Complex sentence: Coal miners in the town of Eaton were boring a hole in search of a new source of coal when, after reaching a depth of about, a loud noise came from the ground and a foul odor began to be emitted from the hole.
Split into simpler sentences: Coal miners in the town of Eaton were boring a hole in search of a new source of coal. After they reached a depth of about, a loud noise came from the ground and a foul odor came from the hole.