The Geothermal Map of North America is based on
terrestrial heat flow as the primary determination
for the earth's crustal/lithospheric thermal conditions.
Heat flow is the measure of earth's transfer of
energy and represents the expression of heat sources
within the earth. It is a key indicator of the potential
availability of heat as a usable resource.
This map illustrates heat transfer from lithospheric
to local (individual geothermal system) scales.
Three types of heat flow data points are included
on the map and used for contours that range from
15–150 milliwatts per square meter. They are shown
by different symbols because they may not be comparable
on a point-by-point basis, but the regional comparisons
are useful.
Heat flow data is from published heat flow values
with strict criteria that limit the numbers of such
data. Bottom hole temperature (BHT) data is from
Canadian, United States, and Mexican oil and gas
wells. Heat flow was estimated using BHT data and
thermal conductivities where they could be appropriately
determined. Western Geothermal Database data is
heat flow from industry thermal gradient measurements
in areas expected to have high heat flow. In geothermal
systems, the gradients are often more than 75 degrees
C per kilometer, and heat flow is more than 120
milliwatts per square meter.
The basemap is from the U.S. Geological Survey's
The National Map for GTOPO30 (shaded relief;
province, state, and country boundaries; and rivers);
ESRI sample data for place-names and city locations;
and General Bathymetric Chart of the Oceans (GEBCO)
data. Other data included is Holocene volcanoes
and hot springs. View the U.S. map data.
http://www.esri.com/mapmuseum/mapbook_gallery/volume20/mining2.html
Countries
Canada | Greenland | United States of America
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