A ground-source heat pump is not a form of geothermal energy at all.

Geothermal:

 1. energy source is underground natural nuclear reactions;
 2. source temperature is over 50°C;
 3. Energy is extracted with passive heat exchangers.

Ground-source heat pumps:

 1. energy source is solar radiation;
 2. source temperature is about the same as annual average air temperature;
 3. Energy is extracted using active technology, compressing and expanding fluids to lift the temperatures to something useful.