ing power.

Lava is molten rock of excessively high temperature, which suddenly
becomes released from the fearful pressures of earth's interior. Hurled
from volcanic vents, or gushing from cracks in the earth's skin, it
spreads rapidly over large neighborhoods, filling valleys and raising
bulky rounded masses.

Often it is soft and frothy, like pumice. Even in its frequent glass
forms, obsidian, for example, it easily disintegrates. There are as many
kinds of lava as there are kinds of rock from which it is formed.

Volcanic scenery is by no means confined to what we call the volcanic
national parks. Volcanoes were frequent in many parts of the continent.
We meet their remnants unexpectedly among the granites of the Rockies
and the Sierra, and the sedimentary rocks of the west and the southwest.
Several of our national parks besides those prevailingly volcanic, and
several of our most distinguished national monuments, exhibit
interesting volcanic interludes.

VII

LASSEN PEAK AND MOUNT KATMAI

THE ONE A NATIONAL PARK IN NORTHERN CALIFORNIA, THE OTHER A NATIONAL
MONUMENT IN ALASKA

Because most of the conspicuous volcanic eruptions of our day have
occurred in warmer climes nearer the equator, we usually think of
volcanoes as tropical, or semi-tropical, phenomena. Vesuvius is in the
Mediterranean, Pelee in the Caribbean, Mauna Loa and Kilauea on the
Hawaiian Islands. Of course there is Lassen Peak in California--the
exception, as we say, which proves the rule.

As a fact, many of the world's greatest volcanoes are very far indeed
from the tropics. Volcanoes result from the movement of earth masses
seeking equilibrium underneath earth's crust, but near enough to the
surface to enable molten rock under terrific pressure to work upward
from isolated pockets and break through. Volcanoes occur in all
latitudes. Even Iceland has its great volcano. It is true that the
volcano map shows them congregating thickly in a broad band, of which
the equator is the centre, but it also shows them bordering the Pacific
Coast from Patagonia to Alaska, crossing the ocean through the Aleutian
Islands, and extending far down the Asian coast. It also shows many
inland volcanoes, isolated and in series. The distribution is
exceedingly wide.

Volcanoes usually occur in belts which may or may not coincide with
lines of weakening in the earth's crust below. Hence the series of
flaming torches of prehistoric days which, their fire