Borealis Glacier Notes

 

The Borealis Glacier is located above the confluence of Thunder Creek and McAllister Creek. This glacier has a terminus elevation slightly above 6,000 feet. Its accumulation area extends up to about 7,600 feet. The lower part of the glacier as can be seen on the above topo is very gentle and has been fed by ice falls, two of which are contiguous with the lower glacier, from the higher steep glacial area above. 

 

Although the Borealis Glacier is located along a high glacier clad spine of the North Cascades, the glacier is located on the dry side of that spine and precipitation drops off significantly to the east. The next ridge over has much more limited glacial ice. The slopes below the Borealis to the east and northeast have forests that have burned on a frequent basis.

 

A review of historic aerials indicates that the area covered by the Borealis of glacier did not change much between 1950 and 1990. 

  

1950

1979

1990

The lack of trees and vegetation around the perimeter of the glacier suggests that it previously extended further east and north. The vegetation has been slow to reestablish as much of the area is bare rock and this area is over 6,000 feet and well back within the range such that winters are much colder. This area is getting into one of the few areas in Washington State where there is a true tree line in the mountains - a tree line defined by cold temperatures versus simply too much snow.

I got to know the Borealis Glacier rather well as I camped for nearly a week adjacent to the glacier and walked across it every day. It was on the Borealis that I encountered my first Moulin. I even ventured up to the top part of the glacier with crampons and ice axe. That venture was rewarded with finding golf ball sized garnets.

Large garnet in pegmatite

At the time I had a general sense that the lower Borealis was wasting and that the supply of ice from the upper glacier area was not enough to maintain the lower glacier. But that was only a guess based on one summer observation. However, subsequent imagery shows that indeed the Borealis is in major retreat. My short cut across the glacier from my old camp site has turned into a lake.

2009

 

One final personal memory note. This trip was a solo venture. Sadly I had a camera/film issue and have no pictures from that venture other than rather dull geology pictures of rocks (that was my purpose). While the solo glacier traverses with crampons and ice axe to the high ridge line may seem dangerous, the hike out through the forested slopes below may have been the most dangerous hike I have ever done. Descending into thick cliffy forests makes route finding seem like a lot of lucky guesses and forces routes towards very uncertain directions. In the end I ended up reaching the valley floor about a mile further west than my initial intent, but greatly relieved to have gotten down without having to spend the night on the slope or doing any significant back tracks.

 

 

Quake Wake Up in Northwest Washington: Short Update

This woke a few people up in northwest Washington.

From the PNSN site

In Bellingham I felt two shock waves about 4 seconds apart. The first was stronger. Can't say much about the quake at the moment. I am sure the seismic folks will have to get busy figuring it out the motion. The quake was fairly deep - generally a good thing.

Update: The depth of the quake corresponds fairly well with the depth of the subducting San Juan Plate. Shifts and movements in the deep part of subducting plat will cause periodic quakes. This movement was not located along the "stuck" part of the subducting slab. That area is to the west and is shallower.

PNSN has a map of the epicenter on the surface. Keep in mind the epicenter is 50 km down as well. For Victoria the epicenter is further down than it is horizontally - hence the epicenter is over 50 km away from Victoria event though the map shows it as 11 km away. The map also shows where the quake was felt. You can go on line and fill out a form to add to this map http://earthquake.usgs.gov/earthquakes/eventpage/uw61114971#impact_tellus. It is useful information for how shock waves travel and where they are felt that casts a larger net than seismic stations.

Image from: 

https://twitter.com/PNSN1/status/682131533725999106?ref_src=twsrc%5Egoogle%7Ctwcamp%5Eserp%7Ctwgr%5Etweet

 

North Cascades Glaciers: Notes from 1990

My graduate thesis field area involved an hypothesized fault and metamorphic gradients. But it was hard not to make note of glaciers in my field area.  

 Inspiration Glacier with Tepeh Towers and Klwatti Peak

Crossing the variety of glaciers in a safe manner took some planning and route consideration. Ice falls below the hanging glaciers were a significant hazard. One noteworthy observation was that lots of bare rock was exposed from areas where there had been glacial retreat.

Eldorado Glacier with moraine in foreground

The bare rock provided for excellent exposures of structures and contact relations as good as any road cut or mine wall.

Easy scramble and great bedrock exposures

At the time of my ventures in this area of the North Cascades in 1989 and 1990 the status of glaciers in the North Cascades was a bit sketchy as was my background on the glaciers. The South Cascade Glacier was the only glacier with mass balance data with other inventories reliant on historic aerial images. The overall pictures was that most of the glaciers had undergone substantial retreat post little ice age maximums. There was some sense that maybe the retreats had slowed. 

While I was not doing any glacial studies other than adding some very minimal mapping of moraines, my sense of glaciers in my field area in 1989 and 1990 was that most were retreating. This was mostly due to seeing large tracts of old ice that was wasting away along the margins of many of the glaciers.    

Wasting layers of glacial ice - note Mike on lower right of ice for scale.

McAllister Glacier

The summer image below gives a sense of where most of the glacial areas are located in the North Cascade range. 

USGS 2013 image

 

The South Cascade Glacier has one of the longest mass balance measurement record, dating back to the 1950s (glacierstudies/scascade). Mauri Pelto began long term mass balance monitoring of several additional North Cascades glaciers starting in the 1980s (http://www.nichols.edu/departments/Glacier/). Many of those glaciers are on Mount Baker. North Cascades National Park began mass balance monitoring several other glaciers in the 1990s (nps.gov/glacial-mass-balance) in the hopes of capturing a range of glacial settings with the Park.

 

One of the glaciers not monitored is the McAllister Glacier, its location noted on the above image. I got a bit of a peak-a-boo view of the lower McAllister Glacier in 1990 when doing field work on the Eldorado Pluton. The view was from the sharp edged divide between Marble Creek and McAllister Creek valleys.

  

 

Views of McAllister Glacier from the west

Crevassed ice in the foreground are small hanging glaciers above the valley

The terminus of the glacier was 3,000 feet below 

The McAllister Glacier is tucked away in a very hard to reach and very rugged valley with no trails deep in the core of the North Cascades. While there are hundreds of glaciers in the North Cascades, very few of them extend down into valleys like the McAllister. What is more, only the Carbon Glacier coming off of the northwest side of Mount Rainier extends to a lower elevation than the McAllister. The Deming on Mount Baker formerly reached to a lower elevation but it has receded to higher elevation terminus. The McAllister Glacier terminus is over a 1,000 feet lower in elevation than the more famous and far more studied South Cascade Glacier. 

 

Despite its low elevation reach, the McAllister is rather poorly suited for mass balance monitoring - it is remote, the glacier is complex, much of it appears dangerous to spend time on and a fair bit of the lower glacier is fed by avalanches off the steep mountain sides above.

 

McAllister Overview

 

Dashed blue outlines are the two areas of upper glacier that feed the lower glacier via ice falls down cliffs to the lower glacier. Blue arrows note other sources of lower glacial ice via avalanches. The upper slopes above the glacier are about 8,000 feet. The glacier terminus is at currently at 4,100 feet.

 

Like most of the North Cascade glaciers, the McAllister has been receding.  

 

1947

1979

1998

Estimated terminus locations based on historic aerials showing ice and vegetation

Note the lake is not present in 1947 but is occupied by ice at that time

The retreat between 1947 and 1979 was moderate

The pictures I took were from 1990 and the lake was present

Substantial retreat has taken place in the 1990s and 2000s

 

A Change of Holiday Plans: Misadventures at Snoqualmie Pass

The scheme was to head down to Seattle and spend the night and then head over the pass this morning. But the shift in weather forecasts was not looking good. The pass reopened yesterday afternoon so we made a run for it. Traffic was light. It looked like the change of scheme was a good one. A half mile short of Denny Creek, where the road steepens, we came to a stop. The pass was closed again. A couple of hours later we began to move as we along with our fellow travelers were routed into a U turn and headed back. Contrary to simply clearing slid cars and trucks off the road, the snow accumulations on the slopes above the pass had reached the avalanche threshold.

The turn around drove home the economic impact of I-90 over Snoqualmie Pass. Miles of trucks lined the road side - blocked from their schemes of goods delivered to wherever they were headed. The cost and practicality of other routes are simply too high. 

From near our stopping point last night

 

Lateral Moraines and Boulders Above the Columbia

Finally got around to fixing a couple of glitches on the blog so I changed the banner picture as well while I was at it.

The pictures is from the upper slopes above the east side of the Columbia River across the river from Chelan. The slope consists of lateral moraines from the Okanogan ice lobe that covered the plateau to the east. As the ice retreated from the area a series of lateral moraines were left behind marking sort pauses of the ice retreat.

The massive boulders are nearly all basalt plucked from the top edge of the plateau. Technically most of them are glacial erratics in that the the underlying bedrock under the moraines is much older orthogneiss and granite.

The picture was taken in late spring while the grass was still green. This area is susceptible to wildland fire. It is wet enough for some pine trees on the upper slope but the fire recurrence in this area is fairly frequent and has minimized the tree establishment. This area partially burned last summer.

A Geophysics Christmas Story

I posted this link to a "Human Intelligence: A Holiday Tale" by Kurt Andersen before. But it is worth linking to again given the season. A good science-based (fiction) explanation of the holiday.

http://www.wnyc.org/radio/#/ondemand/108724