Siim

Hawaiian style joke

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While hiking on a lava field in Hawai’i I suddenly noticed a road sign:

http://picasaweb.google.com/107509377372007544953/Rocks#5878669794529026322

Not that there is a road at the moment but apparently there once was. It may seem funny now but I am sure that it was no joke when this sign was erected. Roads do get cut off there by lava flows and lava does not show any respect to road signs either.

http://picasaweb.google.com/107509377372007544953/Rocks#5878669796744307026

Here is the end of the Chain of Craters Road in southern Hawai’i not far from the sign. This road once connected southeastern part of the island to southwestern but no longer. The road was cut in 1969 but it was reopened ten years later. However, in 1986 it was covered by lava again and since that time there is no road connection anymore and one needs to drive about 100 miles to go and see the other side of the lava field which is about 10 kilometers wide and comes from the Pu’u O’o vent of the Kilauea volcano.

Why is the road still closed? Because we humans are helpless against mother nature. Kilauea and especially Pu’u O’o vent are very active and would certainly destroy the road very soon. I spent several days on this huge lava field and also saw flowing lava. The landscape is full of fantastic lava forms which I hope to soon demonstrate in another post.

Pfeiffer Beach sand

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Pfeiffer Beach in California is famous for its purple sand. I’ve seen it included in lists of colorful beaches of the world. I paid a visit to it to see it with my own eyes. It is purple indeed but not entirely. Most of the sand there is composed of quartz, but garnet, which is mostly responsible for the purple color, forms a significant part of it.

In some patches garnet and other heavy minerals are so abundant that the sand has a deep purple color.

Garnet sand
Heavy minerals are sorted out by running water near the coastline.

http://picasaweb.google.com/107509377372007544953/Rocks#5877841632590234418
Purple sand is mostly composed of garnet. Quartz dominates in yellow sand.

A closer look to the sand. It seems to be composed of garnet, epidote, quartz, magnetite, zircon, and many other interesting minerals. Width of view 8 mm.

Lava haze

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Intense heat from lava entering seawater initiates a chemical reaction between salt ions dissolved in seawater and water which results in hydrochloric acid (HCl) cloud (lava haze). Geologists love to carry small bottles filled with dilute HCl because it makes a great tool for testing carbonate rocks. Actually, we all carry it along because this is the acid that fills our stomachs. It is diluted, though, but so are acid in geologist’s bottles and also the cloud you see on the picture below.

http://picasaweb.google.com/107509377372007544953/Rocks#5877841693091516370
These “smokes” are mostly composed of water vapor but they also contain a significant amount of hydrochloric acid. They rise from the place where lava flows onto the sea bottom from a lava tunnel. These white acidic plumes are also known as laze (lava + haze). Picture taken in Hawai’i.
http://picasaweb.google.com/107509377372007544953/Rocks#5877841703074302994
Lava itself was not visible but you can see the same flow about 6 kilometers “upstream” in this post: Flowing lava of Pu’u O’o.
http://picasaweb.google.com/107509377372007544953/Rocks#5877841697739732866
This place is surrounded by kilometers of absolutely fantastic and otherworldly landscape.

Be careful when you venture near “smokes” like that because they can be hazardous. It is not recommended to expose your lungs, eyes, etc. to it. People have lost their lives because of acidic laze clouds.

Pele’s hair

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Pele’s hair is a term for volcanic glass fibers. Its formation is usually associated with fire fountaining when blobs of flying molten lava are stretched into very thin threads. Theoretically the same could be done with an ordinary molten glass because it is polymerized and can be stretched into very long and thin strands. Pele’s hair fibers may be several meters long while being only a fraction of a millimeter in width. These lightweight fibers are then transported away by wind. They can be carried several kilometers away from vents.

http://picasaweb.google.com/107509377372007544953/Rocks#5877446891106018450
Flying Pele’s hair can stick to the upper crust of a lava flow. Lava flow with Pele’s hair has a bronze-colored hue instead of ordinary black.

It is sometimes assumed that wind stretches these filaments out of a basaltic lava flow but I find it too hard to believe. Lava flow is too compact and thick for that. There must be more intense force involved that puts a real strain on the molten material. However, similarly stretched strands often form as lava tongues break out and stretch the already partly solidified outer crust of the flow. You can see such strand in the last picture, but the majority of Pele’s hair is most likely associated with fire fountaining.

http://picasaweb.google.com/107509377372007544953/Rocks#5877446878256230242
Pahoehoe fibers are golden brown. They may be found in crevices shielded from wind.

The term “Pele’s hair” comes from Hawai’i just as many other volcanological terms. Pele is a local volcano goddess there. For some reason her hair is usually imagined to be black and/or red by artists. There is an obvious inconsistency because these are not the colors of Pele’s hair. At least not the color of the material we call that way. Her hair is therefore not composed of lava flows and should be golden brown. Perhaps we should think again how to really draw her.

Pele’s hair is not associated with Hawaii only. Similar lava threads form in other places too, for example in Nicaragua (Masaya) and Ethiopia (Erta’ Ale)1.

http://picasaweb.google.com/107509377372007544953/Rocks#5877469849895990658
A macrophoto of Pele’s hair. Width of view is 16 mm.
http://picasaweb.google.com/107509377372007544953/Rocks#5877488061213480754
Thin and fragile strand extending from the glassy crust of a basaltic pahoehoe lava flow.

References

1. Francis, P. & Oppenheimer, C. (2003). Volcanoes, 2nd Edition. Oxford University Press.

Xenoliths in Hawaiian lava

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Lava flow in the western part of Hawai’i that originated from the Hualalai volcano and formed in 1800…1801 is remarkably rich in xenoliths. It is an aa lava. Many nice examples of dunite and peridotite (rocks from the mantle) can be found with a little bit of patience and searching.

Aa lava and dunite xenolith
This is how they look. It often pays to turn the other sides of the clinkery chunks of aa lava because some nice xenoliths are not immediately visible.

Collection of xenoliths
I spent maybe 20 minutes looking for the xenoliths and found a nice collection of rocks containing xenoliths of peridotite and dunite for a picture. I scattered most of the pieces after taking the picture for you to find them again.

Dunite xenolith
Only a very small part of this dunite xenolith was initially visible. After spliting the rock with a hammer, this beautiful example of the mantle embedded in vesicular basaltic lava was revealed. The sample is 8 cm in width.

There is a possibility that these xenoliths are not xenoliths in the strict sense of the word. They might be genetically related to the lava which embeds them. If this is the case, they should be called inclusions instead of xenoliths.

The lava flow is quite wide and long. There is little chance that the location I visited is the best place to find xenoliths there. But here are the coordinates if you are interested to follow my footsteps: 19° 46′ 40″ N 155° 54′ 53″ W. Altitude 620 meters.

Telescopes of Mauna Kea

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The summit of Mauna Kea in Hawai’i is one of the best locations on Earth for astronomical observatories. There are many reasons why it is so. The summit is more than 4000 meters above the mean sea level which means that almost half of the mass of the atmosphere is below the telescopes and does not disturb observations. Mauna Kea is also far away from city lights which helps to make the sky above the summit as black as possible and location in the middle of the Pacific guarantees that there is as small as possible amount of industrial pollutants in the air.

The air above the Mauna Kea summit is usually very dry which means lots of cloudless nights. Tropical temperature inversion is well below the summit (it fluctuates between 1200…2400 meters, if present) which protects it from particulate matter from volcanoes and industrial sources and moisture from the ocean. Temperature inversion means that air temperature increases as we go higher. This is unusual situation. As we know, it usually gets colder as we move higher. If there are inversion layer in the atmosphere, it blocks clouds and pollutants from going up because they are cooler and can not penetrate hotter atmosphere above. It is a common phenomenon in many places and when that happens above industrial cities, it means bad air quality for its inhabitants. In Hawai’i, such conditions are very common and associated with prevailing trade winds that blow from northeasterly direction. The inversion is present about 50…70% of the days. Apparently, the inversion was not present on the day I visited the summit because you can see lots of clouds on the pictures below.

Mauna Kea is home to many telescopes operated by scientists from more than 10 countries. Here are some of these telescopes:

http://picasaweb.google.com/107509377372007544953/Hawaii#5875542677695734130
Subaru Telescope (on a cinder cone), Submillimeter Array (small telescopes in the foreground), W. M. Keck Observatory, and NASA Infrared Telescope Facility from left to right. There are no summit crater on Mauna Kea. Its top is covered with conical cinder cones.

http://picasaweb.google.com/107509377372007544953/Hawaii#5875542683681282098
One radiotelescope of the Submillimeter Array.
http://picasaweb.google.com/107509377372007544953/Hawaii#5875542674312206850
Submillimeter Array telescope from another angle.
http://picasaweb.google.com/107509377372007544953/Hawaii#5875542688635676018
W. M. Keck Observatory is the largest telescope in the world. This observatory actually has two domes (picture below), each one hosting a telescope with a 10-meter reflector. This is northeastern dome.
http://picasaweb.google.com/107509377372007544953/Hawaii#5875542703405390738
NASA Infrared Telescope Facility, Canada-France-Hawaii Telescope, Gemini Northern Telescope, and University of Hawaii 2.2 m Telescope.
http://picasaweb.google.com/107509377372007544953/Hawaii#5875542707386797634
Gemini Northern Telescope and Canada-France-Hawaii Telescope.
http://picasaweb.google.com/107509377372007544953/Hawaii#5875542712211504546
Subaru Telescope, W. M. Keck Observatory (both domes visible), and NASA Infrared Telescope Facility.
http://picasaweb.google.com/107509377372007544953/Hawaii#5875542715088458706
Caltech Submillimeter Telescope, James Clark Maxwell Telescope, Submillimeter Array, and Subaru Telescope.
http://picasaweb.google.com/107509377372007544953/Hawaii#5875542724554746322
W. M. Keck Observatory (northeastern dome).

Mushroom Rock

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Mushroom Rock is an interestingly shaped rock in Death Valley. This rock is fairly well known because it is located just by the road running from Furnace Creek to Badwater Basin (lowest point in the western hemisphere).

There are a number of similarly shaped rocks in the world. Most of them are shaped by wind-blown sand grains and are therefore ventifacts. There are some nice examples of ventifacts in Death Valley nearby (read my post about them: Ventifacts and dreikanters). However, this rock is probably shaped by salt erosion, not wind1. Crystallization of salt crystals can be an effective way to disintegrate rocks.

I read from several sources that the sign erroneously claims that Mushroom Rock is a ventifact (shaped by wind). There is no such sign anymore and not even a place to stop a car. Maybe because the rock was vandalized some years ago. It has been repaired and I did not notice anything wrong while I was there. So it must be a job nicely done.

http://picasaweb.google.com/107509377372007544953/California02#5874551929109845714
Small holes in the upper part of the rock (mushroom cap) resemble tafoni to me and may also indicate that salt is responsible for eroding this rock.
http://picasaweb.google.com/107509377372007544953/California02#5874551921375279730
http://picasaweb.google.com/107509377372007544953/California02#5874551925840941986
http://picasaweb.google.com/107509377372007544953/California02#5874551945812586962

Diabase
Mushroom Rock is carved from igneous rock diabase with a nice porphyritic texture. White phenocrysts are plagioclase crystals. Width of the view is about 25 cm.

References

1. Miller, M. & Wright, L. A. (2012). Geology of Death Valley: Landforms, Crustal Extension, Geologic History, Road Guides, 2nd edition. Kendall Hunt Publishing.

Collage of sedimentary rocks

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Hopefully some time during the next week I will publish an article about sedimentary rocks. It is a sequel to my post about igneous rocks. I started to collect pictures and made a collage that contains examples of common sedimentary rocks. Here it is as a teaser to the longer post.

http://picasaweb.google.com/107509377372007544953/Rocks#5873673393573074754
Examples of common sedimentary rocks: Cambrian clay from Estonia; fossiliferous Ordovician limestone from Estonia; Devonian Old Red Sandstone from Scotland; rock salt (sylvine) from The Ural Mountains, Russia; red variety of chalcedony (carnelian) from Kazakhstan, bituminous coal from the Donets Basin, Ukraine; sandstone with abundant phosphatic brachiopod shells (phosphorite) from Estonia; conglomerate from Switzerland; and aluminum ore bauxite.

Fun and work in geology

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Initially when I started writing this blog I had very limited stockpile of images to show and stories to tell. I did not have much to choose and sometimes faced the problem perhaps familiar to many bloggers — I wanted to write something but did not have a good idea or even more importantly lacked appropriate pictures. This blog is very much based on images. Text seems to be of secondary importance to me and serves to describe the pictures. It varies, of course. Some posts are more text-based but I can not imagine myself blogging without pictures.

Hence, I grab my camera whenever I go to some geologically interesting place and now I have thousands of pictures waiting to be edited, described, blogged, uploaded to photo banks, etc. So I am having another type of problem that is actually the reverse of what I was struggling with at the beginning. It is an issue for me because I would really like to make these pictures pay for my travel expenses, at least partly. So far it seems hopeless but I don’t want to give up yet. Otherwise, blogging, photographing, and geotraveling is not financially sustainable way of living. Right now I can do it because my regular job at university allows much flexibility.

But it seems that I am more interested in just one part of the equation. I just want to go out there and see the rocks. I bet many geologists feel the same. They are not particularly interested in writing reports and journal papers but love to see real geology. Unfortunately, we all know it is not sustainable. Somebody has to do the hard work as well.

I just returned from California and Hawaii where I took lots of photos that are waiting for my attention but I already discover myself preparing for another trip. There are so many places I would love to go. It’s like an itch that needs to be scratched. I already started to prepare a list of places I would like to see in Utah and Arizona. This is insane. I have no way to go there any time soon. I don’t have time for that and it would be a financial ruin. Plus it would clearly demonstrate that I fail big time in my pursuit to make my photos earn something. They won’t earn a dime while they are sitting on my computer’s hard drive. Another place I would like to go to is Cyprus. I was there only a year ago but since that time my photographic skills and equipment have improved considerably. I took photos with an iPhone which are almost useless now. There are lots of beautiful places in Cyprus to visit again with a good camera that takes pictures with acceptable quality. Yesterday I saw that right now I could grab some last minute plane tickets cheaply…

But no, it is not time for that now. Perhaps later and maybe even within this year. I guess I just need to find a healthy balance between fun and work. I must lock myself somewhere with only my computer (and preferrably without Internet) and work from morning till night. Then I can catch up with unfinished tasks and can go out sooner. Ok, I don’t believe I am going to be that radical but I need to move towards being more effective. That’s for sure.

http://picasaweb.google.com/107509377372007544953/ProfilePhotos02#5873763187839521762
Out there, playing with rocks.

One pebble with two lives

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I don’t remember when and where I found this pebble. It was probably several years ago somewhere in Estonia. It is very small (about 4 cm across) and composed of limestone. I picked it up because it must have a remarkable geological story.

It had to be a part of some limestone formation. Most likely in northern Estonia where such rocks from the Ordovician Period are exposed. It has a rather distinct appearance and seems to be partly composed of clastic fragments but I am not familiar enough with Estonian bedrock to locate its exact source. I believe it comes from the coast because it is a pebble. Something had to break it from the limestone bed and then polish it to a nicely rounded shape. I guess it was done by sea waves.

What happened after that is harder to explain but it is obvious that something had to crush it. The pebble is now composed of four distinct parts. However, these fragments were not separated from each other which needs some sort of explanation. They are only slightly displaced. Most likely the pebble was surrounded by other rocks which held the fragments in place. What was the crushing force is impossible to tell. It was hardly an earthquake because these occur in Estonia very rarely and are weak. Maybe some bigger rock fell onto it? Maybe the event was associated with glacial activity during the last glacial epoch?

Anyway, the four main fragments of the pebble stayed next to each other and were cemented together again as a single rock and were later liberated from the surrounding material. So the pebble was crushed and then the pieces were glued together again and the same pebble, although seriously wounded, formed again.

http://picasaweb.google.com/107509377372007544953/Rocks#5873362125056612866
Small brecciated limestone pebble with an interesting history.