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At least 1,729 records · Page 96Linked to original sources
USGS1967

Effects of the earthquake of March 27, 1964, on air and water transport, communications, and utilities systems in south-central Alaska

The earthquake of March 27, 1964, wrecked or severely hampered all forms of transportation, all utilities, and all communications systems over a very large part of south-central Alaska. Effects on air transportation were minor as compared to those on the water, highway, and railroad transport systems. A few planes were damaged or wrecked by seismic vibration or by flooding. Numerous airport facilities were damaged by vibration or by secondary effects of the earthquake, notably seismic sea and landslide-generated waves, tectonic subsidence, and compaction. Nearly all air facilities were partly or wholly operational within a few hours after the earthquake. The earthquake inflicted enormous damage on the shipping industry, which is indispensable to a State that imports fully 90 percent of its requirements—mostly by water—and whose largest single industry is fishing. Except for those of Anchorage, all port facilities in the earthquake-affected area were destroyed or made inoperable by submarine slides, waves, tectonic uplift, and fire. No large vessels were lost, but more than 200 smaller ones (mostly crab or salmon boats) were lost or severely damaged. Navigation aids were destroyed, and hitherto well-known waterways were greatly altered by uplift or subsidence. All these effects wrought far-reaching changes in the shipping economy of Alaska, many of them to its betterment. Virtually all utilities and communications in south-central Alaska were damaged or wrecked by the earthquake, but temporary repairs were effected in remarkably short times. Communications systems were silenced almost everywhere by loss of power or by downed lines; their place was quickly taken by a patchwork of self-powered radio transmitters. A complex power-generating system that served much of the stricken area from steam, diesel, and hydrogenerating plants was disrupted in many places by vibration damage to equipment and by broken transmission lines. Landslides in Anchorage broke gas-distribution lines in many places, but the main transmission line from the Kenai Peninsula was virtually undamaged. Petroleum supplies were disrupted, principally by breakage or loss of storage tanks caused by seismic vibration, slides, waves, and fire. Water-supply and sewer lines were also broken in many towns.

Alaska↗
USGS1968

Effects of the earthquake of March 27, 1964, on the Alaska highway system

The great earthquake that struck Alaska about 5:36 p.m., Alaska standard time, Friday, March 27, 1964 (03:36:1.3.0, Greenwich mean time, March 28, 1964), severely crippled the highway system in the south-central part of the State. All the major highways and most secondary roads were impaired. Damage totaled more than $46 million, well over $25 million to bridges and nearly $21 million to roadways. Of the 204 bridges in south-central Alaska, 141 were damaged; 92 were severely damaged or destroyed. The earthquake damaged 186 of the 830 miles of roadway in south-central Alaska, 83 miles so severely that replacement or relocation was required. Earthquake damage to the roadways and bridges was chiefly by (1) seismic shaking, (2) compaction of fills as well as the underlying sediments, (3) lateral displacement of the roadway and bridges, (4) fractures, (5) landslides, (6) avalanches, (7) inundation by seismic sea waves, (8) scouring by seismic sea waves, (9) regional tectonic subsidence, causing inundation and erosion by high tides in subsided areas. The intensity of damage was controlled primarily by the geologic environment (including the depth of the water table) upon which the highway structures rested, and secondarily by the engineering characteristics of the structures. Structures on bedrock were only slightly damaged if at all, whereas those on unconsolidated sediments were slightly to severely damaged, or were completely destroyed by seismic shaking. The low-lying areas underlain by saturated sediments, such as the Snow River Crossing and Turnagain Arm sections of the Seward-Anchorage Highway, were the most severely damaged stretches of the highway system in south-central Alaska. At Snow River and Turnagain Arm, the sediments underlying the roadway are fine grained and the water table is shallow. These factors were responsible for the intense damage along this stretch of the highway. All the bridges on the Copper River Highway except for one on bedrock were damaged by seismic shaking. Lateral displacement of sediments toward a free face, which placed the bridges in compression, was the chief cause for the damage. This type of failure was extensive and widespread throughout the highway system. The chief engineering characteristics responsible for the type and intensity of damage include (1) thickness of roadway fills, (2) type of pile bents and masonry piers, (3) the weight ratio between the substructure and superstructure, and (4) the tie between the substructure and superstructure. The thicker the roadway fills, the more severe the damage. Wood piles did not break as extensively as piles constructed of three railroad rails welded together. Bridges that had relatively heavy superstructures, for example those with concrete decks on wood piles, were more severely damaged than those with all-wood or concrete decks or concrete piers. Failure first occurred at the tie between the superstructure and the substructure; the poorer this tie, the sooner the failure. Seismic sea waves destroyed 12 bridges on the Chiniak Highway on Kodiak Island, one bridge on Point Whitshed road near Cordova, and about 14 miles of roadway. The combination of regional tectonic subsidence and local subsidence and compaction of sediments caused inundation of many miles of highway by high tides, especially around Turnagain Arm. Total subsidence in some places amounted to more than 13 feet.

Alaska↗
USGS1970

The Alaska earthquake, March 27, 1964: Lessons and conclusions

One of the greatest earthquakes of all time struck south-central Alaska on March 27, 1964. Strong motion lasted longer than for most recorded earthquakes, and more land surface was dislocated, vertically and horizontally, than by any known previous temblor. Never before were so many effects on earth processes and on the works of man available for study by scientists and engineers over so great an area. The seismic vibrations, which directly or indirectly caused most of the damage, were but surface manifestations of a great geologic event-the dislocation of a huge segment of the crust along a deeply buried fault whose nature and even exact location are still subjects for speculation. Not only was the land surface tilted by the great tectonic event beneath it, with resultant seismic sea waves that traversed the entire Pacific, but an enormous mass of land and sea floor moved several tens of feet horizontally toward the Gulf of Alaska. Downslope mass movements of rock, earth, and snow were initiated. Subaqueous slides along lake shores and seacoasts, near-horizontal movements of mobilized soil (“landspreading”), and giant translatory slides in sensitive clay did the most damage and provided the most new knowledge as to the origin, mechanics, and possible means of control or avoidance of such movements. The slopes of most of the deltas that slid in 1964, and that produced destructive local waves, are still as steep or steeper than they were before the earthquake and hence would be unstable or metastable in the event of another great earthquake. Rockslide avalanches provided new evidence that such masses may travel on cushions of compressed air, but a widely held theory that glaciers surge after an earthquake has not been substantiated. Innumerable ground fissures, many of them marked by copious emissions of water, caused much damage in towns and along transportation routes. Vibration also consolidated loose granular materials. In some coastal areas, local subsidence was superimposed on regional tectonic subsidence to heighten the flooding damage. Ground and surface waters were measurably affected by the earthquake, not only in Alaska but throughout the world. Expectably, local geologic conditions largely controlled the extent of structural damage, whether caused directly by seismic vibrations or by secondary effects such as those just described. Intensity was greatest in areas underlain by thick saturated unconsolidated deposits, least on indurated bedrock or permanently frozen ground, and intermediate on coarse well-drained gravel, on morainal deposits, or on moderately indurated sedimentary rocks. Local and even regional geology also controlled the distribution and extent of the earthquake's effects on hydrologic systems. In the conterminous United States, for example, seiches in wells and bodies of surface water were controlled by geologic structures of regional dimension. Devastating as the earthquake was, it had many long-term beneficial effects. Many of these were socioeconomic or engineering in nature; others were of scientific value. Much new and corroborative basic geologic and hydrologic information was accumulated in the course of the earthquake studies, and many new or improved investigative techniques were developed. Chief among these, perhaps, were the recognition that lakes can be used as giant tiltmeters, the refinement of methods for measuring land-level changes by observing displacements of barnacles and other sessile organisms, and the relating of hydrology to seismology by worldwide study of hydroseisms in surface-water bodies and in wells. The geologic and hydrologic lessons learned from studies of the Alaska earthquake also lead directly to better definition of the research needed to further our understanding of earthquakes and of how to avoid or lessen the effects of future ones. Research is needed on the origins and mechanisms of earthquakes, on crustal structure, and on the generation of tsunamis and local waves. Better earthquake-hazard maps, based on improved knowledge of regional geology, fault behavior, and earthquake mechanisms, are needed for the entire country. Their preparation will require the close collaboration of engineers, seismologists, and geologists. Geologic maps of all inhabited places in earthquake-prone parts of the country are also needed by city planners and others, because the direct relationship between local geology and potential earthquake damage is now well understood. Improved and enlarged nets of earthquake-sensing instruments, sited in relation to known geology, are needed, as are many more geodetic and hydrographic measurements. Every large earthquake, wherever located, should be regarded as a full-scale laboratory experiment whose study can give scientific and engineering information unobtainable from any other source. Plans must be made before the event to insure staffing, funding, and coordination of effort for the scientific and engineering study of future earthquakes. Advice of earth scientists and engineers should be used in the decision-making processes involved in reconstruction after any future disastrous earthquake, as was done after the Alaska earthquake. The volume closes with a selected bibliography and a comprehensive index to the entire series of U.S. Geological Survey Professional Papers 541-546. This is the last in a series of six reports that the U.S. Geological Survey published on the results of a comprehensive geologic study that began, as a reconnaissance survey, within 24 hours after the March 27, 1964, Magnitude 9.2 Great Alaska Earthquake and extended, as detailed investigations, through several field seasons. The 1964 Great Alaska earthquake was the largest earthquake in the U.S. since 1700. Professional Paper 546, in 1 part, describes Lessons and Conclusions.

Alaska↗
USGS2001

The Quaternary and Pliocene Yellowstone Plateau volcanic field of Wyoming, Idaho, and Montana

This region of Yellowstone National Park has been the active focus of one of the Earth's largest magmatic systems for more than 2 million years. The resulting volcanism has been characterized by the eruption of voluminous rhyolites and subordinate basalts but virtually no lavas of intermediate composition. The magmatic system at depth remains active and drives the massive hydrothermal circulation for which the park is widely known. Studies of the volcanic field using geologic mapping and petrology have defined three major cycles of rhyolitic volcanism, each climaxed by the eruption of a rhyolitic ash-flow sheet having a volume of hundreds of thousands of cubic kilometers. The field also has been analyzed in terms of its magmatic and tectonic evolution, including its regional relation to the Snake River plain and to basin-range tectonic extension.

Idaho, Montana, Wyoming↗
USGS1975

Paleotectonic investigations of the Pennsylvanian System in the United States, Part I: Introduction and regional analyses of the Pennsylvanian System

The Pennsylvanian is the fourth geologic system to be analyzed and synthesized by geologists of the U.S. Geological Survey in the form of a paleotectonic study covering the conterminous United States. Earlier investigations were of the Jurassic, Triassic, and Permian Systems. Results were published as Miscellaneous Geologic Investigation Maps I-175, I-300, and I-450 and in Professional Paper 515. The objective of these investigations is to provide in graphic form the factual basis for recognition of tectonic events of each system on a countrywide scale. The maps in this publication depict rock thickness, generalized lithology, ancient geography, and other regional relations of the Pennsylvanian System. Method of preparation of the maps, the stratigraphic limits of the map units, and various stratigraphic and structural features and their probable tectonic significance are discussed. Pennsylvanian data were largely compiled between 1961 and 196 by 16 geologists, including the late Harold R. Wanless, who covered the five eastern regions and contributed to several of the special studies. The areas of responsibility of the cooperating geologists are indicated in figure 1. Work in Kansas was done by Gary F. Stewart, of the Kansas Geological Survey. Results of this investigation are presented in three units. Part I comprises an introduction and 17 chapters, each describing and discussing one of the regions in which the conterminous United States was divided for purposes of study and mapping. Part II is a synthesis of Pennsylvanian history to accompany interpretive maps of the five divisions of the Pennsylvanian System treated in this publication; it also includes a series of chapters on depositional environments, climatic conditions, and economic products of the system. The final section of part II is devoted to an index of localities and sources used in construction of the principal maps of this publication. Part III consists of the plates on which are presented the major maps and sections.

Professional Paper↗
USGS1976

Metamorphism and plutonism around the middle and south forks of the Feather River, California

The area around the Middle and South Forks of the Feather River provides information on metamorphic and igneous processes that bear on the origin of andesitic and granitic magmas in general and on the variation of their potassium content in particular. In the north, the area joins the Pulga and Bucks Lake quadrangles studied previously. Tectonically, this area is situated in the southern part of an arcuate segment of the Nevadan orogenic belt in the northwestern Sierra Nevada. The oldest rocks are metamorphosed calcalkaline island-arc-type andesite, dacite, and sodarhyolite with interbedded tuff layers (the Franklin Canyon Formation), all probably correlative with Devonian rocks in the Klamath Mountains. Younger rocks form a sequence of volcanic, volcaniclastic, and sedimentary rocks including some limestone (The Horseshoe Bend Formation), probably Permian in age. All the volcanic and sedimentary rocks were folded and recrystallized to the greenschist facies during the Nevadan (Jurassic) orogeny and were invaded by monzotonalitic magmas shortly thereafter. A second lineation and metamorphism to the epidote-amphibolite facies developed in a narrow zone around the plutons. In light of the concept of plate tectonics, it is suggested that the early (Devonian?) island-arc-type andesite, dacite, and sodarhyolite (the Franklin Canyon Formation) were derived from the mantle above a Benioff zone by partial melting of peridotite in hydrous conditions. The water was probably derived from an oceanic plate descending to the mantle. Later (Permian?) magmas were mainly basaltic; some discontinuous layers of potassium-rich rhyolite indicate a change into anhydrous conditions and a deeper level of magma generation. The plutonic magmas that invaded the metamorphic rocks at the end of the Jurassic may contain material from the mantle, the subducted oceanic lithosphere, and the downfolded metamorphic rocks. The ratio of partial melts from these three sources may have changed with time, giving rise to the diversity in composition of magmas.

California↗
USGS2005

Geologic map of the northern plains of Mars

The northern plains of Mars cover nearly a third of the planet and constitute the planet's broadest region of lowlands. Apparently formed early in Mars' history, the northern lowlands served as a repository both for sediments shed from the adjacent ancient highlands and for volcanic flows and deposits from sources within and near the lowlands. Geomorphic evidence for extensive tectonic deformation and reworking of surface materials through release of volatiles occurs throughout the northern plains. In the polar region, Planum Boreum contains evidence for the accumulation of ice and dust, and surrounding dune fields suggest widespread aeolian transport and erosion. The most recent regional- and global-scale maps describing the geology of the northern plains are largely based on Viking Orbiter image data (Dial, 1984; Witbeck and Underwood, 1984; Scott and Tanaka, 1986; Greeley and Guest, 1987; Tanaka and Scott, 1987; Tanaka and others, 1992a; Rotto and Tanaka, 1995; Crumpler and others, 2001; McGill, 2002). These maps reveal highland, plains, volcanic, and polar units based on morphologic character, albedo, and relative ages using local stratigraphic relations and crater counts. This geologic map of the northern plains is the first published map that covers a significant part of Mars using topography and image data from both the Mars Global Surveyor and Mars Odyssey missions. The new data provide a fresh perspective on the geology of the region that reveals many previously unrecognizable units, features, and temporal relations. In addition, we adapted and instituted terrestrial mapping methods and stratigraphic conventions that we think result in a clearer and more objective map. We focus on mapping with the intent of reconstructing the history of geologic activity within the northern plains, including deposition, volcanism, erosion, tectonism, impact cratering, and other processes with the aid of comprehensive crater-density determinations. Mapped areas include all plains regions within the northern hemisphere of Mars, as well as an approximately 300-km-wide strip of cratered highland and volcanic regions, which border the plains. Note that not all of the contiguous northern plains are mapped, because some minor parts of Elysium and Amazonis Planitiae lie south of the equator.

Scientific Investigations Map↗
USGS2007

Geologic Map of the Pahranagat Range 30' x 60' Quadrangle, Lincoln and Nye Counties, Nevada

Introduction The Pahranagat Range 30' x 60' quadrangle lies within an arid, sparsely populated part of Lincoln and Nye Counties, southeastern Nevada. Much of the area is public land that includes the Desert National Wildlife Range, the Pahranagat National Wildlife Refuge, and the Nellis Air Force Base. The topography, typical of much of the Basin and Range Province, consists of north-south-trending ranges and intervening broad alluvial valleys. Elevations range from about 1,000 to 2,900 m. At the regional scale, the Pahranagat Range quadrangle lies within the Mesozoic and early Tertiary Sevier Fold-and-Thrust Belt and the Cenozoic Basin and Range Province. The quadrangle is underlain by a Proterozoic to Permian miogeoclinal section, a nonmarine clastic and volcanic section of middle Oligocene or older to late Miocene age, and alluvial deposits of late Cenozoic age. The structural features that are exposed reflect relatively shallow crustal deformation. Mesozoic deformation is dominated by thrust faults and asymmetric or open folds. Cenozoic deformation is dominated by faults that dip more than 45i and dominostyle tilted blocks. At least three major tectonic events have affected the area: Mesozoic (Sevier) folding and thrust faulting, pre-middle Oligocene extensional deformation, and late Cenozoic (mainly late Miocene to Holocene) extensional deformation. Continued tectonic activity is expressed in the Pahranagat Range area by seismicity and faults having scarps that cut alluvial deposits.

Scientific Investigations Map↗
USGS2017

Bedrock geologic map of the northern Alaska Peninsula area, southwestern Alaska

The northern Alaska Peninsula is a region of transition from the classic magmatic arc geology of the Alaska Peninsula to a Proterozoic and early Paleozoic carbonate platform and then to the poorly understood, tectonically complex sedimentary basins of southwestern Alaska. Physiographically, the region ranges from the high glaciated mountains of the Alaska-Aleutian Range to the coastal lowlands of Cook Inlet on the east and Bristol Bay on the southwest. The lower Ahklun Mountains and finger lakes on the west side of the map area show strong effects from glaciation. Structurally, a number of major faults cut the map area. Most important of these are the Bruin Bay Fault that parallels the coast of Cook Inlet, the Lake Clark Fault that cuts diagonally northeast to southwest across the eastern part of the map area, and the presently active Holitna Fault to the northwest that cuts surficial deposits. Distinctive rock packages assigned to three provinces are overlain by younger sedimentary rocks and intruded by widely dispersed latest Cretaceous and (or) early Tertiary granitic rocks. Much of the east half of the map area lies in the Alaska-Aleutian Range province; the Jurassic to Tertiary Alaska-Aleutian Range batholith and derivative Jurassic sedimentary rocks form the core of this province, which is intruded and overlain by the Aleutian magmatic arc. The Lime Hills province, the carbonate platform, occurs in the north-central part of the map area. The Paleozoic and Mesozoic Ahklun Mountains province in the western part of the map area includes abundant chert, argillite, and graywacke and lesser limestone, basalt, and tectonic mélange. The Kuskokwim Group, an Upper Cretaceous turbidite sequence, is extensively exposed and bounds all three provinces in the west-central part of the map area.

Alaska↗
USGS2008

Geologic Map of the Eastern Three-Quarters of the Cuyama 30' x 60' Quadrangle, California

The map area encompasses a large part of the western Transverse Ranges and southern Coast Ranges of southern California. The San Andreas fault (SAF) cuts the northern part of the map. The area south of the SAF, about 80 percent of the map area, encompasses several distinct tectonic blocks bounded by major thrust or reverse faults, including the Santa Ynez fault, Big Pine fault (and structurally continuous Pine Mountain fault), Tule Creek fault, Nacimiento fault, Ozena fault, Munson Creek fault, Morales fault, and Frazier Mountain Thrust System. Movement on these faults is as old as Miocene and some faults may still be active. In addition, the Paleocene Sawmill Mountain Thrust south of the SAF and the Pastoria Thrust north of the SAF place Cretaceous and older crystalline rocks above Pelona Schist (south of the SAF) and Rand Schist (north of the SAF). South of the SAF, each tectonic block contains a unique stratigraphy, reflecting either large-scale movement on bounding faults or different depositional environments within each block. On Mount Pinos and Frazier Mountain, intrusive and metamorphic rocks as old as Mesoproterozoic, but including voluminous Cretaceous granitoid rocks, underlie or are thrust above non-marine sedimentary rocks as old as Miocene. Elsewhere, marine and non-marine sedimentary rocks are as old as Cretaceous, dominated by thick sequences of both Eocene and Cretaceous marine shales and sandstones. Middle Miocene to early Oligocene volcanic rocks crop out in the Caliente Hills (part of Caliente Formation) and south of Mount Pinos (part of the Plush Ranch Formation). Fault-bounded windows of Jurassic Franciscan Complex ophiolitic rocks are evident in the southwest corner of the area. North of the SAF, marine and non-marine sedimentary rocks as old as Eocene and Miocene volcanic rocks overlie a crystalline basement complex. Basement rocks include Cretaceous intrusive rocks that range from monzogranite to diorite, and Jurassic to late Paleozoic intrusive and metamorphic rocks. The Jurassic to late Paleozoic intrusive rocks include diorite, gabbro, and ultramafic rocks, and the metasedimentary rocks include marble, quartzite, schist, and gneiss.

Scientific Investigations Map↗
USGS2008

Precambrian basement structure map of the continental United States - An interpretation of geologic and aeromagnetic data

The Precambrian basement rocks of the continental United States are largely covered by younger sedimentary and volcanic rocks, and the availability of updated aeromagnetic data (NAMAG, 2002) provides a means to infer major regional basement structures and tie together the scattered, but locally abundant, geologic information. Precambrian basement structures in the continental United States have strongly influenced later Proterozoic and Phanerozoic tectonism within the continent, and there is a growing awareness of the utility of these structures in deciphering major younger tectonic and related episodes. Interest in the role of basement structures in the evolution of continents has been recently stimulated, particularly by publications of the Geological Society of London (Holdsworth and others, 1998; Holdsworth and others, 2001). These publications, as well as others, stress the importance of reactivation of basement structures in guiding the subsequent evolution of continents. Knowledge of basement structures is an important key to understanding the geology of continental interiors.

Scientific Investigations Map↗
USGS2013

Geodynamics map of northeast Asia

This map portrays the geodynamics of Northeast Asia at a scale of 1:5,000,000 using the concepts of plate tectonics and analysis of terranes and overlap assemblages. The map is the result of a detailed compilation and synthesis at 5 million scale and is part of a major international collaborative study of the mineral resources, metallogenesis, and tectonics of northeast Asia conducted from 1997 through 2002 by geologists from earth science agencies and universities in Russia, Mongolia, northeastern China, South Korea, Japan, and the USA.

Asia↗
USGS2009

Geologic Map of MTM 35337, 40337, and 45337 Quadrangles, Deuteronilus Mensae Region of Mars

Deuteronilus Mensae, first defined as an albedo feature at lat 35.0 deg N., long 5.0 deg E., by U.S. Geological Survey (USGS) and International Astronomical Union (IAU) nomenclature, is a gradational zone along the dichotomy boundary in the northern mid-latitudes of Mars. The boundary in this location includes the transition from the rugged cratered highlands of Arabia Terra to the northern lowland plains of Acidalia Planitia. Within Deuteronilus Mensae, polygonal mesas are prominent along with features diagnostic of Martian fretted terrain, including lobate debris aprons, lineated valley fill, and concentric crater fill. Lobate debris aprons, as well as the valley and crater fill deposits, are geomorphic indicators of ground ice, and their concentration in Deuteronilus Mensae is of great interest because of their potential association with Martian climate change. The paucity of impact craters on the surfaces of debris aprons and the presence of ice-cemented mantle material imply young (for example, Amazonian) surface ages that are consistent with recent climate change in this region of Mars. North of Deuteronilus Mensae are the northern lowlands, a potential depositional sink that may have had large standing bodies of water or an ocean in the past. The northern lowlands have elevations that are several kilometers below the ancient cratered highlands with significantly younger surface ages. The morphologic and topographic characteristics of the Deuteronilus Mensae region record a diverse geologic history, including significant modification of the ancient highland plateau and resurfacing of low-lying regions. Previous studies of this region have interpreted a complex array of geologic processes, including eolian, fluvial and glacial activity, coastal erosion, marine deposition, mass wasting, tectonic faulting, effusive volcanism, and hydrovolcanism. The origin and age of the Martian crustal dichotomy boundary are fundamental questions that remain unresolved at the present time. Several scenarios for its formation, including single and multiple large impact events, have been proposed and debated in the literature. Endogenic processes whereby crust is thinned by internal mantle convection and tectonic processes have also been proposed. Planetary accretion models and isotopic data from Martian meteorites suggest that the crust formed very early in Martian history. Using populations of quasi-circular depressions extracted from the topography of Mars, other studies suggest that the age difference between the highlands and lowlands could be ~100 m.y.. Furthermore, understanding the origin and age of the dichotomy boundary has been made more complicated due to significant erosion and deposition that have modified the boundary and its adjacent regions. The resulting diversity of terrains and features is likely a combined result of ancient and recent events. Detailed geologic analyses of dichotomy boundary zones are important for understanding the spatial and temporal variations in highland evolution. This information, and comparisons to other highland regions, can help elucidate the scale of potential environmental changes. Previous geomorphic and geologic mapping investigations of the Deuteronilus Mensae region have been completed at local to global scales. The regional geology was first mapped by Lucchitta (1978) at 1:5,000,000 scale using Mariner 9 data. This study concluded that high crater flux early in Martian history formed overlapping craters and basins that were later filled by voluminous lava flows that buried the impacted surface, creating the highlands. After this period of heavy bombardment, fluvial erosion of the highlands formed the canyons and valleys, followed by dissection that created the small mesas and buttes, and later, formation of the steep escarpment marking the present-day northern highland margin. After valley dissection, mass wasting and eolian processes caused lateral retreat of mesas and buttes

Scientific Investigations Map↗
USGS2011

Geologic map of the Bailey 30' x 60' quadrangle, North-Central Colorado

The Bailey, Colo. 1:100,000-scale quadrangle lies within two physiographic and geologic provinces in central Colorado: 1) the Front Range and 2) South Park. Most of the Front Range is composed of Proterozoic rocks ranging in age from 1,790 Ma to 1,074 Ma. Along the eastern flanks and within the Denver Basin, sedimentary rocks ranging from Pennsylvanian to Cretaceous are deformed and steeply tilted to the east. Upper Cretaceous through Paleocene rocks were deposited in the foreland (that is, the Front Range eastern flank) and hinterland (that is, South Park) of this thrust and reverse fault system developed during the Late Cretaceous to Paleocene Laramide orogeny. Within South Park, rocks range in age from Pennsylvanian to Miocene with Quaternary deposits indicating tectonic subsidence of the basin. These rocks record five major geologic episodes: 1) the Paleozoic Anasazi uplift that formed the Ancestral Rockies, 2) the Late Cretaceous to Paleocene Laramide orogeny, 3) widespread Eocene to Oligocene volcanism, 4) Oligocene-Quaternary tectonics, and 5) Quaternary glacial episodes.

Colorado↗
USGS2011

Bedrock geologic map of Vermont

The Bedrock Geologic Map of Vermont is the result of a cooperative agreement between the U.S. Geological Survey (USGS) and the State of Vermont. The State's complex geology spans 1.4 billion years of Earth's history. The new map comes 50 years after the most recent map of the State by Charles G. Doll and others in 1961 and a full 150 years since the publication of the first geologic map of Vermont by Edward Hitchcock and others in 1861. At a scale of 1:100,000, the map shows an uncommon level of detail for State geologic maps. Mapped rock units are primarily based on lithology, or rock type, to facilitate derivative studies in multiple disciplines. The 1961 map was compiled from 1:62,500-scale or smaller maps. The current map was created to integrate more detailed (1:12,000- to 1:24,000-scale) modern and older (1:62,500-scale) mapping with the theory of plate tectonics to provide a framework for geologic, tectonic, economic, hydrogeologic, and environmental characterization of the bedrock of Vermont. The printed map consists of three oversize sheets (52 x 76 inches). Sheets 1 and 2 show the southern and northern halves of Vermont, respectively, and can be trimmed and joined so that the entire State can be displayed as a single entity. These sheets also include 10 cross sections and a geologic structure map. Sheet 3 on the front consists of descriptions of 486 map units, a correlation of map units, and references cited. Sheet 3 on the back features a list of the 195 sources of geologic map data keyed to an index map of 7.5-minute quadrangles in Vermont, as well as a table identifying ages of rocks dated by uranium-lead zircon geochronology.

Vermont↗
USGS2014

Global geologic map of Ganymede

Ganymede is the largest satellite of Jupiter, and its icy surface has been formed through a variety of impact cratering, tectonic, and possibly cryovolcanic processes. The history of Ganymede can be divided into three distinct phases: an early phase dominated by impact cratering and mixing of non-ice materials in the icy crust, a phase in the middle of its history marked by great tectonic upheaval, and a late quiescent phase characterized by a gradual drop in heat flow and further impact cratering. Images of Ganymede suitable for geologic mapping were collected during the flybys of Voyager 1 and Voyager 2 (1979), as well as during the Galileo Mission in orbit around Jupiter (1995–2003). This map represents a synthesis of our understanding of Ganymede geology after the conclusion of the Galileo Mission. We summarize the properties of the imaging dataset used to construct the map, previously published maps of Ganymede, our own mapping rationale, and the geologic history of Ganymede. Additional details on these topics, along with detailed descriptions of the type localities for the material units, may be found in the companion paper to this map (Patterson and others, 2010).

Scientific Investigations Map↗
USGS2014

Quaternary geologic map of the north-central part of the Salinas River Valley and Arroyo Seco, Monterey County, California

Arroyo Seco, a perennial drainage in the central Coast Range of California, records a sequence of strath terraces. These terraces preserve an erosional and depositional history, controlled by both climate change and regional tectonics. These deposits have been mapped and correlated on the basis of field investigations, digital terrain analysis, stream gradient profiles, evaluation of published regional soil maps, and satellite imagery. Seven of the strath terraces and associated alluvial fans have been dated by optically stimulated luminescence (OSL) or infrared stimulated luminescence (IRSL). The OSL and IRSL dates on seven of the strath terraces and associated alluvial fans in Arroyo Seco are approximately >120 ka, >65 ka, 51–46 ka, 36–35 ka, 9 ka, and 2–1 ka. These dates generally fall within the range of ages reported from many well-dated marine terraces on the California coast that are formed during sea-level high stands. Tectonic movements, consistently upward, result in a constantly and slowly emerging coastline, however, the regional effects of climate change and resulting eustatic sea-level rises are interpreted as the driving mechanism for erosion and aggradation in Arroyo Seco.

California↗
USGS2018

Geologic map of the Hayfield quadrangle, Frederick County, Virginia

The Hayfield 7.5-minute quadrangle is located within the Valley and Ridge physiographic province of northern Virginia. The quadrangle includes the topographical lowland area of the northern Great Valley to the southeast, the narrow ridge of Little North Mountain along the western edge of the Great Valley, and the broad region of elongated valleys and ridges west of Little North Mountain. The most prominent physiographic feature within the quadrangle is Great North Mountain, which extends across the northwestern portion of the quadrangle. All exposed bedrock units are Paleozoic sedimentary rocks ranging from Middle Cambrian to Late Devonian, approximately 513 to 359 Ma. The clastic and carbonate sedimentary strata in the quadrangle reflect nearshore and offshore marine and deltaic depositional environments. The deposits indicate minor sea level transgression and regression cycles along a passive continental margin during the Late Cambrian to Middle Ordovician, and major sea level changes resulting from tectonic uplift during the Late Ordovician Taconian orogeny and the Middle to Late Devonian Acadian orogeny. Compressive forces caused by the continental collision during the Paleozoic Alleghanian orogeny resulted in folding and faulting of the sedimentary rock strata, with northwestward tectonic transport. The North Mountain fault zone, spanning across the southeastern part of the quadrangle, forms the western border of the Great Valley in northern Virginia and is a series of northeast-trending thrust faults with multiple splays that separate the Silurian and Devonian shales, siltstones, and sandstones from the Cambrian and Ordovician carbonate rocks and shales. Topographic ridges in the quadrangle are primarily held up by sandstones and orthoquartzites that are relatively resistant to erosion. Surficial materials include unconsolidated alluvium, colluvium, debris flow, and terrace deposits that are assumed to be of Quaternary age. Alluvium was mapped along the larger streams; locally, some low alluvial terraces exist but have not been broken out within this unit. Debris flow deposits were mapped where recognized in the lidar-derived topographic imagery on the flanks of Great North Mountain. Colluvium (not mapped separately) covers most of the steeper slopes and fills the bottoms of many of the mountain hollows, and is composed mainly of sandstone boulders and cobbles, and fragments of chert.

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