What type of basalt is this?

[Dustin B.]

Some eye candy to start.

 

and y question

Hey I saw this rock today and was wondering if anyone knows whats going on with it? Maybe it is something simple?

 

larger full res image

http://i42.tinypic.com/ofngy9.jpg

 

 

 

 

[RJRiha]

This is columnar basalt. Look it up on wikipedia for an explanation of the shape of the columns. Why it is wavy at the top, I don't know.

[mountainsloth]

cool!

[Off_White]

wondering if anyone knows whats going on with it? Maybe it is something simple?

 

larger full res image

http://i42.tinypic.com/ofngy9.jpg

 

Well, for starters, the rock in your full res image has paint on it...

 

Cool looking stuff though.

[ivan]

i'll need to get much closer to the crag for a full report - gps coordinates please?

[ivan]

hmmm - reading said wiki page seems to indicate you've traveled to turkey in the past few days?

[dhrmabum]

Well, Malcom's answer is correct: columnar basalt. Similar or the same, to what you'd find at Devils Postpile, located near Mammoth Lakes on the eastside of the Sierra. Good stuff. Pooled up lava, cooled,contracting, jointing, etc. All geological terms.

Don't know if you happened to explore the formation in your pic, but, at Devils Postpile, the top of the formation is smooth like glass, polished so by passing glaciers. Very cool stuff.

A copy and paste:

 

The lava cools and cracks reach deep into the formation

 

As the lava flow ceased, the molten rock began cooling into solid rock. Shallow parts of the lava flow would have solidified first, with deeper parts of the lava lake requiring much more time to release the massive amount of stored thermal energy. As the lava lake cooled and solidified from a molten soup to solid rock it began to contract. Contraction stresses developed because the cool solid form of basalt has a lesser volume than the hot liquid form. Cracks, also called joints by geologists, began to form. Jointing releases internal stress created by the cooling and associated contraction. In some locations, such as at the Devils Postpile, the jointing formed columns. Jointing would have begun at the top, bottom and all around the edges of the lava lake where the lava made direct contact with a cooler surface. The cracks would have extended inwards over time as the more insulated locations within the lava lake finally released enough thermal energy to change from a liquid to a solid state.

 

[billcoe]

OMG! Someone hand me a kleenex, I just had an (pleasant) accident....ahhhhhhhhsome.

 

A cliff too far?

 

 

Closer to home:

Gent:

Andrew Trzynka

[Dustin B.]

ok there is some confusion. im takling about the second picture as to the ID. the first pic is from turkey that I found trying to Id the second rock, which im just going to assume is paint and not some sort of strange oxidizing or something. i knew i would feel stupid!

 

Seems like an odd rock to paint... anways, it looked like some solid rock that moves up and left of the main overhang.

[sobo]

 

The painting in blue is obviously man-made; looks like gangers. However, the orange- and green-hued coloring higher up is natural coloring from oxidation of iron or perhaps some other component of the rock. I've seen the orange-hued coloring before in the Tieton, which is almost entirely basalt. Andesite, actually. The green-hued coloring could be an olivine type of basalt. Where was your picture taken?

 

PS: I copied your pic to this post, but can you resize it (on your host server) to something smaller?

Edited May 18, 2010 by sobo

[Dustin B.]

this rock is in the spokane area. not sure how to resize it at this point.

[pindude]

Tell me exactly where it is, and I'll tell you exactly what type of rock.

 

Here it is, resized for ya.

 

[pindude]

OK Dustin, "in the Spokane area" is close enough. It's pillow basalt, basically the same stuff as at Deep Creek. What you've pictured looks fairly sound for pillow basalt. Hopefully it's not too chossy on top as both columnar and pillow basalt can tend to be.

 

Have fun climbing it!

[Dustin B.]

Ok thanks pin, any other thoughts on the coloration?

[pindude]

I'm not a geologist, so my rock study knowledge is limited to the basic stuff. Sobo certainly knows more than me. So when I see those black and orange swirls all I can think of is

 

Really, there is obviously another mineral present in the basalt. Talk to any of the prof's or grad students in EWU's Geology Dept, and they'll likely be able to i.d. the mineral and tell you the exact metamorphic event that created the band of basalt you've got your eyes on.

[kinnikinnick]

basalt is an igneous rock... and the orange is likely from oxidizing iron which is an element not a mineral

Edited May 18, 2010 by kinnikinnick

[pindude]

Kinni, you may likely know more than I regarding geology. Are you a geologist? I admit I know only a little.

 

However, basalt, as an igneous rock, *can* be metamorphosed to host a variety of minerals. At least that's my understanding. Regardless, I think you're right about it being iron oxidation.

[jonesy]

doesn't look as if the rock has been metamorphosed, if it has then the greenish tint could come from chlorite not olivine. I would love to see this in hand sample, identification of a fine grained matrix from an igneous rock is hard to do via photos.

[Frankazoid]

Could that orange stuff be lichen?

[MarkMcJizzy]

basalt is an igneous rock... and the orange is likely from oxidizing iron which is an element not a mineral

 

The resultant iron oxide from the in situ weathering of a basalt is a mineral, hematite. And in any case, iron oxide is not an element, it is a molecule. Chem 101, try taking it.

 

If this rock is in the Spokane area, it probably is a Miocene Columbia River basalt. The metamorphic rocks of the Spokane area are much older, with a greater degree of tectonic jointing, cleavage and schistosity.

 

Pillow basalts are common in the CRB's, are in most cases very obviously the result of a lava flowing into a sediment rich basin. The end product has the basalt pillows violently intermingled with the freshwater debris. Often there is a weathering product known as pillow palagonite through out the basal area of the basalt.

 

Discerning metamorphosed submarine pillow basalt's in massive metamorphic greenstones takes a much keener eye.

 

As shown in the photograph, some of the orange mimics a pattern one would expect from an incipiently developed, sub-horizontal, columnar jointing system. Jointing which develops much less than normal to the top of the lava pool is not uncommon. Columnar jointing can also develop in sills and dikes.

[j_b]

Why it is wavy at the top, I don't know.

 

I have always found curved cooling joints quite interesting but I never saw any as wavy as the ones shown in the picture (must be pretty cool climbing). I call them J cracks because each discrete cracking event makes an inverted (?) J as the crack propagates normal to the direction of maximum tensional stress, which implies that the state of stress changes away from the cooling front as the rock goes from elastic to ductile. I don't believe the phenomenon is entirely explained but I could be wrong.

[sobo]

I luv it when Mark gets on a roll...

[pindude]

I luv it when Mark gets on a roll...

 

+1

 

Thanks Mark--the knowledge is appreciated.