This lake is near 100 degrees C ; it has been around hundreds of years (more likely thousands). Around 100 years ago, it was apparently possible to bathe in it, but it has slowly heated up so it is nearly boiling. The mud pools shown above were actually only created a few years ago; there was an explosion in the park, and mud / rocks were thrown a few hundred feet into the air, after which the mud pools were present. Hence the dead trees etc around them