The results of the volcanic activity can be seen today as the dark
red rocks that form the southern portion of the range. The magma
which did not reach the surface cooled to form a batholith. The
grey granitic pinnacles of the northern organs are remnants of this
slowly cooled magma.
The Organ batholith is interpreted to be an exposure of the
upper, outer part of a magma chamber whose silicic cap erupted as
pyroclastic flows and lavas 33–33.7 million years
ago.
A Batholith is a huge intrusion, covering areas greater than one
hundred square kilometers (40 square miles). Batholiths typically
contain many separate intrusions that form over a relatively long
period of time.
The Organ and southernmost San Andres Mountains in south-central
New Mexico are part of a 150-mi long, west-tilted fault block
extending from El Paso, Texas, northward to central New Mexico. The
Organ Mountains tower nearly a mile above the floor of the Tularosa
Basin on the east and the Rio Grande valley on the west.
Oldest rocks exposed are Precambrian granite, overlain by as
much as 8,500 ft of mostly marine Paleozoic and Cretaceous
strata.
The Organ Mountains, one of the most picturesque and rugged
mountain ranges in the Southwest, form the skyline approximately 10
mi east of Las Cruces, New Mexico, in southern Doña Ana County. The
row of jutting, fluted, bare-rock pinnacles known as the Needles,
the backbone of the range, can be seen on a favorable day from
nearly 100 miles away, making them probably the most familiar
landmark in the region. Their stark, sawtooth profile, their
challenging slopes and changing moods have made the Needles a
favorite of artists, photographers, and mountain climbers, as well
as a daily pleasure to the people who live within their view. From
their summit a broad expanse of southern New Mexico, Texas, and
Mexico spreads out below, from the Magdalena Mountains on the
north, to far into Mexico and from the Arizona border to the
Guadalupe Mountains.
Yet the Needles are just the crown of a jumbled range of stark
peaks, rugged ridges, and deep canyons that stretches for 150 miles
from El Paso, Texas, to central New Mexico.
To log this cache, email me the answer to the following questions
as well as posting your required photo.
1) Looking at the Organ Batholith how many life zones are
represented and what are they?
2) What minerals have been taken out of local area mines?
3) Given that the highest point of the Organ Mountains rises to
9012 feet, estimate the height of Sugerloaf Mountain.
4) Take a picture of you and your GPSr with sugarloaf in the
background.
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