amount and duration to form clearly
defined volcanic craters. The most active craters built up, by
continued eruptions of lava and ashes, a great series of cones now
seen on both sides of the Cordillera, that huge mountain system which
borders the Pacific from Behring sea to the Straits of Magellan.
Tacoma-Rainier is one of the more important units in this army of
volcanic giants.

[Illustration: Mazamas rounding Gibraltar--a reminiscence of the
ascent by the Portland club in 1905. The precipice rises more than
1000 feet above the trail which offers a precarious footing at the
head of a steep slope of loose talus.]

Unlike some of its companions, however, it owes its bulk less to lava
flows than to the explosive eruptions which threw forth bombs and
scoriae. It is a mass of agglomerates, with only occasional strata of
solid volcanic rock. This becomes evident to one who inspects the
exposed sides of any of the canyons, or of the great cliffs, Gibraltar
Rock, Little Tahoma or Russell Peak. It is made clear in such pictures
as are on this page and the next.

This looseness of structure accounts for the rapidity with which the
glaciers are cutting into the peak, and carrying it away. Most of them
carry an extraordinary amount of debris, to be deposited in lateral or
terminal moraines, or dropped in streams which they feed. They are
rivers of rock as well as of ice.

[Illustration: Under the walls of Gibraltar.]

{p.083} That the glaciers of this and every other mountain in the
northern hemisphere are receding, and that they are now mere pygmies
compared with their former selves, is well known. What their
destructive power must have been when their volume was many times
greater than now may be judged from the moraines along their former
channels. Some of these ridges are hundreds of feet in height. As you
go to the Mountain from Tacoma, either by the Tacoma Eastern railway
or the Nisqually canyon road, you find them everywhere above the
prairies. They are largest on the north side of the Mountain, because
there the largest glaciers have been busy. Many of them, on all sides,
are covered with forests that must be centuries old.

Even now, diminished as they are, the glaciers are fast transporting
the Mountain toward the sea. Wherever a glacier skirts a cliff, it is
cutting into its side, as it cuts into its own bed below. From the
overhanging rocks, too, debris falls as a result of "weathering." The
daily ebb and fl