Published Papers and Addresses
John Campbell Merriam
Published by the Carnegie Institution of Washington
Washington, D. C.
Carnegie Institution of Washington, Publication No. 500, The Waverly Press, Baltimore, MD., A. Hoen and Company, Baltimore, MD.
A Brief Guide to the Parapet Views, Sinnott Memorial, Crater Lake National Park
The views from the parapet of
Sinnott Memorial, if observed in order as numbered, present a picture of great
forces in the past which have helped to develop the beauty seen today. The story
of Crater Lake on the following pages is copied from labels describing the views
seen through the instruments.
Origin of the Mountain
This mountain is part of a
Tremendous series of lava flows
In late geological ages enormous flows of molten rock poured out
over an area of more than 200,000 square miles, extending into Oregon,
Washington, Montana, Idaho, Nevada, and California. These masses of lava came to
the surface largely through great fissures in the earth. A typical section of
such extensive flows is shown in the lava beds forming Columbia River Gorge.
Numerous volcanoes in this lava region represent relatively late
outpourings of melted rock through small openings. They have contributed only an
extremely small part to the total mass of lava. The mountain at Crater Lake is
one of these volcanoes.
Building of the Mountain
The mountain in which Crater Lake rests was built by lava flows,
poured out layer upon layer, and the piling up of volcanic ash, soil, deposits
of streams flowing down the mountain, and materials carried by glaciers.
Two sections of the mountain are shown by finders to the right
and left of this box. The one to the right is Dutton Cliff, made up of
successive layers of lava and volcanic ash; the one to the left, near Discovery
Point, shows a series of layers consisting of lava, volcanic ash, and glacial
deposits. Specimens of the rock from each of these sections are shown in this
box. Both localities may be reached by trail.
One can understand Crater Lake in its relation to the volcano
only when the mountain is considered as result of construction extending over a
long period, in which many changes took place.
Lava Outpourings Through
Splitting of Crater Rim
In addition to spilling out as broad flows of melted rock, it is
common for the tremendous mass of molten lava in a volcano to break through the
mountain side. The lava filling of such a crack or fissure is known as a dike.
After it cools the material filling these fissures is often harder than the
surrounding rock. Subsequent wash of water may cut away the softer bordering
material, leaving the hard filling of the fissure as a
Devil's Backbone, seen through the finder at this box, is an
illustration of a
A diagram of the mountain in this box points out other radiating
fissures or dikes. Specimens of these lavas are also shown.
Action of Streams and Glaciers on
the Mountain in the Course of Its Building
In the section of layers forming the rim of the mountain there
are evidences of wash by water. In some places this is shown by cutting of
valleys; at others by accumulation of water-carried ash, gravel, and boulders.
The finder at the left of this box is directed toward a heavily
polished and scratched rock surface on the edge of the crater. This type of wear
is known to be produced by slow movement of ice carrying sand, pebbles, and
boulders. Glacial polish and thick beds of material carried by glaciers are
common around the mountain. They are present on the surface rock and seem also
to appear between earlier layers, showing that glaciers were present at various
stages in the history of the mountain.
Leaflet prepared by a committee of the National Academy of
Sciences and the Carnegie Institution of Washington as an aid to the visitor. 8
pp. Washington: Carnegie Institution of Washington, 1933.
Broad valleys cut at various points around the crater are
characteristic of glacial action. Kerr Notch is such an evidence of glacial
erosion. It was through a similar ancient glacial notch that the lava at Llao
Rock flowed out, as shown in the finder to the right of this box.
Forming of the Crater
Broken Edges of Layers on Crater Slopes Indicate Widening of
Crater in All Directions by Breaking Away of Walls
The edges of rock layers inside the crater wall are clearly
exposed because they have been sharply broken around the entire rim region. This
fracturing took place in course of widening the crater. Increase in size of the
opening at the summit of the mountain may have been caused by tremendous
explosions, or by collapse of the peak, or by combination of such activities.
The precise nature of the story is not yet fully known.
If the activity of a volcano diminishes slowly, growth of the
mountain may end in forming a symmetrical cone. If activity continues by
spasmodic outbursts, explosions may blow away a considerable part of the peak.
Other conditions may bring about undermining of the walls in such manner as to
produce a wide cauldron-like crater, but without tremendous explosions.
Latest Stage in Forming of the Crater, Eruptions Producing
Wizard Island and Two Other Cones
If the lake were removed the crater would be seen as a
relatively flat-floored cavity extending as a maximum about 2,000 feet below the
present lake surface. In this great depression Wizard Island would appear as one
of three small volcanic cones produced by pouring out of lava and cinders in the
last period of volcanic activity. Forming of the present floor probably involved
many stages, during some of which the cauldron-like crater may have been
occupied by wide stretches of molten lava, as in the "lake of fire," at Kilauea,
Origin of the Lake
The water of Crater Lake is derived from rainfall and snowfall
over this crater region, together with snow blown into the depression. The lake
is not known to have outlet except by seepage. The conditions of evaporation,
seepage, and precipitation are in a state of balance which makes possible this
accumulation of water and maintenance of approximately this water level. If the
region were at a different altitude, or in a different location, the lake might
not have been formed.
is conceivable that in
the course of late stages in its history, and under climatic conditions
different from those of the present, the crater may at times have been filled in
part with ice.
Existence of Crater Lake was made possible by building of a
mountain, in the elevated summit of which there could be formed a wide and deep
cavity having no outlet, except by seepage, and no inlet. The conditions
required for accumulation of a body of water with the peculiar beauty of this
lake are furnished in a crater produced by combination of those tremendous
forces found in the power and heat of a volcano.
Exceptional Features in Beauty of the Lake
Color an Outstanding Character of
The color of Crater Lake is generally recognized as the most
attractive feature of this region. Among spectacular lakes of the world there
are none in which depth of color and brilliance of blue are more striking. The
blue of the deeper water is brought out in contrast with the brilliant green of
shallow areas along the margin.
The deep blue of the lake is believed to be caused chiefly by
the scattering of light in water of exceptional depth and clearness. The color
is thought to be due to the same cause that produces blue of the sky where light
passes through deep atmosphere.
The extraordinary beauty of the lake arises in part from its
great depth, clearness of the water and of the atmosphere above it, and from
favorable conditions presented in viewing it from the high crater rim.
Beauty of the Lake in Relation to Its Surroundings
A thing of beauty may
have its value enhanced by the setting in which it appears; so the
attractiveness of this lake varies according to conditions under which it is
seen. In the same way the beauty of other things may be increased by relation to
the lake. Of many possible examples illustrating relation between the lake and
its surroundings the following have been found of interest to visitors:
1. Beauty of color in the lake as
seen through the screen of hemlocks from the path leading to Sinnott Memorial,
and similarly as seen through trees at many points along the rim.
2. Form and reflection of
Phantom Ship seen through the finder next this box. Smooth reflecting surface of
the water is necessary.
4. Reflections of cliffs and
other shore features.