A word or phrase that means to swallow people

Solution 1:

The following biblical passage uses language very similar to your own:

the earth opened its mouth and swallowed them and their households, and all those associated with Korah, together with their possessions (Numbers 16:32)

This passage should convince you that there is nothing wrong with plainly saying "the earth swallowed the people."

You could also say:

the earth opened its maw to swallow them

where maw means "the jaws or throat of a voracious animal."

You could also say:

The earth devoured them

where devour means "eat (food or prey) hungrily or quickly."

All of these examples anthropomorphize the earth (that is, depict the earth with human characteristics like having a mouth). There is nothing wrong with this technique and it can be quite effective, especially when combined with evocative words like maw and devour, which connote viciousness and gluttony.

Solution 2:

Engulf is a good word for this. American Heritage:

To swallow up or overwhelm by or as if by overflowing and enclosing: The spring tide engulfed the beach houses.

More generally, a scene like that might be described as a cataclysm.

something that causes great destruction, violence, etc.

(from Merriam-Webster's Learner's Dictionary)

Solution 3:

Engulf and Swallow are good options. For variety, here's another one:

Envelop

from MW

1: to enclose or enfold completely with or as if with a covering

from the Free Dictionary

tr.v. en·vel·oped, en·vel·op·ing, en·vel·ops
1. To wrap, enclose, or cover: "Accompanying the darkness, a stillness envelops the city" (Curtis Wilkie).

2. To surround: The troops enveloped the town.

This term gives a visual of the ground rising up and surrounding the people, much like engulf.

You might say: