Geothermal handbook: PlanninG and Financing power Generation t e c h n I c a L r e p o r t 2 / 2

Classification of geothermal Systems
6
Geothermal resources are classified in various ways based on heat source, type of heat transfer, 
reservoir temperature, physical state, utilization, and geological settings. When defined on the basis of 
the nature of the geological system from which they originate, the different categories are as follows: 
• 
volcanic geothermal systems
are in one way or another associated with volcanic activity. The
heat sources for such systems are hot intrusions or magma. They are most often situated
inside, or close to, volcanic complexes, such as calderas, most of them at plate boundaries
but some in hot spot areas. In volcanic systems, it is mostly permeable fractures and fault
zones that control the flow of water (Figure 1.4). 
• 
In