Monday, May 28, 2012

Volcanoes at Night

The following exchange is typical of the sometimes unusually informed questions we can receive from young children. In the exchange that follows, the Mom (Jo) wrote to Ask-a-Geologist for her daughter, Samantha, because Samantha wasn’t allowed to have access to the internet yet. Samantha was just 3 at the time these questions arrived!

I am writing to you because I promised my daughter I would send Jeff Wynn the Volcanologist from one of her volcano books an email. The books I read to her every night are Volcanoes! (National Geographic) for Kids, The Best Books of Volcanoes, by Simon Adams, and Time For Kids: Volcanoes.

Not in a million years would I think that my 3 year old daughter would be so obsessed by volcanoes but she talks about them every day at school and always mentions tectonic plates, lava and magma. This phase of hers has lasted since December. :-)

Anyway, questions she had was why does the Volcanologist always have a stick?
==Jo L.

I have not seen volcanologists use sticks except for leveling rods for surveying.  In some cases it would be wise to use hiking poles so you don't fall and do a face-plant in the glass of a recent flow. When we sample some active magma we usually use a piece of wire trolled through an active (glowing red) lobe, or use a trowel to dig out a blob – the hot lava is dense and very sticky (not to mention HOT). It is VERY hard to collect a useful sample, even with heavy gloves.

Can you really walk on hot lava?

Yes you can walk on hot lava, but I don’t recommend it. The human body is a bit more dense than water, but typical basalt lava has a density up to three times this. I've walked over Kilauea magma lobes as they were moving downhill into a forest, and were swelling in thickness – but only after an initial gray crust had formed. The problem is that even the crusted lava is so hot that they will melt your boot soles rather quickly. Cold lava will destroy your boots also - but mainly because cold lava is solidified, crusty glass, and the abrasion tears the boots up at a phenomenal rate. The other problem with walking over hot lava is that the air temperature above it is suffocatingly hot - without a thermometer to say for sure, I would estimate the air temperatures above some flows I've walked over southeast of Kilauea were up in the 120F - 140F (50C – 60C) range. You can't stay in that for very long at all, and if you are downwind you can't stay there either - so in several occasions I had to walk across a new flow just to get out of the heat and back to my helicopter. Helicopters can’t get adequate lift in those high temperatures, which means the pilot could not rescue me unless I moved away from the hot zone.

Why the Pompeii guys not use their cars to get away from the Volcano?

They didn't have cars in those days (79 AD), and I'll bet all the donkeys had already taken off running on their own. The REAL problem with Pompey was that many of the people were likely killed by a rush of hot gas (called a nuee ardent) that roared down the volcano's slopes at high speed - and then they were engulfed and covered by pyroclastic flow debris. This is extremely hot ash and pumice that rained down on the survivors faster than they could run, and engulfed, suffocated, and burned those not already dead. It must have been a fast death, but a very painful one.

Don't know how long she will be so interested in this topic but I try and get books and watch videos of volcanoes as much as we can.

Keep feeding her books, and then just stand back in awe at what you have made.

Have a nice day!

You too.

Hi Jeff Wynn, Samantha was thrilled to hear from you and took your email to share with her class at the NW Montessori School. They all enjoyed hearing about volcanoes. You have a fan!
Samantha has another question.
She always calls Mount Rainier the "Dormant Volcano" but she wants to know why it is a dormant volcano.

And another.
Why do volcanoes erupt at night? I tried to tell her the erupt during the day as well but she is fascinated on how bright they are when she sees pictures of volcanos erupting at night.

Jo L., Mom of Samantha (future Volcanologist?)

Dormant is a fuzzy word. Volcanologists will call a volcano "dormant" after it has been quiet for a long time. How long you would call "long" is still being argued, but generally is up to the individual geologist. She must weigh when the last eruption took place, and what the previous eruptive history was. Mt Rainier had its last "classical" eruption (ash and pumice flew up and out of it, or lava built domes or flowed down its flanks) several thousand years ago, but a big water-and-debris flow called a lahar (the "Electron” flow) roared down into what today is Tacoma, WA, only ~500 years ago. Thus that "dormant" characterization is even fuzzier.

Volcanoes don't care what time of the day it is - no one has ever been able to get a statistical correlation with tides - the Sun, the Moon - for instance. So volcanoes erupt as often in the daytime as in the night-time.  Samantha is probably impressed with some Strombolian activity photographed at night. Glowing yellow-red cinders flying out of a volcano look spectacular in night-time photography, but aren't nearly so in daytime images. 

Samantha is unusually precocious. We usually don’t see questions this sophisticated until kids become teenagers. Keep feeding her books. We need people like Samantha to be the next-after-next generation of leaders in science.

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