How long until Mt. St. Helens will fill the 1980 crater?

Good question! I just spoke with scientists at the United States Geological Survey, and they provided an estimate of 178 years. So in 2185 the moutain's cone would be back! But keep in mind that that estimate is based on the current lava flow of around a cubic meter every two seconds...basically the cargo volume of a pickup truck every two seconds. As this lava flow fluctuates so will that estimate of 178 years.

Why do people talk so much about seeing steam rising from the volcano when that is impossible because steam is an invisible gas?

Hi Patrick,

Excellent point...steam isn't necessarily the correct scientific term for what we are seeing rise from the mountain. Steam does develop, though. And as the invisible steam rises above the mountain, it cools. The laws of physics dictate that, as moist air cools, the water vapor within the moist air condenses - and a cloud forms.

So, what people see when they say they see 'steam' rising from the mountain is actually a condensation plume...or a cloud...forming as steam cools, and the moisture condenses.