Geothermal Energy

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Disadvantage

-The big problem is that there are not many places
-Need hot rocks of a suitable type , at a depth where we can drill down to them 
-The type of rock above is also important , it must be of a type that we can easily drill through . 
-Sometimes a geothermal site may "run out of steam " . perhaps for decades.
-Hazardous gases and minerals may come up from underground , and can be difficult to safety dispose of .