Crevice, fissure
If you are asking what is another word for it... A fissure or Fault(line).
A fissure is a groove, natural division, deep furrow or elongated cleft.
crevasse
CREVASSE!
"In anatomy, a fissure is a deep groove in any of various parts of the body." "The scientists were studying a deep fissure in the ocean floor." "Steam was erupting from a new fissure in the area of the geysers."
There is no English word "hialus" in common use. It could potentially be a misspelling or a variant of another word.
fissure
Fissure
A "fissure" is a crack or break in something. You might use the word "fissure' to describe a steep-sided canyon, something that looks like a crack in the mountain. You would not use "fissure" to describe the mountain itself.
Aperture. Fissure. Celestial (space). Rift. Cosmos. Ether Space. Intersellar. Intercosmic. Metagalactic. "Ocean of emptiness". The Void.
Fissure, fussier