MLK Crust and the Feb 8 Facets at Crystal Mountain

MLK Crust and the Feb 8th Facets
at Crystal Mountain
Chris Morin
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Table of Contents
Introduction .................................................................................................................................................. 3
MLK Crust Formation ................................................................................................................................... 3
February 8th Facets ....................................................................................................................................... 4
First MLK release .......................................................................................................................................... 6
February 20th Surface Hoar .......................................................................................................................... 9
Narsid Event ............................................................................................................................................... 14
First Large Cycle on the MLK layer ............................................................................................................. 17
April 1st Event and Subsequent Avalanches .............................................................................................. 23
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Introduction
The La Nina winter of 2010/2011 started warmer than average but ended with huge snowfall
totals for the PNW. Many sites in Washington were near record snowfall by the end of April,
after being at or behind averages near the end of January. Crystal Mountain had received 240”
of snow by February 1st, but had only 68” of snow settled at 6300’ due to continual spells of
higher than average temperatures. Over the next 2 months temperatures stayed far below
normal with heavy snowfall. In fact Crystal received the equivalent of its yearly average of
snowfall from Feb 1st to the end of the season, some 372” worth. The interface between the
warm 1st half of the season and the abnormally cold and snowy second half of the season
became to be known as the MLK crust and produced one of the largest avalanche cycles at
Crystal Mountain seen to date.
MLK Crust Formation
All weather data is from the Crystal Mountain telemetry run in conjunction with NWAC. Water
amounts are from the base plot at 4480’, which are usually 20-40% less than manual W/E
measurements in Green Valley at 6300’.
The MLK crust began forming during a 2 day period from January 16-17th when 3.5” of rain fell
at high freezing levels starting the melt freeze crust.
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Over the next 20 days, dry weather and moderate to high freezing levels continued to
strengthen this crust:
The Feb 8th Facets
This long warm period was followed by six inches of snow on the night of February 6th.
Avalanche Control that morning produced few results within the new snow, and the bond to
the MLK crust was generally good.
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Early Morning on Feb 8th in P-Bowl
The next 4 days saw freezing levels mostly below the base area, but a slight warming trend on
the 10th and 11th put down a weak crust on top of the Feb 8th snow.
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The First MLK Crust Release
After this brief warmup, temperatures again began to cool with incoming precipitation. The
cooling trend created a relatively good bond to the weak trap crust on top of the Feb 8th
snowfall. However, strong winds from the South did create some wind slabs on Northerly
aspects. These would prove to be reactive on the facets that were beginning to form
underneath the thin trap crust from the 10th and 11th.
A break in the weather allowed decent visibility for touring on the 17 th. At approximately 2pm
that day a snowboarder jumped off a cornice into Little Richards and initiated a 1.5-2’ deep
release (SS-AR-R2-D2-O on a NW aspect at 6600’). Although his partner was in the path as well,
his partner was not caught and the boarder was able to self-arrest on the bed surface. The
path had been cross-loaded from the strong South Winds over the past several days. It failed
on facets that had formed from the Feb 8th snowfall. This snowfall had now had 4 days of dry
weather to weaken while on the surface, and then a following 5 days where it was buried but
temperature gradients were likely high enough to allow it to further weaken as the new snow
load increased. No other activity was observed in the surrounding areas on the MLK crust.
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Fracture Line Profile from Little Richards
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Fracture Line from Little Richards
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Fracture Line in Little Richards, starting to fill in on the 19th
February 20th surface hoar
The four days following the Little Richards release were mostly fair with low freezing levels.
This allowed for surface hoar formation on all aspects. Southerly exposures received enough
radiation for a suncrust to be formed, and in many places this suncrust was then overlaid with
surface hoar.
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The next 3 days saw moderate to heavy snowfall at low freezing levels.
This created a 1-2’ slab on top of the suncrust and surface hoar. On southerly aspects where
the sun crust was well formed both natural and skier released failures were observed over the
next 2 days. The skier R side of Park Place naturally released on a shallow but well propagating
slab during the day on the 24th (N-SS-R2-D2.5-O on a W aspect at 6700’). 67cm deep,200m
across.
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Crown at Park Place
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Crown at Park Place, Suncrust with surface hoar formation is evident at failure plane
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On the next day, Feb 25th, Leah and Ben Landsam popped another slab skiing off of the backside
Boxcar into Crystal Lakes (SS-AS-R2-D2-O on a WSW aspect at 6600’, 18” deep). The release
failed on the same surface hoar and suncrust seen in the Park Place avalanche. Other small
releases were seen in the surrounding backcountry.
Skier releases up the 70 rd on Feb 24th
After the short break in weather on the 25th ,snow continued to fall into the first of March at
low freezing levels.
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Despite putting another 2.4” of water on these persistent weak layers, no signifigant releases
were seen down to the older snow
NARSID Event
On March 1st, at 6PM, a missing person’s report was filed with Patrol at Crystal. At the
time the last seen point was near right angle at 11 AM on the 1st. Due to the recent heavy
snowfall and deep snow conditions a NARSID scenario was deemed the most likely situation.
The right angle and O-meadows areas were searched that night. After that night’s search a
more recent last scene point was found to be Double OO’s Left at 2PM the same day. Over the
next 5 days hundreds of volunteers and professional searchers looked through Crystal but no
further information was found. Search efforts were hampered by continued snowfall and poor
weather. At the end of the 5 day first phase of the search, the settled snowfall in Green Valley
was 120”. The search was suspended until the snow level in Green Valley dropped to 100”.
Due to heavy late season snowfall the depth in Green Valley was still above at 140” on June 1st.
The descision was made to begin a larger scale search on June 18th+19th with the main effort
coming in the next weekend on June 25th and 26th.
On June 15th, an electrician at Crystal Mountain spotted Melby’s body while working on
the Gondola line. The area had been well searched during the initial search effort. He was
found in a position that suggested he had fallen upside down in a tree well and suffocated.
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A warming trend from March 1st to 2nd caused widespread natural and human triggered activity
~2’ deep. None of these releases appeared to fail on the MLK layer, although some may have
run on the suncrust formed on the 20th.
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Fracture Lines at behind Elk Pass from March 2nd
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First Large Cycle on the MLK Layer
From March 3rd – 11th another 4.45” of water came in at moderate freezing levels.
10.84” of water had now fallen on the faceted Feb 8th snowfall. A release was seen March 11th
on these Feb 8th Facets from a 1.6 pound explosive shot in the appliance area on the North Face
of the King (SS-AE-R4-D2.5-O on a N exposure at 6600’ ). 3-4’ crown depth.
Remote triggering can be seen from shot above fracture line in appliances.
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Appliance’s Slide on 3/11
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From March 11th-14th 1.4“of water fell at moderate freezing levels:
There was now 12.24” of water on the Feb 8th facets. On March 14th a triple in the air released
a 3’ deep, 50’ across slab in Bombs Eye on Rockface (SS-AB-R3-D2-O on a NE aspect at 5800’).
It ran on the Feb 8th facets.
Rockface on March 14th
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Ted’s Buttress ran the same day as the rockface release (SS-N-R3-D3-O on a NW aspect at
6000’). Crown depth was ~6’. It released on the Feb 8th facets as well. Only the lower 1/3 of
the start zone came out.
Above and Below, Ted’s Buttress on 3/14
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Ted’s Buttress on 3/14
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Over the next 2 days another 1.49” of water fell at moderate freezing levels.
13.73” inches of water had now fallen on the Feb 8th facets. On the 16th of March 5 pounds of
emulsion in the air released a 3’ slab in Hidden Face on Rockface (SS-AB-R3-D2-O on a NE
aspect at 5800’). The same day Big Bertha in Mt. Rainier National Park slid and hit 410,
presumably releasing on this layer.
Hidden face on 3/16
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Big Bertha on 3/16
April 1st Event and Proceeding Avalanches
The next 2 weeks saw continued low to moderate freezing levels and light to moderate
precipitation:
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No significant avalanche activity on older snow layers was observed at Crystal during this time.
It now had been 50 days of freezing levels at 5000’ or lower. More than 16” of water had fallen
on the Feb 8th facets. Over the next 3 days warm southwest flow finally raised freezing levels to
above 7000’ with 2” of rain.
Warming and rain did what now almost 19” water content could not. On April 1st debris was
found beneath rock face at 11:59 AM. Center chute had released naturally ~4-5’ deep on the
Feb 8th facets. For the next 3 hours teams probed the area while dog, recco, and transceiver
searches took place.
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Above: Center Chute Debris Below: Post Control Work on Rockface
At the conclusion of the search a half bag of anfo was put on the Reynolds tram. It released a 46’ deep slab that propagated down E-Ridge. Debris ran past Lewis Lane and took out a
moderate amount of timber.
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Subsequent control work on Rock Face that afternoon released everything from Center to
Elbow Chute down to the MLK Crust. Releases on Rockface proper were only 2-3’ deep due to
the high amount of mitigation it had experienced during the year.
The next day a number of large test shots were placed on slopes suspected of releasing on the
Feb 8th facets. Niagras and Bear Pits were two of the main targets due to the similar aspect and
elevation to Rockface. Several Air blasts of 3-4 shots each produced large scale avalanching on
the Feb 8th facets in Bear Pits (Most SS-AB-R3-D3-O on NE aspects at 6300’, 5-6’ crown depth).
Everything from Shot 1 - Shot3 released. Similar Results were seen in Niagras, with multiple 4-5’
releases (Most SS-AB-R3-D3-O on ENE aspects at 5700’). However, 13 pounds of explosive on
the upper Niagras Tram produced no result.
Shot 1 on April 2nd.
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Bear Pits runout on April 2nd.
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Crowns in Bear Pits from April 2nd
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Crown In Bearpits with Feb8th faceted layer visible
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On April 3rd a heli mission was set-up to continue putting large test shots in key locations. A
25lb bag was placed near the Niagra’s Old Faithful tram shot that produced no result. The 25lb
bag released the upper Niagra’s field and propagated into employee housing. Debris created a
new path through employee housing tearing down a large amount of timber and stopped 200’
from housing, (AE-SS-R5-D4-O on an ENE exposure at 6200’). A 50lb bag in the hangfire to
skier R pulled out an R3D3 release with more timber being taken out. Other shots out North
and South produced no Result. All employee housing releases were on the Feb 8th facets.
Employee Housing Release
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Employee Housing Fracture line
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Above: Upper part of path in Employee Housing. Below: Failure Layer.
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Flagging in the Employee Housing Runout
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Niagras / Employee Housing Crown
All results over the past 3 days had been on SouthEast aspects, were radiation had caused the
most warming within the snowpack. Snow profiles at each fracture line yielded wet facets on
the MLK crust. No results had been seen on colder, north facing snowpacks. It was decided to
keep North and South closed for the next 5 days to let the snowpack settle, before again testing
with large charges.
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During this time there was a significant decrease in temperatures with light to moderate
precipitation. On April 8th, another heli mission was done, putting large charges in P.D., Left
Angle, 3-Way, and Ted’s Buttress. The only result was seen on the heavily loaded but small
hanging snowfield skier R of the Threeway peak (SS-AE-R3-D3-O on a NNE exposure at 6800’).
Crown depth was 8’-15’, but did not entrain snow on the lower part of the field. This was the
only observed result during the past week that had run on dry facets at the Feb 8 th layer. All
other results had released after the Feb 8th facets were moistened with warmth.
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3 way result initiated by a 50lb bag of ANFO
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Above and Below: 3 way Crown
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On April 9th North and South were opened for the first time since the April 1 st release. No large
releases were seen for the rest of the season at Crystal Mountain on the MLK interface.
Snowfall total at 6300’ was 612” as of June 1st.
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