Can anyone tell me the title. Starts with hikers finding a cinder cone peak where none had existed previously in Death Valley. Aliens had landed nano machines which had spread and started to manufacture H-Bombs and plant them on the seabed along plate boundaries.
Later an anti matter mass is impacted with earth and makes its way towards Earths core. A signal has been detected from the aliens but no one can decode it until someone realizes its a countdown sequence. Meanwhile good alien nanobots are working to take over the powerful people of the world in order to facilitate construction and evacuation of rescue arks to save enough humans mostly children to ensure racial survival.
Earth is destroyed by explosions as the Arks depart Earth. Children are forced to watch earth destroyed to make sure they are pissed enough to seek revenge when possible. Good solid science in this one.