Geothermal rhymes with:
hydrothermal, hydrothermal, isothermal, thermal, bermel, dermal, endodermal, epidermal, hydrothermal, isothermal, kurmel, mesodermal, thermal, turmel
hydrothermal, hydrothermal, isothermal, thermal, bermel, dermal, endodermal, epidermal, hydrothermal, isothermal, kurmel, mesodermal, thermal, turmel