it came up fissures were formed and volcanoes burst forth and poured out
their floods of lava, and now many extinct volcanoes can be seen. The
plateau was built by these volcanoes--sheets of lava piled on sheets of
lava hundreds and even thousands of feet in thickness. But with the
floods of lava came great explosions, like that of Krakatoa, by which
the heavens were filled with volcanic dust. These explosions came at
different times and at different places, but they were of enormous
magnitude, and when the dust fell again from the clouds it piled up in
beds scores and hundreds of feet in thickness. So the Tewan Plateau has
a foundation of red sandstone; upon this are piled sheets of lava and
sheets of dust in many alternating layers. It is estimated that there
still remain more than two hundred cubic miles of this dust, now
compacted into somewhat coherent rocks and interpolated between sheets
of lava. Everywhere this dust-formed rock is exceedingly light. Much of
it has a specific gravity so low that it will float on water. Above the
sheets of lava and above the beds of volcanic dust great volcanic cones
rise, and the whole upper region is covered with forests interspersed
with beautiful prairies. The plateau itself is intersected with many
deep, narrow canyons, having walls of lava, volcanic dust, or tufa, and
red sandstone. It is a beautiful region. The low mesas on every side are
almost treeless and are everywhere deserts, but the great Tewan Plateau
is booned with abundant rains, and it is thus a region of forests and
meadows, divided into blocks by deep, precipitous canyons and crowned
with cones that rise to an altitude of from 10,000 to 12,000 feet.

For many centuries the Tewan Plateau, with its canyons below and its
meadows and forests above, has been the home of tribes of Tewan Indians,
who built pueblos, sometimes of the red sandstones in the canyons, but
oftener of blocks of tufa, or volcanic dust. This light material can be
worked with great ease, and with crude tools of the harder lavas they