and newest terrace is the one shown in Fig. 35, ten
feet above the ocean. Each succeeding terrace is less distinct,
and the highest, fourteen hundred feet in elevation, can now be
distinguished in only a few places. Where the old sea cliffs are
best preserved they form a series of broad, flat steps, rising one
above the other. Each bench, or terrace as it is commonly called,
is a part of an old plain cut out of the land by the waves when the
ocean stood at that level. The steeper slope rising at the back is
the remnant of the cliff against which the waves used to beat. If
we are fortunate, we shall find at its base some water-worn pebbles
and possibly a few fragments of sea-shells. The crumbling of the
rocks and the erosive action of the rills are fast destroying the
old cliffs, so that in many places they have entirely disappeared.

[Illustration: FIG. 34.--OCEAN CAVE AT LOW TIDE

Pebbles of a former beach are seen above]

Upon the seaward face of San Pedro Hill, in southern California,
there are eleven terraces, rising to a height of twelve hundred
feet. What an interesting record this shows! Long ago the land
stood twelve hundred feet lower than at present, and the waves beat
about San Pedro Hill, nearly submerging it. Then the land began
to rise, but stopped after a time, and the waves cut a terrace. The
upward movement was continued, with repeated intervals of rest,
until the land stood higher than it does now.

[Illustration: FIG. 35.--WAVE-CUT TERRACES

Point San Pedro, California]

North of San Francisco there stands a terrace fourteen hundred feet
above the ocean. Numerous terraces appear along the Oregon coast,
but those in Washington are not as high as those in California. It is
probable that the land in this region was not so deeply submerged.

The ancient shore lines of British Columbia and Alaska are now
deeply buried beneath the ocean, as those of California once were.
The fiords, so common in these countries, are old river valleys
which have been drowned by the sinking of the land. The islands
were once portions of the coast mountains, but have been cut off
by the same process.

Let us picture in our minds the changes in the geography of the
Pacific coast of the United States which must have been made by a
sinking of the land to a depth of only six hundred feet. We will
begin upon the north, at the Strait of Fuca.

Puget Sound once opened to the south as well as to the north, so
that the Olym