It is the final melting of crystalline formations that cause earthquake lights, not always pure quartz, but selenite and other crystalline formations caused by the extreme pressure in intraslab earthquake zones. Sea floor as it subducts heats up and releases water under pressure (I hesitate to use the word steam as there isn't enough oxygen to make much steam.) As the pressures increase, water and minerals are released from the subducting plate and the minerals and water form crystal. Just before the final conversion to Magma the crystals rub through small movement which under extreme pressures makes an electrical charge. One can see this principal in action by rubbing two quartz crystals together in the darkness and watch the blue/purple sparks glow in the crystals and on your hands! I have done this experiment many times, and cloudy (less clear) crystals work best.
Just before many large nighttime earthquakes, earthquake lights have been observed and photographed.Blue/purple lights glowing on trees. in the sky and on the ground. Of course moisture conducts electricity up the fault to the surface where it looks for a further conductive route to the upper atmosphere...
Then Kaboom, EARTHQUAKE!
I have a book by Time/Life that has photos of earthquake lights over Japan as an earthquake struck at 7.6m at night (Tangshan, I think it was).
The weather in the Pacific Northwest was sunny and bright when the Seattle tremor occurred, but there were some clouds too.
Minerals contained in hot springs are carried there by the wringing out of water from subducting pressurized ocean floor. Funny things happen to my silver jewellery when I'm in Tofino hot springs (Hot Springs Cove). My silver turns bronze for a couple of days, and I have seen siver being cleaned by some electrical water tank thing. Can electricity also tarnish if it is reversed or something, I wonder? Or is it the Sulpher or other minerals.
Thanks for indulging my ramblings, Take care David, Michael, Roger, Canie and ALL, and look out for the Hoof in Mouth disease which is in Argentina and will not be confined to that area of S America for long I'm sure. How about travellers returning to N. America from there. Are they carrying it (Humans DO)and how could we tell anyway without testing? I'd buy fish farm and chicken farm stocks as they can only go up if the hoofed food sources are compromised.
Anyway we are seeing more prophecies coming about than I care to....mb.