Mysterious Holes in Russia

These are pictures of a mysterious hole being explored in a remote part of Russia. There's no good explation, natural or artificial, that explains how this hole came ...

Could these holes be linked to the UFO phenomenen? According to the Talmud, 'aliens' or 'demons' live in holes and lakes in remote locations. There could be a natural explanation though, some say that molten rock melted a tree leaving a hole - perhaps there are other explanations