The horizontal entrance is called a portal. If there are two portals, then you call the excavation a tunnel. If there is only one, it is call a drift or adit.
Adit
Adit
A horizontal mine shaft is called an adit. en.wikipedia.org/wiki/Adit
how are they supposed to mine above ground? mining is defined by making an entrance underground, otherwise it isn't called mining anymore.
horizontal layer of soil is called horizon
A horizontal entrance to a mine is known as an adit.
An adit. In North America, the horizontal or sloped entrance to a mine is called a "Portal". Portal more specifically refers to the portion of the shaft visible from the outside of the mine. In some areas, the Portal portion of a horizontal shaft is called the "Drift Mouth" or "Drift Portal" as this shaft leads into a "Drift Mine". With a vertical shaft, that portion would be called a "Collar".
A mine entrance is technically an 'adit'
Adit
Adit
Adit
Adit
Adit
An entrance or passage. Specifically: The nearly horizontal opening by which a mine is entered, or by which water and ores are carried away; -- called also drift and tunnel., Admission; approach; access.
A horizontal mine shaft is called an adit. en.wikipedia.org/wiki/Adit
adit
how are they supposed to mine above ground? mining is defined by making an entrance underground, otherwise it isn't called mining anymore.