This lecture extends the previous discussions by exploring hot springs, which are formed by geothermally heated groundwater emerging onto the Earth's surface. These springs can be heated by magma intrusions in volcanic areas or by deep circulation through faults in non-volcanic regions, with heat primarily sourced from radioactive decay in the Earth's mantle. Hot spring water often contains significant amounts of dissolved minerals, providing medicinal value and supporting unique microbial communities. Human use of hot springs spans thousands of years for bathing, relaxation, and medical therapy, though some springs are dangerously hot. The CO2 emissions from Himalayan geothermal springs are significant, necessitating consideration in global carbon cycle assessments.