Science Explorer

Exploring: Geologic Time Scales

Divisions of Geologic Time - Major Chronostratigraphic and Geochronologic Units

Modified 2012-02-02
https://pubs.er.usgs.gov/publication/fs20073015 (HTML Document 17.17 KB)

geologic time scales. Since the mid-1990s, geologists from the U.S. Geological Survey (USGS), State geological surveys, academia, and other organizations ... , especially divisions of geologic time. A geologic time scale is composed of standard stratigraphic divisions based on rock sequences and calibrated in years ... have sought a consistent time scale to be used in communicating ages of geologic units in the United States. Many international debates have occurred ... over names and boundaries of units, and various time scales have been used by the geoscience community. Additional publication details Series title: Fact Sheet Series number: ...

Divisions of geologic time-major chronostratigraphic and geochronologic units

Modified 2012-02-02
https://pubs.er.usgs.gov/publication/fs20103059 (HTML Document 17.59 KB)

years, the development of new dating methods and the refinement of previous methods have stimulated revisions to geologic time scales. Advances in ... of geologic time. A geologic time scale is composed of standard stratigraphic divisions based on rock sequences and is calibrated in years. Over the ... stratigraphy and geochronology require that any time scale be periodically updated. Therefore, Divisions of Geologic Time, which shows the major ... chronostratigraphic (position) and geochronologic (time) units, is intended to be a dynamic resource that will be modified to include accepted changes of ...

Compilation of various geologic time scales

Modified 2012-02-02
https://pubs.er.usgs.gov/publication/ofr0152 (HTML Document 14.20 KB)

Open-File Report 2001-52 Series title: Open-File Report Series number:

What is geologic time?

https://www.usgs.gov/media/audio/what-geologic-time (HTML Document 43.15 KB)

science. I'm Jessica Robertson. Today's question is... What is geologic time? Geologic time is the period of time extending from the formation of the ... earth to the present. Many international debates have occurred over names and boundaries of units, and various time scales have been used by the ... of American State Geologists developed Divisions of Geologic Time. For more information about the various eras and the Divisions of Geologic Time ... Listen to hear the answer. (Public domain.) Location Taken: US [Music fades in] Welcome to CoreFacts, where we're always short on time and big on ...

What is geologic time?

https://www.usgs.gov/atom/11797 (HTML Document 43.15 KB)

science. I'm Jessica Robertson. Today's question is... What is geologic time? Geologic time is the period of time extending from the formation of the ... earth to the present. Many international debates have occurred over names and boundaries of units, and various time scales have been used by the ... of American State Geologists developed Divisions of Geologic Time. For more information about the various eras and the Divisions of Geologic Time ... Listen to hear the answer. (Public domain.) Location Taken: US [Music fades in] Welcome to CoreFacts, where we're always short on time and big on ...

Critical Zone Processes Across Landscapes

Modified 2016-12-16
https://crustal.usgs.gov/projects/critical_zone_processes/index.html (HTML Document 7.39 KB)

, and time scales from geologic to chemical reaction times. The research conducted by this project also emphasizes that the real base of all ecosystems ... . Our focus is to understand the geologic, geochemical, geomorthologic and geobiological evolution and functioning of regions of the Nation that share ... common geologic, geographic, and hydrologic characteristics. The term critical zone refers to the earth's near surface between bedrock and tree top ... of geology, hydrology, geomorphology, and biology on the critical zone over distance scales ranging from large regions of the Nation to microscopic ...

Decoupling processes and scales of shoreline morphodynamics

Modified 2017-01-23
https://pubs.er.usgs.gov/publication/70177923 (HTML Document 23.07 KB)

processes and large-scale geologic, oceanographic, and morphologic processes. Improved understanding of coastal behavior at multiple time scales is required ... Behavior of coastal systems on time scales ranging from single storm events to years and decades is controlled by both small-scale sediment transport ... controls on shoreline response along a geologically-variable barrier island on time scales resolving extreme storms and decadal variations over a ... period of nearly one century. An empirical orthogonal function analysis is applied to a time series of shoreline positions at Fire Island, NY to identify ...

Issues of scale, location and geologic terrain related to Salt Lake City and Baltimore-Washington metropolitan areas

Modified 2012-03-12
https://pubs.er.usgs.gov/publication/70026453 (HTML Document 16.83 KB)

physiographic units at national, regional, local and site scales serve to communicate relevant geologic constraint and natural resource information. Additional ... Issues of scale, location and geologic terrain related to Salt Lake City and Baltimore-Washington metropolitan areas By: Edited by: The Publications ... Warehouse does not have links to digital versions of this publication at this time Download citation as: RIS Planning and development of expanding ... metropolitan regions require consideration of earth science issues related to issues involving scale, space (location), geologic terrain and ...

Modern sediment yield compared to geologic rates of sediment production in a semi-arid basin, New Mexico: Assessing the human impact

Modified 2012-03-12
https://pubs.er.usgs.gov/publication/70026639 (HTML Document 20.45 KB)

different time-scales provides the opportunity to contrast the human impact on erosion with background or geologic rates of sediment production ... . Arroyo Chavez is grazed and we were interested in whether differences in erosion rates observed at the two time-scales are due to grazing. The geologic ... Modern sediment yield compared to geologic rates of sediment production in a semi-arid basin, New Mexico: Assessing the human impact Earth Surface ... with sediment traps and dams with long-term, geologic rates (???10 000 years) of sediment production measured using 10Be. Examination of erosion rates at ...

Volcanoes: observations and impact

Modified 2015-01-16
https://pubs.er.usgs.gov/publication/70047253 (HTML Document 18.00 KB)

direct and indirect impacts on human lives and society. As is the case with many geologic phenomena, the time scales over which volcanoes evolve ... Abstract Volcanoes are critical geologic hazards that challenge our ability to make long-term forecasts of their eruptive behaviors. They also have ... greatly exceed that of a human lifetime. On the other hand, the time scale over which a volcano can move from inactivity to eruption can be rather short ...

Geomedia: Mapping Colorado at a fine scale

Modified 2012-03-12
https://pubs.er.usgs.gov/publication/70025754 (HTML Document 18.15 KB)

geologic hazards. Most maps of Colorado are at much broader scales, failing to show detail of basic geology crucial to safe engineering and building ... Geotimes By: The Publications Warehouse does not have links to digital versions of this publication at this time Download citation as: RIS Abstract ... Currently, only 24 percent of Colorado's spectacular geology has been mapped at the fine scale of 1:24,000. At the same time, the state hosts many ... , remains one of the fastest growing. Detailed geologic maps also aid the mineral industries that help fuel such growth. Since 1992, the Colorado ...

Field Reconnaissance Geologic Mapping of the Columbia Hills, Mars: Results from MER Spirit and MRO HiRISE Observations

Modified 2013-02-23
https://pubs.er.usgs.gov/publication/70003790 (HTML Document 27.96 KB)

dozen outcrops shows that Mars is geologically complex at meter length scales, the record of its geologic history is well exposed, stratigraphic ... with techniques commonly employed in terrestrial field geology. Despite their burial during the course of Martian geologic time by widespread ... Field Reconnaissance Geologic Mapping of the Columbia Hills, Mars: Results from MER Spirit and MRO HiRISE Observations Journal of Geophysical ... , and J. Hurowitz Abstract Chemical, mineralogic, and lithologic ground truth was acquired for the first time on Mars in ...

Field reconnaissance geologic mapping of the Columbia Hills, Mars, based on Mars Exploration Rover Spirit and MRO HiRISE observations

Modified 2012-03-12
https://pubs.er.usgs.gov/publication/70036435 (HTML Document 27.01 KB)

several dozen outcrops shows that Mars is geologically complex at meter length scales, the record of its geologic history is well exposed, stratigraphic ... with techniques commonly employed in terrestrial field geology. Despite their burial during the course of Martian geologic time by widespread ... Field reconnaissance geologic mapping of the Columbia Hills, Mars, based on Mars Exploration Rover Spirit and MRO HiRISE observations Journal of ... , and J. Hurowitz Abstract Chemical, mineralogic, and lithologic ground truth was acquired for the first time on Mars in ...

Cyclostratigraphic calibration of cretaceous magnetic polarity events (Cismon, Southern Alps, Italy)

Modified 2012-03-12
https://pubs.er.usgs.gov/publication/70017533 (HTML Document 17.66 KB)

Mathematical Geology Abstract In an introductory section the problems of constructing a geologic time scale and the role of magnetic reversals and ... subchrons between CM10N and CM8. The new estimates are shorter than in most published time scales by a factor of two to three. More research along these ... lines may make a revision of the Early Cretaceous time scale necessary. ?? 1994 International Association for Mathematical Geology. Additional publication details Series title: Mathematical Geology ...

Emergent biological patterns and surface-subsurface interactions at landscape scales

Modified 2014-02-14
https://pubs.er.usgs.gov/publication/70093912 (HTML Document 17.00 KB)

By: Edited by: The Publications Warehouse does not have links to digital versions of this publication at this time Download citation as: RIS Abstract ... In this chapter, we focus on emergent biological patterns in riverine ecosystems at landscape scales resulting from surface-subsurface water ... interaction. Our objectives are to examine (1) how the balance of physical and chemical factors on the "natural" geologic template affects biological patterns ...

Quaternary geomorphology and modern coastal development in response to an inherent geologic framework: An example from Charleston, South Carolina

Modified 2012-03-12
https://pubs.er.usgs.gov/publication/70029006 (HTML Document 20.81 KB)

categorical scales of spatial and temporal influence on the coastal system. The near-surface, geologic framework was delineated using high-resolution ... Quaternary geomorphology and modern coastal development in response to an inherent geologic framework: An example from Charleston, South Carolina ... Publications Warehouse does not have links to digital versions of this publication at this time Download citation as: RIS Coastal landscapes evolve over wide ... -ranging spatial and temporal scales in response to physical and biological pro-cesses that interact with a wide range of variables. To develop better ...

Effects of multi-scale environmental characteristics on agricultural stream biota in eastern Wisconsin

Modified 2012-03-12
https://pubs.er.usgs.gov/publication/70023081 (HTML Document 20.50 KB)

between fish, invertebrate, and algal metrics and multiple spatial scales of land cover, geologic setting, hydrologic, aquatic habitat, and water ... this time Download citation as: RIS Abstract The U.S. Geological Survey examined 25 agricultural streams in eastern Wisconsin to determine relations ... vegetation, geologic, and hydrologic conditions affected the response of biotic metrics to watershed agricultural land cover but the relations were ... aquatic assemblage dependent. It was difficult to separate the interrelated effects of geologic setting, watershed and buffer land cover, and base flow ...

Emerging methods for the study of coastal ecosystem landscape structure and change

Modified 2013-07-31
https://pubs.er.usgs.gov/publication/70047312 (HTML Document 19.90 KB)

heterogeneous, dynamic, and evolve over a range of time scales due to intertwined climatic, geologic, hydrologic, biologic, and meteorological ... managers across local, regional, and national scales. Emerging remote-sensing methods associated with a diversity of instruments and platforms are a key ...

Time series Of suspended-solids concentration, salinity, temperature, and total mercury concentration in San Francisco Bay during water year 1996

Modified 2016-07-27
https://pubs.er.usgs.gov/publication/70174319 (HTML Document 22.65 KB)

Annual Report Abstract Many physical processes affect how constituents within San Francisco Bay vary. Processes and their associated time scales ... ), ecological and climatic changes (years), and geologic changes (thousands of years). The effect and relative importance of physical processes on the ... Bay can be determined from continuous time series of suspended-solids concentration (SSC), salinity, and water temperature. SSC time series and ... Regional Monitoring Program (RMP) waterquality data can be used to calculate time series of some trace-element concentrations (Schoellhamer, 1997). The ...

Inner shelf morphologic controls on the dynamics of the beach and bar system, Fire Island, New York

Modified 2015-08-25
https://pubs.er.usgs.gov/publication/70041586 (HTML Document 20.83 KB)

over time scales greater than a half-century, and their length-scales are similar to the spacing of the offshore ridge-trough system. The first-order ... consistent bar morphology and patterns of shoreline change demonstrate that there is a feedback occurring between the regional geologic framework and ... spatially persistent. The fixed nature of the nearshore morphology is further supported by time series camera data that indicate persistent bars with ... breaks that re-form in the same locations. A long-term time series of shoreline change shows distinct zones of erosion and accretion that are pervasive ...