projection
fissure
A volcanic vent or fissure (depending on the type of eruption).
Magma can erupt from a volcano through either a central vent or a fissure. A central vent is a single opening at the summit of a volcano, while a fissure is a long crack in the Earth's surface from which lava can flow.
A crevice is a fissure or narrow opening, typically found in rocks or ice.
A fissure can mean a split in the geological structure of the earth or any opening in the body. A foramen is an opening that can connect the bodily systems together. Foramen does not pertain to geological structures but just biological things. See related links below for more information and sources
....opening?
is a depression
A meatus is an opening; therefor, it's a depression, not a projection.
projection
projection
projection
projection
fissure
A sulcus is a depression or fissure in the surface of the brain.
"A crest is a projection or ridge, especially of bone; cresta"source: chacha.com
A rounded opening through a bone is called a foramen. Foramen provides a passage for nerves, blood vessels, and other structures to pass through the bone.
Fissure