Tuesday, April 30, 2013

Logged to 1398.5 feet, learning more about fracture fill

We logged 95.1 ft of boxed rock core today, ending the day at a depth of 1398.5 ft.  Most of the day was spent logging, with a brief break to move boxes between the different buildings and areas we use.  We're starting to get to depths with a lot of "fracture fill," which interestingly remains a bit wet even after days in the drying area.  My current theory about this material is that it is water-absorbing clay produced by chemical interaction of the rock and volcanic glass with groundwater.  We hope to study this fracture fill material over the summer and figure out the details of its composition.  Here is a picture of what it looks like in a pahoehoe flow, filling multiple fractures in and around the vesicular lava:

Monday, April 29, 2013

Logged to 1303.4 feet

Today we had all three core loggers hard at work with no distractions, and we were able to log 129.8 ft of rock down to 1303.4 ft.  Most of the rock was pahoehoe, we only logged one ʻaʻa flow.  We hope to get a lot of logging done this week, all three core loggers will be working most days.  The only thing that will slow us down a bit is moving core boxes into and out of the drying area, the logging area, and the storage area. 

Sunday, April 28, 2013

Logged to 1173.6 feet, moving boxes around, drilled through the flank of a cinder cone!

Yesterday much of our day was spent moving core boxes from the rock lab to the armory, bringing new boxes to the lab to be logged, and bringing deeper boxes into the drying area.  As a result, we didn't get that much logging done until today.  We have now logged another 111.5 ft to a depth of 1173.6 ft, and we still haven't quite reached the base of that alternating pahoehoe/cinder sequence I mentioned in the last post.  Here's a representative image from our log reports of one of the box units within the sequence:
As you can see, this box unit contains the 31st and 32nd cinder fall deposits of the sequence.  At the depth shown in the photo, there are 32 mineralogically similar pahoehoe flows in the sequence as well.  I suspect we've drilled through the flank of a stratified cinder cone that may have almost constantly produced both lava flows and cinder fall deposits as it grew.  Thin, hot pahoehoe flows like the ones we've been logging are known to dominate the near-vent flanks of such cones.  From top to bottom, this sequence is ~190 ft thick and contains 40 cinder/pahoehoe intervals.  For comparison, the currently active Puʻu Oʻo cone on Kilauea's east rift zone had 44 eruptive episodes in only three years while building to its maximum summit height of 837 ft, and produced both lava flows and cinder fall deposits during this time.     

Friday, April 26, 2013

Logged to 1062.1 feet, an olivine cumulate xenolith

Today we logged rock core boxes to a depth of 1062.1 ft, 73.5 ft deeper than yesterday.  Interestingly, almost all of our logging was dedicated to a single unit that we still haven't found the base of yet.  This unit is a series of alternating cinder fall units and pahoehoe lava flows that all exhibit the same distinct mineralogy: moderately olivine plagioclase-phyric basalt (the mineral plagioclase is present as phenocrysts composing 3-10% of the rock, and plagioclase is always more abundant than olivine the olivine phenocrysts).  Hopefully tomorrow we'll finish logging this unit and by then we'll understand it better.
The photo above is a close-up shot of one of the pahoehoe flows from the unit we spent most of the day logging.  I think the photo shows a xenolith or grouping of olivine crystals that accumulated in the magma chamber just before eruption.  Olivine is a dense mineral that often accumulates along the bottom or sides of magma chambers, but we haven't seen a grouping like this but once before in the core.

Thursday, April 25, 2013

Logged to 988.6 feet, a piece of transitional core

Today we were able to log core boxes to a depth of 988.6 ft, 57.1 deeper than yesterday.  We encountered another transitional flow, and here is an illustrative example of how sudden the transition between pahoehoe and ʻaʻa can be in these types of flows:
The piece of core I'm holding in my hand shows a sharp transition from spongy pahoehoe to typical ʻaʻa with no associated process at all.  The transitional flow we logged today routinely switched back and forth between flow types without producing any contacts, while of course maintaining the same mineralogy throughout.

Once we finish logging this unit, the rocks only get trickier just below.  Stay tuned to see what we decipher tomorrow.

Wednesday, April 24, 2013

Logged to 931.5 feet, another tricky transitional unit

We were able to log core boxes to 931.5 ft today, 62.9 ft of material that was difficult to interpret.  After finishing logging an intrusion and sampling some glassy scoria, we ran into another unit that showed both characteristics of pahoehoe and ʻaʻa.  On top of that there was a lot of extra "cave-in" material due to rock falling in around the drill string at the time this core was recovered, so we had to proceed slowly and carefully while logging today.  Eventually we were able to determine the top, bottom, and internal boundaries of this transitional unit and get it logged.  Tomorrow's boxes contain rock that is quite different but also challenging to interpret for different reasons, stay tuned to hear what we manage to figure out about these rocks. 

Tuesday, April 23, 2013

Logged to 868.6 feet, first transitional unit

Today we were able to log core boxes to a depth of 868.6 ft, that's 125.6 ft logged in a single day.  Not bad since I was called away multiple times to help out with other duties.  Since we're doing so much logging, I thought I'd show you an example of the annotated photos that we're including in our log reports:
As you can see, there are two core boxes in each logging photo.  We add a distance and color scale on the left side of the photo, and label the top and bottom depths of rock shown in the photo in red.  Features are usually circled or pointed to and labeled in blue, and any contacts (none in this photo) are drawn with a thick blue line.  The purple dashed lines refer to internal boundaries within a unit (e.g. pahoehoe flow lobe boundaries that are formed when lobes with the same lithology are emplaced on top of each other during the same eruptive event).  The green box and "pc" inside show the location where a point count was taken to quantify the mineralogy and vesicularity of the rock unit.  The rock in the photo above is interesting because it has characteristics of both an ʻaʻa and a pahoehoe flow, this was the first unit we've logged where we had to call the flow type "transitional."  There is additional information about the rock in each photo in text form on the facing page of the photo in our final log reports.

Monday, April 22, 2013

Logged to 743 feet

Today we processed the final PQ run of core from the first hole, and switched our focus to primarily logging boxes of rock all day long.  Even starting late in the morning and stopping early in the afternoon to move boxes over from the armory, we logged about 70 ft.  I'll try and keep track of our logging progress each day, and periodically there should be new box photos added to that archive (see the Photos tab above).  We're seeing features for the second time now, and the rock is fully dry so interpreting it is a little easier.   

Sunday, April 21, 2013

2918 feet, casing the hole

Today we processed rock core to a depth of 2908 ft, and there should be one more run of rock arriving soon that will take us to 2918 ft.  Yesterday evening, it was decided that it was time to start casing the first half of this hole.  The drill crew spent all day today carefully lowering PQ casing (3.378" inner diameter) into the hole to protect and stabilize the sidewalls for when we drill even deeper.

After the casing is in place, the drillers will take a break while we continue to log the core boxes and Don Thomas samples the groundwater in the hole.  It's hard to say exactly how long this break will last, but it will be at least a couple weeks.  I'll continue to update the blog almost every day as we try to catch up on our backlog of rocks to describe.

When the drill crew returns, the plan is to cement the casing in place and continue coring with an HQ bit (2.625" inner diameter) to our goal depth of ~6000 ft.

Saturday, April 20, 2013

This rock is not what it appears to be

Today we processed 110 ft of rock core to a depth of 2868 ft.  As of the time of this post, our nightly delivery of rock is on its way but has not arrived yet.  I'll give a drilled depth update tomorrow, in the meantime here's something I've never seen before in any of the core I've looked at:
The photo above shows a single, unbroken piece of rock core.  In the center of the photo, what looks like a horizontal fracture is not a fracture at all.  Rock has been cut all the way around the core, but only to a shallow depth into the core cylinder.  I don't know exactly how such a cut could occur, but I'll ask our head driller tonight and find out.  My best guess is that a piece of rock got jammed between the cutting teeth of the bit, and rode in that position for a few revolutions around the core cylinder before the stuck rock piece broke, came loose, or wore away.  However it happened, this is a rare occurrence when drilling and I can't imagine any natural process that would produce this effect.

Friday, April 19, 2013

2808 feet, a rapid contrast in rock type

Today we processed rock core to a depth of 2758 ft, and received more at the end of the day that stretched down to 2808 ft.
The image above shows about 1.5 ft of rock from two consecutive trays that make up a single run of core.  The tray on the left has loose, baked soil and broken fragments of ʻaʻa clinker.  The tray on the right contains the massive interior of the same ʻaʻa flow.  Within this 10-foot run, the recovered core changes from some of the least cohesive material we have drilled to some of the most cohesive over only a few feet of depth.  This illustrates a challenge of drilling through a basaltic shield volcano: Although the rock can be drilled relatively easily, there are many abrupt changes in cohesion and internal resistance to stress that require the driller to make rapid adjustments in order to keep drilling smoothly.

Thursday, April 18, 2013

2698 feet

Today we processed rock core to a depth of 2658 ft, and received newly drilled material from as deep as 2698 ft.  We saw many interesting features, from baked soil at flow contacts to slickensides/slickenfibres to delicate flow surface textures.  I wanted to take a picture of the latter, but got distracted by the multitude of other tasks that had to be completed.  Hopefully I'll have a chance to get a few good pictures for this blog tomorrow.

Tuesday, April 16, 2013

2548 feet, and a high-angle baked contact

Today we processed rock core to 2548 ft, 80 ft deeper than what we processed yesterday.  The drill crew had to trip out and dislodge a loose piece of rock that fell into the hole, so we didn't get a delivery of core this evening.  Here's another of the pictures we've been taking of the core:
This is an end view of a cylinder of rock core.  The brown region is a layer of baked soil, while the darker part is lava rock.  We rarely get to see views like this because fractures usually don't cut straight through adjacent materials with such different properties.  The image shows that the lava flowed over the soil  at a significantly high angle, probably on a slope - otherwise the soil would have been laid down horizontally and a fracture of this orientation would show no lava rock at all from this view.   
 

Monday, April 15, 2013

Over 2500 feet, a new recovery record for the project, and weathered sand

Today we processed rock core to a depth of 2468 ft, and the rock delivered at the end of the day carried us over the 2500 ft mark.  The drilling has been going so well lately that the past 24 hours produced a new record of 120 ft recovered in a single day! 
Above is a picture of some interesting sand that was recovered recently.  We have seen a couple intervals of loose, black sand but this sand is lighter and more coherent (it will still crumble if you aren't careful handling it!).  My hypothesis is that low-temperature chemical alteration and growth of secondary minerals within this sand has both lightened its color and cemented it together somewhat.  Perhaps deeper in the hole we will find sand that has been compacted and cemented enough to call it sandstone.   


 

Sunday, April 14, 2013

2400 feet, intrusion alteration patterns

Today we processed rock core to a depth of 2348 ft, and our end-of-day delivery contained rock to 2400 ft.  It was a busy day for sure processing over 110 feet, but the core is starting to hold together a little bit better and that makes it a little easier on us.  As promised, here are some pictures of interesting features we're seeing in the rocks:



















The photo on the left shows an intrusive contact with an olivine-rich lava flow on top and a fracture surface of the intrusion exposed below the contact.  The photo on the right shows the bottom contact of that same intrusion over that same lava flow, with a different fracture surface exposed again.  The psychedelic colors you see are probably all within the smectite clay mineral family, formed by low-temperature alteration of the intrusive rock as it was chemically weathered by groundwater.  This four-foot-thick unit is the first intrusion we've seen for hundreds of feet, but it was well worth the wait!

Saturday, April 13, 2013

2268 feet, photos of drill site activities

Today we processed core to a depth of 2238 ft, and received a shipment of rock at the end of the day that reached 2268 ft.  We saw mostly ʻaʻa flows today, which is surprising since this hole has been dominated by pahoehoe so far.  Over the next few days we'll see if that is just coincidence or the start of a trend.  Close-up pictures of the rock will have to wait until tomorrow, CSAV Educational Specialist Darcy Bevens provided us with some great photos of activity up at the drill site today:
Above, Donnie (left) and Nainoa (right) extract core from the barrel into the trays.  The darker material next to Donnie's hammer is the rock itself, the lighter material is the end of the core barrel.  Donnie slides the rock out and into the tray while Nainoa makes sure that the core pieces fill the tray completely and are arranged in the proper vertical orientation (top side up).
Head Driller Ron Fierbach (left) and Principal Investigator Don Thomas (right) examine and discuss the newly extracted run of core. 

Friday, April 12, 2013

Over 2200 feet and another interesting contact

Today we processed rock core to a depth of 2158 ft, and this evening's delivery of core runs just beyond 2200 ft.  We saw some interesting features in the rock for sure, hopefully I'll be able to take photos of those features soon...but first, here's another example of an intriguing baked soil contact between pahoehoe flows:
Note that the clasts within the baked region are angular, have diverse lithologies, show no particular sorting with depth, and do not resemble the lava rock above or below.  I can also inform you that the baked region is quite solid and cohesive, probably the result of being welded together by baking and/or compaction by all the feet of rock that was recently on top of it.  One possible origin for this layer of conglomerate is glacial outwash, though as I mentioned yesterday we can't be sure of that without knowing more information.  I'm currently reading up on the glacial history of Mauna Kea to better understand and interpret features like this.    

Thursday, April 11, 2013

Baked soil contacts

Today we processed core to a depth of 2083.6 ft.  We are seeing more contacts between units marked by baked soil layers, the picture below is an example:
This is an ʻaʻa flow on top of a pahoehoe flow.  Between them is a layer of soil that was baked and oxidized to a rusty orange color when the ʻaʻa flowed over it.  In this case there are angular clasts of rock and large sediments in the contact area, which don't look like weathering products of the pahoehoe flow.  One possible explanation for them is that they are products of glacial erosion that washed down the paleo-slope of the volcano.  There is extensive evidence of glaciation on Mauna Kea dating back as far as 180,000 years ago, so if the rocks we're currently drilling are younger than the oldest glaciation, we could see glacial deposits in the core.

Wednesday, April 10, 2013

Over 2000 feet!

Today we processed core below another milestone, to a depth of 2000.1 ft.  In addition, the core that was delivered at the end of the day was at least another 40 ft of rock that will await processing until tomorrow morning.
Here is a photo of some of the core processing in action.  Eric is drying the rock core with a heat gun so he can write a foot marker on it with permanent marker, while Katie is in the background rinsing drilling mud off the next run of core.  The white rectangle on the left side of the photo is the open cover of a core box that awaits insertion of the processed rock. 

Tuesday, April 9, 2013

Over 1900 feet

Today we processed rock core to 1898 ft, and received more at the end of the day from depths well over 1900 ft.  We had a few hours of time to log boxes as well, we have logged to about 600 ft so far. 
The photo above was taken at the drill site, thanks again to Dr. Nicole Lautze for pictures of the recent activity up there!  In the picture, Principal Investigator of this project Don Thomas is loading up the trailer with trays of newly drilled rock core for transport to UH Hilo.  There are also two pallets of core boxes in the truck and trailer, we have limited space on campus and keep most of the project supplies up at PTA until we need them.     


Monday, April 8, 2013

Thank You to our visitors

My apologies for the lack of updates lately, things have been extremely busy here at the project.  Not only have we continued to get lots of rock core (now processed to a depth of 1848 ft), but today we also hosted some expert guest volcanologists.  Researchers from the Hawaii Volcano Observatory and the University of Hawaii at Manoa came to look at and help us interpret the rock.
 
Dr. Don Swanson was able to examine the finely bedded material that I had identified earlier on this blog as ash, and determine that it was actually a windblown sand deposit.  The characteristics of that sand were much like what he has seen in the field from sand dunes at Kilauea volcano.

Additionally, volcanologists Frank Trusdell and Dr. Nicole Lautze also provided valuable insight into the complex history of glaciation on Mauna Kea and the characteristics of different types of explosive fall deposits that we have sampled during this drilling project.  I would like to extend a sincere mahalo to all these visitors for their help and support, we now have a much better understanding of the complexities shown in the rocks we've recovered.  We look forward to your continued involvement in this project!  

Saturday, April 6, 2013

Slickensides vs. Slickenfibres

Here are a couple images of a feature we've been seeing on fracture surfaces lately.  The striations on the photos below look like slickensides.
Slickensides are striations on rock, created by the friction between rocks when they slide past each other along a fault plane.  The slickensides shown here are probably not part of a major fault, but they may be part of small regions within a larger fault zone where rocks under stress slide against each other.  We have seen more than a handful of slickensides within the past few days, these two are the most photogenic.
It should be noted that these slickensides may be made up of secondary minerals rather than the original rock itself.  Such minerals are called slickenfibres, and they commonly form along fault surfaces in areas where the rocks slowly creep past each other along a fault, instead of sliding suddenly.  In these photographed examples the striated surfaces look and feel much different than the surrounding rock, so we might be seeing slickenfibres rather than slickensides.  Either way, they indicate at least a small amount of motion among fault surfaces within this borehole.

Drilling Update: We processed core to a depth of 1768 ft today.

Friday, April 5, 2013

Over 1600 feet, and another interesting intrusion

Today we processed rock core to over 1600 ft depth, mostly pahoehoe flows.  We didn't see any intrusive rock today, but yesterday we saw an intrusion with such interesting contacts that I decided to upload photos of them today:
The intrusion itself makes up most of the rock core piece shown in this photo, the more vesicular rock along the bottom of the image is a pahoehoe flow.  Note the irregular shape of the intrusive contact, particularly in the lower right corner where it surrounds a thin bit of pahoehoe lava.  Additionally, on the left side of the photo there is a piece of pahoehoe that was completely surrounded and separated from the rock it was part of before, a typical intrusive "capture" of the invaded rock.  As a side note, the darker areas of rock are mostly surface water that we weren't able to remove completely before taking the photo.  The edges of intrusions can also be dark even when dry though, as a result of rapid cooling to glass or extremely fine-grained material.  The other contact from the same intrusion illustrates this point:
The darker rock close to the contact is called a "chilled margin," and is often the first part of an intrusion to cool to solid rock.  The rest of the intrusion cools from its sides toward its center after magma has stopped flowing through (note elongate vesicles on the far right of the photo that indicate magma flow). 

Thursday, April 4, 2013

Fracture Fill

Today we processed rock core to a depth of 1538 ft.  Over the last couple days, the drillers have had to pull up some of the drill string when the torque gauge on the rig indicates that loose material is accumulating on the outside of the pipe.  When they then advance back down the hole, they drill through the rubble that has fallen in and then the entire pipe turns more smoothly as the drill bit advances downward.  This is called a "wiper trip," because the drill string clears debris to the bottom of the hole somewhat like how a windshield wiper clears water droplets off a windshield. 
Above is a photo of the "fracture fill" that I mentioned yesterday.  We've been seeing quite a bit of this material, the fill itself is the brown band in the middle of the photo.  If you look closely, the fill appears muddy and a bit smeared.  This material can at times be quite solid because it has been compacted by all the weight on top of it, but it is sediment rather than solid rock.  It seems that fine-grained silt and mud has been washed into some fractures by groundwater and then compacted in place.  There are still plenty of fractures that have no fill in them, but this fill can help hold otherwise broken rock core pieces together.  As we progress deeper, it will be interesting to see if this fracture fill material persists and if it will help hold together the core even more. 

Wednesday, April 3, 2013

1485 feet

It was another full day of processing core for us, down to 1485 ft.  Much of the core was highly fractured, and there was even some fine-grained sediment in some of the runs that we looked at.  The sediment occurred in two different styles: 1) unconsolidated and mixed with other, larger rock over a distinct depth interval within a run, or 2) strongly compacted into a fracture and giving the appearance of solid rock.  I'll try and get a good photo of the latter style (fracture fill) to post on the blog tomorrow. 

Tuesday, April 2, 2013

Another 117 feet

The number 117 must be our lucky number, because we received almost exactly that same footage of rock core again today.  The picture below shows the 27 boxes that we filled today.  We stack the core boxes with their lids off during the day so the sun can dry the rock, then bring the boxes inside at the end of the day so they can be dried even further by a dehumidifier.
As of early this afternoon, drilling progress stood at 1416 ft.  As we progress downward, the hole is "cleaning up," which means there is less cave-in material falling in around the drill string as we drill.  In turn, this is leading to more maximum length (10 ft) core runs and longer drill bit life.  The longer a drill bit lasts, the less often removal of all the pipe to change the bit is necessary.  Finally, it all adds up to more rock per day!

Monday, April 1, 2013

The most productive day of drilling so far

Today we processed 117 feet of rock core, all of which had been drilled the day and night before.  So far, that is the most rock drilled in a 24 hour period on this project.  Luckily our core processing team was at full strength today and able to handle all the rock.  I didn't have time to take a picture, but rest assured we are seeing interesting features in the rocks every single day.  Some of today's highlights include processing rock extremely rich in olivine, finding numerous distinct pahoehoe flow lobes with preserved ropy surface textures, and thin nonvesicular regions within pahoehoe flows that I haven't come up with an explanation for yet.