AGI/It's About Time

Obtain a topographic map of California.

• Topographic map of Cayucos, California (includes Morro Rock, an extinct volcano)
• Topographic map of Mount Dome, California (an extinct volcano)

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Find a topographic map of a cascade volcano in California.

• Topographic map of Medicine Lake-Mount Shasta area in Northern California.

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USGS - Topographic Map Symbols
Read more about topographic maps, view and learn what what different symbols mean, and find out how to purchase them.

Maps, USGS
Search for maps by zip code or city and state. You can download or purchase maps.

Topographic Maps Online
57,000 U.S. Geological Survey topographic maps were digitized and are now available on the Web.

How to find topographic maps, USGS
Provides helpful links for finding geologic maps.

TopoZone
Find topographic maps by place name, latitude and longitude, or UTM coordinates under the Get A Map section. Allows you to download topographic maps (including USGS maps) for free, at various scales (from 1:100,000 to 1:24,000).

MapServer
Enter place name or zip code and state at the top to view maps. Offers free online viewing of topographical, nautical and aeronautical charts plus high altitude digital ortho quads (nav photos).

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Composition of Magma
Find out more about how the chemical composition of magma varies in igneous rocks. The discussion is not limited to just extrusive rocks, but includes intrusive rocks as well.

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Volcano World - Types of Volcanoes
An index page with links to short descriptions about different volcanic landforms. Descriptions do not include images.

USGS - Principal Types of Volcanoes
Read a more detailed description of the principal types of volcanoes. Text does include pictures for each example (but are all in black and white).

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