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USGS1999

Fossils, rocks, and time

We study our Earth for many reasons: to find water to drink or oil to run our cars or coal to heat our homes, to know where to expect earthquakes or landslides or floods, and to try to understand our natural surroundings. Earth is constantly changing--nothing on its surface is truly permanent. Rocks that are now on top of a mountain may once have been at the bottom of the sea. Thus, to understand the world we live on, we must add the dimension of time. We must study Earth's history. When we talk about recorded history, time is measured in years, centuries, and tens of centuries. When we talk about Earth history, time is measured in millions and billions of years. Time is an everyday part of our lives. We keep track of time with a marvelous invention, the calendar, which is based on the movements of Earth in space. One spin of Earth on its axis is a day, and one trip around the Sun is a year. The modern calendar is a great achievement, developed over many thousands of years as theory and technology improved. People who study Earth's history also use a type of calendar, called the geologic time scale. It looks very different from the familiar calendar. In some ways, it is more like a book, and the rocks are its pages. Some of the pages are torn or missing, and the pages are not numbered, but geology gives us the tools to help us read this book.

Report↗
USGS1993

Fossils, rocks, and time

We study out Earth for many reasons: to find water to drink or oil to run our cars or coal to heat our homes, to know where to expect earthquakes or landslides or floods, and to try to understand our natural surroundings. Earth is constantly changing--nothing on its surface is truly permanent. Rocks that are not on top of a mountain may once have been on the bottom of the sea. Thus, to understand the world we live on, we must add the dimension of time. We must study Earth's history. When we talk about recorded history, time is measured in years, centuries, and tens of centuries. When we talk about Earth history, time is measured in millions and billions of years. Time is an everyday part of our lives. We keep track of time with a marvelous invention, the calendar, which is based on the movements of the Earth in space. One spin of Earth on its axis is a day, and one trip around the sun is a year. The modern calendar is a great achievement, developed over many thousands of years as theory and technology improved. People who study Earth's history also use a type of calendar, called the geologic time scale. It looks very different from the familiar calendar. In some ways, it is more like a book, and the rocks are its pages. Some of the pages are torn or missing, and the pages are not numbered, but geology gives us the tools to help us read this book.

General Interest Publication↗
USGS1981

United States Geological Survey Yearbook, fiscal year 1980

It is not very often that a single event is so overwhelming that it changes public perceptions of natural hazards for generations. Perhaps for the U.S. Geological Survey, the explosive volcanic activity of Mount St. Helens began such a change. After 101 years of careful science of the Earth's past and meticulous observations and assessments of the present, predictive earth science was in full public view. However vague and faint the glimpse of the future made possible by earth science, it was enough. Warnings were issued, thousands of lives were saved, and the age of real-time geology began. The Survey's basic mission has not changed, but the power of our analytical tools has increased by several orders of magnitude. The Survey's efforts to understand Earth processes and hydrologic principles continued with the collection, during fiscal year 1980, of valuable new data on the geologic origin and framework, seismicity, and mineral and energy resources of the United States. The Survey is also responsible for classification of the leasable minerals on Federal lands and the regulation of mineral exploration and development activities on Federal and Indian lands. As the principal earth science fact-gathering agency, the Survey provides information for sound decisionmaking by government and private industry. Industry uses the Survey's information in exploring for energy and minerals and improving their efforts to make development of energy and minerals compatible with environmental protection standards. Government uses the Survey's information in conducting leasing operations on public lands, in regulating the safe design and siting of nuclear plants, and in establishing guidelines for determining and locating areas that are subject to geologic hazards such as landslides, earthquakes, and volcanic eruptions. The Yearbook reports a broad range of the Survey's accomplishments during the past fiscal year and provides an overview of future directions. Many of the topics covered will continue to be important natural resource and earth science issues of the 1980's.

Yearbook↗
USGS1963

Geology of the Jewel Cave SW Quadrangle, Custer County, South Dakota

The Jewel Cave SW quadrangle is in the southwestern part of the Black Hills in Custer County, S. Dak., about midway between Edgemont, S. Dak., and Newcastle, Wyo. All the rocks that crop out within the quadrangle are of sedimentary origin and range in age from Pennsylvanian to Early Cretaceous. The Minnesota Formation of Pennsylvania and Permian age, which is about 1,000 feet thick, was studied in outcrop and from two diamond-drill cores. In the subsurface the upper part of the formation consists of gray sandstone, very fine grained dolomite, and anhydrite. The anhydrite has been leached from the formation near the outcrop, perhaps in the early part of the Cenozoic Era, and the resulting subsidence has produced collapse breccias in the Minnelusa and milder deformation in the overlying units. In the collapse breccias the rocks have been oxidized and are red, whereas in the subsurface they are gray. The anhydrite cement of the subsurface sandstone has been replaced by calcite, and the dolomite beds have been partially converted to limestone. The Opeche Formation of Permian age consists of 75 to 115 feet of red siltstone and shale and two thin gypsum beds. The Minnekahta Limestone of Permian age is about 40 feet thick. The Spearfish Formation of Permian and Triassic age is about 550 feet thick and consists of red siltstone red sandstone, dolomite, and gypsum. The dolomite and gypsum beds are restricted to the lower half of the formation. In the northeast corner of the quadrangle the gypsum beds have been dissolved by ground water. The Sundance Formation of Late Jurassic age is divided into five members that have a total thickness of about 360 feet. The Morrison Formation of Late Jurassic age ranges in thickness from 60 to 120 feet. It consists of blocky weathering noncarbonaceous mudstone and subordinate beds of limestone and sandstone. The Inyan Kara Group of Early Cretaceous age has been subdivided into the Lakota Formation and the Fall River Formation. The Lakota Formation consists of 200 to 300 feet of carbonaceous siltstone blocky-weathering claystone, and fine-grained to conglomeratic sandstone. These rocks were deposited in stream channels, flood plains, and ponds. The Fall River Formation is about 110 to 130 feet thick. Along the northeast side of the outcrop the formation consists of fine- to medium-grained sandstone, which forms an elongate body at least 1-1/2 miles wide and more than 25 miles long. To the southwest the formation consists of thinly stratified interbedded sandstone, carbonaceous siltstone, and varicolored mudstone. The Skull Creek and Mowry Shales of Early Cretaceous age consist of black fissile shale. The Mowry contains abundant fish scales and weathers to a silver gray. Alluvium fills the bottom of many intermittent streams, and small gravel-covered terraces mark the former high levels of these streams. Gravel, which caps hills at altitudes of 4,460 to 4,620 feet, is believed to have been deposited by a Pleistocene stream that drained southeastward toward the town of Minnekahta. Many landslides are present along the northward- and eastward-facing scarp of the Inyan Kara hogback. The Dewey fault, trending N. 75 deg E., crosses the quadrangle. It is probably a vertical dip-slip fault, and has an apparent displacement of 250 to 440 feet. Two northwest-trending anticlines are in the quadrangle - one extends from the Edgemont NE quadrangle to near the center of the Jewel Cave SW quadrangle, and the other is limited to the center of the Jewel Cave SW quadrangle. Collapse structures, which were produced by the solution of anhydrite, are (a) breccias in the Minnelusa Formation, (b) limestone-dolomite breccias in the Spearfish Formation, (c) undulations and normal faults in the formations overlying the Minnelusa and (d) breccia pipes that extend upward from the Minnelusa to at least as high as the Lakota Formation. The leaching probably occurred in early Cenozoic time. Minor deformationa

Bulletin↗
USGS1960

Areal geology of the Little Cone quadrangle, Colorado

The Little Cone quadrangle includes an area of about 59 square miles in eastern San Miguel County in southwestern Colorado. The quadrangle contains features characteristic of both the Colorado Plateaus physiographic province and the San Juan Mountains, and it has been affected by geologic events and processes of two different geologic environments. The continental sedimentary rocks of the Cutler formation of Permian age are the oldest rocks exposed in the quadrangle. Deposition of the Cutler was followed by a long period of erosion and peneplanation. There is no marked angular discordance between the Cutler and the overlying Dolores formation in the Little Cone quadrangle, but there is in areas some tens of miles east and west of the quadrangle where some crustal warping took place. The continental sedimentary rocks of the Dolores formation of Late Triassic age are red beds that are similar in gross lithology to those of the Cutler. The Dolores formation is subdivided into five general units that persist throughout the quadrangle and for some tens of miles to the north, south, and east. A second long period of erosion followed deposition of the Dolores. The Entrada sandstone of Late Jurassic age overlies the Dolores formation, and is in turn overlain by the Wanakah formation, also of Late Jurassic age. The Wanakah consists of the Pony Express limestone member at the base, the Bilk Creek sandstone'member near the center, and a "marl" member at the top. The Morrison formation, which overlies the Wanakah, consists of the Salt Wash sandstone member in the lower part and the Brushy Basin shale member in the upper part. A period of erosion, probably of relatively short duration, followed deposition of the Brushy Basin member. The Burro Canyon formation of Early Cretaceous age occurs as discontinuous bodies that fill channels cut in the top of the Morrison formation. Deposition of the Burro Canyon formation was followed by another period of erosion, which in turn ended with deposition of the Dakota sandstone of Late Cretaceous age. The Dakota sandstone grades upward into the Mancos shale, also of Late Cretaceous age. The Paleozoic and Mesozoic formations were broadly folded during Laramide time as part of an orogeny of regional extent, and the San Juan Mountains area was uplifted as a broad dome. Extensive erosion followed deformation, and the Cretaceous rocks in the area of the Little Cone quadrangle and the Mesozoic and Paleozoic rocks eastward from the quadrangle were successively bevelled. The Telluride conglomerate of Oligocene(?) age was laid down on this surface. In the Little Cone quadrangle several hundred feet of the Telluride was deposited upon a considerable thickness (probably 3,000 feet or more) of the Mancos shale. At Telluride, about 12 miles east of the quadrangle, the Telluride conglomerate lies upon the Dolores formation. Volcanic rocks of Miocene (?) and Miocene age were deposited widely upon the Telluride conglomerate; at one time they had a thickness of probably 1,000 feet or more in the quadrangle. They have been eroded completely from the quadrangle, but are present in the San Miguel Mountains a few miles to the south and southeast. During the middle Tertiary, probably during the Miocene, the sedimentary rocks were cut by many igneous bodies. Four major rock types are represented; in decreasing order of abundance they are granogabbro, granodidrite, rhyolite(?), and microgabbro. The granogabbro is by far the most abundant, and it forms the Flat Top Peak plug, the Little Cone laccolith, several sills in the Dakota sandstone and the Mancos shale, and a few dikes. The granodiorite forms sills in the Dakota sandstone and the Mancos shale, and the rhyolite(?) forms a single major sill in the Dakota. The microgabbro forms dikes that cut rocks as young as the Mancos shale. Metamorphic effects adjacent to the intrusive bodies generally are restricted to baking that extends only a few feet out into the enclosing rocks; in many places no metamorphic effects are evident. The rocks in the Little Cone quadrangle were displaced along numerous faults in middle Tertiary time, probably after the igneous rocks were injected. All of the faults are normal, and have vertical or very steep dips. In part, the faults form two long and narrow northward- and northwestward-trending grabens that extend into the adjoining Placerville quadrangle to the north. The graben faults form two systems, one trending northward to northwestward, and the other trending northwestward, that are probably contemporaneous. Other faults trend eastward to northeastward; some of these appear to be related to the intrusion of the igneous rocks. At the end of the Tertiary, probably in the early Pleistocene, the general area was again uplifted and subjected to extensive erosion. The Mancos shale was stripped from the northern part of the Little Cone quadrangle, and in this part of the area, the upland surfaces formed on top of the Dakota sandstone were largely controlled by the geologic structure. During the Quaternary a basalt flow was erupted on Specie Mesa on a surface that cuts both the Mancos and the Dakota. The surface preserved beneath the flow has virtually the same position and slope as the adjacent present-day surfaces. Pleistocene deposits consist of (a) high-level or older drift that is unrelated to the present drainage systems and is correlated with the Cerro glacial stage of early Pleistocene age, and (b) younger drift and valley fill within the valleys of the present drainage systems that are correlated with the Durango or Wisconsin glacial stages and may represent both. Recent surficial, landslide, and spring deposits are also present. Within the Little Cone quadrangle and in the Placerville quadrangle to the north and the Gray Head quadrangle to the east, the Entrada sandstone of Late Jurassic age contains vanadium deposits with which are associated large but low-grade amounts of uranium. These deposits form a practically continuous layer about 10 miles long and 1 to 1% miles wide, and possibly a second layer of smaller dimensions. Placer gold deposits in terrace gravel and valley fill of Pleistocene age and in alluvium of Recent age contain the only other ores.

Colorado↗
USGS1961

Geology and mineral deposits of the Carlile quadrangle, Crook County, Wyoming

The Carlile quadrangle-is along the northwestern flank of the Black Hills uplift in Crook County, Wyo. The area-is primarily one of canyons and divides that are a result of downcutting by the Belle Fourche River and its tributaries through an alternating succession of sandstone, siltstone, and mudstone or shale beds. The present topography is also influenced by the regional structure, as reflected by the beds that dip gently westward and by the local structural features such as anticlines, domes, synclines, basins, and terraces, which are superimposed upon the regional setting. Rocks exposed include shale and thin limestone and sandstone beds belonging to the Redwater shale member of the Sundance formation and to the Morrison formation, both of Late Jurassic age; sandstone, siltstone, and mudstone of the Lakota and Fall River formations of Early Cretaceous age; and shale and sandstone of the Skull Creek shale, Newcastle sandstone, and Mowry shale, also of Early Cretaceous age. In the southwestern part of the quadrangle rocks of the Upper Cretaceous series are exposed. These include the Belle Fourche shale, Greenhorn formation, and Carlile shale. Gravel terraces, landslide debris, and stream alluvium comprise the surficial deposits. The Lakota and Fall River formations, which make up the Iriyan Kara group, contain uranium deposits locally in the northern Black Hills. These formations were informally subdivided in order to show clearly the vertical and lateral distribution of the sandstone, siltstone, and mudstone facies within them. The Lakota was subdivided into a sandstone unit and an overlying mudstone unit; the Fall River was subdivided, in ascending order, into a siltstone unit, a mudstone unit, a sandstone unit, and an upper unit. The lithologic character of the Lakota changes abruptly locally, and the units are quite inconsistent with respect to composition, thickness, and extent. This is in contrast to a notable consistency in the lithologic character and thickness among all the Fall River units, with the exception of the upper unit. Petrographic studies on selected samples of units from both formations show differences in composition between Lakota and Fall River rocks. The Carlile quadrangle lies immediately east of the monocline that marks the outer limit of the Black Hills uplift, and the rocks in this area have a regional dip of less than 2° outward from the center of the uplift. Superimposed upon the regional uplift are many subordinate structural features anticlines, synclines, domes, basins, and terraces which locally modify the regional features. The most pronounced of these subordinate structural features are the doubly-plunging Pine Ridge, Oil Butte, and Dakota Divide anticlines, and the Eggie Creek syncline. Stress throughout the area was relieved almost entirely through folding; only a few small nearly vertical normal faults were found within the quadrangle. Uranium has been mined from the Carlile deposit, owned by the Homestake Mining Co. The ore minerals, carnotite and tyuyamnuite occur in a sandstone lens that is enclosed within relatively impermeable clayey beds in the mudstone unit of the Lakota formation. The ore also includes unidentified black vanadium minerals and possibly coffinite. Uranium minerals are more abundant in and adjacent to thicker carbonaceous and silty seams in the sandstone lens. A mixture of fine-grained calcium carbonate and calcium sulfate fills the interstices between detrital quartz grains in mineralized sandstone. Selenium and arsenic are more abundant in samples that are high in uranium. Drilling on Thorn Divide about 1 mile west of the Carlile mine has roughly outlined concentrations of a sooty black uranium mineral associated with pyrite In two stratigraphic intervals of the Lakota formation. One is in the same sandstone lens that contains the ore at the Carlile mine; the other is in conglomeratic sandstone near the base of the Lakota. These deposits are relatively deep, and no mining has been attempted. The mineralogy of the Carlile deposits and the lithologic features of the sandstone host rock suggest that uranium and vanadium were transported in the high-valent state by carbonate or sulfate solutions, were extracted from solution by organic material, and were reduced to low-valent states to form an original assemblage of oxides and silicates. These primary minerals were oxidized in place, and the present carnotite-tyuyamunite assemblage was formed. In general, radioactivity analyses correspond fairly closely with chemical analyses of uranium, thus it is believed that only minor solution and migration of uranium has occurred since the present suite of oxidized minerals was formed. The factors responsible for ore localization are not clear, but probably a combination of three lithologic and structural elements contributed to provide a favorable environment for precipitating uranium from aqueous solutions: abundant carbonaceous material or pyrite in a thin, permeable sandstone enclosed within relatively thick impermeable clays; local structural basins; and a regional structural setting involving a broad syncline between two anticlines. The structural features controlled the regional flow of ground water and the lithologic features controlled the local rate of flow and provided the proper chemical environment for uranium deposition. Bentonite has been mined from an opencut in the Mowry shale in the southwest part of the quadrangle. A bentonite bed in the Newcastle sandstone also seems to be of minable thickness and quality. Exploration for petroleum has been unsuccessful within the quadrangle; however, some wells that yielded oil were recently drilled on small anticlines to the west and southeast. It is possible that similar structural features in the Carlile area, that were previously overlooked, may be equally productive.

Wyoming↗
USGS1964

Geologic reconnaissance of the Antelope-Ashwood area, north-central Oregon, with emphasis on the John Day Formation of late Oligocene and early Miocene age

This report briefly describes the geology of an area of about 750 square miles in Jefferson, Wasco, Crook, and Wheeler Counties, Oregon. About 16,000 feet of strata that range in age from pre-Tertiary to Quaternary are exposed. These include the following units: pre-Tertiary slate, graywacke, conglomerate, and meta-andesite; Clarno Formation of Eocene age - lava flows, volcanic breccia, tuff, and tuffaceous mudstone, chiefly of andesitic composition; John Day Formation of late Oligocene and early Miocene age - pyroclastic rocks, flows, and domes, chiefly of rhyolitic composition; Columbia River Basalt of middle Miocene age - thick, columnar jointed flows of very fine grained dense dark-gray basalt; Dalles Formation of Pliocene age - bedded tuffaceous sandstone, siltstone, and conglomerate; basalt of Pliocene or Pleistocene age - lava flows of porous-textured olivine basalt; and Quaternary loess, landslide debris, and alluvium. Unconformities separate pre-Tertiary rocks and Clarno Formation, Clarno and John Day Formations, John Day Formation and Columbia River Basalt, and Columbia River Basalt and Dalles Formation. The John Day Formation, the only unit studied in detail, consists of about 4,000 feet of tuff, lapilli tuff, strongly to weakly welded rhyolite ash flows, and less abundant trachyandesite flows and rhyolite flows and domes. The formation was divided into nine mappable members in part of the area, primarily on the basis of distinctive ledge-forming welded ash-flow sheets. Most of the sheets are composed of stony rhyolite containing abundant lithophysae and sparse phenocrysts. One sheet contains 10 to 20 percent phenocrysts, mostly cryptoperthitic soda sanidine, but including less abundant quartz, myrmekitic intergrowths of quartz and sanidine, and oligoclase. The rhyolitic ash flows and lava flows were extruded from nearby vents, in contrast to some of the interbedded air-fall tuff and lapilli tuff of dacitic and andesitic composition that may have been derived from vents in an ancestral Cascade Range. The John Day is dated on the basis of a late Oligocene flora near the base of the formation and early Miocene faunas near the top of the formation. The middle Miocene and older rocks in the Antelope-Ashwood area are broadly folded and broken along northeast-trending faults. Over much of the area the rocks dip gently eastward from the crest of a major fold and are broken along a series of steeply dipping antithetic strike faults. Pliocene and Quaternary strata appear to be undeformed. At the Priday agate deposit, chalcedony-filled spherulites (thunder-eggs) occur in the lower part of a weakly welded rhyolitic ash flow. The so-called thunder-eggs are small spheroidal bodies, about 3 inches in average diameter; each consists of a chalcedonic core surrounded by a shell of welded tuff that is altered to radially oriented fibers of cristobalite and alkalic feldspar.

Oregon↗
USGS1967

Volcanic hazards at Mount Rainier, Washington

Mount Rainier is a large stratovolcano of andesitic rock in the Cascade Range of western Washington. Although the volcano as it now stands was almost completely formed before the last major glaciation, geologic formations record a variety of events that have occurred at the volcano in postglacial time. Repetition of some of these events today without warning would result in property damage and loss of life on a catastrophic scale. It is appropriate, therefore, to examine the extent, frequency, and apparent origin of these phenomena and to attempt to predict the effects on man of similar events in the future. The present report was prompted by a contrast that we noted during a study of surficial geologic deposits in Mount Rainier National Park, between the present tranquil landscape adjacent to the volcano and the violent events that shaped parts of that same landscape in the recent past. Natural catastrophes that have geologic causes - such as eruptions, landslides, earthquakes, and floods - all too often are disastrous primarily because man has not understood and made allowance for the geologic environment he occupies. Assessment of the potential hazards of a volcanic environment is especially difficult, for prediction of the time and kind of volcanic activity is still an imperfect art, even at active volcanoes whose behavior has been closely observed for many years. Qualified predictions, however, can be used to plan ways in which hazards to life and property can be minimized. The prediction of eruptions is handicapped because volcanism results from conditions far beneath the surface of the earth, where the causative factors cannot be seen and, for the most part, cannot be measured. Consequently, long-range predictions at Mount Rainier can be based only on the past behavior of the volcano, as revealed by study of the deposits that resulted from previous eruptions. Predictions of this sort, of course, cannot be specific as to time and locale of future events, and clearly are valid only if the past behavior is, as we believe, a reliable guide. The purpose of this report is to infer the events recorded by certain postglacial deposits at Mount Rainier and to suggest what bearing similar events in the future might have on land use within and near the park. In addition, table 2 (page 22) gives possible warning signs of an impending eruption. We want to increase man's understanding of a possibly hazardous geologic environment around Mount Rainier volcano, yet we do not wish to imply for certain that the hazards described are either immediate or inevitable. However, we do believe that hazards exist, that some caution is warranted, and that some major hazards can be avoided by judicious planning. Most of the events with which we are concerned are sporadic phenomena that have resulted directly or indirectly from volcanic eruptions. Although no eruptions (other than steam emission) of the volcano in historic time are unequivocally known (Hopson and others, 1962), pyroclastic (air-laid) deposits of pumice and rock debris attest to repeated, widely spaced eruptions during the 10,000 years or so of postglacial time. In addition, the constituents of some debris flows indicate an origin during eruptions of molten rock; other debris flows, because of their large size and constituents, are believed to have been caused by steam explosions. Some debris flows, however, are not related to volcanism at all.

Washington↗
USGS1969

Surficial Geology of Mount Rainier National Park, Washington

Much of the ground surface around Mount Rainier volcano is directly underlain by loose geologic deposits that veneer the hard rock formations. Examples of these deposits are sand and gravel bars along the rivers, ridges of loose rock debris beside the glaciers, and sloping aprons of rock fragments beneath almost every cliff. Even though they are generally thin and inconspicuous when compared with the rock formations, these surficial deposits are clues to geologic events that have profoundly influenced the shape of the park's landscape. Thus, from the character and extent of glacial deposits one can judge the age and size of former glaciers that carved the cirques and deep canyons of the park; from the mudflows which streamed down nearly every valley one can infer the age and size of huge landslides of the past that helped determine Mount Rainier's present shape; and from the pumice deposits some of the volcano's recent eruptive activity can be reconstructed. The map (plate 1, in pocket) that accompanies this description of the surficial deposits of Mount Rainier National Park shows the location of the various geologic formations, and the explanation shows the formations arranged in order of their relative age, with the oldest at the bottom. The text describes the surficial deposits in sequence from older to younger. A discussion of the pumice deposits of the park, which were not mapped, is followed by a description of the formations shown on the geologic map. Inspection of the geologic map may lead the viewer to question why the surficial deposits are shown in more detail in a zone several miles wide around the base of the volcano than elsewhere. This is partly because the zone is largely near or above timberline, relatively accessible, and the surficial deposits there can be readily recognized, differentiated, and mapped. In contrast, access is more difficult in the heavily timbered parts of the park, and surficial deposits there are generally blanketed by a dense virgin forest and are rarely exposed. Geologic investigations in such areas of the park were of a reconnaissance nature.

Bulletin↗
USGS1994

Geologic studies in Alaska by the U.S. Geological Survey, 1993

This collection of 19 papers continues the annual series of U.S. Geological Survey reports on geologic investigations in Alaska. Contributions include 14 Articles and 5 shorter Geologic Notes that report results from all corners of the State. USGS activities in Alaska cover a broad spectrum of earth science topics, including the environment, hazards, resources, and geologic framework studies. Three articles focus on the environmental geochemistry of parts of south-central, west-central, and southwestern Alaska. An article on methane released from permafrost near Fairbanks and a note on paleowind direction indicators on the Arctic coastal plain contribute to ongoing climate and paleoclimate investigations. Landslide hazards in the Talkeetna Mountains and Wrangell-St. Elias National Park are discussed in two notes. Possible active fault traces near Alaska's main population center are described in an article on the Castle Mountain fault. An article on Aniakchak volcano presents evidence for a previously unrecognized catastrophic flooding event. Resources and resource assessment on gold, base metals, and coal are discussed in several articles and a note. Geologic framework studies cover tectonics, paleontology, stratigraphy, and metamorphic petrology. One contribution involves field methods; it evaluates the relative accuracy of global positioning systems and topographic map-based methods for deriving location data for field stations. Two bibliographies at the end of the volume list reports about Alaska in USGS publications released in 1993 and reports about Alaska by USGS authors in non-USGS publications in 1993.

Alaska↗
USGS1996

Geology of the Harpers Ferry Quadrangle, Virginia, Maryland, and West Virginia

The Harpers Ferry quadrangle covers a portion of the northeast-plunging Blue Ridge-South Mountain anticlinorium, a west-verging allochthonous fold complex of the late Paleozoic Alleghanian orogeny. The core of the anticlinorium consists of high-grade paragneisses and granitic gneisses that are related to the Grenville orogeny. These rocks are intruded by Late Proterozoic metadiabase and metarhyolite dikes and are unconformably overlain by Late Proterozoic metasedimentary rocks of the Swift Run Formation and metavolcanic rocks of the Catoctin Formation, which accumulated during continental rifting of Laurentia (native North America) that resulted in the opening of the Iapetus Ocean. Lower Cambrian metasedimentary rocks of the Loudoun, Weverton, Harpers, and Antietam Formations and carbonate rocks of the Tomstown Formation were deposited in the rift-to-drift transition as the early Paleozoic passive continental margin evolved. The Short Hill fault is an early Paleozoic normal fault that was contractionally reactivated as a thrust fault and folded in the late Paleozoic. The Keedysville detachment is a folded thrust fault at the contact of the Antietam and Tomstown Formations. Late Paleozoic shear zones and thrust faults are common. These rocks were deformed and metamorphosed to greenschist-facies during the formation of the anticlinorium. The Alleghanian deformation was accompanied by a main fold phase and a regional penetrative axial plane cleavage, which was followed by a minor fold phase with crenulation cleavage. Early Jurassic diabase dikes transected the anticlinorium during Mesozoic continental rifting that resulted in the opening of the Atlantic Ocean. Cenozoic deposits that overlie the bedrock include bedrock landslides, terraces, colluvium, and alluvium.

Bulletin↗
USGS2000

Lateral ramps in the folded Appalachians and in overthrust belts worldwide— A fundamental element of thrust-belt architecture

Lateral ramps are zones where decollements change stratigraphic level along strike; they differ from frontal ramps, which are zones where decollements change stratigraphic level perpendicular to strike. In the Appalachian Mountains, the surface criteria for recognizing the subsurface presence of lateral ramps include (1) an abrupt change in wavelength or a termination of folds along strike, (2) a conspicuous change in the frequency of mapped faults or disturbed zones (extremely disrupted duplexes) at the surface, (3) long, straight river trends emerging onto the coastal plain or into the Appalachian Plateaus province, (4) major geomorphic discontinuities in the trend of the Blue Ridge province, (5) interruption of Mesozoic basins by cross-strike border faults, and (6) zones of modern and probable ancient seismic activity. Additional features related to lateral ramps include tectonic windows, cross-strike igneous intrusions, areas of giant landslides, and abrupt changes in Paleozoic sedimentation along strike. Proprietary strike-line seismic-reflection profiles cross three of the lateral ramps that were identified by using the surface criteria. The profiles confirm their presence and show their detailed nature in the subsurface. Like frontal ramps, lateral ramps are one of two possible consequences of fold-and-thrust-belt tectonics and are common elements in the Appalachian fold-and-thrust belt. A survey of other thrust belts in the United States and elsewhere strongly suggests that lateral ramps at depth can be identified by their surface effects. Lateral ramps probably are the result of thrust sheet motion caused by continued activation of ancient cratonic fracture systems. Such fractures localized the transform faults along which the continental segments adjusted during episodes of sea-floor spreading.

Pennsylvania↗
USGS2001

Geology and natural history of the San Francisco Bay area: A field-trip guidebook

A National Association of Geoscience Teachers Far Western Section (NAGT-FWS) field conference is an ideal forum for learning about the geology and natural history of the San Francisco Bay area. We visit classic field sites, renew old friendships, and make new ones. This collection of papers includes field guides and road logs for all of the Bay-area trips held during the NAGT-FWS 2001 Fall Field Conference and supplemental chapters on other aspects of the area’s natural and human history. The trips touch on many aspects of the geology and natural hazards of the Bay area, especially urban problems associated with living on an active tectonic plate margin: earthquake faults, coastal erosion, landslides, and the utilization of land and natural resources. We hope this conference not only provides a two-day learning opportunity for conference participants but that students and educators will use this field guidebook for future teaching and research. Many thanks are due to the U.S. Geological Survey (USGS) and San José State University (SJSU) for cohosting the conference. We are grateful to each of the field trip leaders for preparing the trips and writing the accompanying guides. We especially appreciate the many hours put in by the guidebook reviewers, Robert I. Tilling (USGS) and Paula Messina (SJSU), and to the USGS Western Publications Group for editing, layout, and web posting. Additional guidebook contributions include articles by John Galloway, Scott Starratt, Page Mosier, and Susan Toussaint. During the conference guest speakers include Robert I. Tilling (USGS Volcano Hazards Team) and Ross Stein (USGS Earthquake Hazards Team). Workshops prepared for the conference include GIS in the classroom, using USGS data by John Vogel (USGS) and Paula Messina (SJSU), and The Best of BAESI (Bay Area Earth Science Institute), a teacher training organization under the direction of Ellen Metzger (SJSU) and Richard Sedlock (SJSU). The conference provides an opportunity to showcase USGS scientific and education resources with self-guided tours of the USGS Library, the Earth Science Information Center (ESIC), the Visitor Center, and various laboratories on the USGS campus and includes a half-day participatory tour of the USGS research vessel the R/V Polaris and the USGS Marine Facility at the Port of Redwood City under the direction of Cynthia L. Brown, Francis Parchaso, and Tara Schraga. Beyond the names mentioned above, a host of USGS and SJSU staff, SJSU students, and NAGT-FWS members contributed to the preparation and orchestration of the conference. We couldn’t have done it alone. Leslie C. Gordon (USGS), Philip W. Stoffer (USGS), and Deborah Harden (SJSU) NAGT-FWS 2001 Fall Field Conference Organizers.

California↗
USGS2003

Field guide to hydrothermal alteration in the White River altered area and in the Osceola Mudflow, Washington

The Cenozoic Cascades arcs of southwestern Washington are the product of long-lived, but discontinuous, magmatism beginning in the Eocene and continuing to the present (for example, Christiansen and Yeats, 1992). This magmatism is the result of subduction of oceanic crust beneath the North American continent. The magmatic rocks are divided into two subparallel, north-trending continental-margin arcs, the Eocene to Pliocene Western Cascades, and the Quaternary High Cascades, which overlies, and is east of, the Western Cascades. Both arcs are calc-alkaline and are characterized by voluminous mafic lava flows (mostly basalt to basaltic andesite compositions) and scattered large stratovolcanoes of mafic andesite to dacite compositions. Silicic volcanism is relatively uncommon. Quartz diorite to granite plutons are exposed in more deeply eroded parts of the Western Cascades Arc (for example, Mount Rainier area and just north of Mt. St. Helens). Hydrothermal alteration is widespread in both Tertiary and Quaternary igneous rocks of the Cascades arcs. Most alteration in the Tertiary Western Cascades Arc resulted from hydrothermal systems associated with small plutons, some of which formed porphyry copper and related deposits, including copper-rich breccia pipes, polymetallic veins, and epithermal gold-silver deposits. Hydrothermal alteration also is present on many Quaternary stratovolcanoes of the High Cascades Arc. On some High Cascades volcanoes, this alteration resulted in severely weakened volcanic edifices that were susceptible to failure and catastrophic landslides. Most notable is the sector collapse of the northeast side of Mount Rainier that occurred about 5,600 yr. B.P. This collapse resulted in formation of the clay-rich Osceola Mudflow that traveled 120 km down valley from Mount Rainier to Puget Sound covering more than 200 km2. This field trip examines several styles and features of hydrothermal alteration related to Cenozoic magmatism in the Cascades arcs. The morning of the trip will examine the White River altered area, which includes high-level alteration related to a large, early Miocene magmatic-hydrothermal system exposed about 10 km east of Enumclaw, Washington. Here, vuggy silica alteration is being quarried for silica and advanced argillic alteration has been prospected for alunite. Clay-filled fractures and sulfide-rich, fine-grained sedimentary rocks of hydrothermal origin locally are enriched in precious metals. Many hydrothermal features common in high-sulfidation gold-silver deposits and in advanced argillic alteration zones overlying porphyry copper deposits (for example, Gustafson and Hunt, 1975; Hedenquist and others, 2000; Sillitoe, 2000) are exposed, although no economic base or precious metal mineralized rock has been discovered to date. The afternoon will be spent examining two exposures of the Osceola Mudflow along the White River. The Osceola Mudflow contains abundant clasts of altered Quaternary rocks from Mount Rainier that show various types of hydrothermal alteration and hydrothermal features. The mudflow matrix contains abundant hydrothermal clay minerals that added cohesiveness to the debris flow and helped allow it to travel much farther down valley than other, noncohesive debris flows from Mount Rainier (Crandell, 1971; Vallance and Scott, 1997). The White River altered area is the subject of ongoing studies by geoscientists from Weyerhaeuser Company and the U.S. Geological Survey (USGS). The generalized descriptions of the geology, geophysics, alteration, and mineralization presented here represent the preliminary results of this study (Ashley and others, 2003). Additional field, geochemical, geochronologic, and geophysical studies are underway. The Osceola Mudflow and other Holocene debris flows from Mount Rainier also are the subject of ongoing studies by the USGS (for example, Breit and others, 2003; John and others, 2003; Plumlee and others, 2003, Sisson and others, 2003; Vallance and others, 2003). Studies of hydrothermal alteration in the Osceola Mudflow are being used to better understand fossil hydrothermal systems on Mount Rainier and potential hazards associated with this alteration.

Washington↗
USGS1999

Sustainable growth in America's heartland: 3-D geologic maps as the foundation

The Central Great Lakes States of Illinois, Indiana, Michigan, and Ohio constitute one of the most productive and economically important regions in the country—America’s heartland. The agriculture, industry, business, recreation, and ecology of these States are based on a common geologic heritage. During the last 1.8 million years, glaciers repeatedly advanced and retreated across the region, leaving behind a thick, complex blanket of intermixed layers of mud, clay, silt, sand, and gravel. These glacial deposits contain bountiful resources—rich soils; plentiful ground water; minerals for construction; land for agriculture, development, recreation, and wildlife habitat; and lakes and rivers for recreation and wildlife habitat. These materials are also subject to natural hazards—floods, erosion, landslides, radon, and earthquakes—and manmade problems such as soil, sediment, and water contamination from point and nonpoint sources. Resulting land degradation has impaired and restricted human use and enjoyment of the land and caused degradation and loss of wildlife habitat. The continued economic growth of the region and the security of its population and environment are related to fundamental issues involving land, water, mineral, and biological resources. Addressing the conflicting demands on these resources without adequate information can result in land-use decisions that are not compatible with sustainable development and a continued high quality of life for future generations. Decisionmakers need knowledge of the glacial deposits— their characteristics, three-dimensional (3-D) distribution, and thickness. To provide this knowledge, a coalition of State and Federal Geological Surveys (Illinois State Geological Survey, Indiana Geological Survey, Michigan Geological Survey Division, Ohio Division of Geological Survey, U.S. Geological Survey) has formed to conduct the necessary studies in these four States to depict the 3-D nature of these glacial and related deposits and to interpret these data in cooperation with the user community for specific societal needs.

Illinois, Indiana, Michigan, Ohio↗
USGS2013

Challenge theme 6: Natural hazard risks in the Borderlands: Chapter 8 in United States-Mexican Borderlands: Facing tomorrow's challenges through USGS science

Natural hazards such as earthquakes, landslides and debris flows, wildfires, hurricanes, and intense storm-induced flash floods threaten communities to varying degrees all along the United States–Mexican border. The U.S. Geological Survey (USGS) collaborates with Federal, State, and local agencies to minimize the effects of natural hazards by providing timely, unbiased science information to emergency response officials, resource managers, and the public to help reduce property damage, injury, and loss of life. The USGS often mobilizes response efforts during and after a natural hazard event to provide technical and scientific counsel on recovery and response, and it has a long history of deploying emergency response teams to major disasters in both domestic and international locations. This chapter describes the challenges of natural hazards in the United States–Mexican border region and the capabilities of the USGS in the fields of hazard research, monitoring, and assessment, as well as preventative mitigation and post-disaster response.

United States-Mexico Borderlands↗
USGS2013

U.S. Geological Survey natural hazards science strategy— Promoting the safety, security, and economic well-being of the Nation

Executive Summary The mission of the U.S. Geological Survey (USGS) in natural hazards is to develop and apply hazard science to help protect the safety, security, and economic well-being of the Nation. The costs and consequences of natural hazards can be enormous, and each year more people and infrastructure are at risk. USGS scientific research—founded on detailed observations and improved understanding of the responsible physical processes—can help to understand and reduce natural hazard risks and to make and effectively communicate reliable statements about hazard characteristics, such as frequency, magnitude, extent, onset, consequences, and where possible, the time of future events. To accomplish its broad hazard mission, the USGS maintains an expert workforce of scientists and technicians in the earth sciences, hydrology, biology, geography, social and behavioral sciences, and other fields, and engages cooperatively with numerous agencies, research institutions, and organizations in the public and private sectors, across the Nation and around the world. The scientific expertise required to accomplish the USGS mission in natural hazards includes a wide range of disciplines that this report refers to, in aggregate, as hazard science. In October 2010, the Natural Hazards Science Strategy Planning Team (H–SSPT) was charged with developing a long-term (10-year) Science Strategy for the USGS mission in natural hazards. This report fulfills that charge, with a document hereinafter referred to as the Strategy, to provide scientific observations, analyses, and research that are critical for the Nation to become more resilient to natural hazards. Science provides the information that decisionmakers need to determine whether risk management activities are worthwhile. Moreover, as the agency with the perspective of geologic time, the USGS is uniquely positioned to extend the collective experience of society to prepare for events outside current memory. The USGS has critical statutory and nonstatutory roles regarding floods, earthquakes, tsunamis, landslides, coastal erosion, volcanic eruptions, wildfires, and magnetic storms—the hazards considered in this plan. There are numerous other hazards of societal importance that are considered either only peripherally or not at all in this Strategy because they are either in another of the USGS strategic science plans (such as drought) or not in the overall mission of the USGS (such as tornados).

Circular↗
USGS2018

Science for a risky world—A U.S. Geological Survey plan for risk research and applications

Executive Summary Natural hazards—including earthquakes, tsunamis, volcanic eruptions, landslides, hurricanes, droughts, floods, wildfires, geomagnetic storms, and pandemics—can wreak havoc on human communities, the economy, and natural resources for years following an initial event. Hazards can claim lives and cause billions of dollars in damage to homes and infrastructure as well as lost or compromised economic activity and threats to national security. They also can have adverse environmental, social, economic, and health effects that extend well beyond the immediate area, sometimes with global implications. Changes in population growth, climate, and urbanization may exacerbate hazard impacts. Because of the potential severity of a single hazard event, reducing risk—the potential loss of societally important assets caused by these hazards—is a high priority for everyone, including policy makers, community members, emergency managers, resource managers, utility operators, business owners, and planners. These stakeholders demand usable, user-centric information to support decisions for planning a resilient future and for responding to and recovering from unanticipated events in more adaptable and cost-effective ways. Meeting this demand requires maximizing the use of environmental observations; hazards science; and research on communications, social stressors, and human behavior to deliver risk information in forms that are accessible by decision makers and the public alike. To achieve this, scientists and stakeholders must collaborate to match community needs with actionable insights, research, products, and tools, using advances in technology to improve information discovery and delivery.

Circular↗