Hot dry rock geothermal energy makes use of hot fluids found naturally in basement rock; but such HWR conditions are rare. By far the bulk of the world’s geothermal resource base (over 98%) is in the form of basement rock that is hot but dry—with no naturally available water. This means that HDR technology is applicable almost everywhere on earth (hence the claim that HDR geothermal energy is ubiquitous). Typically, the temperature in those vast regions of the accessible crystalline basement rock increases with depth. This geothermal gradient, which is the principal HDR resource variable, ranges from less than 20 °C/km to over 60 °C/km,
Echoes from the Underground dedicated to troops overseas, but as the song developed, he shifted it to more personal themes, and instead wrote "A Song for Someone" for the troops overseas instead. All songs written by Matt Scannell, except where noted. Echoes from the Underground Echoes from the Underground is the sixth studio album from the band Vertical Horizon, released on October 8, 2013. "Broken Over You" was released as the lead single. Rush drummer Neil Peart played the drums on two songs on the album, including "Instamatic". After the band's 2009 album, "Burning the Days", band co-founder Keith Kane left the band shortly