Happy Easter! Farther down the rabbit hole we go...

We have been logging the past few days because of some drilling issues that needed to be taken care of.  A couple nights ago, some sticks found their way into the mud tank and blocked the flow of drilling mud into the hole.  Below is an image of what happens to a drill bit when there is no mud lubricating the cutting face (these are PQ drill bits with an inner diameter of 3.378 inches):

 The bit on the left is "used" and needs to be replaced.  The bit on the right is "abused" and has had its cutting teeth ripped off by turning on bare rock without drilling mud to lubricate the cutting face. Here's another view to illustrate the point:

Note that the bit on the right is also bowed beneath the teeth, a response to the weight of the drill string on top of the bit as it tried to cut without the help of drilling mud. 

The drill crew was able to recover from this issue, and after spending yesterday doing maintenance on the rig, we are back to standard coring operations. 

Logging from post-shield to shield stage

Today we changed gears from core processing and logged 20 core boxes, completing from Box 57 to Box 76.  This was interesting work, as we probably covered some of the earliest post-shield material of Mauna Kea and then got to the shield-stage lavas that we will continue to log for the rest of this hole. 

Please feel free to browse the newly uploaded high-resolution box photos in our archive, we have added through Box 100 today (there is a link in the Photos tab above)

The ash deposit

Today we processed rock core to a depth of 1198 ft.  The weather has been cooperating and we can dry the boxes of rocks in the sun before photographing and logging them.

Speaking of photography, we finally got a decent picture of the ash I've been mentioning lately.  For a sense of scale, the rock shown here is 3.5 inches across.  Feel free to click on the photo to look at the ash beds in greater detail.  The cross bedding seen in the upper left of the picture might just be a surface scratch, I didn't notice any other cross bedding.  This is by far the finest and most well-bedded ash we have seen so far, from a depth of ~950 ft below the surface.  Such ash is an indicator of an explosive eruption, which is an eruptive style thought to be relatively uncommon from Hawaiian volcanoes.  However, there are a number of historical accounts of explosive eruptions from Kilauea volcano, as well as ash deposits found all over the island that date long before the first Polynesian explorers arrived.  Such fine ash can be carried far by the wind, so we can't say yet which volcano may have produced it. 

Another day, another 83 feet of rock core

Today we processed rock core to a depth of 1118 ft, and received nine more trays of rock at the end of the day.  We will start processing again right away tomorrow morning; lately the drilling seems to be proceeding a bit more smoothly than before.

Apologies again for no photo of the finely bedded ash, I'm working on getting a good close-up shot of it under good lighting conditions.  

Over 1000 feet of core processed!

We processed rock core to 1035 ft today, only 5000 or so more feet to go before the first hole is finished!  Over the past 10 days, the drill crew has penetrated over 750 ft for an average of ~75 ft/day. The average run length has been just over seven feet, less than the maximum ten feet because there has been so much loose material that has been blocking the core barrel and causing early run pulls to the surface.  This drilling rate is as good as can be expected, considering how fractured the rock has been. 

My apologies for the lack of a photo in today's update.  I took pictures of some fine ash beds that we saw today when logging, but the lighting was poor and the photos are all too dark.  I'll post a picture of this layered ash tomorrow.

We rock the dock

Today we processed rock core to a depth of 947 ft, and the trays that were dropped off at the end of the day will carry us over the 1000 ft mark.  As always the rocks were interesting to interpret, but I forgot to take a picture of anything photogenic.  Instead, here's a look at yesterday's lineup of full core trays at our loading dock:

This isn't even all the trays we processed yesterday, there are more on our work table that you see on the far left.  Each core tray is six feet long and has a painted top end, so the drill crew can extract the rock into the tray in proper vertical orientation.  The trays also have circular foam end pieces to keep the rocks from sliding out, and tray covers to prevent rocks from bouncing out of the trays during transport to UH Hilo from PTA. 

The effect of intrusions

Today we processed a lot of core, to a depth of 858 ft.  Last night, the drillers were able to advance downward a significant amount because the rock was so loose that they could push right down through it without the bit having to cut much.  You may recall that they encountered conditions like this before, when we drilled through what we believe was the cinder of a cinder cone.  However, this time the loose rock was created by a different process.

The photo above (co-worker's hand for scale) shows the bottom contact of an intrusion that measures ~16 ft thick.  The rock on the upper side of the photo has been welded together, but the rest of that unit is intensely broken (as unconsolidated as the cinder we encountered earlier in the hole).  Similarly, the rock above the intrusion is also broken to a cindery mush.  The intrusion itself is in great shape, as you can see by the unbroken nature of the lower part of the core shown in the photo.

I think that this intrusion caused the breakup of the rock above and below it, both fracturing it and baking it (there is abundant, black baked olivine in the rock above and below the intrusion, not to mention the intense baking of the loose rock fragments themselves to a bright orange color).  In addition, there may have been groundwater in the vesicular rock that was invaded, which was turned to steam by the intrusion's heat.  The expansion of this steam probably contributed significantly to baking and breaking apart the surrounding rock, particularly above the intrusion where the most extensive baking is found. 

This intrusion is different from the one described yesterday in that it is at least five times thicker.  Yesterday's intrusion didn't significantly affect rock above and below it, because it was thinner and cooled more quickly.  Both intrusions support the idea that we are drilling in an area not far from the eruptive source of the lavas that the drilling is sampling.

Drill rig servicing day

The night crew drilled to a depth of 805 ft last night.  Today the day shift drill crew serviced the rig, changing its oil and filters and performing other routine maintenance.  Meanwhile, the core processing team boxed rock to 737 ft and logged core boxes to 371 ft. 

One of the more interesting finds from processing today's rock was an intrusion only a few feet thick.  This intrusion (rock above the fracture) is almost glassy at its top and bottom margins, and has invaded a weak point in an olivine-rich flow (rock below the fracture).  Although this intrusion is thin and does not necessarily indicate on its own that we are drilling near a rift zone of Mauna Kea, the high abundance of extremely vesicular pahoehoe flows suggests that the lavas we're drilling through didn't travel very far before they covered the area beneath the drill site. 

Because it is so vesicular, the rock core doesn't have much internal strength and can't hold itself together well.  Fragments of rock break loose from the sidewalls and cave in onto the drill pipe, making the drillers lift up the drill string a bit and then re-drill back down on that cave-in material until the sidewalls of the hole are clean.  Drilling loose cave-in material quickly eats away at the drill bit, head driller Ron Fierbach estimates that we've had to change the bit every 150 feet or so since we started drilling shield-stage lava flows.  Changing the bit is a time-consuming and tiring process for the drillers, as all the drill pipe has to be pulled out of the hole. This process is also expensive, each bit costs $800 and the drill hands are tripping pipe in and out of the hole instead of the bit cutting on bottom and extracting more rock.  Bit life in the less vesicular Hawaii Scientific Drilling Project lavas averaged many hundreds of feet, with one bit cutting over two thousand feet!  We'll be keeping our fingers crossed for a slight change of lava type that would enable such drilling conditions again.       

Baked soil contact

Today we were kept extremely busy processing rock core down to 700 ft.  The day's core was less fractured than what we typically have been seeing, so the drillers didn't have to pull out short runs or lift the drill string and re-drill cave-in material as often as they have had to recently.

The photo above shows a striking contact between two lava flows.  The upper flow has both large and small vesicles, and some of the large ones show irregular (non-spherical) shapes.  This upper flow has almost no phenocrysts at all.  In contrast, the lower flow has abundant small round vesicles, and is loaded with olivine (click on photo for a larger view).  The material between the flows is soil that accumulated via weathering of the lower flow and then was baked and oxidized when the upper lava flowed over it.  This baking extends down into the upper portion of the lower flow as well.

Rock shaped by water

Today we processed core to a depth of 585.5 ft and logged boxes of rock to a depth of 325.9 ft.  One of the many interesting features we examined while logging is shown below (nickel for scale):

The piece of rock core on the left has an interior surface with a light coating of clay on it, indicative of low-temperature alteration of the rock via chemical interaction with water.  For comparison, the dark material at the top of this piece is a new, drilling-induced fracture surface that has not been altered.  Both of those features are common, but the strongly curved core interior is not.  It appears that over a long period of time, groundwater wore a smooth channel through this rock fracture.  Although this example is on a smaller scale, it is the same process by which rocks in a riverbed are rounded by the flow of water over them and rivers carve canyons down through solid rock.

Ropy pahoehoe

As promised, here's a representative picture of some of the pahoehoe we've been seeing.  The black rock has been cut by the drill bit, the brown rock is an exposure of the "ropy" surface of a pahoehoe flow.  In this case, it appears that there was a void space that was not completely filled when pahoehoe lobes were emplaced next to and on top of each other.  Later flows buried this void space, and that way the ropy surface texture was protected and preserved all this time.  We have seen lots of this kind of ropy pahoehoe lava flow morphology over the past couple days.

We boxed rock to a depth of 534.8 ft today, and logged the previously boxed rock to a depth of 296 ft.    

Probably pahoehoe

The drilling slowed down a bit last night due to encountering some unconsolidated material, but that issue appears to be resolved now.  As a result, the core processing crew got to do some logging this morning.  The picture below shows all the boxes we have in our lab that have been photographed and are ready to be logged into the database. 

The logging for these boxes should actually go pretty quickly, if we can find the time to get to it.  Most of our time so far has been spent trying to get the core boxed fast enough to keep up with the drilling.  We processed rock to a depth of 491 ft today, and saw what appeared to be our first pahoehoe unit(s).  This could be a significant find, because post-shield stage flows generally don't produce this lava type.  The pahoehoe flows also contain no xenoliths, another indicator that they are from Mauna Kea's shield stage rather than it's alkalic cap. 

Another interesting contact

Today the high rate of drilling penetration continued, we processed core down to 450 ft.  In doing so, we eventually saw the end of the massive unit mentioned in yesterday's update: it was almost 100 feet thick!  Our best initial interpretation is that it is an intrusive body, probably a sill.  The picture below shows the bottom contact of this unit with the underlying thick soil or ash layer that it invaded and baked. 

Note the entrainment of the underlying unit, a classic intrusive characteristic.  In addition, the dark region at the center of the photo is incredibly fine-grained, almost glassy.  This indicates that the rock cooled very quickly here along the lower margin of the unit, the underlying material may have been wet and aided in this cooling.

The last unit we looked at today was highly vesicular and had lots of olivine, more than any units we've seen so far...every day we see something new and interesting! 

Great progress, a change of rock type

Last night and today, the drillers have really gone a long way.  We got a huge delivery of core this morning, and processed it to a depth of 335 ft.  Up at the drill site, they are at least 50 feet deeper than that at the time of this blog post.  Below is a picture of an interesting transition that we saw while processing the rocks today:

Remember in yesterday's update that all we were seeing was loose cinder?  Well we saw lots more of that...until this contact.  Note that the oxidized cinder on the left holds together in a coherent manner, which was surprising on its own.  In addition, the contact between cinder and nonvesicular rock beneath it is extremely sharp, a change so sudden that you could hardly get two more physically different rock types next to each other in such a setting.  We will have to carefully consider the meaning of this contact when logging both rock units later.  

Drilling with mud is working well

Since yesterday's update the drilling has advanced downward significantly; this afternoon we reached a depth of over 250 ft.  Part of the reason drilling has gone so quickly is because we are advancing downward exclusively through cinder.  The drilling runs have produced no consolidated cylinders of core, only small collections of cinder measuring much less than the downward advance of the drill bit.  We believe what is happening is that we are doing some cutting, but mostly pushing our way down through a cinder cone.  Although it would be nice to sample more solid rock, the cinder isn't caving into the hole and we're making good progress.

The drillers feel that making the switch to drilling mud instead of using foam has helped stabilize the hole as well.  Above, you can see the crew mixing up a batch of drilling mud (as well as another basin and a water tank for mixing even more).  Although this mud is a little more expensive to use in a place like PTA where the cost of water is high, the additional expense is worth it if it helps keep the sidewalls from caving in around the drill pipe.       

A drilling breakthrough

Apologies for the delay in posting this update, I have been waiting for some good news to share on the drilling front. 

Over the past week or so, the drillers have filled the hole with cement and then drilled through that cement in an attempt to stabilize the loose upper portion of the hole.  In addition, casing was set at a depth of very solid rock, about 90 ft below the surface.  This casing was also cemented in place and will prevent any cave-in material along its length.  More cement was poured into the hole and allowed to harden, and then Master Driller Ron Fierbach went in with an unconventional setup to try and drill alongside the material stuck in the hole.  He drilled without the stiff core barrel, instead using only a drill bit attached to regular drill pipe.  This enabled him to deviate slightly from the old hole, and once the bit started to cut some rock instead of only cement, it was drawn into the rock and away from the cement.  Below is a picture that from left to right shows progressively deeper core samples drilled by this method. 

The far left core shows a combination of rock and cement, but the amount of cement decreases in the downward direction.  The second core piece shows significantly less cement at its bottom.  The third piece shows even less cement and the curved, cut face of the sidewall of the old hole.  The last piece shows some of this curvature as well, but advances down to a complete cylinder composed entirely of newly drilled rock.  The significance of this image is that it indicates we are now out of the old hole and drilling alongside it.  Although we aren't in the clear yet, this is a big step in the right direction.  The next question is whether we can drill past 130 ft, where the collapse occurred before.  This time most of the hole is cased, so hopefully encountering a lava tube void space won't cause so many troubles.  We don't know how much more loose material we may have to drill through, but hopefully we'll be through it soon.   

Logging and more difficulties drilling

Today we had a lot of rock core to process.  It took all morning to wash, dry, mark and box the rocks to a depth of 128 feet.  The afternoon was spent photographing and logging the rocks, and trying to decipher their complex geologic relationships.  Below is a photo of most of the boxes lined up and waiting for us to interpret them.

Drilling Update: Poor drilling conditions continued today, and we encountered an open void space that was larger than any we had passed through before (probably a lava tube).  As a result, circulation of foam was lost into the opening and loose material collapsed in around the bottom section of pipe, pulling it completely off the rest of the drill string.  In order to continue drilling, we first have to clear the hole down to the broken-off piece of pipe with a rotary bit, and then fish out the lost pipe.  This will be a challenging endeavor, and will take at least a few days because of the need to ship in more rotary bits.  Please wish the drill crew luck, they have a lot of tricky work ahead of them in order to continue to advance this borehole. 

Looking for a few good lavas

Over the last 24 hours, drilling has progressed slowly because of the unconsolidated nature of most of the rock we've been drilling through.  This does not come as a complete surprise, since the PTA area of the saddle where the drill rig is located can be viewed as a basin that collects erosional products from Mauna Kea.  In addition, the post-shield stage cones of this volcano (see below for an example) have erupted and deposited loose cinder that we have to drill through as well.  The best drilling has been through solid lava rock, but so far we haven't encountered much of it.

Last night it was necessary to trip out and change the bit, because unconsolidated material eats away at drill bits much faster than hard rock does.  As of about 3:00 pm today, we have progressed to 98 feet below the surface.  The goal is to keep drilling slowly through this section until we encounter solid rock in which to set casing.  At that point, we will attempt to widen the hole with a rotary bit and set casing on the solid rock formation at the bottom.  The casing will extend to the surface and keep loose material from caving into the top of the hole as we continue to drill downward.  Stay tuned for further updates on our attempts to stabilize the hole for better drilling penetration and recovery.     

Drilling with foam

Today we began our regular drilling schedule.  In an attempt to limit our water use in the upper, dry portion of the hole, we are using foam as a lubricant.  It will take some time to determine the proper foam/water mix for the drilling conditions, but so far the foam is doing its job well.

    By the end of the day shift, drilling had progressed to a depth of 60 ft.  At 100 ft we will stop and widen the hole with a rotary bit, then set and cement casing to that depth.  This casing will help prevent the loose rock near the surface from caving into the drillhole. 

Our first core run of the project!

Drilling began today and we took it slowly so that our new drill hands could get some training in what working on a drill rig is like.  All the drillers and drill hands, as well as the Principal Investigator and Rock & Data Manager were present at the drill site for the first drilling day of the project.  Pictured below is the first recovered run of core.  Preliminary examination of this run has revealed a xenolith-rich unit from Mauna Kea's alkalic post-shield stage.   

Our 24-hour-a-day, 7-day-a-week drilling schedule begins tomorrow.  After the core is recovered from drilling at PTA, it will be transported down to UH Hilo where the core processing crew will be washing, drying, marking, photographing, and logging the rocks.  Soon in addition to these blog updates, lots of photos and data will be added to the other pages of this web site.