Redoubt sets a pattern and how to tell if you have juvenile magma in your eruption

Redoubt seems to be setting its pattern for this part of the new eruptive period. There was another small explosion this morning that produced at 15,000 foot / 5,000 meter ash column that moved to the NNW. The seismicity has settled down since the early morning eruption today (3/25) as well.

These types of explosions producing plinian and subplinian eruption clouds that will likely lead to dome building – the same pattern seen at Mt. Saint Helens in 2004-2008 and the previous Redoubt eruptions in 1989-1990. These explosions, producing ash columns that reach tens of thousands feet, will likely continue to occur for weeks to months.

Image courtesy of AVO/UAF-GI by Izbekov, Pavel and Shipman, Jill

AVO has posted some excellent SEM (scanning electron microscope) pictures of ash from the Redoubt eruptions (see above) along with a myriad of other eruption-related images. If you’re curious about one way to tell the different between juvenile (fresh) magma ash and old (accidental) ash made from crushing dome rock, check out the difference between these pictures: ash from the 3/15 explosion -or- ash from the 3/23 explosions. Can you tell the difference? The 3/15 ash, made from pulverizing the old dome rock of Redoubt, is jagged and angular, lacking vesicles (air bubbles). The ash from 3/23 is clearly cuspate and contains lots of stretched vesicles, indicating it was initially made of magma that was molten enough to all gas bubbles to form, try to escape and stretch (see also the image above). This makes it very clear that the 3/15 explosion did not release any juvenile magma, while the 3/23 and beyond eruptions have.

It also looks like the eruption has now shut down the Drift River oil terminals, just like one might expect when you put an oil terminal in the outwash fan of a river that is at the base of an active volcano. The terminal is undamaged according to the Coast Guard, but the shutdown will likely cause some problems with oil movements within the Cook Inlet in the short term.