[Music]
We're on Yosemite Creek
below Lower Yosemite Falls,
it's a cold early April morning,
and we're watching the frazil ice formation.
Frazil ice are these small crystals of frozen mist
that forms in Upper Yosemite Falls and Lower Yosemite Falls.
The particles of ice wash down the stream with the liquid water
in a flurry, a slushy, slurpee, goopy mass
that in many cases flows like lava.
So if you can imagine in your mind a giant slurpee machine
that is putting out millions of gallons of slurpee
into Yosemite Creek,
it's amazing;
it's not snow, it's not ice,
it's something in the middle
and to watch it move underneath Yosemite Creek Bridge
is pretty incredible.
This is one of the more unique phenomenon
that you'll see in Yosemite,
if you're lucky enough to be here in March and April,
which is the prime season for this,
but it's an amazing thing
to watch something this dynamic in Yosemite Creek.
You see something that the millions of visitors
who come in the summertime
never imagine something like this.
It behaves a little bit like cement in some ways,
where it stops and it forms kind of a stationary piece
and then the flowing pieces go past that stationary piece.
The ice will surge into place
and with enough thickness it stops
and the creek will flow a different direction.
The water will drain out of where it has just deposited it,
leaving this, what looks like snow,
but again, it's soft, it's unconsolidated,
you would plunge right into that.
Now we see this dynamic change
as the frazil ice has built up its own levy
and caused the channel to clog up and it's coming toward us,
we're going to have to be ready to move here,
as the Yosemite Creek in all of its might is coming toward us.
But you'll see this lava flow effect,
where the ice is going to accumulate
and build up blockages
that stop it from coming in a certain direction.
It's the full force of Yosemite Creek,
which can be up to say a 100 cubic feet per second,
when that is moving along in a place where we don't expect it,
where engineering of building roads and trails and bridges
hasn't anticipated
this full flow of the Yosemite Creek,
has caused problems
with damage to buildings on the side of the creek
and our footbridges,
at least one has been destroyed,
one another was displaced by frazil ice,
picking it up off of its footings
and others have been inundated
by the frazil ice deposits at times.
So a lot of people that are in the park in March and April
will be walking along the trail near Yosemite Creek
and see piles of what appears to be snow.
If they took a little more time to observe,
they would notice the snow is very selectively deposited,
only in the stream channels here,
there is none up in the woods off to the side.
It's the first thing people think of,
of course it looks like snow, so...
what else could it be?
Here's where frazil ice becomes quite dangerous,
because you can't tell how thick it is
or how solid it is
or how much water is underneath.
If you were to walk out into this,
you might make it a few steps
and you might plunge through over your head
into icy moving water underneath this frazil ice deposit on top.
Every winter at the base of Upper Yosemite Fall,
a big conical mound of ice and snow develops.
We call it the Ice Cone or the Snow Cone
and it can grow to be hundreds of feet tall.
The Snow Cone builds up from falling water
that freezes while it's falling.
It freezes in a couple of places;
some freezes at the bottom,
some of it freezes on the rock on either side
of Upper Yosemite Falls,
when the sun comes around during the late part of the morning,
it starts to loosen that ice
and it falls and builds up onto the Snow Cone too.
And you can hear them throughout the Valley,
and it's pretty amazing how loud those ice sheets
can be when they come crashing down.
There is a persistent myth
that directly connects the Snow Cone's disappearance
to the apparition of our frazil ice deposits.
There is not a direct connection.
This is not the Snow Cone
we see lying on the floor of Yosemite Valley washed out.
The Snow Cone gradually melts away as temperature warms up.
As temperature warms up,
the volume in Yosemite Creek increases,
but the subfreezing nights
will turn some portion of Yosemite Falls to ice
that flows in the liquid water and the frazil ice,
as we call it,
is only indirectly connected to the Snow Cone.
I do have heard people refer to frazil ice
as the Snow Cone breaking up,
but if that were the case,
then these other places where it exists in Yosemite Valley,
that wouldn't be true.
I've also observed it at Royal Arches Cascade
and I do know that it happens at Ribbon Creek,
also over at Bridalveil Falls and Salmon Creek.
This is a marker for many of us in Yosemite Valley
when the frazil ice flows,
it means that springtime is here,
where the snowmelt is increasing,
but we still have subfreezing temperatures at night,
so yeah, it is very much a marker of the season.
You won't see this in June,
you won't see this in October,
you'll only see it in March and usually in April.
Well, Yosemite gets close to 4 million visitors a year
and the vast majority of those visitors
come in June, July, and August,
so they're here in the summer months.
And I think that a lot of people are missing
some of the magical events that happen in the wintertime.
For example, Horsetail Falls,
it looks like a glowing fire fall in February,
and the Snow Cone at the base of Upper Yosemite Fall,
you're just not going to see that in June, July, and August.
And the fact that frazil ice is flowing
a lot of times in spring is pretty incredible.
So I think that Yosemite in late winter
and early spring
holds a lot of very special and unique natural phenomenon
and that more people would probably come here in winter
if they just knew that they could experience these things.