In the near future, observers say, many standard maps should become available online, including historic maps that have languished, dusty and forgotten, in warehouses and libraries. Before too long, you may be able to download and print a map of your hometown as it looked in 1910, or a view of Australia from a National Geographic atlas. Start with a detailed map of Yosemite. Click on the point where you stood looking at Half Dome, and up comes a photo you took of the scene. Because information is so readily available, people can make changes to maps and customize them for themselves.
Geologic maps are a case in point.
By tradition, they identify types of rock and soil that appear on the surface of the ground. Their creation has been driven by the need to explore new territory and find minerals, oil and other natural resources. The first comprehensive map of California was produced in 1839 by the British Navy, according to the state Division of Mines and Geology. The first one to cover the geology of the Santa Clara Valley came 18 years later, drawn up by the War Department as it scouted possible railroad routes. Today, he said, geologic maps are used by people looking for things as diverse as gold, sand, gravel, tar and table salt.