Metadata record for the dataset depicting the Continental Divide of the United States at the scale 1:2,000,000; link to zip file download in record.

This line shapefile represents the Continental Divide of the United States. The map layer was created by extracting Hydrologic Unit Boundary line features from an existing National Atlas layer. The source data are aligned with the individual 1:2,000,000-scale Digital Line Graph (DLG) hypsography files produced by the U.S. Geological Survey. This layer is part of the 1997-2014 edition National Atlas of the United States.

Thirty-nine types of surficial geologic deposits and residual materials of Quaternary age are described and mapped in the greater Denver area, in part of the Front Range, and in the piedmont and plains east of Denver, Boulder, and Castle Rock. Descriptions appear in the pamphlet that accompanies the map. Landslide deposits, colluvium, residuum, alluvium, and other deposits or materials are described in terms of predominant grain size, mineral or rock composition (e.g., gypsiferous, calcareous, granitic, andesitic), thickness of deposits, and other physical characteristics. Origins and ages of the deposits and geologic hazards related to them are noted. Many lines between geologic units on our map were placed by generalizing contacts on published maps. However, in 1997-1999 we mapped new boundaries, as well. The map was projected to the UTM projection. This large map area extends from the Continental Divide near Winter Park and Fairplay ( on the west edge), eastward about 107 mi (172 km); and extends from Boulder on the north edge to Woodland Park at the south edge (68 mi; 109 km).

The Pacific Crest is far less defined than the Continental Divide and there are a handful of rivers that breach this divide making it an imperfect divide. These rivers include the Columbia River in Washington and Oregon, the Klamath River in Oregon, and the Pit and Feather Rivers in northern California. 8-digit HUC unit polygons cannot be used to map this boundary and the Pacific Crest trail itself doesn't follow the divide. Therefore, I used HUC12 units to define the Pacific Crest following topographic drainage divides and crossing as few major rivers as possible while still trying to maintain the general shape of the Cascade-Sierra spine.

The Leadville North 7.5' quadrangle lies at the northern end of the Upper Arkansas Valley, where the Continental Divide at Tennessee Pass creates a low drainage divide between the Colorado and Arkansas River watersheds. In the eastern half of the quadrangle, the Paleozoic sedimentary section dips generally 20–30 degrees east. At Tennessee Pass and Missouri Hill, the core of the Sawatch anticlinorium is mapped as displaying a tight hanging-wall syncline and foot-wall anticline within the basement-cored structure. High-angle, west-dipping, Neogene normal faults cut the eastern margin of the broad, Sawatch anticlinorium. Minor displacements along high-angle, east- and west-dipping Laramide reverse faults occurred in the core of the north-plunging anticlinorium along the western and eastern flanks of Missouri Hill. Within the western half of the quadrangle, Meso- and Paleoproterozoic metamorphic and igneous rocks are uplifted along the generally east-dipping, high-angle Sawatch fault system and are overlain by at least three generations of glacial deposits in the western part of the quadrangle. 10Be and 26Al cosmogenic nuclide ages of the youngest glacial deposits indicate a last glacial maximum age of about 21–22 kilo-annum and complete deglaciation by about 14 kilo-annum, supported by chronologic studies in adjacent drainages. No late Pleistocene tectonic activity is apparent within the quadrangle.

On July 28, 1999, about 480 debris flows were triggered by an afternoon thunderstorm along the Continental Divide in Clear Creek and Summit counties in the central Front Range of Colorado. This cover shows the outlines of debris-flow source areas, travel zones, and deposits. Jonathan Godt and Jeffrey Coe mapped the debris flows from 1:12,000 scale color aerial photography using a Kern PG-2 photogrammetric plotter. The photographs were scaled and oriented to the topographic base map using prominent topographic landmarks and plotted on a transparent polyester overlay registered to the topographic base maps at 1:12,000 scale. The mapped landslides were digitized manually in ArcInfo. The final scale of the data are 1:24,000.

The map and descriptions offer information that may be used for: land-use planning (e.g. selecting land fill sites, greenbelts, avoiding geologic hazards), for finding aggregate resources (crushed rock, sand, and gravel), for study of geomorphology and Quaternary geology. Geologic hazards (e.g., landslides, swelling soils, heaving bedrock, and flooding) known to be located in, or characteristic of some mapped units, were identified.

Surficial deposits in the quadrangle partially record depositional events of the Quaternary Period (the most recent 1.8 million years). Some events such as floods are familiar to persons living in the area, while other recorded events are pre-historical. The latter include glaciation, probable large earthquakes, protracted drought, and widespread deposition of sand and silt by wind. At least twice in the past 200,000 years (most recently about 30,000 to 12,000 years ago) global cooling caused glaciers to form along the Continental Divide. The glaciers advanced down valleys in the Front Range, deeply eroded the bedrock, and deposited moraines (map units tbg, tbj) and outwash (ggq, gge). On the plains (east part of map), eolian sand (es), stabilized dune sand (ed), and loess (elb) are present and in places contain buried paleosols. These deposits indicate that periods of sand dune deposition alternated with periods of stabilized dunes and soil formation.

Thirty-nine types of surficial geologic deposits and residual materials of Quaternary age are described and mapped in the greater Denver area, in part of the Front Range, and in the piedmont and plains east of Denver, Boulder, and Castle Rock. Descriptions appear in the pamphlet that accompanies the map. Landslide deposits, colluvium, residuum, alluvium, and other deposits or materials are described in terms of predominant grain size, mineral or rock composition (e.g., gypsiferous, calcareous, granitic, andesitic), thickness of deposits, and other physical characteristics. Origins and ages of the deposits and geologic hazards related to them are noted. Many lines between geologic units on our map were placed by generalizing contacts on published maps. However, in 1997-1999 we mapped new boundaries, as well. The map was projected to the UTM projection. This large map area extends from the Continental Divide near Winter Park and Fairplay ( on the west edge), eastward about 107 mi (172 km); and extends from Boulder on the north edge to Woodland Park at the south edge (68 mi; 109 km).

Compilation scale: 1:250,000. Map is available in digital and print-on-demand paper formats. Deposits are described in terms of predominant grain size, mineralogic and lithologic composition, general thickness, and geologic hazards, if any, relevant geologic historical information and paleosoil information, if any. Thirty- nine map units of deposits include 5 alluvium types, 15 colluvia, 6 residua, 3 types of eolian deposits, 2 periglacial/disintegrated deposits, 3 tills, 2 landslide units, 2 glaciofluvial units, and 1 diamicton. An additional map unit depicts large areas of mostly bare bedrock.

The physical properties of the surficial materials were compiled from published soil and geologic maps and reports, our field observations, and from earth science journal articles. Selected deposits in the field were checked for conformity to descriptions of map units by the Quaternary geologist who compiled the surficial geologic map units.

FILES INCLUDED IN THIS DATA SET:

denvpoly: polygon coverage containing geologic unit contacts and labels. denvline: arc coverage containing faults. geol_sfo.lin: This lineset file defines geologic line types in the geologically themed coverages. geoscamp2.mrk: This markerset file defines the geologic markers in the geologically themed coverages. color524.shd: This shadeset file defines the cmyk values of colors assigned to polygons in the geologically themed coverages.

description: In FY2012 Camas National Wildlife Refuge (NWR) obtained a grant through the U.S. Fish and Wildlife Service (FWS) to map and treat invasive weeds not only Refuge lands, but adjacent lands as well. In 2010 Pheasants Forever Inc., acting as a conservation buyer purchased a 2,700 tract of land owned by the Joe Marty family. This acquisition allows Camas NWR (10,500 acres) to now be connected with Mud Lake State Wildlife Management Area (8,853 acres). This connection allows the State of Idaho and FWS the opportunity to manage a larger tract of wildlife habitat in coordination. Much of the Pheasants Forever Inc. tract had been abused by over grazing of cattle and horses. This has led to a serious invasion of Russian knapweed which has gained a strong hold on the landscape. Canada thistle, musk thistle, white top, black henbane and leafy spurge are also present on all three tracts. Funds from this grant helped implement three measures (mapping, biological controls and chemical) to control the invasive plants on all three properties. Three main cooperating agencies have spent time and resources treating invasive species on this newly acquired land. These agencies or groups are: Idaho Fish and Game Department, USFWS, and the Continental Divide Weed Management Area group and its partners (for a complete list of partners see the partnership section of this document).; abstract: In FY2012 Camas National Wildlife Refuge (NWR) obtained a grant through the U.S. Fish and Wildlife Service (FWS) to map and treat invasive weeds not only Refuge lands, but adjacent lands as well. In 2010 Pheasants Forever Inc., acting as a conservation buyer purchased a 2,700 tract of land owned by the Joe Marty family. This acquisition allows Camas NWR (10,500 acres) to now be connected with Mud Lake State Wildlife Management Area (8,853 acres). This connection allows the State of Idaho and FWS the opportunity to manage a larger tract of wildlife habitat in coordination. Much of the Pheasants Forever Inc. tract had been abused by over grazing of cattle and horses. This has led to a serious invasion of Russian knapweed which has gained a strong hold on the landscape. Canada thistle, musk thistle, white top, black henbane and leafy spurge are also present on all three tracts. Funds from this grant helped implement three measures (mapping, biological controls and chemical) to control the invasive plants on all three properties. Three main cooperating agencies have spent time and resources treating invasive species on this newly acquired land. These agencies or groups are: Idaho Fish and Game Department, USFWS, and the Continental Divide Weed Management Area group and its partners (for a complete list of partners see the partnership section of this document).

Yukon Territory has been glaciated by Cordilleran and montane glaciers at various times throughout the Pleistocene, as well as by continental ice, the Laurentine Ice Sheet in the Late Pleistocene. Throughout the Late Cenozoic, each successive glaciation appears to have been less extensive than the previous one. In west-central Yukon the earliest glaciation occurred between 2.6 and 2.9 Ma. ago (Duk-Rodkin and Barendregt, 1997). This glaciation was the most extensive and formed a continuous carapace of ice covering all the mountain ranges, except for a small area of Dawson Range and a more extensive area in northern Yukon. The Mid Pleistocene Cordilleran glaciation was less extensive than older glaciations but it formed an extensive ice sheet covering most of the northern Cordillera. The Late Pleistocene glaciation was the most restrictive and formed a continuous carapace of ice from the continental divide to the Saint Elias Mountains, but only restricted ice caps formed on the Ogilvie Mountains. During the last glaciation, the Laurentide Ice Sheet, flowing from the east, reached the northeast part of the Yukon Territory ca. 30 ka ago. Distributed from GeoYukon by the Government of Yukon . Discover more digital map data and interactive maps from Yukon's digital map data collection. For more information: geomatics.help@yukon.ca

Yukon Territory has been glaciated by Cordilleran and montane glaciers at various times throughout the Pleistocene, as well as by continental ice, the Laurentine Ice Sheet in the Late Pleistocene. Throughout the Late Cenozoic, each successive glaciation appears to have been less extensive than the previous one. In west-central Yukon the earliest glaciation occurred between 2.6 and 2.9 Ma. ago (Duk-Rodkin and Barendregt, 1997). This glaciation was the most extensive and formed a continuous carapace of ice covering all the mountain ranges, except for a small area of Dawson Range and a more extensive area in northern Yukon. The Mid Pleistocene Cordilleran glaciation was less extensive than older glaciations but it formed an extensive ice sheet covering most of the northern Cordillera. The Late Pleistocene glaciation was the most restrictive and formed a continuous carapace of ice from the continental divide to the Saint Elias Mountains, but only restricted ice caps formed on the Ogilvie Mountains. During the last glaciation, the Laurentide Ice Sheet, flowing from the east, reached the northeast part of the Yukon Territory ca. 30 ka ago.Distributed from GeoYukon by the Government of Yukon. Discover more digital map data and interactive maps from Yukon’s digital map data collection.For more information: geomatics.help@yukon.ca