Nature Notes From Crater Lake
Volume 4, No. 3, September 1931
Snow Pressure Bend
By Clyde E. Gilbert, Ranger-Naturalist
The trees inside the rim of Crater Lake
and on the steep slopes of the surrounding peaks show a distinct bend
near the base. The bend might be accounted for by some as due to soil
creep. "Soil creep" is the gradual downward slipping of the soil on the
steep hillsides. This is usually caused by alternate freezing and
thawing of the soil aided by the water table in the early spring. Since
the soil on the slopes is quite shallow and many of the tree roots are
anchored in solid rock, it is very improbable that soil creep is
responsible for the bend. Also in the case of soil creep the base would
have moved down slope and the tops tilted upward. If a resulting bend
occurred it would be in the opposite direction to that found in Nature.
It appears more probable that snow
pressure on the trees for six months or more of the year forces the
trees out of the line of normal growth and causes a distinct crook that
is called "snow bend". The tree is most affected while it is very small.
Some times it is pressed flat on the ground beneath huge drifts of snow
for several months. During the growing season the sun draws the tree
back into an upright position but before it can completely straighten
the snow falls and again presses the tree out of line. Every year the
growing tree, aided by the sun, gains a bit in the battle, but even the
larger trees show a distinct "snow bend" that is never outgrown.