deposits in the – in the –

at the top of the crater
wall are getting thicker.

This picture was taken a little bit later,
and now see, looking at the summit

of Lassen Peak here,
how smoothed off it is from deposition

of ash on top of the craggy outcrop.
And you can now see the crater

wall deposits are even
thicker than they were before.

So in mid-May of 1915,
after 11-1/2 months of phreatic activity,

the character of the eruption
changed dramatically.

Beginning on May 14th of 1915,
incandescent glow was seen

at the summit of Lassen Peak,
mostly reflecting off clouds.

And it was seen
from Manton,

a small town about 20 miles
to the west of Lassen Peak.

Well, this meant that magma
had appeared in the crater.

And it was filling the crater
and building a small lava dome.

Over the next six days,
the small lava dome got bigger

and bigger until, on the evening of
May 19th, it was over-topping

the edge of the crater,
and blocks of rock – hot rock,

that were red, were seen bounding
down the slopes of Lassen Peak.

This is a picture of what the
now-devastated area looked like

before the 1915 eruption.
It was an area of mature forest,

primarily red fir and mountain hemlock.
Those trees were hundreds of years old.

Late in the evening of May 19th,
there was a large explosion

at the summit of Lassen Peak.
The winter of 1914 and 1915 was an

El Niño year, and there was about

of Lassen Peak, which is a lot of snow.
So hot blocks of rock from the dome

that was fragmented by this eruption
fell onto the upper slopes of Lassen Peak

and started an avalanche of snow,
carrying the hot blocks of dacite that

roared down through the mature
forest on the northeast flank.

Trees were ripped out of the ground
and carried along in the avalanche.

Melting of the snow by hot blocks
created a mudflow that quickly

followed the avalanche.
This Loomis photograph,

taken on the morning of May 22nd –
three days later – shows the path

of the May 19th avalanche
and mudflow on the northeast flank

down to the lower
slopes of Lassen Peak.

This area is now called
the devastated area.

Here’s a schematic geologic map.
Summit of Lassen Peak is here.

This darker pattern marks
the path of the May 19th avalanche.

It came down – devastated
area parking lot is right here.

This area is a small recessional
moraine about 50 feet high.

A moraine is a pile
of rocks left by a glacier.

There were glaciers
here about 20,000 years ago.

And it just went right up
over that little moraine

and down into Hat Creek
and ended up about here.

It came to rest and immediately
started to melt a lot of the snow

because of the hot rocks in it,
and that created a flood

that went down Lost Creek –
or, Hat Creek.

Immediately beyond the – behind the 
avalanche was a large mudflow

that was created by melting of the
snow that was in the avalanche deposit.

The mudflow didn’t have enough
strength to surmount Immigrant Pass,

so it was diverted and turned
and went down Lost Creek.

Here’s a view down Lost Creek of the
area that the mudflow went through.

And if you look at this tree over here,
you can see that the bark on this tree

has been smashed off by rocks in the
mudflow and trees that were being

carried by the mudflow and bashed
into this tree but didn’t take it out.

What this indicates is that the
thickness of the mudflow,

as it was traveling down Lost Creek,
was 18 to 20 feet deep, even though it

left a deposit that was only
a few meters thick, or a few –

maybe 5 or 6 feet thick, depending
on where you dig holes in it.

So this just shows that mudflows pass as
a big wave as they go down drainages.

You probably can’t see this picture
very well because it didn’t come out

very well, but this is
another geologic map,

and I just want to show you
how far the mudflow went on this.

Here’s Lassen Peak.

Here’s the devastated area
parking lot where we just were.

We’re looking down
Lost Creek in that last picture.

The mudflow went down
Lost Creek for about 15 kilometers,

out to about here, where it stopped.
And mudflows are just full of water.

They have about 50% water –
sometimes more than 50% water.

When they come to a stop,
all that water is released.

And there was a big flood that went
further down Lost Creek and

Hat Creek on the evening and early
morning hours of May 19th and 20th.

This caused some damage to
homesteads down in Old Station

and in the Hat Creek Valley.
And the very muddy water killed fish

in Hat Creek as far north as the Pit River
where Hat Creek joins the Pit River.

There were fish kills, and we know
this because the California Fish and

Game Commission was alerted,
and they went and checked all this out.

And they were worried about poisonous
gases and poison in the water. It turns

out it was just the mud and lack of
oxygen in the water that killed the fish.

Well, these mudflows are capable
of carrying huge blocks of rock.

Many of the huge blocks of rock
that you see in the mudflows are derived

from talus slopes of Lassen Peak.
They were old – 27,000-year-old

Lassen Peak material.
But many of them are pieces

of the dacite dome that had been
growing at the summit and

were disrupted and thrown onto
the upper flanks of the volcano.

This rock, which is about 20 feet in
diameter, weighed about 100 tons.

So it takes a big chunk of stuff – flowing
mud – to carry something that big.

This is called Hot Rock.
It’s now a tourist attraction in the park.

It was called Hot Rock
because it was still hot for

several weeks after
emplacement of the mudflow.

And this is just internal heat
from emplacement as a lava dome

that it takes – rock are insulators. It takes
a long time for that heat to get out.

Here’s another view of the margin of
the mudflow in the Lost Creek Valley.

All the trees that were ripped out
from the mature forest on the flanks

of Lassen Peak and in Lost Creek Valley
floated in the mudflow, and they’re –

as they go down,
they’re sort of pushed to the sides.

And they pile up on the
margins of the flow,

and you can actually use them to map
where the flow went and where it didn’t.

There were many piles of trees
like this along the margins of the

mudflow into the 1980s and 1990s.
And that’s about how long it

takes for trees to decay at Lassen,
and now they’re disappearing.

They’re becoming piles of wood
rather than nicely formed logs.

You can also see Lassen Peak in this
picture still steaming in the background.

Another feature of the mudflows
are these little craterlets.

These were formed by blocks of rock –
the hot rock that were left behind in –

buried in the mudflow
that boiled water in the mudflow.

And when that steam vents at the
surface, it creates these little craters.

These were – I don’t know whether
anybody said anything about them

in 1915 because I just found
this picture relatively recently,

but at Mount St. Helens these were
quite common in 1980 where they

were created by blocks of ice
that were in the deposits,

which boiled and vented
and created these little craters.

Here there wasn’t any ice on
Lassen Peak to have formed these,

so I think they were formed
by hot rock that boiled water.

Well, the explosion that disrupted
the lava dome and the summit –

at the summit and precipitated
the avalanche and the mudflow

also re-opened the conduit
that had been underneath

the lava dome that
formed at the summit.

And more new lava came out
and filled up the summit area

and created two lava flows as it
spilled over the margins of the

crater rim – one on the west side,
which you can’t see in this direction –

but one on the northeast flank,
which you can see here in this

picture that was taken on
the morning of May the 22nd.

The original glass
plate of this negative –

the original glass plate of this picture
was one that was lost a long time ago.

Perhaps Loomis gave it away because he
didn’t like this fogged corner up in here.

But he was wont to
give away many of his pictures

to his friends,
family, et cetera.

There is another picture taken from
the same spot at the same time

in his book that doesn’t
have this fogged corner.

But it’s taken at a slightly different time,
and this steam cloud that you see

at the summit here is in the way
of seeing the lava flow.

It turns out that being able to see this
lava flow that was still in place on May

of the history, and I’ll get to that later.

Well, prior to our rediscovery of
this picture, most volcanologists

attributed the May 19th mudflow
to the lava flow coming out onto snow,

not being stable, and collapsing,
and starting the avalanche.

Here we see the avalanche
and the lava flow still in place.

So obviously it did
not cause the avalanche.

After May 19th, there was
no further activity for two days.

On the morning of May 22nd,
Loomis visited the devastated area,

and he took this picture. Note also
this rock in the foreground here.

We’re going to see that
in some other pictures.

And they left the area about noon
after running out of glass plates.

[audience reacts]
About 4:00 or 4:30 in the afternoon

of May 22nd, after Loomis had left,
a large vertically directed eruption

column of dacite pumice, ash,
and gas rapidly reached a height

of about 30,000 feet.
The eruption lasted about 30 minutes.

This view of the eruption column
is taken from the Sacramento Valley

about 50 miles west of Lassen Peak.
It was taken by a guy named Stinson.

Here the eruption cloud is seen to be
still expanding upwards and is

bending over by being blown
in the wind toward the east.

Another photograph taken slightly
later shows the eruption column

after it’s reached its maximum height
and is spreading out at the top.

Basically, it’s lost its upward
momentum and is spreading out,

just like you see
atomic bomb columns do.

This picture looks fake, doesn’t it?
Well, it is. [laughter]

Loomis was very unhappy that he
didn’t get any pictures of the eruption.

This was taken by a guy named
Meyers from the Sacramento Valley

near the town of Anderson.
Loomis bought it from him because

he wanted to have a monopoly of the
pictures so that he could sell them.

And he actually created
a lot of postcards and

sold pictures in the
Park Service for quite a while.

But he didn’t like the foreground
on the Meyers picture.

So he Photoshopped it.

Basically made a copy negative,
put a new foreground on the eruption

column, and stuck the mushroom cloud
picture onto his own background.

So it’s a real picture,
but it’s been messed around with.

The important part of it is that it
shows the eruption column at its

maximum height, which is
estimated to be about 30,000 feet.

Here’s a view from downtown
Red Bluff, which is about

of Lassen Peak.

The eruption column was visible
for much of northern California,

as far west as Eureka on the coast,
and at least as far south as Sacramento.

I haven’t been able to
accumulate any evidence

that it was any further
south than Sacramento.

Well, partial collapse of this big eruption
column produced a pyroclastic flow.

And that pyroclastic flow is a
flowing mass of hot pumice

and gas that’s driven by gravity.
So it flows down the flank

of the volcano. When it gets
down to the flat, it spreads out.

It basically followed the same path
as the avalanche three days earlier.

The area affected by – in the area
affected by the pyroclastic flow,

the trees were blown down by the 
shockwave that advances in front of it.

The shockwave shears off the trees,
leaves behind stumps that are still a

few feet high, and leaves the trees
laying on the ground pointing away

from the direction that the
pyroclastic flow was coming.

You’ve probably all seen the
pictures of Mount St. Helens

with the forest that
was knocked down,

where the trees are all in big
waves following the topography.

Here it was much flatter than
it was at Mount St. Helens,

and the trees are all basically
pointing away from Lassen Peak.

In contrast – and this is
in contrast to the mudflow path,

which rips the trees out
and carries them away.

The pyroclastic flow covered a much
wider area than the avalanche on

May 19th, and it passed over areas that
were still covered with lots of snow.

The hot gas in the pyroclastic
flow melted this snow and

generated another mudflow.
This mudflow followed the same path

as the one on the 19th, went down
Lost Creek, went about 5 kilometers

further than the May 19th one
because it had more water in it

and it was more mobile.
And when it came to rest,

it released water that created another
flood in the Hat Creek Valley.

Most of the people that lived in the
Hat Creek Valley at that time had

experienced the first flood, and
they were out of town. [chuckles]

And so there was not – and there
were no injuries in any of these eruptions

other than a few minor things
about people running away from

the mudflow and tripping and
getting their feet cut because it

happened at night
and stuff like that.

There were no serious
injuries and no deaths.

The mudflow – it followed the same
path and – yeah, I already said that.


The pyroclastic flow and the
mudflow affected the same area

where Loomis had
taken his picture.

This is a second picture taken on
June 1915 after the May 22nd eruption.

If they had still been there,
he would be dead.

If they had still been there when this
eruption occurred, they’d be dead.

Fortunately, Loomis and his party were
back at Manzanita Lake at this time.

Unfortunately, they had no glass
plates left to take new photographs.

This photo shows the much wider area
affected by the pyroclastic flow and

the fluid mudflow than the avalanche
and mudflow of the May 19th.

And we’ll compare the
pictures in a few minutes.

Note that the lava flow is still in –
that was still in place on the

previous picture is
now gone in this picture.

The May 22nd eruption basically
blasted the lava flow off the summit

of Lassen Peak, and it was
incorporated into May 22nd deposits.

This picture is the one that most
geologists in the early days looked at,

saw that the lava flow was gone,
didn’t necessarily recognize that

there were two eruptions,
and therefore, interpreted the origin

of the mudflows as
destabilization of the lava flow.

Well, that big eruption column was
still full of pumice and ash and gas,

and a lot of it fell on
the upper slopes of Lassen Peak.

The big stuff – the meter-sized
blocks and the football-sized blocks

of pumice don’t travel very far,
and they fall back on the volcano.

They fell onto still much
snow-covered areas and created

a number of smaller mudflows later
on in the – in the evening of May 22nd.

Here you can see three of those
mudflows – one over here,

one coming down here, and one coming
down here into Manzanita Creek.

These were very viscous.
They didn’t have as much water in them.

They’re not very mobile.
They have a lot more rock in them.

And they don’t flow very
far once they get to the flat.

They basically went to the
base of the volcano and stopped.

That big eruption column
was also blown to the east.

This figure shows areas that were
documented to have ash fallout,

mostly on the next day,
from May 22nd.

This map was compiled
by Jonathan Davis in the 1980s

from contemporary
newspaper reports.

So Lassen Peak is here.

On the actual edifice of the volcano,
the pumice is about 30 centimeters thick.

As you get about 25 miles away,
it thins to a deposit where you

can’t really find a continuous
layer of pumice anymore.

That’s about how far
we can track it today.

But ash fell over this large area,
including probably a millimeter or so

in Winnemucca and traces
of ash even further than that.

Most of the volume of that big
eruption cloud is in the distal component

of the ash. Very little of it,
volume-wise, falls on the volcano itself.

Okay, so now I want to compare the two
eruptions from May 19th and May 22nd.

Here’s the May 19th picture.

And here is the pre-1915 view
of the Lassen Peak superimposed on

that picture showing
where the forest was.

You can also see, behind it, that there
are no – there is no vegetation left.

In particular, pay attention to these
three areas of forest that are still in place

on the morning of May 22nd.
Over here on the east side

of the devastated area and on
the lower flanks of Crescent Crater.

When we put the two pictures
from May 19th and post-May 22nd

together, you can see that –
here’s these areas of trees still in place.

Now you can see that those trees
are gone here and over here.

So it’s pretty clear that the area that was
affected on May 22nd by the pyroclastic

flow was a much broader area than
was affected on May – on May 19th.

Well, after May 22nd, the magmatic
part of the eruption was over.

It had built for a year
up to the magmatic part.

The magmatic part
lasted about 10 days,

and then activity returned to phreatic
and declined over the next few years.

There were a number of phreatic
explosions, beginning right away

after May 22nd, and continuing
into about October of 1915.

And there was renewed activity in
the spring of both 1916 and 1917,

especially in 1917
when a new crater was blasted out

at the summit of Lassen Peak
by these phreatic eruptions.

Then the volcano went into repose,
but there was still a lot of steam

emitted into about 1921.
If you read a lot of the history of

Lassen Peak, they will tell you that
the eruption continued until 1921.

But in fact, these were
mostly just big volumes of steam

that were being emitted
in the late ’19s and into 1921.

There was no explosive
activity after June of 1917.

What I’d like to do now is
show you a few pictures

of recovery of
the devastated area.

Recovery has been very slow,
and that’s because the area

was completely buried by these
sterile lahar and avalanche deposits.

The old soil is several feet or
meters below the ground, and it’s

really difficult for new trees to get
started growing in this barren substrate.

It takes a while.
Once they do get started,

they start to create soil, which holds
moisture and provides fertility.

And annual plants, especially lupine,
for example, provide nitrogen

that are necessary for
the trees to get going.

Once they do get going,
they start to provide protection

for each other from the elements –
the wind and snow that this area gets –

a good 8 or 10 feet or snow every year
buries those little trees and can kill them.

One interesting thing to note
about recovery of the area is that

most of the trees that started growing
in the lower devastated area were

trees that you normally find
at much higher elevations

like red fir and mountain hemlock.
Apparently what happened is that

seeds were carried by the
pyroclastic flow from high up

in the slopes of the mountain
and deposited in the lower slopes.

Today, new trees that are growing
are the white fir and Jeffrey pine

that are typical of this elevation,
and they grow much faster than those

trees from higher elevations, and they’re
shading them out and killing them.

So this is a true forest succession
kind of situation that’s going on here.

This view – I should say this
view was taken in 1948

by a park naturalist named [Lynn]
who was also an accomplished

photographer and took a lot of
pictures of the Lassen Peak area.

And note that this
picture was taken from

the same spot as the
Loomis photographs.

Here’s the same rock that’s in
the Loomis photograph pictures,

and this rock today – when Bob
Christiansen and I rediscovered

this rock in the early 1980s, the
Park Service said, oh, that’s cool.

We didn’t know where that was.

And they needed, at that time –
it was a time when they were

trying to develop handicapped-
accessible trails in the park.

So they said, wow,
this is a relatively flat surface.

This would be a great place
to put a handicapped trail in.

So what they did –
and it’s only a few hundred meters

from where
the parking lot is.

What they did was built this
handicapped trail that was

wheelchair-accessible for people
to go and make a little tour

around the devastated area and
see the various deposits and rocks

and go back to where the Loomis
pictures were taken and things like that.

One of the issues with the
Park Service is that they have very

rapid turnover of personnel in parks.
And a lot of information that’s

developed by park naturalists
or accumulated by park naturalists

is lost when these people go to
other parks and new people come in.

It gets stored away in file cabinets and
stuff, but a lot of people don’t access it.

So it’s been really interesting for me
to work with the Park Service on

these kinds of projects because
I have the accumulated 30-year-long

knowledge of information that
they could have access to

but they just don’t bother.

This picture was taken by
Bob Decker, who was another

famous survey geologist, in the 1950s.
And it shows how many trees

are actually starting to grow
about 40 years after the eruption.

But they’re small.
They’re basically waist-high trees.

Today, if you go – this picture was
taken in the 1980s, and it shows the

devastated area parking lot
and a view of Lassen Peak.

If you go there today, those trees
that are in the foreground have grown up

so much that Lassen Peak is
barely visible from the parking lot.

And if you go back to the Loomis Hot
Rock, Lassen Peak is not visible at all.

I think it would be really interesting
for the Park Service to take out a

few of those trees so that they
could have a nice exhibit. [laughter]

Well, I’ve given you a pretty
good overview of the eruption.

But I want to talk a little bit
about what it is that allowed us to

put together the story of the
eruption and improve upon

the work that was
done by early geologists.

So here’s one line of
evidence that is interesting.

In most years the summit of Lassen
Peak is partially snow-covered.

Even at the
end of summer.

However, during the drought year
of 1986, the summit area was nearly

devoid of snow, and a critical
relationship in the deposits was exposed.

In this photograph, you can see the
explosion deposit, which is this berm of

material here – this is the explosion that
destroyed the May 19th lava dome.

And you can see that it’s
overlain by the lava flow here.

So this particular deposit had not been
recognized by previous geologists,

and that’s why they didn’t have any
mechanism to explain the May 19th

avalanche and mudflow because it just
hadn’t been visible to them in the past.

And here we have it underneath the lava
flow, that came out on the same evening,

but they had attributed the avalanche
to the lava flow coming out on snow,

but we have already shown you
in the picture that that can’t be right

because the lava flow still existed
on the morning of May 22nd.

Well, this kind of information and
a few other things – for example,

the presence at the summit of the
remnants of the lava dome, this was

recognized by previous geologists, but
they didn’t really pay any attention to it.

And they didn’t recognize
that it had been partially destroyed

by an explosion – the explosion
deposit at the summit of Lassen Peak,

which I just mentioned.

Another thing that we found were large
blocks of dacite that were deposited

on the ground surface in areas that were
beyond where the mudflows went.

So the mudflows down here
in the trees, this is old surface.

It’s actually
avalanche surface.

And here’s this big block –
it’s about 10 feet across – of dacite.

It’s way too big to have been thrown
there by any kind of explosion.

Well, how did it get there?

The deposit that it’s in is
only a few centimeters thick.

Yet, in order to carry a block of rock this
size, whatever the flowing deposit is has

to have enough matrix to be thicker than
the biggest blocks that it’s carrying.

Otherwise, they sink to the bottom,
and they drag on the ground

and drop out
of the deposit.

And in fact, that’s how they dropped
out of the deposit here because this is a

place – this is Immigrant Summit,
and it was going up over the summit.

When that – when that
block grounded, it stopped.

Well, how did they get there if they
weren’t carried by a mudflow?

They must have been carried
by some deposit that was inflated

enough to be that thick
but left no deposit behind.

The obvious answer to that, although it
wasn’t obvious at the time, is snow.

This was being carried in a snow
avalanche, or a snow matrix avalanche.

And after we spent a lot of time
looking at these deposits, we figured out

that that was in fact the case, this,
to my knowledge, at that time,

had not been explained
in the geologic literature.

But we subsequently found that
other people have found these

kinds of deposits, particularly
in South America on big volcanoes

that have lots of ice
and snow on them.

A couple of other things that we
recognized were that the May 19th and

the May 22nd deposits have dacite
in them with different characteristics.

This was not previously recognized
by previous geologists.

So I can now go out there and
pick up a piece of rock and say,

oh, this is May 19th,
or oh, this is May 22nd.

That, in combination with the Loomis
photographs, allowed us to determine

which deposits were in place on
May 19th and which ones on May 22nd.

So it’s a bit of geologic sleuthing that we
sometimes can do and sometimes can’t.

But the key issue here is that the Loomis
photographs were absolutely critical,

in particular, the one that shows
the lava flow still in place

on May 19th before any
May 22nd deposits were erupted.

So we know that
the deposit that’s there,

where that rock is,
was in place on May 19th.

So that’s the end of my story,
but before I finish, I’ll say,

will Lassen Peak ever erupt again?
And the answer is, probably not.

But the Lassen Volcanic Center
is active, and it will erupt again.

It’s only a
matter of time.

The Lassen Volcanic Center
has had at least 13 eruptions

in the last 100,000 years.
That doesn’t sound like very often.

It’s a recurrence interval
of about 7,500 years.

However, there’s been three
eruptions in the last 1,100 years.

Chaos Crags is 1,100 years old.

Cinder Cone erupted in 1666 A.D.
And the 1915 eruption.

So the eruptions are
not evenly spaced in time.

They clearly occur in groups, i.e.,
the volcanic activity is episodic.

Also, in the area surrounding the
Lassen Volcanic Center, there have

been at least 58 eruptions that we have
recognized in the last 100,000 years.

These are smaller basaltic
Hawaiian-style volcanism.

And that’s a recurrence
interval of about 1,500 years.

These also occur
in little bunches.

They’re episodic rather
than spaced out evenly in time.

So Lassen will erupt again,
and maybe, if some of us are lucky,

it’ll be in our lifetimes.
Thank you.

[ Applause ]

- I think Mike would be
happy to entertain questions.

And as usual, so that everyone
can hear you, including those

of you who are watching online,
please use the microphones.

There’s one in that aisle and
one right over here in this aisle.

And we’ll just
go back and forth.

Why don’t you start with the
first question over there?

- I saw the devastated area first in
about 1962, and was amazed at the

difference when I went back in the
late ’80s, how much it had grown up.

I thank you very much for telling
what caused it to wait so long to start.

But do you have a fairly
current picture of it at all?

The latest one I saw up here
was the – 1980-something.

And I’ve seen it that way, but you’re
saying it’s totally invisible?

Are they doing anything
to preserve it at all?

- No. The park is using it as a natural
resource area – research area to

allow it to recover naturally.
That’s the way the park operates.

- Well, it’s amazing difference, so I
thank you for telling why it took so long.

- Yeah. Why did Loomis use
wet plate glass, which was an

obsolete technology by that time?
Cut film and roll film were available,

and he could have done
quite a bit more if he hadn’t

tried to emulate Matthew Brady.

- He probably could have, and I do not
know why he used that technique.

It’s perhaps that he enjoyed working
that way, like some photographers do.

He enjoyed working with a view camera.
And I suppose if sheet film was

available, it certainly was available

in 8-by-10, and they had film holders –
what they needed at that time.

So it’s a good question.
I don’t have an answer for that.

- Hi, Mike. That was a great talk.
- Thank you.

- You talked about how that large
rock was displaced by snow.

And that begs the question,
what about the Hot Rock?

I mean, the Hot Rock
could not be displaced by snow

because it would
melt the snow.

Do you have any idea
how the Hot Rock …

- Well, there’s two
factors involved in that.

One is, the first Hot Rock was carried by
the mudflow, not by the snow matrix.

The second is that the snow
matrix avalanche must have

happened very quickly.
It basically was just the

head of the avalanche that
was coming off Lassen Peak.

And the only place that we see it nicely
preserved is on Immigrant Summit,

or Immigrant Pass, where
the mudflow did not go.

And in fact, what led to our
development of that idea was the

fact that the mudflow didn’t go there,
but there were still these big blocks

of rock that were carried.

And I showed you a picture of one
of them, but there are many more.

So it must have happened so fast,
as the thing was actively turbulently

tumbling and turning, that –
what you just suggested – that the snow

around it would be melted very quickly.
Yeah, that must have happened,

and that’s as far as it got,
basically, before that happened.

- Hi. I think you said that red fir –
the higher-elevation tree

had come down to lower elevations,
was carried by the flow.

I would imagine all the seeds would
have been sterilized in a flow that hot,

so I’m just puzzled about that.
- It must be, and it’s true that

any seeds that were deposited
in the pyroclastic flow would have

been sterilized because we
actually find a lot of burnt vegetation

in the pyroclastic
flow deposits.

However, it’s very delicately preserved.
You can find pine – or, fir bows

that are still intact with a little twig

and all the needles still sitting on it
but completely sterilized.

What must have carried the
seeds was the shockwave

in front of the pyroclastic
flow that was not hot.

- Hi. Thank you for your presentation.
I enjoyed it.

- In the [inaudible] …
- Oh.

- In the [inaudible] …

- Go ahead with your question.
- I’ll get back to you.

- Hi. Thank you for your presentation.
When you said that this was a lava –

a dome volcano, I think you called it?
- Right.

- Are the Cascades made up of
strata volcanoes and these kind?

And, if so, why? I don’t understand
why they have different kinds.

- The Cascades are made up of a
whole variety of types of volcanoes.

The ones that we see – the famous
ones – Mount Rainier, Mount Shasta,

Mount Adams, Crater Lake –
those are typical strata volcanoes.

They are the ones that
everybody sees and are

common knowledge
of the Cascade Range.

And they are spaced out at 50
or 100 miles apart on each one.

However, in between those volcanoes
are lots and lots of smaller volcanoes

that are smaller lava shields, lava domes,
cinder cones, and lava flow fields.

We only get the big volcanoes at
places where there’s a lot of magma

coming through the crust,
and it interacts with the crust

and builds this big
volcano in one spot.

In the rest of the arc –
and it’s a continuous arc –

there are many, many
smaller volcanoes.

The Lassen Volcanic Center is a
little different than most of those

big strata volcanoes because it’s a place
where there’s a lot of silicic volcanism,

or volcanism with a much higher
silica content in the rocks than

the big strata volcanoes,
which are mostly andesites.

The silicic rocks are
much more viscous magma.

And instead of coming out of
the top of a – of a lava cone that builds

up a big edifice by many, many, many
lava flows, these are volcanic domes.

The lava is too viscous to flow
away from the vent, and it just

makes a big pile on top of the conduit.
And then the next eruption is

somewhere nearby instead of
coming out of that same conduit.

So there’s a lot of
diversity in Cascade volcanoes.

- Two questions. One a comment,
and the second a question.

On the – why was he doing the wet
plates process, notice his birthday.

He was around when the
wet plate was in wide use.

Wet plate is also – you can
make your own emulsions.

It’s a do-it-yourself process.
- Mm-hmm.

- You have more control.
You can vary your emulsions.

You can make it out of
chemicals and so on.

For the do-it-yourselfer, enthusiast,
it would have been more –

plus it’s cheaper.
Cut film would have – you know,

it would have been pretty expensive
in those days, and if you fog it,

you’re out, but if you – if you –
with wet plate, you just make more.

Just – all you have to do is
keep the dry chemicals with you.

- Good point. And I don’t
know that Loomis was

that enthusiastic about doing it
himself, but he may have been.

- He must have started earlier.
I’m guessing here.

- Well, no, he definitely started earlier.
He was in his 50s at the

time of the eruption.
- I was noticing his birthday.

- Yeah.
I forget when that was.

- And his death – and then
his death in ’35 and stuff.

- 1857.
- 1857 he was born?

Okay, so he was in his –
in his 50s at the time – early 60s.

- The question I have is, what –
the cause of the – of the Cascade Range,

what produced the Cascade Range
and the volcanoes associated with it?

And if there any connection with the
tectonic plate activity in that region.

- Oh, absolutely.
Cascade Range is part of the

Ring of Fire, which surrounds the
Pacific Ocean, and it’s caused by

subduction of oceanic plates underneath
continental and other oceanic plates.

So for example, the Aleutian Chain,
the Cascade Chain, the chains of

volcanoes – the Andes and all the way
around to Indonesia and Japan are all

part of the same plate tectonic process.
They’re caused by subduction of

oceanic plates that carry water
down into the mantle.

That water lowers the melting
temperature of mantle rock,

and it comes back up
to the surface as magma.

- Like the pictures on the – behind that.
- Yes. Exactly.

The picture down there at the bottom.
- Thank you.

- So you – so you said that the lava cap
was still in place after the avalanche.

So then where did the heat come to
turn the avalanche into the mudflow?

- It was contained in the blocks of
rock that were thrown out onto the

upper surface of the volcano
from the growing lava dome.

- Okay, but it didn’t displace
the lava dome itself.

There was additional eruptions?
- Well, the lava dome is mostly gone.

If you calculate
its original volume,

I think only about 10 or 15%
of it is left in place.

And in fact, the only way we
can recognize it is that it has –

the rock in the lava dome has a different
character than the rock in a lava flow.

It’s a different joint pattern.
It’s much thicker.

And you can see – in fact,
I probably have a picture.

- So hot rock was ejected
to cause the avalanche?

- Right.
- Okay.

- The explosion disrupted
the growing lava dome.

Okay, so here is a picture
of the summit of Lassen Peak.

This is the lava flow in the foreground.
This is the May 22nd crater.

Here is part of the lava dome.
So you can see here a piece,

and then you can see some more.
This is old Lassen Peak rock here.

And you can see some
more of the lava dome.

So it sat right in this area.
It’s mostly gone now.

And it was still hot.
It was only a few days old.

It had temperatures of

And when that thing was disrupted,
all of those pieces of hot rock fell on

the upper part of the volcano.
- Okay, so …

- Into the 30 feet of snow.
- So hot lava did erupt,

but not at that particular place?
- Yeah. Well, no, that was hot lava.

It just was only –
it was a few-days-old hot lava.

And it was solid because it was
below its solidest temperature,

but it was still at a temperature of 600
or 700, 800 degrees in the interior.

- To melt the snow. Okay, thank you.
- Yeah.

- Well, St. Helens, obviously
the peak of the mountain looks

very different after the volcanic action.
What was the nature of

the peak area before and after?
How did that change?

What was the – was the elevation of
Mount Lassen changed by very much?

In other words, what happened
to that part of the …

- Well, I showed you a number of
pictures early on of the crater area.

And the summit of Lassen Peak prior to
the eruptions was basically a flat area

with a few little peaks on the top of it
that were 100 or 150 feet high.

The area where the

was a saddle between
those two peaks, or three peaks.

It was a relatively
smooth, flat place.

The actual summit of Lassen Peak –
the 10,457-foot peak was not affected

by the eruption.
It’s still the highest spot.

The area that was
affected was the saddle.

It, first of all, was blown out
and got lower, but then was filled up

by this lava flow. So the – in this picture,
the summit of Lassen – this picture is

taken from the summit of Lassen Peak,
so it’s not in the picture.

This was another
little high spot over here,

and there’s another high spot
off the picture on this side.

But the main difference is that,
instead of this saddle of

old 27,000-year-old rock,
you now have this very craggy lava flow

at the top and a bunch of explosion
deposit on the rest of the summit

of Lassen Peak
and the craters.

This is – the May 19th crater
was filled in by the lava flow.

The May 22nd crater is here.
And just over this little divide here –

the 1917 crater is on the other side of
that. So in the sense of topography,

the summit of Lassen Peak
was not dramatically changed.

In the sense of going up there and seeing
a rock that’s only 100 years old versus

something that was 27,000 years old,
I count that as a pretty dramatic change.

- Thanks. How long did it take
you to do all this work? [laughter]

Was it – was it continuous?
Or was it just sort of a on and off?

- No. It was not continuous.
And that’s really a long story.

I started working at Lassen in 1975
as a field assistant to a person

who was doing a geologic map there.
That map was never finished.

A few years later, I was asked to start
working on that geologic map because,

at that time, I had as much knowledge
about the area as anybody else.

It took about 10 years to create
the geologic map of Lassen Volcanic

National Park – ten field seasons.
And I don’t have a copy of the map,

but I could go get one in my
office, and we could look at it.

And then I spent about another five
years mostly working in the office,

which is the writing and the creation
of the map and stuff like that.

The actual work on the 1915 eruption
took about three summers.

And it was based – it was mostly
working with Bob Christiansen,

who was working on the young
deposits at Lassen in those days.

So it’s continuous in the sense of
many years in a row, but it’s

intermittent in the sense that you can
only do this work in the summer.

And in the winter, we do things
like getting rocks analyzed

and stuff like that.
It actually turns out that my part of

the work on the 1915 eruption was
basically – it’s chemistry and petrology.

That is the origin of the rocks.
What happened to them in the

magma chamber, and how did
they get to the rocks that they are?

The Lassen eruption –
oops, I went past that.

Oop, there it is.

The Lassen eruption
actually is extremely interesting.

It’s a – it’s a classic location of
mixed magmas, meaning there were

two different magma types in the magma
chamber that mixed together to form

the rocks and produced these
four different kinds of rocks.

This one is the lava dome and the lava
flow, which was the May 19th eruption.

This lighter-colored material
is the May 22nd eruption.

These are inclusions of basalt
that you find in these other rocks.

And this is the famous banded pumice,
which is part of the 1915 eruption.

And it includes both of these
two different types of magma

mixed together, where they were
both coming up from the magmatic

system in the conduit together. Anyway,
that was my part of the eruption.

Bob Christiansen’s part of the –
of looking at this was primarily to

interpret the volcanology, although
we did all the field work together.

- Was it a lot of work tracking down
the photographs and interviewing

the locals to see if anybody still …
- Most of the photographs

came from park archives.
So we were able to go into the park

and take a look at stuff.
There was nobody there that

curated them – nobody that
really knew what they had.

So it was a fair amount of work
to go through them, pick out the

ones that we thought were important.
Among 1,000 photographs,

there are 50 that are important –
make copies of them and

then study what they actually were.
Because they were not curated.

Some of them had dates.
Some of them had

other minimal information.
But a lot of it we had to figure out.

Then there also – you can accumulate
photographs from other archives.

UC-Davis has an archive. There’s an
archive at State Library in Sacramento.

And occasionally, you can
find things on the internet.

This is a copy – an original print of
the critical May 19th photograph.

As far as I know, there are
only two of these in existence.

One in the park archives, which has a
bunch of annotations on the back

written by a guy named Dittmar
who was instrumental in getting the

park created as a park, and this one,
which I bought on the internet for $15.


I search for Lassen stuff
on the internet all the time.

I came across this picture,
and I recognized that it was a

very important picture, and I
wanted an original copy for myself.

So there are probably others out there
that Loomis printed and gave away.

But I don’t know of any.
- Where was this one?

- It was on eBay.
- No, I mean …


- Who put it on there?
- There was a woman about

five or six years ago –
and I got this before that,

but there was a woman about
five or six years ago who –

Loomis had no sons.
So his family name did not continue.

He had one daughter that
died young – in her early 20s.

And she did not
have children, either.

So the Loomis side of
the family died out with him.

But his wife’s side of the family
continued on, and I think that this

person was a grand-niece or something
like that that was selling a lot of Loomis

glass plate negatives on the internet.
Very few of them were interesting.

They were all kinds of photograph
that I wasn’t particularly interested in,

although the park was
interested in some of them.

But so I really don’t remember the
details about where this came from.

I had some information at one time,
but I could probably go back and

read and see what I wrote at the time.
I just don’t remember it tonight.

- Yes, we went on a
family vacation to Lassen years ago.

And what I remember is this
boardwalk that we walked along.

And over here were these fumaroles
with bubbling hot water – whatever.

And then there was a story of
a schoolteacher that had – her

leg fell in, so the children were all –
we were very, you know, cautious

about walking on this boardwalk.
But I wanted you to comment on

these fumaroles because at the
time I had no idea what they were.

And so now, it’s interesting.
What are they from?

- Well, Lassen has the best geothermal
system in the Cascade Range –

the biggest and most developed.
And it’s actually the biggest in

the United States
outside of Yellowstone.

- Wow.
- Which is, of course, world-famous.

The fumaroles are water that is
basically meteoric water –

percolates down into the Earth
from snow melt and rainfall

and is heated by some body of
hot rock that’s underneath Lassen.

So we know that there’s still rock down
there that’s at at least 500 degrees.

And in fact, we think there’s
magma down there that’s probably

at a temperature
of about 750 degrees.

So this stuff, it percolates down there,
gets hot, comes back up toward

the surface, and boils from a
reservoir that’s about a mile down

beneath where the fumarolic areas are.
So the fumaroles are basically steam

that’s coming off of that boiling reservoir
that’s about a kilometer down.

- Has the area where the fumaroles
are, has that changed? Is it …

- The areas where the fumaroles are …
- [inaudible]

- … change dramatically
from year to year.

Old fumaroles die. New ones start up.
- I see.

- One of the people that I’ve been
working with here at the Survey,

Patrick Muffler, is an expert in this area.
He’s done a lot of mapping

of the fumaroles systems and
been able to document changes.

One of the places that we were
consulted on relatively recently

was Sulphur Works, where fumaroles are
coming up underneath the park road.

[audience reactions]
And we were able to document

their migration, beginning in the
early 1980s, toward the park road.

And last year – two years ago now,
the Park Service did an extensive

renovation of that part of the road.
- [chuckles] I imagine.

- But they engineered it very nicely
so that it’s actually slightly elevated

with an airway underneath it
to allow the steam to vent and

come out the side [laughter]
rather than eat the road.

- I’ll have to go again and see that.

- It’s so well done that you
won’t even notice unless somebody

takes you and shows
you what they did.

- So you’ve had many
of the serious questions.

I have a somewhat
more flippant question.

There are some coincidences here
that I think need to be addressed.

One is that we have a May 19th episode of
eruption in two major volcanoes in

North America in the last 50 years or so.
Okay, so Goldfinger told James Bond

that once was coincidence,
twice was something or other.

The third was enemy action.

But the question I really have –
and this is the more serious one –

is both of these volcanoes seem to have
blown in a direction to the northeast.

Is there some structural characteristic of
the way the plate tectonics occurs here

that makes it more likely that these
volcanoes will blow to the northeast?

And is there
predictive value there?

- That depends on what you mean
by “blowing to the northeast.”

The eruption columns are
primarily ejected vertically.

And they are blown by whatever wind
patterns that you have on that given day.

So that the wind, on average,
is probably 50% - on 50% of days,

the upper-level winds are to the
northeast in the Pacific Northwest.

So that’s the most common
direction for deposits to go.

However, for example, in Mount St.
Helens, on July 22nd, the winds were

in the opposite direction, and the ash
went to Portland instead of Montana.

However, I will also say that
most volcanic edifices have some kind of

structural control that is either internal to 
the volcano itself – the way it’s actually

been constructed, or is related to
faults that underlie the volcano.

So structure is very important in the
individual growth and history of

volcanoes. But there’s no one rule
that solves all of those questions.

As for the coincidence of May 19th
versus May 18th, I’ve thought a lot about

that, and you’re not the first person
to ask that question. [laughter]

And it’s interesting to note,
Mount St. Helens probably had

nothing to do with it being springtime.
Because it was a bulge

that was created by intrusion
of magma into the volcano.

And as the bulge grew and grew,
it destabilized the volcano,

and it went when it was
ready to go – when it got over –

de-stabilized enough
to avalanche.

And there’s still some controversy
about whether the earthquake

triggered the avalanche or the
avalanche triggered the earthquake.

We really don’t have
a firm answer for that.

And I see Jim Moore sitting in the
audience here who was a person

who was there at the time. So Jim
might have something to say about that.

As for Lassen, there was repeated
activity in the spring of each year,

and for many years, I have assumed that
that had something to do with snow melt

percolating down into the volcano.
But if you talk to hydrologists,

they’ll say that you can’t get
the water down there fast enough

to make some kind of regular –
every spring that happens.

In addition, my work on the
magma mixing that created this eruption

suggests that the mixing event happened
about 18 months before the eruption

itself and that it’s controlled by
turbulence in the magmatic system

and that churning over
and assent of the magma,

and it just erupts
when it wants to.

It doesn’t care about what
time of the year it is. [laughter]

So there’s – nevertheless,
there’s a coincidence.

- Two-part question.

I’m interested in the future,
and I’m wondering what you

have learned
about Lassen.

Is that helpful in predicting when the
next eruption of Lassen might occur?

And also, when and where
might the next major eruption

in the Cascade Chain occur?

- Okay, I’ll take the second question first
because that’s the simple one to answer.

Mount St. Helens is clearly the
most active – the youngest,

most active volcano
in the Cascades.

It’s the one that’s had the most activity
over the last, let’s say, 4,000 years.

And it is the one that’s
most likely to erupt again.

Nevertheless, that doesn’t
mean that it will be.

It’s just the one that’s most likely on a
statistical basis and a recent history basis.

As for Lassen, we’ve learned a
tremendous amount in the last 30 years,

and we’re continuing to
get new information.

For example, we didn’t know for sure
that there was magma underneath

Lassen until very recently.
A study that was recently done on

zircon crystals, which are a kind of
crystal that grows in the magma and

has enough uranium and thorium in them
that you can actually date these things,

and we date them using the ion
microprobe over at Stanford,

has told us that there is an active
magmatic system beneath Lassen.

There’s magma down there.
But that it is mostly crystalline.

So it’s about 50% crystals
floating in 50% liquid.

That’s probably too
viscous to erupt on its own.

The crystals – once the crystals basically
start touching each other in the

magmatic system, it behaves
more like a solid than it does a liquid.

It’s much more difficult to deform.
It’s much more difficult to make it erupt.

So what happens in a system like
Lassen is you have this stuff,

which is basalt that comes from
much deeper in the crust.

It intrudes the crystal network and,
because that kind of magma is

much hotter, it heats it,
melts some of the crystals,

stirs it up, and turns it
back into an eruptible liquid.

So that each of the eruptions at
Lassen over the last 100,000 years

has been the result of intrusion
of basalt into the magmatic system,

stirring it up,
and basically rejuvenating it.

After the eruption, which removes most
of that basalt and the stirred-up magma,

it goes back to its quiet repose
of an interlocking crystal network

and becomes un-eruptible. So how often
do those magma-mixing events occur?

Well, on average,
it takes about 7,000 years,

but in reality, they tend to
occur in little clusters.

One of the things that we’re doing at
Lassen now is we have a very nice

seismic network set up there that
we can see intrusion of basalt

that’s coming from
much deeper in the Earth’s crust

and watch its migration
coming up to the surface.

So the next eruption,
we’ll probably have some warning.

And it could be
weeks or months.

It could even be longer than that if
we’re paying enough careful attention.

- Thank you.
Can you add two more parts?

One is, what about Mount Rainier?
And the second part is, what is the status

of funding for volcanology in the current
environment of the United States?

- I don’t want to say too much
about the current environment

in the United States.
The volcano science …

- No, I asked about funding.
- Yeah, the Volcano Science

Center has a stable funding.
It’s enough to run what we have,

to do the monitoring that we do,
and some of the mapping and

other volcanological
studies that we do.

If we had more money,
we could do a lot more.

We could learn more
about the young volcanoes.

We could study them more extensively,
develop more of their history, and put

a better monitoring system in place
that would give us early warning.

Now, unfortunately,
the Cascades are not the biggest part

of volcanoes in the United States.
Most of them are in Alaska.

And they mostly are on trans-Pacific
airline routes, cargo routes …


And it’s very important to study
those to understand when those

volcanoes are going to erupt
to get planes out of the way.

I mean, you’ve probably all seen the
stories about planes that fly into volcanic

ash clouds and how it melts in their
engines and basically kills the plane.

So it’s very important to keep those
routes open, and that’s where we’re

spending most of our money on
monitoring Aleutian volcanoes.

Which, most of the time, you can’t
see because of the bad weather.

So there’s many pictures that we
have of – satellite pictures, for example,

of eruption plumes
coming up through clouds.

People on the ground –
there’s no people in the Aleutian Islands,

but there – there’s very few people.
People on the ground don’t know

the volcano is erupting,
but we can see it from satellites.

Now, I missed the first part.
- Mount Rainier.

- What about Mount Rainier?

- I’ve heard that an eruption there may
be coming in the reasonable future.

- Well, there’s no evidence that Mount
Rainier is going to erupt anytime soon.

It’s an old volcano, as opposed to
Mount St. Helens, for example, that’s

a young volcano. And it does not have
eruptions very frequently anymore.

The last was
about 2,000 years ago.

However, Mount Rainier
is a huge pile of unstable,

partially hydrothermally
altered rock.

The biggest dangers from Mount Rainier
are collapse of part of the volcano.

And this has happened in the past.
There are two major collapse

deposits that reached the area
of Seattle in the last 5,000 years.

So any kind of magmatic activity on
Mount Rainier could provoke a

major collapse that would be
a serious problem for Seattle.

- And the time …
- And it doesn’t even

have to be magmatic.
It could collapse on its own.

- And the time constant
is 1,000 years or so?

- Well, there aren’t – there aren’t that – 
there’s two of these deposits.

One’s about 500 years old, and the
other one’s about 5,000 years old.

But as I mentioned earlier, these things
don’t happen on regular time scales.

They’re episodic, and for an event
like Mount Rainier collapsing,

it probably needs
some kind of trigger.

However, for example,
the big earthquakes that we have

here in California they also have in
Washington on the subduction zone.

There hasn’t been a big one since the year

And they have this

for the really big earthquakes.
So last one was 300 years ago,

but one could happen at any time.
And that could cause – have a –

it would have a serious effect
on the city of Seattle and Portland,

not just because of the earthquake,
but because of the potential collapse

of a mountain like Mount Rainier.
- Thank you.

- A second bite
of the apple.

Two items.
One is the fumaroles.

If I heard you correctly, was it
meteoric water? Very old water?

- They are mostly meteoric water.
There’s a very small component

of magmatic water that’s
coming off the – whatever lava –

whatever magma body
there is down there.

And some of the gas that is
in the fumaroles is also

coming from the magmatic body.
But the large – more than 90% of

the water that’s coming up is
meteoric water – just rainwater

that’s percolated down
to become groundwater.

- Oh, not really old, ancient water.
So the isotopic –

the isotopic profile is not really old?
- No, it’s not old.

- It’s not ancient. Okay.
- The isotopic profile

is the same as rainwater.
- Yeah, okay. I misunderstood.

- Yeah.
- The second one was, in spring,

you have the time of the moon, the sun,
are more aligned in a straight line,

and you get your eclipses and so on.
- Mm-hmm.

- You get a bigger – you have those,
of course, twice a year.

Once the other time is in spring, but –
no, in fall, but in spring, the change –

the delta change would be bigger.
Because – and it might not be

direct cause, but it could be a
factor in priming the pump,

if you would,
for a susceptible system.

- Well, I don’t know very much
about that topic in particular.

But I will say that there are people that
work on this stuff, and they add Earth

tides to the stresses that are involved in
volcanic edifices and magma chambers.

And they are relatively small
compared to the stresses that are

created by having this body
of hot magma in the Earth.

However, you’re talking
about a potential tipping point.

- Mm-hmm.
- I.e., a trigger for a system

that’s otherwise primed
and ready to erupt.

It’s entirely possible that some
kind of Earth tide situation

could trigger the event.
- Thank you very much.

- This has been a wonderful collection of
good questions from everyone tonight.

- One more, please?
- Is it quick?

- Yes.
- Okay.

- Mount Rainier. You said …
- I’m here for the duration.

- All right.

- I’m from Seattle. And you mentioned
Mount Rainier collapsing and reaching

Seattle. What do you mean by reaching
Seattle? Does some muds flow?

- Yeah. What happened is –
what has happened in the past

is that the upper part of Mount
Rainier is hydrothermally altered.

And that means that the rock has a
significant clay component in it.

You get clay wet, it’s very slippery.
And it collapses, it gets water from

the water that’s contained in the rock.
It gets water from

valleys that it flows down.
And it basically creates a mudflow.

So the Electron and the Osceola,
which are the two mudflows

that have affected Seattle –
mostly the Tacoma area,

but into the outskirts of Seattle,
those were mudflows that traveled

down – I guess it’s the Puyallup River?
- Puyallup, yeah.

- Yeah. And one of the
other river valleys there.

And because they’re confined by river
channels, they can flow a long way.

Just like they did at Lassen.
The bigger the volume,

the more the water, the farther it goes.
- Thank you.

- Well, I do want to thank Mike Clynne
for a wonderful talk about Lassen.

[ Applause ]

I want to thank all of you
for joining us tonight.

Join us at the park on
Memorial Day weekend.

We’ll have hikes and talks and all
kinds of interesting things in the park.

And join us again next month on May

Thank you
and good night.