Monday, March 27, 2017

On lava.


The Pu'u'O'o eruption of Kilauea Volcano on the Island of Hawaii (the Big Island) has been going on for 34 years.  Its lava has traveled above and below ground in different directions at different times, occasionally resulting in devastation to communities and infrastructure. Towns have been buried under meters of lava.  A few homeowners have rebuilt, on greatly changed properties.



Recently, the eruption has been sending a firehouse-stream of molten lava into the ocean from Vent 61g at Kamokuna. I hope I'm getting the details correct.  This is far from my area of expertise.  

I've always found volcanoes fascinating.  What science boy/girl didn't get in trouble at least once for using up the kitchen supplies of vinegar and baking soda?  

Why this, now?  

Partly because there have been plenty of neat pictures of Vent 61g on Instagram.  I follow a number of Hawaiian Instagram accounts.  Looking at places I've been before makes it easier to believe I'll return.



Here is a picture of Vent 61g from the Instagram account of @surrealshotz.  It was posted in late January 2017. Imagine being there.  Magma! Steam!  Explosions!

We were there the year before, well, not quite there, and saw no magma.  We did see a lot of lava though, the ropy, frozen, black pudding, the pahoehoe, of previous events in the Eastern Rift Zone of the Big Island. 

It is probably nothing more than a strange coincidence, but the the Big Island looks like the head of a French Bulldog in right-side profile. Hilo is nestled in above the nub of a nose.  On the picture below, the five shield volcanoes that make up the Big Island are indicated.  As the name implies, shield volcanoes are relatively flat and spreading, as opposed to conical composite volcanoes such as Mount St. Helens and its Cascadian family. 


Big Island (Hawaii)

The bulldog's lower jaw contains what is called the East Rift Zone, mostly within the south-eastern Puna district.  

In the Puna district, lava can flow above ground, or below ground, or both, considerable distances from Kilauea's caldera, which is inland, above the angle of the jaw.  Close to the caldera, there have been numerous surface flows in recent decades, and much of the land remains blanketed in lava.  

More distally (east), forest and agricultural fields cover a large proportion of the land, though scattered throughout are remnants of older lava flows.  In places, lava layers from old eruptions have subsided and fractured, leaving the ground rife with deep fissures.  It's a complicated geology, and driving around, it's hard to make sense of what has gone on, and is going on, underground, especially in green and bucolic eastern Puna.  One could be forgiven for having no clue that the whole place is part of very active volcano. 

We were on an interpretive tour from an ecotourism company based in Hilo.  Interpretive tours are busman's holidays for me.   Interpreters are the same everywhere.  Our interpreter took us to see fissures.



Old, overgrown ones look like this.  It was difficult to tell how deep it is.  It's behind a fence to keep you from finding out.

We were at Lava Tree State Monument, close to the tip of Bulldog's jaw.  Fissures were a side show.  The main event was lava trees. 


He cuts down trees, he eats his lunch
He goes to the lava tree.
On Wednesdays he goes shopping...  

  Sorry.



Lava trees are mostly-hollow tubes that form when red-hot lava flows through a forest, and then retreats. (I have a hard time imagining the retreat part, but apparently there's an ebb and flow aspect to lava.)  Contact with tree trunks cools the lava, which solidifies.  In return, the tree usually burns up, resulting in a hollow cast after the rest of the lava ebbs away. These lava trees were formed in 1790.

Lava tree and the interpreter (but not the interpreter).



Some lava trees have a hole on two on the side, into which you can stick your head, or at least a camera.  Some are mostly empty.  Others have greenery and other life inside.




Lava Tree State Monument has a short trail that loops among the trees and through interesting forest and forest-edge.  It doesn't take long, and soon we were headed west to see the lava of more recent events.



This is Kaimu Bay, which previously featured a spectacular, coconut-fringed, black sand beach.  It and the town of Kaimu were buried by lava from the Kupa'ianaha vent of Kilauea in 1990.  Coconut palms have been planted to hasten the return of lava-bed to beach. It will take a while.

Kaimu is about halfway along the bulldog's jaw. The lava is 15 m thick, and meets the sea as crumbling cliffs.


The surf was active that day.  Hurricane Olaf was passing to the south-east.

West of Kaimu is the town of Kalapana.  It also was consumed by the lava, in the 1980s.  I believe it is within the middle lava swath in the picture below.



On the horizon, mid-picture, there is a plume, whiter than the surrounding clouds.  It is steam from the caldera of Kilauea, about 20 miles (33Km) from this spot.  Vast sheets of lava spreading left to right notwithstanding, this gentle rise doesn't much look like a volcano, does it? Not at all like the conical papier mache, vinegar and baking soda landscapes of childhood.



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