From today's Gospel reading (Luke 16:19-31): My theory that Sheol becomes Gehenna after the Crucifixion

Sheol = "the realm of the dead" in pre-christian Judaism

Gehenna = eternal hell (aka the "Second Death")

In Christianity, there are only two places you can go once you die: heaven (eternal life) and hell (eternal punishment).

In Judaism before Christ, the afterlife was called Sheol: The good part was called "the bosom of Abraham" which was a place of comfort where the righteous went. The bad parts were places of torment where the unrighteous went.

In the Nicene Creed, when we say "He descended into hell, on the third day He rose again from the dead," we believe that Jesus descended into Sheol ("the realm of the dead") to preach and judge the dead souls who were trapped there (1 Peter 4:6).

We don't believe that Christ descended into Gehenna. We believe that He descended into Sheol.

"The bosom of Abraham" was separated from the places of torment by rivers and chasms.

What is a chasm? It's a deep fissure in the earth. What do you find when a chasm cuts all the way through the earth's crust? Lava and fire, or more specifically the magma layer.

(It's worth noting that volcanoes and lava are themes throughout the Old Testament (google it). Therefore were no volcanoes in Israel so they were probably just symbolism. The point is, the ancient Israelites had a basic grasp of geology where "under the earth = magma.")

What happened during the Passion? A weird event that is often overlooked.

Matthew 27:51-54

"51 And behold, the curtain of the temple was torn in two, from top to bottom; and the earth shook, and the rocks were split; 52 the tombs also were opened, and many bodies of the saints who had fallen asleep were raised, 53 and coming out of the tombs after his resurrection they went into the holy city and appeared to many. 54 When the centurion and those who were with him, keeping watch over Jesus, saw the earthquake and what took place, they were filled with awe, and said, “Truly this was the Son of God!”

1. There was an earthquake and the rocks were split: the chasm in Sheol widened until it broke into the magma layer, exposing the "lake of fire" (Gehenna).

2. The first Judgement of the souls in Sheol (1 Peter 4:6) and the first Resurrection of the dead (of those righteous in the bosom of Abraham). These righteous souls and their bodies were raised and they appeared throughout the city like Jesus did after His Resurrection (Matthew 27:52-53). Presumably then, the unrighteous would have been judged and cast into the newly exposed lake of fire.

That's why we call the Second Coming the "LAST Judgement" or the "FINAL judgement," because the first Judgement was of the souls in Sheol.

Also, whether the image of "lake of fire" is literal fire or an image is a different question.