The streaming crater of Turrialba in an image taken in mid January 2010.
I have a moment to spare here at WMU, so I thought I would pass some of this confusing news along concerning Turrialba. Some of the latest reports refer to a "crack" in the crater of the volcano ... specifically:
Geologists and volcanologists were at least able to confirm that the crack on the wall of the volcano is getting larger, confirmed by flybys by helicopters during a break in the weather. The experts say the constant spewing of gases is causing the crack to get bigger and could collapse the volcano's crater wall, causing the volcano to spew out the falling material.
Now, I'm not entirely certain what this is referring to - a fissure at the crater where fumarolic activity is focused; a crack caused by upward deformation of the edifice; a crack caused by a collapse of part of the crater rim. None of the articles are very clear. Apparently a small ridge that formed between two of the phreatic craters that formed last week has collapsed, which is not surprising if it was made of loose, unconsolidated volcaniclastic material. There has been no sign of juvenile material (i.e., new magma), but ash continues to be generated at the summit - mostly made of crushed older erupted rock. The volcano will remain on yellow alert status even though it has quieted some - however, when the evacuees can return is still anyone's guess.