Some of the photos featured in my post on Green Sands Beach in Hawai'i have been added to "Hawaii Wow," a website that features intersting information about Hawai'i.

Labels: hawaii, minerals, sediment, travel

It shows current atmospheric measurements of carbon dioxide in parts per million, as sampled at Mauna Loa, Hawai'i.

Want one? Here's where to pick up the HTML code.

Labels: climate change, CO2, global warming, hawaii

Kilauea Iki is the name given to a lava lake that formed in Hawai'i Volcanoes National Park in 1959. It erupted from Pu'u Pua'i, the mound you see in the middle distance of this photograph:

The lava pooled in a pre-existing crater below to a maximum depth of about 400 feet, and has been solidifying ever since. Researchers have drilled though the cooling crust of Kilauea Iki to determine how fast the lava cools. By 1981, a good 200 feet of solid rock had formed at the top of the lava lake.

Here's a view into Kilauea Iki from a different angle, with me rotated about 90 degrees along the crater rim relative to the first photograph:



As you look down there, you'll see that Kilauea Iki does not display a nice smooth surface. Instead, it's fractured, and those fractures have a familiar shape: polygonal and relatively regularly-spaced. They look kinda like the tops of ginormous columns...


When you get down inside, it's pretty flat. You really get the feeling you're walking on a giant layer of soup scum:


...But it's not completely flat. There are cracks and crevices, buckles and upwarps:


Dynamics playing out in this mega-scum layer atop a roiling lava lake are thought to be human-scale analogues of the motion and dynamics of tectonic plates. Here, for instance, two "plates" of cooled lava have drifted towards one another. This meso-scale "convergent boundary" has raised up a mountain range fit for Lilliputians:


Elsewhere, "plates" of lava scum have drifted apart, opening up a "rift" between them. Here, I lie down to bridge the rift:


These cracks are utilized by plants because they offer a shaded nook where moisture isn't immediately evaporated by the sun:


Lastly, I thought I'd point out some neat mass wasting and structural geology I saw there. Here's a shot looking roughly westward across Kilauea Iki, towards the cinder cone of Pu'u Pua'i:

I know it's kind of washed out, but in this photo, you can see a big solidified lava flow that came over the lip of the crater, and then solidified, and then partially collapsed downward.

This sequence resulted in the big talus pile you can see at center-right, but there are remnants of the original sheet (or "tongue") of basalt there.





















Zooming in and cranking up the contrast, let's label a few things:
Up at the top, we can see some fault scarps that have developed as the massive tongue of basalt pulled downward.

A major scarp marks the edge of the cliff, and then below it you see a big slab of basalt with an edge that's just barely in the sunshine, and a bunch of more fragmented pieces below that (marked "breakdown"). Another big slab is seen alongside the breakdown.

What really caught my eye, though, was the en echelon array of pull-apart fractures seen in between the arrows. Here, the stress of the main tongue of basalt sliding downhill sheared this slab of rock, causing it to develop fractures at a ~40 degree angle to the shearing direction. These pull-aparts therefore represent a big surface-condition analogue for tension gashes that can form in subterranean rocks experiencing shear stress.

Labels: analogies, basalt, hawaii, landslide, mass wasting, plate tectonics, structure, travel

It's the 50th anniversary of Chinua Achebe's Things Fall Apart, a reminder that things continue to fall apart. Like... rocks. ...and steel. Today, I'd like to share a "compare & contrast" of two kinds of fractures I saw on my Thanksgiving trip to Hawai'i. One is caused by a decrease in volume; the other is caused by an increase in volume.


Type 1: Columnar jointing (shrinkage fractures)









Columnar jointing results from the decrease in volume as hot lava crystallizes into cool rock. The overall shrinkage in the rock's volume is accomodated by fractures that (all else being equal) are oriented at 120-degree angles on the surface of the flow, and then propagate downward into the flow, perpendicular to the cooling front (isotherm of the critical fracturing temperature, which here is subparallel to the surface of the lava flow). Similar fractures form in drying mud, where the volume loss is due not to cooling but to the evaporation of water. Generally, these mud contraction fractures (a) don't go as deep, and (b) experience more volume loss, resulting in wider fractures. These are in the Mauna Lani resort area, on the western shore of the big island of Hawai'i.
_________________________________________________________________


Type 2: Rust blisters (expansion fractures)








Here, we see fractures forming not due to a loss of volume, but the opposite: an increase in volume! Here the metal (steel, presumably?) in the pole is oxidizing, and in completing that reaction, rust is forming. The layer of paint probably got nicked, water (probably saltwater?) got under it, and then the paint kept the water down there, facilitating the rusting reaction. As the rust formed, it swelled relative to the volume of the original metal. It expanded in the direction that offered the least resisting stress (out away from the surface of the pole). As the rust bumps grow, they impart a new stress on the metal/rust, and this causes fractures to form subparallel to the pole's surface. These are near Ka Lae ("South Point"), near the start of the hike to Green Sands Beach.

Labels: basalt, hawaii, structure, travel, weathering

I've got a few more stories to tell from Hawai'i... Today I'd like to share the tale of a backpacking trip that my friend Lily and I took along the northern coast of the big island. From the road's end at the Pololu Overlook, we descended into the Pololu Valley, across its excellent beach, then up the adjacent ridge to the east, down into the next valley, up another ridge (and further east), and then down into the third valley, where we camped.

The route is shown on this Google "My Maps" map:


Here's a look eastward into that final valley:


Descending into the final valley:


The view from our campsite:


The substrate of our campsite: a poorly-lithified conglomerate:


The thing that stands out in my mind most about this excursion was a landslide scar that had cut off the trail at one point. This landslide occured in the middle valley (between Pololu and our campsite valley). The landslide scar is nice and visible in the lower-left of this Google Maps image:


It happened in 2006, triggered by the big earthquake that struck the big island that year. It was one of several landslides that were set off by that shaking. (Wikipedia has a nice "live-action" photo of another cliff collapsing up the coast at Waipio.)

Here's the landslide scar viewed from the east, looking west (on our hike back towards Pololu):


Another shot from the same perspective shows the run-out of debris below the source:


The tricky thing about this was that we had to get past this landslide, since it wiped out the trail. On our way in, we somewhat stupidly climbed down the face of the landslide itself, gingerly picking our way down the steep slope, so we didn't trigger any further mass wasting. Here, for instance, is a poorly-put-together composite photo showing Lily descending into the valley:


(On the way out, we found some ropes in the vegetation next to the slide, and hauled ourselves up those rather than getting on the slide surface again.) But on the way in, when we got to the bottom, we weren't sure where the trail was, and plunged through some dense bamboo forest. I felt like I was in LOST, where the characters are perpetually fighting their way through similar vegetation:


Eventually we found the trail, and continued along. Because of the landslide blocking access, this part of the trail hasn't been used as much for the past two years. Lots of pandanus leaves had been shed off and blanketed some parts of the trail. Hiking across these dried pandanus leaves was a noisy affair:


On the eastern side of the ridge between "Landslide Valley" and "Campsite Valley," we saw this two-inch-wide crack opening up along the trail, parallel to the ridge/valley trend. The edge of the ridge was about twenty feet away towards the east (direction my boot toe is pointing). Certainly something like this portends a future episode of mass wasting...

Labels: hawaii, landslide, mass wasting, sediment, travel

Holy lava, geoblogosphere!

On my recent trip to Hawai'i, I saw a variety of different kinds of holes in the basaltic "lava rock" that makes up the majority of the island. The largest examples were lava tubes, like the Thurston Lava Tube near Kilauea Iki in Hawai'i Volcanoes National Park:

This is a conduit through which molten lava once flowed. Once the source of that lava ceased producing, though, the lava drained out and the tube was left empty, like a cave. (Caves, of course, are holes produced through an entirely different process.) The ceiling of this lava tube is about twenty feet high.

Not too far distant, there's a nice area where you can see tree molds:


These are holes left in the rock as the lava flowed around a tree. The heat of the molten rock burst the tree's cells, releasing water and quenching the lava in a cylindrical tube around the tree. The dewatered tree then burned up, leaving a hollow mold showing the shape of its (former) trunk:


The holes are kinda deep:


Inside the tree mold, you can see the texture of the (in this case, pahoehoe) lava that flowed around the tree trunk:


Looking up the invisible tree trunk, and out the hole towards Lily:


Here's a bigger hole, the Halema'uma'u Crater within Kilauea Caldera:

It's venting a lot of steam, hydrogen sulfide, and other gases.

Google Map for reference on how this hole relates to the even bigger hole that is the caldera:


The photo of Halema'uma'u above was taken from the Hawai'i Volcano Observatory adjacent to the Jagger Museum in the park. Stepping back a bit from the window, you can see that I'm not the only one taking this particular photo... This is the same spot where the Halema'uma'u Crater webcam is filmed. That's what all these cameras are doing in the foreground:


Janet Babb took some time out of her day to show us around the place (thanks, Janet!), and I made sure to sign into the guest book. There, I was pleased to see past visitors, including (I think) Ron Schott's crew from Fort Hays State University Lake Superior State University, the William and Mary crew, and most recently, the NOVA crew headed by my colleagues Ken Rasmussen and Nancy Chamberlain:


Janet let me hold a chunk of recently erupted basalt. This one erupted in early October, I think she said. It was about a month old when I held it -- that's my record for a really recent rock:

As noted in a previous post, this vesicular texture displayed by this sample is one more example of (smaller) holes in lava.

Labels: basalt, hawaii, travel, volcano

There's more than rocks in Hawai'i. Another thing that might catch the naturalist's eye is the diverse suite of interesting animals and plants. Today, I'd like to share some images of neat lifeforms I encountered on my Thanksgiving trip to the big island. I'll start with sea turtles, then move on to jellyfish, crayfish, endemic freshwater fish, chameleons, wooden tiki carvings (not technically alive), and plants.

Let's start with the turtles. These are green sea turtles, and they're pretty common in Hawai'i. They have certain beaches they frequent, where they haul themselves up and out onto the beach to rest. Here's one at Pu'uhonua o Honaunau National Historical Park:


Here's one feeding on algae at Punaluu Harbor:




Video of the same foraging turtle:


A short distance further along the shore, a snoozer:




But there's more in the sea than turtles... On a hike to the Polulo Valley, we found half a dozen small "Portuguese Man O' War" jellyfish on the beach:




A few valleys down, we spied these native crayfish and freshwater fish in a stream:


One of the real charmers is an invasive species, the Jackson's chameleon, native to Africa:




Look at those hands! Three "thumbs" and two "fingers."


Males have three prominent horns on their heads:


Video:




Baby Jackson's:


Do these count as "critters"? Not sure where else to put them... Tikis outside the chief's house at Pu'uhonua o Honaunau National Historical Park:


And lastly, a couple of botanical images:

Labels: anthropology, critters, hawaii, plants, travel

What's the tallest mountain on Earth?

Everest, right? Well, yeah: if you're measuring from sea level. If you're measuring from the top of the crust the mountain rises from though, it's Mauna Kea, Hawai'i. It's about ~13,800 feet above sea level, but it rises ~33,500 feet from the oceanic crust to the peak (that's compared to Everest's mere ~29,000 feet from base to peak. So... you could say that Mauna Kea is the tallest mountain on our planet... (you could!)

On Thanksgiving day, my friend Lily and I took a drive up to the top of Mauna Kea, and did a little hike up there at high elevation. Today, I'd like to share some photographs of that excursion. We saw some pretty cool geology.

On the drive up the mountain, we saw an animal which was apropos, considering the day:

Gobble, gobble, gobble. Watch out turkeys, we'll be back after we work up an appetite...

Here's Lily's jeep in the "saddle" between Mauna Kea and Mauna Loa, looking north (with Mauna Kea in the background and basaltic lava flows from Mauna Loa in the foreground):


Some cider cones (the Hawai'ian word for cinder cone is pu'u) in the saddle:


Turning the other way (looking south), you can see the bulky form of "the long mountain," Mauna Loa. What a classic shield volcano shape! I love the fact that it's so dang wide it makes a lousy photograph. You just can't capture its spread-out bulk in a photo; it's too massive:


This was the spot where I pretended to have my toes overrun by a pahoehoe flow:


As we drove up the road to the top of the mountain, I was amazed at the raw volcanic landscape, decorated with cinder cones like this one:


At one point, we passed a neat little angular unconformity on the roadside. Here it is, with a nickel (white dot left of center) for scale:


Here's a closer-shot of this small angular unconformity. Earlier layers of ash and lapilli were deposited at a steep angle, and then eroded (perhaps by glaciation? pure speculation there) before more ash and lapilli were deposited atop it, at a lower angle. There's not likely to be much time missing here, and so perhaps it's better to think of this as the top of a cross-bed, an advancing front of pyroclastic deposition moving down the mountainside, overrun by later eruptions, which may have scoured off the upper few inches (??? pure speculation) or so before deposition.

Really, the truncated tops of cross-beds are mini-angular-unconformities, when you think about it; just not with the same amount of time missing at a "real" angular unconformity (with millions of years missing) due to mountain building like the one at Siccar Point. (Video of cross-beds forming)

Here's something else which the clueless geologist might mistake for a sign of mountain building:
No, those aren't originally-horizontal strata that have later been folded. They're layers (again of ash and lapilli) deposited on the originally-rough topography of the mountainside, covering small ridges and filling small valleys. Where a given layer is exposed at higher elevation, I interpret to be a paleo-topographic high; where that same stratum is exposed at lower elevation, that's a paleo-topographic low. The roadcut reveals these layers have undulating shapes, but this is unlikely to be folding that results from tectonic compression: instead, I think it's showing us the lay of the ancient land surface.

Looking south, we could see past Mauna Loa to the actively erupting steam vent coming out of Halemaumau Crater at Kilauea Caldera (source of the vog!):


Near the summit of Mauna Kea, there are a bunch of astronomical observatories:






On the summit is where you find those examples I mentioned the other day of hawaiite, a rock of basaltic composition that is very dense (ostensibly due to erupting beneath the extra pressures of a Pleistocene ice cap):


Here's me on the summit:


View to the north from the summit: More cinder cones...


Here's a YouTube video of me pointing stuff out from the summit (Kilauea, Hualalai, Mauna Loa, observatories, hikers, etc.). Unfortunately the wind makes it all but unintelligable, but I filmed it, doggone it, so I'm going to post it:



I found a beautiful example of a volcanic bomb up there:


After the visit to the summit, we went for a hike to a small supposedly-glacially-gouged-out lake below the summit (Lake Waiau):


Here's a Google Map, showing the lake's location:


I was surprised to see a thick biofilm on the bottom of the lake:


Encrusting the pebbles and cobbles there, it reminded me of Nora Noffke's modern and Archean biofilm photos in the recent GSA Today, as well as my "Life in Extreme Environments" class this past summer at Montana State University.


We saw some nice examples of structural geology on this hike. Previously, I've mentioned plumose structure, a branching pattern on the topography of fracture surfaces in fine-grained rocks. We saw some of that on blocks of basalt atop Mauna Kea, as in this example (again a repeat photo, but the other day I showed it to you for the vesicle; today I'm showing it to you for the plumose structure.)


A similar feature are arrest lines, which again are minute variations in the surface of a fracture. Like plumose structure, which branches from a source point (where the fracture initiated) and branches out in the direction of propagation, arrest lines tell us about the development of a joint. Unlike plumose structure, though, they are not parallel to the propagating fracture front. Instead, they form perpendicular to it, and record how the fracture propagates in small "steps." Each of these arrest lines is interpreted as being a spot where the fracture grew a little bit, then stopped ("arrested") and then grew some more. In this case, the fracture face we're looking at started at the bottom of the picture and grew towards the top of the photo. You can even see some less-discernible plumose structure backing this up:

Similar arrest lines can be seen in basalt images here and here...

We also saw some pretty spectacular xenoliths. Here's one of gabbro in basalt:


Here's one of peridotite in basalt:


And a few more:



My boots, with another volcanic bomb:


Driving back down the mountain afterwards, we got this nice view of the cinder cones (pu'us!) in the eastern part of the "saddle" between Maunas Kea and Loa:


This Mauna Kea excursion was one of my favorite things that I did on my all-too-brief trip to Hawaii. It was great to get up in the high country, where the air is thin (and vog free!) and the skies are deep blue, and the geology is surprisingly varied (at least it was surprising to me, and pleasantly so). The hike let us work up a good appetite, so we headed back down the mountain and straight to Thanksgiving dinner!

Labels: basalt, birdies, geology, glacial landforms, hawaii, igneous, mountains, msse, primary structures, structure, travel, unconformities, volcano, xenoliths

This is what I saw upon waking in Hapuna Beach State Park, my first morning on the big island:

Labels: hawaii, sun, volcano

Contrary to what you may have heard, it's not all basalt. Even the basalt is astonishingly varied: the extrusive rock of a thousand faces... Here I'll share some pictures I took of rocks in Hawai'i:

There's pahoehoe:


...and there's a'a:


Here's a pahoehoe flow oozing over my boot (just kidding; it was cold when I did this):


Pahoehoe lobes can drain out, leaving only the outer skin as rock, but with a hollow center. These are lava tubes (nickel for scale):


Another one (nickel for scale):


Cool texture on the inside of this lava tube (nickel for scale):

...and zooming in a bit closer (it looks like wrinkled cellophane!):


A stack of cross-sectioned pahoehoe flows, showing their tubular (totally tubular, dude) shape:


Some Hawai'i basalt is massive, like this cobble...


...or like this cobble of hawaiite, a dense form of basalt found atop Mauna Kea (where it apparently erupted beneath Pleistocene ice caps):


But the majority of Hawai'i's basalts are vesicular, meaning they contain "Swiss Cheese" type holes that result from gas bubbles. When the lava erupts, it experiences less pressure at the Earth's surface than it was subjected to at depth. As a result, many gases (steam, CO2, sulfur dioxide, chlorine, argon, others) exsolve from the lava solution and make bubbles. If these bubbles don't get a chance to pop before the lava sets up into igneous rock, then they are preserved as vesicles. Sometimes the vesicles are small:


...and sometimes they are big:


Sometimes, they are really big. Here's one I could fit my entire Nalgene water bottle into:


When vesicles later get filled in with mineral deposits, we call them amygdules. Here's some vesicles that have gotten a light coat of a white mineral on their interiors: the first step to converting a vesicle into an amygdule:


Some of the vesicles show strain (almost certainly due to late-stage flow in the increasingly-viscous lava, getting stretched out like air bubbles in pouring honey). Surface tension on the bubble wants to make it spherical, and the lower the lava's viscosity, the easier it will be to attain that perfect spherical shape, minimizing the surface-area-to-volume ratio. So when we find them in cigar-shapes or pancake-shapes instead, that's a clue that they've been deformed. Deformed not by tectonic forces (ductile flow at depth in an orogen), but ductile flow as a result of their formation, in a sluggishly oozing blob of lava:


Another example of stretched-out vesicles:


A lonely vesicle in an otherwise massive basalt:


Not sure what's going on here, but it looks cool (popped vesicles in sticky lava?):


Another thing you see a lot of in these Hawai'ian basalts are phenocrysts of certain minerals. Here, for instance, is a cobble showing nice olivine phenocrysts:


...and another:


Here's one I showed you last week when we discussed Green Sands Beach:


Here's an outcrop which shows phenocrysts of plagioclase feldspar instead:


And a river cobble (also vesicular) bearing a healthy population of feldspar phenocrysts:


Holy feldspar, Batman! This rock has a huge proportion of feldspars (you'll note that it's still vesicular, though: in spite of the overwhelming volume of macroscopic crystals, this is still an extrusive rock):


Here's something else caught up in a finer grained (and yes, vesicular) basaltic matrix: another piece of basalt!

This is a xenolith of slightly-older basalt showing flow banding in its own trains of vesicles, that after solidification got broken off and included in younger flows of basalt. I'll post some additional xenolith photos later this week.

It's not all basalt, though. Here's a breccia made of basaltic cobbles (penny for scale):


And a closer shot of the same outcrop (penny for scale):


Finally, a rock I was surprised to see: an intermediate-composition extrusive igneous rock called benmoreite (nickel for scale, and note the rock hammer impact marks):


Benmoreite is way more felsic that anything else on the island. According to my volcanic advisor Jess, it's the result of late-stage partial melting of basaltic source rocks in the island's oldest volcano, Kohala. In other words, it's a distillation of basalt: concentrating the most felsic components in this decidedly-lighter-complected rock (nickel for scale):

Labels: basalt, geology, hawaii, igneous, national parks, pleistocene, primary structures, volcano, xenoliths

I had planned to write about vog next week, but NASA's Earth Observatory has forced my hand this morning by publishing this:

What you see in this image of the Hawaiian islands is a lot of vog, an acrid mix of sulfur dioxide, water, and oxygen that results when volcanic emissions mix with the atmosphere.

When I was there last week, I experienced some vog, starting with the source. Here's Halema'uma'u Crater (part of Kilauea Caldera), steaming away in Hawai'i Volcanoes National Park, spewing water vapor, carbon dioxide, sulfur dioxide, and other gaseous goodies upward and downwind:

The prevailing winds keep these nasty gases close to the ground west of the crater, resulting in the park service closing down the roads in that area of the park.

From there, the gases drift west and north, mixing and interacting with the atmosphere, forming vog. If the trade winds aren't active, the vog kind of stalls on the western side of the big island, and even drifts along the archipelago to plague Maui and the other islands.

On Thanksgiving day, I was standing on top of Mauna Kea, one of the five volcanoes that makes up the island, and on the descent back down the mountain, looking south towards Mauna Loa, where I could see a curtain of vog on the western flank of the big mountain (obscuring Kona and the coast):


Now here's a zoomed-in shot, augmented with a dotted line to show you approximately where the silhouette of Mauna Loa would be, if you could see it through all the vog there on the western side of the mountain. Honestly, it looked just like a curtain of greyish white hanging from the sky: palpable and with a discrete edge:


Down in the thick of it:


It wasn't as noxious as I thought to be in it and breathe it, but the vog definitely had a distinct scent and taste, and my eyes were watery (though that may have been psychosomatic, because it was kind of freaky how thick it was).

According to my friend Lily in Waimea, the trade winds have picked up in the past day or so, though, and scrubbed away the vog. So: clear skies return to Hawai'i... but for how long?

Labels: clouds, geology, hawaii, national parks, travel, volcano

Yesterday, I showed you some sand, including some green sand from Green Sands Beach on the big island of Hawai'i. Today, I'll show you some more images from Green Sands. Let's start by orienting ourselves: We're on the south side of the island, just east of Ka Lae (a.k.a. South Point). Here's a Google Map of the cove (Mahana Bay) where Green Sands Beach (a.k.a. Papalakoa Beach) is located:


To get there from the Ka Lae parking area, you can either drive a four-wheel-drive vehicle over some very rough "roads" or you can hike about 2 miles along the coast. When I visited last week, we hiked. It's a pleasant walk, and there's plenty of green sand to be seen en route to the official Green Sands Beach. Here's the coast: basalt and grassy pastureland, with plenty of wind:


A view looking down into the cove where the green sand beach is located:


So, just why is the sand here green? It's full of olivine, which is weathering out from the local rocks. At first, I assumed the source was the local porphyritic basalt. The fine-grained basalt contains many large phenocrysts of olivine, and when the basalt breaks up, these dense grains tend to be concentrated together. Here's some of that olivine-rich basalt:


But apparently the major local source of olivine are some ash/lapilli layers that make up the prominent headland on the cove's eastern edge, as seen as the "backdrop" in this photo:


A close-up of the sand on the beach, with my fingertip for scale:


And a (repeated showing) of a handful of the stuff:


These green grains don't last especially long -- olivine isn't stable over geologic timescales at the earth's surface, and so it chemically degrades and weathers away. Thus, green sand beaches are extraordinarily rare on the planet Earth (according to Wikipedia, there are two: this one, and one in Guam). You've got to have a source of olivine right there, continually adding new green grains to the mix at a rate which matches or exceeds the rate at which they are being chemically broken down.

On the back side of the beach, draped up against the outcrops of ash and lapilli, is a big slope of sand piled up at the angle of repose. I really liked the patterns made between the olivine and the dark grains as small "avalanches" flowed down the "slip face" of this pile:


I even made a pointless little movie showing these mini-avalanches of green sand:

...Or not pointless? Maybe the sandman, new on the geoblogoblock, can tell me more about what's happening here.

A poorly-lithified chunk of green sandstone (cemented with halite from seawater, apparently, as it crumbled readily in my hands):


Some green sand on a basalt cobble (which itself hosts plenty of olivine phenocrysts):


And now a closer look at some of these ash/lapilli layers which are supposedly the main source of all this olivine. These ash layers were erupted by a cinder cone called Pu'u Mahana, and apparently date to 49,000 years ago:


Some of these layers are better lithified (probably due to welding, a phenomenon that occurs when pyroclastics are erupted at higher temperatures and then deform around one another as the particles settle) and thus stand out as little 'shelves' that are more resistant to erosion by the waves and wind:


Close-up of the ash/lapilli layers, with my fingertip again providing a sense of scale:


After an hour of swimming and relaxing on the beach, we climbed back up to the plateau above the beach, where we noticed this contact between lower ash/lapilli layers and overlying basalt flows:

Notice also all the white stuff filling in fractures here. I'm betting it's calcite, especially considering the little stalactites hanging down, but I didn't have any acid with me, and I neglected to collect any to confirm that assumed identity once I got home. Mea culpa.

Hiking back along the coast to the west, we encountered more beautiful olivine basalt. Porphyritic and vesicular, this stuff just about made me cry, it was so beautiful:


I was delighted when we detoured along one of the little unnamed coves between the official Green Sands Beach and the car, and found this:


This green sand was greener than the official Green Sands Beach:


A reprise of yesterday's image of this beautiful stuff:


We noticed some footprints of a mongoose (introduced species) crossing the green sand:


Close-up of the mongoose tracks:


There was also a nice accumulation of basaltic cobbles (some porphyritic, some not, almost all vesicular) mixed in with chunks of coral:


Wow. What a cool place! Unique in my experience, and pretty close to unique in the world. If you're ever on the big island, you've got to check it out. As a geologist, visiting Green Sands Beach imparts big bragging rights: it will make all your friends green with envy!

Labels: basalt, hawaii, oceans, sediment, travel

As I mentioned a few posts back, I spent the week of Thanksgiving on the big island of Hawai'i. I had an exam scheduled in one of my classes, and I pre-recorded the lecture for my other class (via Smartboard), so I was free to kick back and relax on my travels. However, I find it's difficult to turn the inner geologist off, and so I spent a lot of my time checking out the cool geology of this unique island. I've got a lot of photos to share and stories to tell, but I'll start off simple: here are sand samples from four beaches in Hawai'i:






As you can no doubt tell, these sands are dominated by, respectively from top to bottom: calcareous hash (fragments of shells and corals), basalt fragments, olivine crystals flavored with basalt fragments, and a greater proportion of olivine crystals. They are respectively from "Sixty-Nines" Beach (west side of island; named for the milepost on the nearby road, so get your mind out of the gutter), Punaluu Harbor (south side of island), Green Sands Beach (south side of island), and a nameless cove between Green Sands and Ka Lae (a.k.a. South Point, on the south side of the island -- and in fact the southernmost point in the entire United States).

Labels: hawaii, minerals, oceans, sediment, tech, travel

I'm on the big island of Hawai'i for the Thanksgiving break; and I've really enjoyed trooping around and checking out the volcanic features. (Photos once I get back to DC...) The other night I saw Bela Fleck and the Flecktones perform in Waimea, and they were playing lots of Christmas tunes from their brilliant new album. The next day, hiking on Mauna Kea, the residual music mixed in my brain with the cool igneous geology I was seeing. The result? The Twelve Days of Volcanoes... Enjoy!

On the first day of Christmas my island sent to me:
a bunch of pahoehoe

On the second day of Christmas my island sent to me:
2 Pele's hairs
and a bunch of pahoehoe

On the third day of Christmas my island sent to me:
3 aa's
2 Pele's hairs
and a bunch of pahoehoe

On the fourth day of Christmas my island sent to me:
4 falling blocks
3 aa's
2 Pele's hairs
and a bunch of pahoehoe

On the fifth day of Christmas my island sent to me:
5 volcanoes
4 falling blocks
3 aa's
2 Pele's hairs
and a bunch of pahoehoe

On the sixth day of Christmas my island sent to me:
6 basalts flowing
5 volcanoes
4 falling blocks
3 aa's
2 Pele's hairs
and a bunch of pahoehoe

On the seventh day of Christmas my island sent to me:
7 tubes of lava
6 basalts flowing
5 volcanoes
4 falling blocks
3 aa's
2 Pele's hairs
and a bunch of pahoehoe

On the eighth day of Christmas my island sent to me:
8 steam explosions
7 tubes of lava
6 basalts flowing
5 volcanoes
4 falling blocks
3 aa's
2 Pele's hairs
and a bunch of pahoehoe

On the ninth day of Christmas my island sent to me:
9 green sand beaches
8 steam explosions
7 tubes of lava
6 basalts flowing
5 volcanoes
4 falling blocks
3 aa's
2 Pele's hairs
and a bunch of pahoehoe

On the tenth day of Christmas my island sent to me:
10 billion vesicles
9 green sand beaches
8 steam explosions
7 tubes of lava
6 basalts flowing
5 volcanoes
4 falling blocks
3 aa's
2 Pele's hairs
and a bunch of pahoehoe

On the eleventh day of Christmas my island sent to me:
11 craters glowing
10 billion vesicles
9 green sand beaches
8 steam explosions
7 tubes of lava
6 basalts flowing
5 volcanoes
4 falling blocks
3 aa's
2 Pele's hairs
and a bunch of pahoehoe

On the twelfth day of Christmas my island sent to me:
12 voggy lungfuls
11 craters glowing
10 billion vesicles
9 green sand beaches
8 steam explosions
7 tubes of lava
6 basalts flowing
5 volcanoes
4 falling blocks
3 aa's
2 Pele's hairs
and a bunch of pahoehoe

Labels: basalt, hawaii, humor, music, travel, volcano

Two weeks ago, my friend Lily took a hike up Mauna Loa. Lily teaches science at a middle school on the big island of Hawaii, and we became friends this summer at MSSE Dino Camp. I would think that living on the island of Hawaii would have some major disadvantages over time (my guess is that I'd get cabin fever living on an island), but you can also imagine that it would have some major advantages too.

In addition to live volcanic activity, surfing, exotic birds, and just general paradise-like conditions, add this to the list: climbing a tropical volcano to see giant frost crystals forming on top! Here's an image she took at sunrise, looking west over the summit caldera:



Mauna Loa is the largest volcano on the planet Earth. Rising 5 kilometers from the Pacific seafloor to sea level, then an additional 4 kilometers to its summit, Mauna Loa has an estimated volume of 80,000 cubic kilometers! It's big.

Because it's so tall, the weather at the top is much colder than the tropical sultriness at the beachfront resorts. Lily and her hiking partner found this out when they camped out on top, and woke to find that overnight, giant crystals of frost had grown spike-like from the tops of the exposed cobbles and boulders of basalt. I don't have a sense of scale here, but I'm guessing these are a centimeter tall or so... Here's a close-up of the lower-left corner of the upper image:



Pretty cool, eh? Literally. Maybe Hawaii has more variety than I had assumed. I think this calls for a field trip to investigate!

Thanks to Lil for sharing the photo!

Labels: hawaii, ice, volcano