Visiting Hawai'i...for the Limestone Caverns? (Part one)

People visit Hawai'i for a great many reasons. There are the stereotypical reasons: beautiful beaches, surfing, palm trees, luaus and so on. There are other reasons: a wish to learn about the culture of the many people groups who call the island home, some of them for upwards of a thousand years. There are others who find fascination with volcanoes and lava flows. And the biology! The isolation of the islands has resulted in the evolution of hundreds, even thousands of species that exist nowhere else in the world.

I'm willing to bet that very few people come to the islands to tour the limestone caverns...

Limestone? Caverns? On the Hawaiian Islands?

Outcrop of limestone (!?) on the Mahaulepu Coast of Kauai.

There are actually a great many caves on the islands, but they are not the kind of caves that most people find familiar. They are called lava tubes, and they form when a lava river forms a ceiling of congealed basalt. When the lava flow ends, it drains out the tube leaving behind a long cylindrical cave. Hawaii has one of the longest such caves in the world, Kazimura, with a total length of 40 miles. The much shorter Nahuku Cave (formerly Thurston Cave) in Hawai'i Volcanoes National Park is well-known to park visitors.

Nahuku Lava Tube in Hawaii Volcanoes National Park

But limestone caverns are not a familiar sight on the islands. Before my last trip I didn't know that there were any such caves in Hawai'i. For one, a limestone cavern requires limestone and the islands are composed largely of volcanic basalt. There are coral reefs around the islands in many places and they are composed of calcium carbonate (calcite), the mineral that makes up limestone. But coral forms at sea level, and caverns form from the dissolving action of fresh water, usually above sea level. And the islands are sinking, not rising, so on the face of it there seems to be no opportunity for the development of large bodies of limestone, much less caverns in Hawaii. 

Photo courtesy of Allie Brown

And yet it happened here, on the island of Kauai (and also, upon researching the subject, in downtown Honolulu; check out Moiliili underground caverns if you dare). It was a unique situation, a cavern formed in a sand dune environment. The cavern has been known as Warrior's Cave, Grove Farm Cave, Limestone Quarry Cave and others, but some extensive research revealed the ancient name (from an 1885 student essay) to be Makauwahi, or "source of the smoke".

Sand dunes hardly seem like a place for cavern formation because most of the time sand is composed of quartz and other silicate minerals. Hawai'i's sands are not. They are composed sometimes of basalt fragments (the black sand beaches), but the white or yellow sandy beaches of the islands are mostly composed of bits and pieces of coral reefs, in other words, calcite, the ingredient making up limestone. On the south side of Kauai near the extensive resort complexes of Poipo Beach there are some extensive coral sand beaches. Over the millennia the constant trade winds have blown sand off the beach inland, forming sand dunes above the shoreline. This happened in stages starting about 435,000 years ago during an interglacial period when sea level was higher than today.

Cliff of eolian limestone showing the tilted layers of cross-bedded dune sands at Makauwahi.

When the dunes were stabilized by vegetation, thick layers of soil developed on the surface. Beneath the surface the sand was lithified (glued together) by dissolved calcite and silica derived from the overlying soil. Then the climate changed and dunes moved in again. Over time thick layers of solid limestone resulted from the petrified dunes.

Makauwahi Cave, courtesy of Tylor Ghaffari

The soil layers provide the last part of the process, carbonic acid. Mixed with groundwater, the acid ate away at the lower layers eventually producing the caverns themselves. Later on, dripping and flowing water produced a variety of cavern formations (speleothems) like stalactites, stalagmites, and flowstone. Makauwahi Cave has around 500 feet of passageways, accessed through a small passageway. And so we paid a visit during our field studies exploration of Kauai.

The thing is, if Makauwahi were simply a cave it would merit some attention, but that is not what makes it extraordinary. Makauwahi was the site of three catastrophes, one of which was local, and two others that were island-wide. And from these catastrophes, an amazing story unfolds about life on Kauai, past, present and future. That will be the subject of part two, coming soon (I hope)!

Landslides and Slope Mitigation in California's Great Valley...Wait...What?

 

I used to talk to my students about the geological hazards that we face as inhabitants of California's Great Valley (or Central Valley, for those who don't appreciate its actual greatness). I would go down the list of things to worry about: earthquakes, droughts, wildfires, volcanic eruptions, flooding, and so on. But then I somewhat jokingly described things we didn't have to worry about such as hurricanes (Florida's problem), tsunamis (a problem for coastal cities), tornadoes (Oklahoma's problem), and mass wasting (also known by the generic term 'landsliding').

Unfortunately, over the years I've become aware that some of those unlikely hazards actually can be a factor in living in the valley. We've had a fair number of tornadoes in recent years, including two that came within a few miles of my house (they weren't anything like the monsters of Tornado Alley in the Midwest, but still a bit scary). A powerful tropical storm hit Southern California last summer that came up just short of being a hurricane, and the heavy downpours were statewide. And then there is mass wasting (slope failures and landslides). I know of at least two fatalities caused by mass wasting in the last few years. One was a homeless person who had dug a tunnel into a river embankment that later collapsed, and another was a person who was driving along a freeway in heavy rains when the freeway embankment collapsed as a mudflow and spread across the lanes causing a fatal accident.

The Great Valley is famously flat so mass wasting doesn't seem to be much of a danger to those who live here, since landslides and other slope failures require, well, a slope to happen. But the valley is not quite so flat as people may think. The valley is 400 miles long, and most of it is close to sea level. Much of it is low-lying river floodplains, but other sections sit at slightly higher elevations because of complex history of climate change and glacial ice ages over the last 1,000,000 years. These bluffs and terraces protect my city and others nearby because even the worst floods are contained within the floodplains and do not spill over onto the terrace surfaces where cities like Modesto and Turlock have been built near the Tuolumne River.

During the ice ages glaciers never reached the valley floor, but meltwater from the Sierra Nevada glaciers swelled the rivers to several times their average flow, and they carried tremendous amounts of muddy sediment that spread widely across the valley floor building up alluvial fans. When the glaciers receded, the rivers flowed less, but carried clear water that was more capable of eroding the soft sediments of the alluvial fans, forming channels and floodplains several tens of feet deep. Once these channels developed, floods never covered the terraces again. It's the bluffs that form the boundaries of these terraces that provide the conditions that can result in slope failure.

The heavy rains of 2022-23 led to widespread flooding across many parts of California including some real problems on the Tuolumne River Parkway Trail when I regularly go birdwatching. I wrote about these in January of 2023 in the aftermath of one of the biggest storms. The most serious problem was the access road to our town's water treatment plant. It's on the river floodplain about 60 feet below the river terrace. Slumping had caused major cracks to form in and near the pavement.

Eventually the rains subsided and the soil dried up. The slide seemed to stabilize, but the threat to the roadway remained and would eventually have to be dealt with. That is what was new this week: the cranes and were in place to start the slope mitigation process.

The main problem is that the access road traverses unstable debris and soil that slumped in the 2023 event. They would need to re-engineer the slope by rebuilding it from scratch. Their strategy was complicated by the fact that all the equipment and materials had to traverse the very road they were trying to repair. Truckloads of heavy boulders were going down the road every few minutes. Meanwhile a huge long-reach excavator was digging away at the slope below the road!

After digging away and smoothing off the slope they covered it with felt matting and then started piling many tons of boulders on the slope. The boulders are intended to buttress the slope and hopefully keep it stable during future weather events.

It's a lot of work being done to keep a single paved road open, but it's a pretty important road since it provides the only access to the water-treatment plant for the city of Waterford. And thus we are dealing with slope mitigation in what is supposedly the flattest place in the country!

Geotripper on How to Plan a Perfect Volcanic Eruption, Hawai'i Style!

So you want to demonstrate a volcanic eruption for your field geology course, and are unsure how to proceed? Let the crew (of one) here at Geotripper help you to plan out the very best eruption experience for your students! There are several important steps and considerations:

1) Pick a volcano

This is a pretty important first step. Some volcanoes can be very dangerous, and we at Geotripper feel that safety is a hugely important consideration. We have chosen the Big Island of Hawai'i for our demonstration, as eruptions there TEND to be on the quiet side, although there are important exceptions.

Kilauea Caldera and Kilauea Iki in the distance

2) Do a site evaluation

Take a hike out to the potential eruption site. This is kind of critical, because we want to choose a site that is isolated and away from buildings and populated areas. Yet we also want the site to be visible once the eruption begins, since this is the whole point of planning such things.

Hiking out to the Ka'u Desert ("Footprints Trail") on May 29, 2024

3) Consult with the local volcanic deities:

Painting of the Hawaiian goddess Pele at the Kilauea Visitor Center with the artist, Arthur Johnson (Source: NPS).

Once again a critical factor. One doesn't conduct eruptions without the permission and cooperation of the deities that inhabit the place. In our current example we are dealing with Pele, also known as Pele-honua-mea ("Pele of the sacred land") and Ka wahine ʻai honua ("The earth-eating woman"). 

A side note: the gist of this post is tongue-in-cheek, but I take Pele pretty seriously. Check out my interaction with a mysterious woman on the flanks of Kilauea a few years ago. Who was she??

4) Start the Field Trip

Taking twenty students to the Hawaiian Islands for two weeks is no small task, and we here at Geotripper strongly suggest planning the trip many months in advance of the eruption. Remember to consider such logistics as hotels, transportation, airline flights, food, and group interpersonal interactions.

5) Educate your students on the basics of volcanoes and vulcanism

There are many ways to do this. One of my favorites is to pay a visit to the 
Hawaiian Volcano Observatory (currently based in Hilo, Hawai'i after their original home on the brink of the Kilauea caldera was damaged by an eruption in 2018). Our expert host provided an excellent introduction to the methods and technology of volcano monitoring.

6) Subtly prepare the group for the experience of the eruption

This step requires some public relation skills. We don't want to have the experience spoiled by high expectations and the like. We want our group to be both surprised and prepared when the eruption happens. There are a number of ways to do do this. For instance, have them look at seismic records and see if they notice the uptick in earthquakes in recent days. Ask a Hawaii Volcanoes National Park ranger leading questions like "why did you close the Devastated Area Trail yesterday?" You can make jokes, like "Wouldn't it be interesting if an eruption were to happen while we are on the trip?". Don't overdo it, though.

7. Conduct the Eruption

In many ways this is the easiest step, since the Earth does all the work. If you arrange for the eruption overnight, you can plan on an early departure from the hotel to beat the tourists to all the best overlooks. If you have prepared in the way that we have put forth here, your students will be duly impressed even if they can't stick things into the lava flow or even see spewing lava. Seeing the ash and steam rising from the distant rift zone will be more than enough!

Oh, I see a hand in the back...what was your question? How do we actually cause the eruption to happen at the perfect time? Oh, it's kind of complicated. We don't really have time enough to explain...

8. Provide a cooling down period

Go to the national park visitor center and hang around for awhile. Get interviewed by the local news media. Use the restrooms. Then continue on the rest of your trip, wondering how you'll ever top this experience!

So yeah, it pretty much happened this way while we were in Hawai'i recently (except for the actual organizing of any eruption). Our students and my co-leader were in fact interviewed on local Hawaiian news (see the story here: HVO: Eruption at Kilauea’s summit has paused, but activity in region remains dynamic (hawaiinewsnow.com)).

The eruption itself was somewhat of a surprise. There had been upticks in the seismicity and uplift in some nearby areas, but the precise spot where the rift opened up was unexpected. It was a very short-lived eruption, lasting only about 12 hours, and the volume of lava was limited. You can see the USGS review of the eruption here: https://www.usgs.gov/observatories/hvo/science/recent-eruption.

Source: USGS Hawaii Volcanoes Observatory

All things considered, it was one of the most satisfying moments of my teaching career... 

Here's my video of the eruption from the site of the old Jagger Museum and Hawaiian Volcano Observatory: https://vimeo.com/959288135?share=copy

Here's the direct access: 

A Stunning Night: The Aurora Borealis from Central California

It has been a stunning night. I never believed the auroras would make it into Central California, and most of the predictions suggested it wouldn't. But then reports started pouring in; sightings in South Carolina, northwest Florida, Houston, and then Death Valley. I had to give it a chance. Mrs. Geotripper and I hopped in the car and headed out to the California Prairie south of Knights Ferry.

As we pulled up at the small stock pond on Willms Road, it didn't look like much was going on. I convinced myself that there was a bit of a red glow in the sky, and I started taking pictures with my phone (my regular camera turned out to be useless for once). On the screen it wasn't obvious, but there was indeed some color. 

I would have been satisfied with that, as I have seen the aurora only twice before. The first time was from within the Grand Canyon on my very first geology field studies trip in 1975. It was just a glow in the sky then, and we thought it was light pollution from Las Vegas or St. George, but it turned from red to green. We were awestruck, but there was no structure to be seen. The other time was in the late 1990s when we were in Montana on a mostly rainy night, but for a short moment a filament appeared through the clouds. And that was that.

Having so little experience with the phenomena, I simply didn't know what to expect, but we were becoming aware that the lights were changing as we watched. Spires came and went, and the glow moved to different parts of the sky. The colors were changing as well.

We watched until midnight when the cold breeze and lack of facilities forced us to start the drive home, but as we went around each bend, we couldn't resist stopping a moment to see what changed.

The changes were many. More and more green was showing near the horizon, and blue or purple appeared off to the west.

Needless to say maybe, but it was an astounding thing to see. I should note that while I have not modified the pictures (especially the saturation), the phone camera did see more vivid color than I did. I was using the night shot setting, so it was collecting light for two or three seconds, so the pictures are more colorful. But even so, it was easy to understand why the ancients thought these lights emanated from the gods.

We have our own mythology about these strange lights in the sky. They are the magnetic force shields protecting us from deadly emanations from the sun. Without our magnetic field, life on Earth might never have appeared, and we continue to thrive as long as the field continues.

After studying the Earth and the cosmos for more than forty years, I still can be impressed by the incredible processes that operate on and around our planet. What a privilege to live in and understand our world.

The storm is expected to continue through the weekend. I encourage you to find a dark place and check it out, but if that isn't possible, I hope this gives you an idea of what it was like!
 

George Lucas Had It Wrong. A Day of Fierce Pride at Modesto Junior College Yesterday

I had conflicting responsibilities and to my regret had to miss my school's graduation ceremony yesterday. I know that many of my students had the honor of walking that stage, and I can only say: I am proud for all of you. So, about that title...this is something I wrote a few years ago about the special and talented people I serve as a teacher.

No, I'm not talking about the prequels to Star Wars! It was something much earlier. People could be forgiven for not knowing this, but Star Wars was not George Lucas's first successful film. He was known for another great movie, American Graffiti, a semi-autobiographical film that recalled his days as a young man in Modesto, California. Yes, Lucas is perhaps our most famous native son. He also attended Modesto Junior College for a time.

So what was it that he got wrong? It was a fairly minor plot point, but in the movie, the two friends Curt and Steve were on the same pathways for their lives. They were planning to leave town to attend a "northeastern" college (let's presume an Ivy League school), but after a series of events over the space of one long night, Steve is convinced to stay in Modesto, attending the "junior" college, while Curt heads off to great success, and was eventually a writer living in Canada. Steve ended up selling insurance in Modesto.

What's wrong with this picture? It was the insinuation that attending a community college was somehow a lesser option for achieving success, that it is in some way a second-rate education. As I sat proudly through our graduation ceremony tonight, I would fiercely argue that getting a degree at a community college is a wonderful achievement, and that I would proudly put my students up against any Ivy League student at the two-year mark in their academic career.

It doesn't take long to realize that a lot of (but certainly not all) the students at a Harvard or Yale are children of privilege, people who have never really had to struggle to get ahead in life. They started in private upscale schools, got in on the fast-track to an Ivy League school with the best preparation possible. It's hardly a surprise that they would excel and succeed.

The students I work with come from many different backgrounds, and most of them are poor and disadvantaged. They come from many cultures. Our elementary and secondary schools are underfunded and sometimes dangerous, and alcoholism and drug use are epidemic in our region. The kids in our schools have the decks stacked against them at every turn. They come to us unprepared and unskilled. We have veterans suffering from PTSD, abused spouses, and laid-off laborers. We have huge numbers of people who are the first in their families to ever attend college. We have resources at our school, but sometimes the challenges facing our students are overwhelming. And yet these students persist, and they fight, and they cry, and fail, and then they come back again. And in the end they master the skills required to pass their classes. When you see a group of these students decked out in blue robes, and receiving an AA or AS degree, you are looking at some of the most successful people in the world.

If you are an employer, and you see a community college on the resume of a potential employee, you are looking at a person with persistence, stamina, and an incredible work ethic. They've been through impossible challenges and they've succeeded.

I couldn't be more proud of my students on this great day.

The End of the Tuolumne River! (It's not as bad as it sounds...)

The slough at the headquarters area of Dos Rios State Park

Back in the 1980s, Douglas Adams published his hilarious "trilogy" of the Hitchhiker's Guide to the Universe. The second book, The Restaurant at the End of the Universe, was not about a restaurant at the edge of the Universe, but rather it was a place where you dined and watched the actual destruction of the Universe (you had to use a time machine to get there). 

Today's blog is about the end of the Tuolumne River. But it isn't as bad as it sounds: it's about the spot where the Tuolumne River ends by flowing into the San Joaquin River. The confluence was on privately-owned ranch lands for many years, but a profound change is coming that will touch lives across our county and Central California. It is becoming California's newest State Park!

The confluence of the Tuolumne and San Joaquin Rivers

Dos Rios State Park is the product of years of cooperation between the owners of the Dos Rios Ranch, River Partners, and the Tuolumne River Trust. In the last decade or so, the partners worked to return the former croplands to a landscape that functions like the original primeval environment that existed before the invasion of industrial agriculture. In other words, a riot of canopy trees like oak and cottonwood with a tangled undergrowth of willows, elderberries and numerous other native plants. This floodplain woodland acts as a giant sponge, absorbing and slowing down floodwaters and helping to recharge the groundwater underneath.

The lower Tuolumne River near the confluence. The state park is on the right-side shore

The riparian environment provides a marvelous habitat for the wildlife that once thrived throughout the Great Valley of California (only about 5% of that original habitat remains). Dos Rios State Park will be a fantastic place to search for hundreds of bird species (more than 200 are known from just across the river at the San Joaquin River National Wildlife Refuge), and all manner of animal and plant species. The highly endangered Riparian Brush Rabbit is only found in an extremely small area within the San Joaquin Delta and the wildlife refuge across the river. I was told they intended to transplant a small group from the refuge to the park, but that the rabbits confounded the plan by crossing the river somehow and establishing a population all by themselves!

There are a number of ancient remnant environments tucked away in corners of the park. The most striking was a growth of valley oaks growing on a slightly elevated hill adjacent to the San Joaquin near the south end of the new park. There was a cacophony of bird songs in the canopy above, including Yellow-rumped Warblers, Oak Titmouse, White-crowned Sparrows, Tree Swallows, and Bush-tits.

The oak forest is a two mile walk from what will be the park headquarters area, and there are ideas of developing the site into an environmental walk-in campsite where local children can experience wilderness only a few miles outside their cities.

Much of the park will be a trailless, roadless morass of trees and brush on the floodplain. This is the area meant to serve for flooding relief, where it might remain underwater for weeks at a time. Volunteers have spent a decade planting native vegetation, and many of the trees are already tens of feet tall. They were irrigated for three years, but they will be able to survive on their own in the years to follow, watered by the higher groundwater table and occasional floods.

A "bunny hill" on the right side, a floodplain to the left.

Several elevated areas across the park provide refuge for mammals during flooding events. I believe they called them "bunny hills". I've seen these in action during floods across the river at the wildlife refuge, where everywhere I turned, rabbits were waiting for the floodwaters to subside.

The tangled thicket of native vegetation: the valley floodplain as it once was.

One of the most valuable aspects of the park is that it will allow visitors to experience the valley habitat as it once was, and how many parts can once again be. On our tour, we mentioned the wonderful resource of the Great Valley Museum at Modesto Junior College where I teach. Visiting the museum, children can view dioramas of the natural environments of the valley and even see a few live animals. But what if...they could learn about these environments, and then drive a short distance and actually experience them? That's the incredible value of the Dos Rios State Park.

Double-crested Cormorant in the slough

When our tour ended, I spent a few moments wandering the only developed part of the park. There is a picnic area that has been constructed adjacent to the farm buildings serving as the park headquarters for the moment. There is a slough below the picnic structures with a short walkway providing panoramic views. It didn't take long to find some interesting birds, like the Double-crested Cormorant drying its wings on a stump.

I only occasionally see Downy Woodpeckers along the Tuolumne upstream, but it was the first one I sighted today. I also saw Northern Flickers and Nuttall's Woodpeckers.

A Great Egret was watching for fish on the far side of the slough. 

Turtles were basking on logs down in the slough below.

Dos Rios State Park will open this coming summer with the picnic area and slough area open for visitation. A master plan will be developed over the next few years, with proposals for a campground, trails, and all manner of interpretive programs. Even better, the park will function as an environmental buffer, providing habitat and flood protection. The park is starting with about 2,100 acres, but other adjacent tracts are being "de-developed" to resemble their original habitat. 

It was a real privilege having the opportunity to see this park and renewed floodplain in the making. I'm looking forward to seeing what lies ahead for this beautiful new park in coming years. It is a marvelous resource for our community.

Source: River Partners and the Tuolumne River Trust