GEOLOGY OF OLYMPIC NATIONAL PARK:
PART I OLYMPIC GEOLOGY
Gravity:
The Great Leveler
In the
long run, gravity is the force behind all the processes that tend to
drag the mountains back to the sea. The spherical earth is a restless
creature whose internal troubles keep wrinkling up its skin, but because
it is so massive, that thing we call gravity keeps smoothing out the
wrinkles, trying to reform the earth into a perfect sphere.

Fig. 36.
Deep creep produced this depression along a ridge top. The fallen trees from a recent fire emphasize the feature.
|
In the
Olympics, gravity often moves soil and rock downhill
with only minor help from water or ice. Slow movement is called creep
and fast movement, landslide and rockfall. Creep is commonly shallow:
the surficial cover of weathered rock, moraine, or soil slides slowly
downhill, wrinkling like a rug on a tilted floor. Deep creep
The soft
rocks of the Olympics appear to have crept and slid valley-ward most
actively right after glacial retreat, when the walls of the deeply carved
valley channels were most unstable . But even today a creek or river
gnawing into the toe of a slope may remove support from upslope material,
causing the whole mass to slide gradually or catastrophically down (fig.
37).

Fig. 37.
Landslide scar above Dosewallips River, west of Constance Pass. |
Creep
and landslide processes tend to smooth steep and jagged ridges into
low, rounded hills. They turn the steep-walled gorges sawed by rivers
into V-shaped valleys and destroy the U shape of glacier channels. The
smoother and lower the hills get, the slower the descent of rock and
debris to the rivers and the slower the removal of the material to the
sea by the rivers. But gravity never relents and, given enough time,
will smooth even the boldest peaks of the Olympics into low, rolling
hills.
|