| Interactive Maps (Main, Arctic,
Antarctic)
- Index Map: Toggle on/off. Shows selected area with respect
to full map.
- Zoom In (default mode): Drag cursor from one corner to another
of the desired area or click on the center of the desired area.
- The map that is returned may not be the same shape. The maximum dimension
of your rectangle is retained, and "bonus" area is added to give default
square. In order to get a non-square shape, change the size/shape of
the browser window before zooming.
- Some graphics (e.g. Notable numbers) continue to scale when zooming
in and appear very large with respect to surrounding data.
- Zoom Out: Click anywhere on map to zoom out by increments.
Zoom out to full size by drawing a small box.
- Pan (hand): Drag cursor in direction you want map area to shift.
- Identify: To get data on a specific symbol, select its layer
(from list at right margin) then click on symbol of interest.
- See below for explanation of data.
- In some cases the pop-up blocker must be disabled in order to view
the "identify" results.
- Get X-Y: Click on point of interest for its decimal latitude
and longitude, N & E are positive (+) and S & W are negative (-).
- Legend/Layers: Toggle to legend (for the best quality, print
the main map legend via "printable pages".)
- To include (or exclude) a layer when constructing a map, check (or
uncheck) that layer's box in the "Visible" list then click the "Refresh
Map" button (most layers are visible by default). Unfortunately, earthquake
depth groups cannot be selected as a layer independent of magnitude.
- Print/Save: Opens a new window with the option to either print
or save the current map view.
- Printing via the browser's print function has mixed results. On Windows
machines you can also print the current view by selecting "Alt - Print
Screen" and then pasting into an image processing program.
Other Elements (Front and Back)
- Click on map or section of interest. To zoom in, select the "+" symbol
at the bottom of the page, or click and drag the triangle above the
"+" and "-" symbol controls to fine tune. Once zoomed in, navigate by
selecting the arrows or dragging cursor. Zoom out by "-" symbol. Some
are difficult to read, click on "printable page" for better resolution
PDF files. Printable pages are best read with an increased zoom percentage.
- The "printable page" PDF files are best viewed using Adobe Acrobat
6.0 or later with an optimal screen setting of 1024x768.
- The Latitude/Longitude grid is 20° intervals when zoomed
out beyond 1:20,000,000 and 5° intervals when zoomed in beyond
1:20,000,000. Grids labeled only at full map's margins: use "Get X-Y"
tool to identify
"Identify" Data
- Volcano: Elev = summit elevation above sea level; Lat/Long
of volcano center in decimal degrees, N & E are positive (+) and S &
W are negative (-); Erupted = last known eruption (see main legend);
VNUM = number in Smithsonian data file ( http://www.volcano.si.edu/world/volcanocriteria.cfm).
- Earthquakes: Date (Year, Month, Day); Time = UTC (GMT); Depth
= kilometers below sea level; Mag = Magnitude; (see main legend). When
selecting desired magnitude layer, beware scale changes of zoomed image
– symbol sizes will not equal those shown in legend
- Impact Craters: Age, in million years (Ma), with uncertainty;
(see main legend).
- Notable Events: 25 numbered events (see table); Red = volcanoes;
Black = earthquakes; Purple = impact craters.
Boundaries
- Divergent boundaries are not shown with line width proportional to
spreading rate, as on published map (see legend)
- Convergent boundaries, shown only on the interpretive map on the
published map, are available here as an option. Beware, though, that
many of these boundaries are broad, diffuse zones, rather than crisp,
sharp junctions.
- National boundaries, not shown on the published map, are an option
here for geographic reference. When selecting this layer, it is a good
idea to deselect the "coastlines" layer, to avoid overlapping coastlines.
Downloaded Earthquake Data
- File sorted by date within individual magnitude ranges.
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