Isotopes of helium a thousand times lower than helium-4 (2.17 K). This difference is explained by quantum statistics, since helium-3 atoms are fermions, while helium-4 atoms are bosons, which condense to a superfluid more easily. The most common isotope, , is produced on Earth by alpha decay of heavier radioactive elements; the alpha particles that emerge are fully ionized nuclei. is an unusually stable nucleus because its nucleons are arranged into complete shells. It was also formed in enormous quantities during Big Bang nucleosynthesis. Terrestrial helium consists almost exclusively (99.99986%) of this isotope. Its boiling point of 4.2 K is the lowest of
Boiling Lake down to the lava and is heated to the boiling point. The trail leads through another volcanic area called the Valley of Desolation. The air around the area is hot, steamy and moist, supported by the sharp, acrid smell of sulphur. The area is known to have been filled with vapors and gases that escape from bubbling and boiling sulphur-water pots, small spraying and hissing geysers, cracks and holes, and a small stream that runs through and beneath the terrain. Tiny invisible sprays of steam will easily burn an ankle or foot. There is no road leading directly to the