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combining Landsat data with other digital data sets, such as elevation data, for analysis in automated geographic information systems.

High Plains Regional Aquifer System Analysis Project

• The High Plains, a 174,000-square

mile area of flat to gently rolling
terrain east of the Rocky Moun-
tains, is underlain by unconsoli-
dated alluvial deposits that form a
water-table aquifer capable of
sustaining well yields of 100 to
more than 1,000 gallons per minute.
Irrigation from this aquifer has
made the High Plains one of the
Nation's leading agricultural areas.
In 1978, as part of the Regional
Aquifer System Analysis (RASA)
Program, the U.S. Geological
Survey began a study of the High
Plains aquifer to understand the
flow system and to evaluate the
effects of the irrigation develop-
ment on a regional scale. This
study indicated that data on pump-
age for irrigation and recharge to
the aquifer from irrigation return
flow are essential to evaluate
water-level declines due to irriga-
tion development; these data, how-
ever, were not readily available. To
develop a method of estimating
these data with an acceptable con-
fidence level, a follow-up project to
the RASA Program, Phase II, was
started in 1983, and two areas, one
in the southern High Plains of
Texas and the other in the northern
High Plains of Nebraska, are being
studied currently.

Energy Geologic Studies

• During fiscal year 1984, several

geological and hydrological studies
at Newberry Volcano, Oregon,
were completed under the Geother-
mal Research Program. Results of
these studies provided (1) evidence
from hydrothermal alteration
analyses that a hot, young hydro-
thermal system still is evolving
beneath the volcano, (2) a con-
ceptual model of the shallow hydro-
thermal system that estimates fluid

recharge to the system, and (3) a
related numerical model of conduc-
tive heat flow that refines esti-
mates of the age and size of a
shallow magma chamber which
would be the heat source for the
hydrothermal system. These studies
followed test drilling by the U.S.
Geological Survey at Newberry
Volcano in 1981 that demonstrated
that high-temperature geothermal
fluids exist in permeable rocks
beneath a cool zone of hydrologic
masking. The investigations at
Newberry have substantiated the
concept that the potential for
exploitable geothermal energy in
the Cascade Range of the Pacific
Northwest is high and have pro-
vided incentives for additional
industry exploration in the region.

• Assessment of the undiscovered oil

and gas resources of the United
States and worldwide continued in
fiscal year 1984. A major focus has
been on the pattern of worldwide
hydrocarbon exploration drilling,
and methods of predicting oil and
gas reserves from past production
records are being developed.
Results of this research indicate
that areas for new exploration still
are expanding at the relatively
rapid rate of 50,000 square miles
per year (now covering 1.5 million
square miles outside North Amer-
ica and Communist countries), but a
large fraction of new additions to
reserves may be generated from
already discovered fields. Another
topic being studied is the pattern of
oil and gas field size distributions
in mature basins. The results of
this study will allow future regional
resource estimation methods to be
expanded to include predictions of
field size distributions as well as
aggregate amounts of petroleum.

• Two maps showing the location and

names of basins and the total thick-
ness of sedimentary rocks in the
conterminous United States and
two maps showing the location of
wells drilled for oil and gas deeper
than 15,000 and 20,000 feet,
respectively, in the onshore and off-
shore conterminous United States
were released January 1984. These
maps are now being refined and,

when formally published, will be the first components of an Atlas of Oil and Gas Data.

Digital Systems

• Digital systems used by the U.S. Geological Survey to collect, process, edit, and display digital cartographic data are in a state of rapidly changing technology. During the 1970's, such systems were simply tools to digitize manually features from maps and aerial photographs and to store the data onto magnetic tapes. Currently, systems are available which not only collect data but have the interactive capability to display and edit the data, greatly improving the accuracy and economy of producing digital data with a high level of data integrity and completeness. One type of digital system is used to scan maps automatically and uniformly, to digitize features of a particular overlay or of a certain color, and to store the data in a televisionlike format. An associated computer and an edit station then are used to correct errors, to label features, and to reformat the data. Another type of digital system is used to trace lines and to digitize their coordinates directly, with feature labels or attributes being added concurrently. The digitizing may be accomplished manually and then viewed and edited interactively, or it may be accomplished automatically by a line-following sensor with some interactive assistance. Edit systems now have color capability to aid in complex interpretation and computers large enough for extensive processing and analysis. As digital systems continue to evolve, the economic acquisition of digital data, the plotting of cartographic products, and the application of data in geographic information systems for resource analysis will increase dramatically. These evolving capabilities will revolutionize map production and geographically based resource analyses.

Movement And Fate

Of Contaminants From

Treated Sewage

Infiltrated

To Ground Water,

Cape Cod, Massachusetts

• Since 1936, secondarily treated

domestic sewage has been
discharged to the ground on
surface sand beds at a sewage-
treatment plant at Otis Air Force
Base, Massachusetts. Infiltration of
the sewage through sand beds to
an underlying sand and gravel
aquifer and the subsequent
movement of the sewage-
contaminated ground water in a
southerly direction have caused a
plume of contamination to form that
is 3,000 feet wide, 75 feet thick,
and more than 11,000 feet long.
Most contaminants move readily
through the sand and gravel that
make up the aquifer on Cape Cod,
and little discernible attenuation by
sorption of solutes on the aquifer
material is evident. Transverse and
longitudinal spreading of the plume
is significant, but little vertical
mixing occurs. After 10,000 feet of
movement, the plume is only about
75 feet thick, with a core zone 20
to 30 feet thick where the
contaminants remain at concentra-
tions more than one-fourth of what
they are in the treated sewage.

Land-resource
Investigations

• An extensive subduction melange

complex, the Macon melange,
which underlies at least 5,000
square miles in Georgia, has been
recognized through detailed
geologic mapping conducted under
the Geologic Framework Program in
the Georgia Piedmont. A melange is
a deformed mixture of rocks made
up of slabs and blocks, some of
them miles in length, that have
been mixed together by movements
between the continent-sized plates
that form the Earth's crust. The
Macon melange may be comparable

in size to the Franciscan melange

complex in California, which is one of the best known in North America. Evidence from structures preserved in the rocks indicates that this mixture of diverse rock materials formed above an "African" subduction zone at which the crustal plate that formed the floor of the ocean at that time was pushed beneath the African continent, and sediments resting on the plate were scraped off and piled up on or near Africa. This event occurred when Africa, North America, and South America were joined together as a single continent about 225 million years ago. Geologic mapping and chronological studies conducted under the Geologic Framework Program continue to increase our knowledge of past and present interaction between the huge plates that make up the Earth's crust. These studies have extensive practical applications for industry and government in such diverse fields as mineral and energy exploration and geologic hazard studies.

Continued detailed geologic mapping in California is redefining the origin of the San Andreas and other faults and the amount and rate of displacement on them. This mapping bears heavily on regional multidisciplinary syntheses which are documenting the accretion of exotic terranes (microcontinents that did not originate in North America) from around the Pacific onto the western margin of North America. Mapping older rocks in areas adjacent to the San Andreas fault system has increased our understanding of its evolution. Geologists doing the geologic mapping have reconstructed the distribution pattern of these older rocks before to their offset by the San Andreas and related faults that transect the mountain ranges of southern California.

An early 20th century uplift of a major part of southern California closely matches a mid-20th century uplift in areal extent and magnitude, as well as in its history of

episodic growth and partial collapse. The detection of this earlier uplift, together with the previous recognition of its modern analogue in southern California, demonstrates that a very large part of southern California, including the major mountain ranges bounding the north side of Los Angeles, has sustained cyclic deformation over a period of about 50 years. This

finding is critical to an assessment

of the tectonic evolution of the boundary between the actively moving North American and Pacific crustal plates and will be an important consideration for any tectonic model used for earthquake prediction in this heavily populated and economically vital region.

• Exciting new analytical techniques

are being employed which now
make it possible to determine the
ages of rocks and sediments that
previously could not be dated. An
example is the laser argon-
40-argon-39 method, by which ages
of single grains of mica can be
measured without having to go
through the time-consuming and
expensive process of separating the
mineral from the rock. This dating
process aids greatly in under-
standing the chronology of mineral-
ized zones where micas are present
in such small quantities or are so
small that they cannot be
separated for conventional dating.

LASER OPTICAL DISK STORAGE

• Research and development are

underway to implement laser
optical disk storage technology for
the storage, retrieval, and mainte-
nance of the rapidly expanding
National Digital Cartographic Data
Base. Optical disk technology
involves the use of laser beams to
read and record digital information
onto and from the surface of a
rotating reflective disk. The optical
disk unit records information on the
reflective surface by burning
microscopic patterns of digitally
encoded pits with a high-powered
laser. The unit reads the informa-
tion from the disk with a second

laser which illuminates the burned areas, reflects the encoded pattern to a photoelectric sensor, and converts the resulting electrical impulses to digital signals for data processing. This promising technology offers significant advantages over conventional storage and retrieval devices. For instance, magnetic tapes and disks normally degrade after 2 or 3 years, while optical disks are expected to last at least 10 years. Optical technology also offers far higher data storage capability. A single disk can store up to 4 X 109 characters of data—an amount equivalent to 40 magnetic tapes. When the new software is developed, the use of optical disks will reduce significantly the costs of the National Digital Cartographic Data Base and other archival storage. Current research and development efforts are moving toward improving data structures, data access methods,

and data processing procedures to efficiently use the technology.

Disintegration Of The Lower Reach Of Columbia Glacier, Alaska, Now Under Way

• During the time in the mid 1970's when the Trans-Alaska Pipeline terminal was being built, ice in the shipping lanes of Valdez Arm was encountered rarely and was not considered to be a problem. Now, however, icebergs are seen frequently in Valdez Arm, and, occasionally, tankships have to be diverted or delayed because of ice. Icebergs in Valdez Arm are increasing because the Columbia Glacier is beginning to disintegrate rapidly, resulting in a large increase in the breaking off (calving) of icebergs. This rapid disintegration was predicted by U.S. Geological Survey glaciologists

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in 1980. Never before have scien-
tists been able to observe the begin-
ning of glacier instability and
drastic retreat, and careful obser-
vations of this glacier are adding
much valuable new information,
some of which is surprising and
unanticipated.

Mapping Of Irrigated
Cropland With
Landsat Digital Data

• Research in the use of multispectral
Landsat digital data has proved
that this type of data can be used
to estimate indirectly water with-
drawal from irrigated cropland
acreage. The High Plains aquifer,
covering parts of eight Midwestern
States, supplies water for one-
quarter of the Nation's irrigated
agriculture, and the aquifer is
being depleted rapidly with little
natural recharge. A computerized
hydrologic model is being developed
by staff members of the U.S. Geo-
logical Survey's High Plains
Regional Aquifer Systems Analysis
Project to assist in evaluating
effects of future ground-water
pumpage. The key evaluation factor
is current water pumpage, which is
estimated from measuring the
amount of land that is irrigated and
knowing how much water is used to
irrigate an average acre. Multi-
spectral Landsat digital data were
used to map rapidly the irrigated
cropland over the aquifer. The data
were computer processed to
establish spectral classes, and,
through a clustering process, each
Landsat scene was classified to
identify accurately irrigated crop-
land. In some areas, the variation
in crops required scenes spanning
several seasons. The final area

measurements were combined with estimated pumpage rates to successfully provide input to the hydrologic model. This method provided classification of the cropland rapidly and accurately.

Planetary Geology

• The first in a series of three

l:15,000,000-scale geologic maps of
Mars made from Viking Orbiter
spacecraft images has been com-
pleted for the National Aeronautics
and Space Administration. The
series will supersede the Geologic
Map of Mars (l:25,000,000 scale)
completed in 1978 from Mariner 9
spacecraft pictures. The new map
of the Western Equatorial Region
shows 60 individual rock-
stratigraphic units and includes
descriptions of major tectonic,
volcanic, and fluvial (river
development) episodes interpreted
from the spacecraft image data.
The expanding Martian data base
includes a new series of photo-
mosaics and a new planetwide
topographic data control net.

• Evidence of prehistoric, large-scale

climate change was observed from
space shuttle orbit. Ground investi-
gation of buried ancient stream
channels in the eastern Sahara
dicovered by U.S. Geological Survey
and other scientists resulted from
analysis of images made by the
Imaging Radar System in an early
1982 shuttle flight. The field
observations, in addition, are
providing important new data to
evaluate subsurface radar
responses for water and mineral
resource potential, and for defining
habitation patterns and migration
paths of early stone age man about
200,000 years ago.

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