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SECTION MENU
- Site Description |
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The Yucca Mountain
site is located on the western boundary
of the Nevada Test Site where scientists
have conducted geologic investigations
related to nuclear weapons testing
since the 1950s and studies related
to nuclear waste disposal since the
late 1970s.
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At its crest, Yucca mountain
reaches an elevation of 4,950
feet and is comprised of layers
of volcanic rock, called “tuff.” This
rock is made of ash that was
deposited by successive eruptions
from nearby volcanoes, between
11 and 14 million years ago.
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Among the geologic research activities,
scientists drilled, extracted, and
analyzed numerous core samples of
rock. They also excavated a five-mile-long
tunnel through Yucca Mountain called
the Exploratory Studies Facility
(ESF). The ESF provided scientists
the optimal environment in which
to study the rock in greater detail.
Yucca Mountain is within a geologic
area called the Great Basin. The
Great Basin encompasses nearly all
of Nevada and parts of Utah, Idaho,
Oregon and California, and extends
into northern Mexico. The Great Basin
is characterized by mountain ranges
separated by basins containing thick
deposits of sand and gravel.
The mountains and valleys surrounding
Yucca Mountain formed over the past
10 million years from faults moving
on one or both sides of the ranges.
Rocks and sedimentary deposits surrounding
Yucca Mountain range in age from
more than 570 million years old in
the mountains to about 10,000 years
old in the valleys.
Yucca Mountain itself consists of
a series of ridges extending 25 miles
from Timber Mountain in the north
to the Amargosa Desert in the south.
The mountain was deposited in layers
by successive eruptions of gases
and ash from nearby volcanoes between
approximately 11 and 14 million years
ago.
Yucca Mountain is made of layers
of rock, called tuff. The tuff is
either “welded” or “nonwelded,” depending
on the circumstances when the ash
was deposited. If the temperature
was high enough, the ash compressed
and fused together, producing layers
of welded tuff — a hard, brick-like
rock with very little open pore space.
Other times, the erupted material
compacted and consolidated at lower
temperatures, producing layers of
nonwelded tuff — with less
density and higher porosity.
The potential repository will be
located in the unsaturated zone in
a layer of welded tuff about 1000
feet beneath the surface of the mountain
and on average about 1,000 feet above
the water table. The rock at the
repository level is important to
all aspects of repository design
and performance. Simplified geologic
maps show geologic relations at a
repository scale. In addition, stratigraphic,
structural, and rock property data
have been combined to form an integrated
site geologic model. This geologic
model provides a common framework
for developing the repository design
and assessing the performance of
the repository system.
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