ple
left their homes in the pueblos and by the streams and constructed
temporary homes in the cliffs and canyon walls. Such cliff ruins are
abundant throughout the region, intimately the ancient pueblo peoples
succumbed to the prowess of the Navajos and were driven out. A part
joined related tribes in the valley of the Bio Grande; others joined the
Zuni and the people of Tusayan; and stall others pushed on beyond the
Little Colorado to the San Francisco Plateau and far down into the
valley of the Gila.

Farther to the east, on the border of the region which we have
described, beyond the drainage of the Little Colorado and San Juan and
within the drainage of the Rio Grande, there lies an interesting plateau
region, which forms a part of the Plateau Province and which is worthy
of description. This is the great Tewan Plateau, which carries several
groups of mountains. The western edge of this plateau is known as the
Nacimiento Mountain, a long north-and-south range of granite, which
presents a bold facade to the valley of the Puerco on the west.
Ascending to the summit of this granite range, there is presented to the
eastward a plateau of vast proportions, which stretches far toward Santa
Fe and is terminated by the canyon of the Rio Grande del Norte. The
eastern flank of this range as it slowly rose was a gentle slope, but as
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 volcani