Geologic Atlas of the City of Alexandria, Virginia and Vicinity
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Welcome to the Geologic Atlas of the City of Alexandria. You can navigate directly to each of the maps, expanded explanations, and databases that make up the Atlas by clicking on the corresponding links below. If you are a first-time user, or new to either the city or the science of geology, we recommend proceeding first to the brief overview of the Atlas, where you can learn about the various components of the atlas and how to use them. For best resolution, you may want to open the plates in a different viewer, such as Adobe Acrobat, once they have loaded into your browser. |
Geologic Maps and Expanded Explanations
Plate 1. Map Showing the Distribution and Sources of Geologic Data
Plate 2. Geologic Cross Sections
Read the Expanded Explanation of Plates 1 and 2 to learn about the kinds of geological data available in the city and how the maps and other parts of the atlas were constructed. This document also explains what geologic cross sections are and how they illustrate the “third dimension” of Alexandria’s geologic architecture
Read the Expanded Explanation of Plate 3 to learn about the bedrock under the city, its history, where it is exposed, and why its buried topographic surface is so important
Plate 4. Geologic Map of the Potomac Formation
Read the Expanded Explanation of Plate 4 to learn about this formation of river deposits, which dates from the “Age of Dinosaurs” and makes up the great bulk of the geologic section beneath the city
The Expanded Explanation of Plate 5discusses the types of rocks and unconsolidated sediments found at the surface in different parts of the city: their history, properties, and relationships to the major landforms
Read the Expanded Explanation of Plate 6 to learn about water in the City of Alexandria: streams, aquifers, wetlands, stormwater runoff, and more
This map shows which parts of the city are the most and least susceptible to landslides and expansive soils, and explains why
Part 8. Overview of Tectonic Setting, Fault Systems, and Seismic Hazards
Many Alexandria residents felt the shaking from the August 23, 2011 Mineral, Virginia earthquake, which caused significant damage to several iconic structures in and around DC. This section of the atlas provides an overview of the potential seismic hazards in the city, how certain kinds of soils can amplify seismic shaking while others attenuate it, and the locations of known and suspected faults
Geologic Data
Alexandria Exposures
MS-Excel database of natural outcrops and excavations
Alexandria Geotechnical Borings
MS-Excel database of geotechnical boring sites
Alexandria USGS Wells
MS-Excel database of historical wells catalogued by the USGS
Drillers Logs for 5 Deep Wells (PDF)
Formation descriptions for five deep public water supply wells from the USGS historical collection
Sample Locations and Field Descriptions
MS Excel database of the particle size and clay mineralogy samples analyzed and presented in the atlas
VDOT Woodrow Wilson Bridge-Capital Beltway Cross Sections (PDF)
Series of geologic fence diagrams generated from VDOT’s geotechnical boring database along the route of this major construction project
Schematic Interpretive Diagrams of Geotechnical Boring Sites (PDF)
Simplified cross-section diagrams for most of the geotechnical boring sites in the database
Glossary of Geological Terms
Opens a glossary containing geological terms used in the atlas
Bibliography
Full list of references, with links to downloadable publications