Dr. Carl Norman studies sinkholes and salt domes. "In the greater Houston area, Beaumont, we've got about 50, 53 of these salt domes," he said.

He's been on the scene of most of the major Texas collapses in the last 40 years.

Meeting here with emergency crews on the scene of a huge collapse in Daisetta, class is in session.

"Let's think about a house that has a dome-shaped roof and the walls keep moving out," Dr. Norman explained. "This is like solutioning in this cavity. Eventually, that roof is not going to be able to support."

And you have a collapse. What comes next? That depends.

In 1983 in Boling, Texas, another hole opened up. It was 250 feet across and 25 feet deep. It formed in hours.

"You had the one event and that was it. It never widened," said Dr. Norman.

But near Wink in 1980, one hole grew over six months and is now a lake. A nother began nearby in 2002 and is still growing years later. It's now more than 1,000 feet across.

The salt domes themselves are huge.

The entire town of Daisetta sits on a salt dome, so another collapse in another area is possible, according to Dr. Norman.

The sinkhole was caused by a collapse of a small cavern -- either natural or man-made.

"The size of the cavity that collapsed is going to be the size of this hole or larger. This is not the size of that cavity underneath," explained Dr. Norman.

That's likely much larger.

"It is going to be critical the next few days to see what happens," Dr. Norman said.