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Browse more than 160,000 publications authored by our scientists over the past 100+ year history of the USGS.  Publications available are: USGS-authored journal articles, series reports, book chapters, other government publications, and more.

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Vitrinite reflectance analysis

Vitrinite is a maceral group (a set of organic matter types with similar properties and appearance) derived from the remains of woody material from vascular plants and is composed of the thermally evolved products of lignin and cellulose. Vitrinite is the dominant component of humic coal and is found as a minor component dispersed into sedimentary rocks, especially mudrocks, the primary source roc

Lognormal distribution

No abstract available. 

Dam removal and river restoration

The removal of dams from rivers has become a common and widespread practice in the United States and Europe. Although often initiated by factors like economics and safety, ecosystem restoration is often a desired benefit and outcome of dam removal. We describe the physical and ecological effects that the placement and removal of dams have on rivers. We then focus on the drivers of dam removal, pre

Total alkali-silica diagram

The total alkali-silica (TAS) diagram is a scatterplot of the chemical concentrations of silica oxide (SiO2) versus total alkali-sodium oxide (Na2O) plus potassium oxide (K2O) – in volcanic rocks.

Random forest

This entry defines and discusses the random forest machine learning algorithm. The algorithm is used to predict class or quantities for target variables using values of a set of predictor variables. It uses decision trees that are generated from bootstrap sampling of the training data set to create a "forest". The entry discusses the algorithm steps, the interpretative tools of the resulting mode

International importance of Percids: Summary and looking forward

Research presented in the preceding chapters emphasizes recent advancements in the research, management, and aquaculture of Walleye, Sauger, and Yellow Perch in North America. These percid fishes, along with the European Perch and Pikeperch, are economically and ecologically important fishes in their native geographic range. Advances in techniques to evaluate current habitat and predict future hab

Multilayer perceptrons (MLPs)

Artificial neural networks (ANNs) are adaptable systems that can solve problems that are difficult to describe with a mathematical relationship. They seek relationships between different types of datasets with their abilities to learn either with supervision or without. ANNs recognize patterns between input and output space and generalize solutions, in a way simulating the human brain’s learning e

Genetic attributes and research interests

Book chapter with broad description of the genetics used and topics being studied in the GYA within separate sections for bighorn sheep and mountain goats.


In statistics, a realization is an observed value of a random variable (Gubner 2006). In mathematical geology, the most important realizations are those in the form of maps of spatially correlated regionalized variables.Spatial description of random variables within complex domains and making certain decisions about those require complete knowledge of the attribute of interest at each point in spa