Debris flow on Mt. Rainier: Why volcanoes are dangerous even when not erupting

We talk a lot about the hazards that are present at Washington's Rainier mostly in terms of what might happen if the volcano erupts. However, remember that even when Rainier is showing no signs of activity, volcanic hazards can still be present (video). Case in point is the debris flow that occurred on Rainier last week. The Landslide Blog posted an excellent video of the June 25 event that seems to start as a debris avalanche/landslide but as the flow runs down the slopes of the volcano, some parts begin to appear lahar-like as meltwater from the snow, ice and glaciers on the volcano is incorporated into the flow itself. This footage is pretty spectacular as you can see the dust portion of the flow get left behind from the faster moving ground debris that runs out downslope. (And for those of you who might be curious, that initial part of the avalanche is as close to what a pyroclastic flow on Rainier might look like if you were near the summit).


A debris flow captured on video from Mt. Rainier, June 25, 2011.

Rainier has a long history of lahars (see map below), many of which are not related to volcanism  - they are mostly glacially-derived meltwater releases that pick up debris along the way. This is why the volcano has a sophisticated lahar-warning system installed on the volcano as part of the hazard mitigation on the volcano because these types of lahars can occur with little-to-no warning. The lahar warning system utilizes sirens to warn the towns downvalley from Rainier that a lahar has been detected and to move to higher ground. Most of the town would have ~40 minutes (or more) to move people to safety (out of the river valleys) if a lahar is detected on the main edifice of Rainier. Usually flows like this are caused by heavy rains or melting, which prompts the collection and then release of water high on the slopes of the volcano. Rainier is also a very unstable volcano as much of the summit area has been extensively hydrothermally altered (pdf), so it is not surprising to see lahars and avalanches such as these on the volcano.

Lahar/mudflow inundation of the Rainier area over the last 5,600 years. Image courtesy of the USGS.

UPDATE 1:30 PM Eastern: Oh wow, here is a great look at the June 25 debris flow at Rainier.

Just a reminder that volcanoes are hazardous even if they haven't erupted in over a century.

Top left: Mt. Rainier in Washington.

Big Think Edge
  • The meaning of the word 'confidence' seems obvious. But it's not the same as self-esteem.
  • Confidence isn't just a feeling on your inside. It comes from taking action in the world.
  • Join Big Think Edge today and learn how to achieve more confidence when and where it really matters.

To boost your self-esteem, write about chapters of your life

If you're lacking confidence and feel like you could benefit from an ego boost, try writing your life story.

Personal Growth

In truth, so much of what happens to us in life is random – we are pawns at the mercy of Lady Luck. To take ownership of our experiences and exert a feeling of control over our future, we tell stories about ourselves that weave meaning and continuity into our personal identity.

Keep reading Show less

Futuristic inventions and emerging technologies that will change the world

What do the inventions of the future look like?

(Photo Credit: Rick Guidice/NASA)
Technology & Innovation
  • Self-sustaining space colonies and unlimited fusion energy would bring humanity to a new point in our evolution.
  • Flying cars and robot butlers could be the next paradigm shift in our tech appetite for change.
  • Death and consensus reality might soon become obsolete.
Keep reading Show less

Ashes of cat named Pikachu to be launched into space

A space memorial company plans to launch the ashes of "Pikachu," a well-loved Tabby, into space.

GoFundMe/Steve Munt
Culture & Religion
  • Steve Munt, Pikachu's owner, created a GoFundMe page to raise money for the mission.
  • If all goes according to plan, Pikachu will be the second cat to enter space, the first being a French feline named Felicette.
  • It might seem frivolous, but the cat-lovers commenting on Munt's GoFundMe page would likely disagree.
Keep reading Show less