When most of us think of caves, we probably think of underground worlds of stalactites and stalagmites. You may not realize that lava tubes are another common type of cave – and they are fascinating features of earth’s geography. Let’s flow our way around these molten-molded wonders and learn the ins and outs of what they are, how they form, and what that means for humans and the broader ecosystems we inhabit.
To put it simply, lava tubes are caves formed from volcanic eruptions. Think Sam and Frodo in Mordor, or Moana in Disney’s well-loved film of the same title. Volcanos are like our planet’s architects – defining the features and formations of the crust where we walk, talk and live our lives. These eruptions, flow fields, and lava tubes are all a part of that.
In what scientists call subduction zones, volcanos form near or parallel to coasts. Examples of this include Mt. Rainier in Washington and the Cascades. Alternatively, volcanos also form at “hotspots” – examples of this include Yellowstone National park and the Islands of Hawaii. Lava tubes form under certain conditions of these eruptions and are found all over the world.
So how do these molten lava caves form exactly? Well, lava flow is thousands of degrees hot and moves like a river. When the top of this molten river is closer to the surface air, it cools as a result of exposure to brisker temps. With the colder temps, the molten lava cools into rock, forming caves. According to the NPS, these caves are chambers of black rock, and places where lava can continue to flow.
If the idea of a rushing lava river cave makes you nervous, you are not alone. These are not places most humans hope to find themselves. But as time goes on, the rock continues to cool, it thickens and widens, and eventually forms a roof.
As the disruption ceases or moves areas, the lava tube drains of lava – but the tunnel remains. Once cooled, these tubes become relatively stable in temperature. This means that they also, over time, become important niches within an ecosystem. Packrats and other rodents, owls, bats, and tree roots are just a few examples of organisms that make eventually make their homes in these spaces.
These caves and tubes are home to what scientists refer to as “troglobites”. This is a term for animals specifically adapted to live in the dark.
In particular tubes, species of spiders and crickets have evolved through the millennia to develop alongside microbial colonies found nowhere else on planet earth. It is this sort of specificity that showcases the stunning variety on our planet.
Additionally, though not exclusively, humans have used these tubes and caves for generations too. We’ll touch on more specifics around that a bit later on.
Skylights are all the rage – but in case you haven’t seen the photos floating around on the internet, here’s a quick breakdown:
Skylights are a term used to describe an instance when a lava tube‘s ceiling features an opening and onlookers can observe flowing lava as it moves underneath and through the cave. It is a stunning occurrence that enchants and sometimes horrifies our imaginations.
Photos of skylights have become popular images, inspiring movie scenes, special effects, and comic book art to name just a few areas. Buzzfeed articles have gone viral, click-baiting millions of social media users into “images of hell”.
Really, these are areas where only trained scientists and other professionals should lurk. Skylights are very dangerous to approach and are usually off-limits to everyday visitors to national parks. There is always a possibility that further areas of the roof could collapse. Plus, burning hot air shoots out of the holes and can cause serious damage to equipment and unprepared onlookers.
The longest lava tube we know of is the Kazumura cave on the island of Hawaii. It is both the longest and deepest known tube in the world, stretching 40 miles long and over 3,000 ft down. Tubes may be up to several dozens of feet wide, depending on the area of the cave.
This cave is between four hundred and five hundred years old – which is extremely young when looking at things through a geological lens. Kazumura cave is the result of an erupting vent on the east side of Kilauea Caldera. As we touched on above, the lava cooled from the outside in, thickening the crust over time and forming tubes and caves.
Because lava tubes are found all over the world, there are various stories, legends, and uses that humans have found for these natural formations.
For instance, in Hawaii, humans use lava tubes as shelter and storage. The caves were places where people could take shelter from the elements, hide from threats, and conduct ceremonies. Because the caves are thermally stable, they made for effective cellars, keeping food and other necessities consistently cool.
These tubes are also a source of fresh water on the beloved islands: the saltwater of the surface filters through the volcanic rock and then drips into the lava tunnels. Collecting the dripping water from the ceilings was an important method of gathering for the ancestral people of this landscape.
Additionally, lava tubes were used as burial sites. Today in Hawai, the national park service protects these lava tube burial sites, as visitors are not permitted into the specific areas.
Another example of significant lava tubes sites includes the Jeju volcanic island, part of South Korea. This area became a UNESCO world heritage site in 2017. This island includes the Geomunoreum Lava Tube System, which is still in pristine condition today and scientists continue to study the area.
The narratives around lava tubes, cave walls, and flowing lava are not merely limited to the creative forces on planet earth alone. Indeed – lava tubes are features of other planets as well.
On the moon and Mars. in particular, lava tubes have caught the eye of astrobiologists and explorers. This is because of the way in which lava tubes provide environments that are relatively stable once cooled. This stability means these areas are more likely to be hospitable to life than many of the conditions found on a planet’s surface.
In the words of one scientific study, this makes lava tubes particularly appealing for extraterrestrial life forms of all sizes – human or otherwise. There may be evidence of life in extraterrestrial lava tubes. Additionally, these areas may become vitally important for humans exploring space and in need of stable environments to utilize.
Inside a lava tube, you can observe all sorts of incredible phenomena including lava stalactites, also known as lavacicles, and the sometimes expansive lava tube systems that stretch for miles. Volcanic vents become entry points for scientists, tourists, and local inhabitants to enter into the belly of our wild planet.
The national park service maintains many sites that include cave systems. And you can do research beforehand to understand any accessibility concerns or regulations in these areas. Many caves within the U.S. national parks service system are closed due to covid concerns and resource protection. So be sure to do your research before jumping in the car with high hopes.
But fear not! With a little research, time, and resources, you are able to see these tubes for yourself. Below are some listed examples of lava tube systems
that you can explore within the United States:
Probably one of the most famous lava locations on the planet is the kingdom of Hawaii. And of course, with active volcanos come ripe conditions for lava tubes. We already covered the longest lava tune in the world in these beautiful islands, but there’s plenty more to explore as well.
For instance, Nahuku, also known as the Thurston lava tube, is a popular day hike. Visitors walk through a vibrant rainforest and then enter the tube. It is a moderately difficult hike, but still wildly popular. The tube is a vital ecosystem on the island, so officials urge people to not disrupt the area. This reverent approach cannot be stressed enough. When this cave was discovered in 1913, lava drippings or “lavacicles” disappeared entirely from the cave, as souvenir collectors broke them off and carted them away.
Kilauea volcano is the most active of the five volcanos that form the Big Island of Hawaii.
While it isn’t currently erupting, there is always the possibility of lava tubes continuing to materialize into the future. Mauna Loa, the largest subaerial volcano, is nearby as well.
Hawaii volcanoes national park has a plethora of hiking and exploring options that you can learn more about with some extra research. Piping-hot lava is a bit extreme of a spectator sport for most of us. Pahoehoe is an indigenous word for basalt lava that forms into smooth, bulbous masses and eventually cools into stunningly beautiful rock formations. It is this sort of aspect of the volcanic landscape that anyone can appreciate. And people certainly make the trip. In Hawaii alone, there were over ten million tourist visits in 2019 alone. If that seems like a stressful amount of people to you, you are completely right. We’ll touch on this further along.
The deserts of New Mexico may seem like a far cry from the rainforests of Hawaii, but volcanos are spread out – therefore lava tubes are as well. Rest assured, the land of enchantment is also home to lava tubes.
El Malpais is a national monument in the state of New Mexico. Within the monument is the “big tubes area” – a rugged and challenging landscape that includes lava tubes. As with any outdoor excursion, it is important to stop at the visitor center for maps and other information before visiting the area.
According to the USDA, Coconino national forest is another lava tube site in North America. The mile-long lava cave within the forest formed 700,000 years ago when molten rock erupted from a nearby volcanic vent.
This tube stays as cool as 42 degrees, even with the stifling heat of this landscape at the surface. You’ll want to bring a jacket when you go to visit!
Deschutes National Forest is a site of lava tubes in the Pacific Northwest and was one of the first of these formations to be discovered in the area. The “lava river cave” is home to bats and is regularly frequented by tourists. Visitors descend down 55 stairs and can walk along 1.5 miles of lava rock to explore the bulbous world of molten rock.
In Idaho, there is a national monument called “Craters of the moon” – and if you’re like me, your imagination is running wild at the mere mention of such a name. As it turns out, these “craters” or “caves” are lava tubes. There are more than 500 discovered caves, with more adding to the list with each passing year.
In addition to lava tubes, there are fissure caves and differential weather caves as well. The caves in this area are accessible via trail for any curious adventurers.
As you dream of where and when to travel, there’s more to consider than simply “where are the lava tubes?”.
Lava tubes are, of course, an exciting feature of our planet’s makeup. They are spaces that record what has happened in the past that we can (usually) safely traverse after the fact to imagine and study the phenomenon. It makes sense that so many people are drawn to the mysticism of underground rivers of molten lava that look ominously like portals to some hellish underbelly.
So it is all the more important that we stress habits of responsible travel for ourselves and members of our communities. Many of these striking landscapes are at risk due to human-related pressure on the planet. We need to make plans accordingly.
For instance, as people receive COVID vaccinations and begin to travel, there have been calls to action by indigenous groups and local inhabitants of precarious areas to limit, restrict, and modify tourism in deference to local needs and conservation efforts.
This is especially true in Hawaii right now, where millions of tourists are flocking after a year stuck at home. Hawaii is regarded as a real-world paradise for good reason, but even paradise has its limits.
Hawaiian activists are actually urging officials to take bolding measures while urging tourists to stay home. National news outlets are chronicling the dialogue unfolding in real-time over sustainable tourism, indigenous land, and how we travel post-pandemic.
Lava tube caves are a sublime example of the ways in which our planet shapes and shifts through time. Lava channels are a geologic record of past eruptions and other eras . They are an exciting way for us to understand the geology – past, present, and future – of Earth. Far from a “portal to hell“, these tubes are a threshold into deeper understanding and connection to the natural processes that unfold around us each day.