Big Four Ice Caves
The Big Four ice cave trail #723 has several opportunities to
view geology. For the first .03 of a mile you walk on boardwalks
over a montane wetland, meaning a highland wetland that is below
the tree line. In physical geography, a wetland is an environment
"at the interface between truly terrestrial ecosystems and aquatic
systems making them inherently different from each other yet highly
dependent on both" (Mitsch & Gosselink, 1986). In essence,
wetlands are transition area between two adjacent ecological
communities.
At about .04 you arrive at the South Fork of the Stillaguamish
River. When the water is low you can see the bedload of boulders,
which are moved downstream during high water and flood conditions.
Just a bit further, a bridge crosses over a tributary stream where
the bedload of boulders are bigger yet, even though the stream is
much smaller. Streams flowing down steeper slopes have higher
velocities, and thus more energy to move larger size sediments.
As the trail starts to rise from the valley, you will see clays
with fine layering and lack of pebbles and boulders of till
deposits that make them lake deposits. There are 2 theories about
how this lake formed. The first is that a large landslide
downstream working as a dam, blocked the flow of the South
Stillaguamish. The second is that the Puget Lobe of the Cordilleran
Ice Sheet pushing up the Stillaguamish Valley from the Puget
Lowland.
After hiking 1 mile you will see what you came for.. The Big
Four Ice Caves! The ice caves are not glaciers but rather a debris
field. During the winter months, huge snow avalanches fall down a
vertical 4,000 foot rock wall of the Big Four Mountain to
accumulate at the base of the slope. Much more snow builds up in
the winter than melts in the summer, so the deposits at the base
are under constant pressure from the weight of the snow above
causing metamorphic recrystallization from snow to ice. This is a
similar process forming glacial ice, except the Big Four ice does
not flow downslope. Instead during the summer months most of the
overlying snow disappears and meltwater streams cut a pathway
through the base of the ice. These tunnels are enlarged by warm air
flowing through, at the end of the summer they are tens of feet
high and wide. The ice caves provide a natural air conditioning
system as meltwater and cold air flow through them. The cool
downdrafts minimize vegetation on the rocky plateau and allow
subalpine wildflowers to grow at an unusually low altitude. The ice
walls show a characteristic blue color caused by the fact that ice
molecules absorb all of the frequencies of sunlight except the blue
band, which escapes to reach your eyes.
To log this cache please provide a current photo of yourself at
the caves, (will take foreheads if you can’t get your face in the
shot if you are caching alone) also email me why the caves are
extremely dangerous to enter. (hint it has to do with how they are
formed). Sign can be found here N 48 03.391 W 121 31.089. Don't
wait for for a confirmation email from me to log this cache. Go
ahead and log (with your photo posted), but if I don't receive your
email in one week I will have to delete your log. Earthcaches have
a unique set of guidelines for the cache write up, and logging that
must be met. Most importantly have fun!!
Sources: Hiking Washington’s Geology by Scott Babcock and Bob
Carson
Wikipedia Ice
Cave
Wikipedia
Big Four Ice Caves
Glacier National
Park
Congrats
Logbear on FTF!! He gets and A+!