This site describes how and when 100-year floods occur. It states that flood designations are based on statistical averages, not on the number of years between big floods. It also suggests that it would make more sense to refer to 100-year floods as 1-in-100 chance floods. This resource is a United States Geological Survey (USGS) Fact Sheet. It can be used in teaching quantitative skills.

This USGS site explains what an aquifer is and defines the different types of aquifers based on six principal lithologies; sandstone, carbonate, sandstone-carbonate, igneous and metamorphic, sand and gravel, and other rock types. The site features maps and descriptions of the major aquifers in the United States as well as general information about groundwater occurrence and quality. The site also provides links to additional maps and data about specific aquifers across the nation.

This site provides information about the distribution of arsenic in ground water of the United States. The site features links to publications such as fact sheets, research and reports, as well as numerical data collected from over 20,000 wells. The site also provides maps that show where and to what extent arsenic occurs in ground water across the country. Links to additional resources related to arsenic and drinking water are also included.

This resource is a part of the USGS document entitled "Preliminary Compilation of Descriptive Geoenvironmental Mineral Deposit Models". This chapter of the document describes gold, silver and tellurium vein deposits. Topics include a summary of relevant geologic, environmental, and geophysical information, geologic factors that influence potential environmental effects, and environmental signatures.

This USGS Canyonlands Research Station site features a series of web pages focusing on biological soil crusts. Biological soil crusts are the community of organisms living at the surface of desert soils. The site provides a menu of links to biological soil crust pages including Crusts 101: an introduction to biological soil crusts, an advanced page with a downloadable 90-page report on soil crusts, a gallery of biological soil crust images and figures, references, the Canyon Country Ecosystems Research Site (CCERS), and other related links.

This USGS site contains information on the geology units, topography, and precipitation rates of the Black Hills as it relates to the hydrology. Included is a map defining the study area, precipitation graphs, a stratigraphic column, a map denoting the distribution of hydrogeologic units, a geologic cross section, and a photo of the hydrogeologic setting. Links to an introduction to this study, objectives, products, references, and digital map services are also available through this site.

This website features multiple links to geologic resources relating to the Columbia River Plateau and Columbia River Basalt Group. The types of resources available include background information, special items of interest, maps, graphics, images, and educational outreach for multiple levels of experience.

This USGS document provides a summary of characteristics of gold-silver-tellurium vein deposits. The data includes the geological environment of the deposits such as rock types, textures, age ranges, depositional environment, tectonic setting, and associated deposit types. The deposit description includes information about mineralogy, texture/structure, alteration, ore controls, and weathering. Also included is a list of examples where these vein deposits are found.

Sand covers only about 20 percent of the Earth's deserts. Nearly 50 percent of desert surfaces are gravel plains where removal of fine-grained material by the wind has exposed loose gravel and occasional cobbles. This web page, produced by the U.S. Geological Survey, features text and photographs that describe desert landforms, soils, plants, and the role of water in the formation of desert landscapes.

Desertification, the degradation of formerly productive land into desert, is a complex process. It involves multiple causes, and it proceeds at varying rates in different climates. This web page, produced by the U.S. Geological Survey, features text and photographs that explain what desertification is, how human activities may contribute to it, how satellite imagery is used for monitoring vulnerable areas, and how its effects may be mitigated by improved agricultural and land management practices.

This document outlines the development of the theory of continental drift and how many lines of evidence collected over several decades by various researchers were brought together to explain how the seafloor spreads and the continents move about. Links to additional information are included.

This site offers frequently asked questions about earthquakes, research on earthquakes, and more. Visitors can follow recent seismic activity around the world, view hazard maps, or learn what a geophysicist does.

This USGS site has an online form that lets the user select parameters to perform a rectangular area search for earthquakes. The user must define the output file type, data base, and input rectangular area search parameters and has the option of defining the date, magnitude, depth and intensity of an earthquake.

This is part of the U.S. Geologic Survey's Water Science for Schools website. It consists of a set of links to other parts of the site dealing with groundwater-related topics such as groundwater flow and distribution, trends in groundwater use, importance of groundwater, and groundwater quality. Graphic illustrations and photographs are provided.

Exploring Caves is an interdisciplinary set of materials on caves for grades K-3. Using earth science, hydrology, mapping, biology, and anthropology, the unit provides teachers with detailed lesson plans to explore these rich environments with very young students.

This site lets students display on maps a range of data: population, transportation, political boundaries, oil, water, other natural resources, and more. Students can explore geographic relationships by combining and co-displaying these data on maps of Africa, the Americas, Asia, the Middle East, and other parts of the world.

Examine human impact on the land surface of the Earth as well as evidence of natural processes in this key that emphasizes hands-on interpretation of USGS imagery. This quiz introduces students to the concepts of Remote Sensing, and challenges them to think about the human and physical processes at work that are changing the Earth's surface.

This tutorial will help students learn and understand the concepts of geologic time and the age of the Earth. They will investigate the geologic time scale and learn about the use of index fossils and radiometric dating to determine the age of rock formations and fossils.

Global change is a relatively new area of scientific study using research from many disciplines to determine how Earth systems change, and to assess the influence of human activity on these changes. The Global Change section of the Teaching Packet consists of an introduction and five activities. In teaching these activities, four themes are important: time, change, cycles, and Earth as home.