Peri Sasnett of the Department of Earth and Environmental Sciences at Columbia University has lead a team of researchers to study Ubehebe. Ubehebe is a large volcanic crater in the north of Death Valley. Using technology taken from the dating of moon rocks, he believes the volcano was formed much earlier than previously thought.
What he has also discovered is that the volcano is in the middle of an eruption cycle. Apparently these eruptions happen in clusters and the magma levels beneath the surface of the earth are much higher than expected. Essentially this thing could erupt at any time.
In a very simplified explanation, there are water pools beneath the ground, the magma is rising, and once it hits the pools, steam will form and create pressure. Once enough pressure has built, the magma will erupt!
So california residents can look forward to a very dangerous ecological event coming very soon. At last measurement, the magma was 500 feet below the water pool. Nobody knows how fast it's rising.