Lava is what makes Hawaii famous, and probably the reason why most of us signed up for this class. There are only a few places you can travel in the world and see molten rock ooze past you, and it is an experience impossible to forget.
We spent four days studying the active lava flows on the Big Island, learning of the most recent eruptive history that began in 1983, and that continue to erupt to this day. For a detailed look at the lava we saw during our visit, continue reading below. For a brief synopsis of Hawaii’s past 20 year eruptive period, click on the BOOM!
Don’t know the difference between aa and pahoehoe? Follow this link and learn more about the nature of lava.
Volcano National Park provides an open experience for all to enjoy Hawaii’s volcanic wonders. Beyond the price of admission and a warning of the dangers that befall unprepared and careless visitors, VNP requires only one further stipulation: all rocks found in the park remain in the park. Beyond that, the massive national park is yours to explore as you like, and in our trip in March 2003, the Regional Geology class did just that. Below is a record of what we experienced.
Sulfur Banks: After visiting the Kilauea Visitor’s Center and watching several videos on volcano safety, we made a short drive down the Rim Trail, pulling off at the Sulfur Banks. This rather massive pile of sulfurous blocks fumed in the afternoon heat, the characteristic smell of sulfur ever-present here. What we were seeing was actually a fumarole, a vent from which gas escapes from a magma body. In the Sulfur Banks, this vent is actually a big crater rim fracture. The blocks were ubiquitously greenish-yellow and white. The greenish-yellow color is the result of hydrothermal alteration from water and other chemicals present in the ground rock, while the white alteration is the result of iron being dissolved away from the rock.
Normal basalt contains 0.01% sulfur. The original gas from the volcano is a toxic combination of sulfur and water, but as the gas comes to the surface, the chemical can oxidize to sulfur-oxide or sulfuric acid. Sulfuric acid is a strong acid that oxidizes in groundwater and which dissolves many parts of the rocks, such as the iron in the Sulfur Banks rocks. We commonly see sulfur in the form of sulfur-containing minerals, like chalcopyrite and pyrrhotite. While sulfur is the most notable gas coming off the basalts, carbon-dioxide is the most common.
For additional information about the Sulfur Banks, visit the Tour of Kilauea Volcano
March 7, 2003 Chain of Craters Road Lava Flow: It was the first molten lava most of us had ever seen.
The drive from the Sulfur Banks to what was ‘unofficially’ the end of Chain of Craters Road (unofficially, as lava covering the pavement made it impossible to pass) was comparable to an alien landscape. We drove past lava flows of size and dimension impossible to comprehend from our small, Midwestern school. And associated with each of these flows, like gravestones recalling great molten lives, were markers that read “1977 Flow” or “1982 Flow”. The flows were hard, glassy, basaltic deserts of lava, with layer flowing upon layer. But they were dead – as immobile as the earth in Michigan. What we wanted to see was flowing lava, like the kind we’d seen in movies and documentaries.
|There are two surprises that await the explorer who ventures to Hawaii’s lava flows. The first is that lava flows don’t move fast. In fact, they creep forward at a painfully slow rate. Much of what we’ve been fed back on ‘the continent’ are glimpses into some of the most spectacular flows ever recorded, but they are not representative of the everyday flows. The second shock to the viewer is the smell. Active lava has a very particular smell – not foul, but not worthy of making a cologne, either.|
|Thom shares his profound appreciation for the smell of fresh lava.
Photo by Tim Lincoln
As we walked the half mile to the active flows over recently molten rock that is several shades darker than the aged and weathering flows, this is precisely what met us. But the slowness of the lava flow didn’t alarm us or cause anyone to throw up their arms – we were simply happy to see lava.
The March 7 flow oozed forward in tiny ‘fingers’, like polyps, about 1000 feet from the ocean. This type of flow is characterized as digitating. Much of the lava we walked across is classified as shelly pahoehoe, a form of pahoehoe lava that is only a few centimeters thick at the surface, and thus susceptible to breaking beneath one’s feet. This thin layer forms as the result of a foamy lava mixture hardening at the surface (creating the thin layer) and successively separating into a gas-only top and a lava-only bottom. When the lava drains from the hardened pahoehoe, a hollow chamber is left behind.
Jen chasing after a digitating lava flow, notebook in one hand, vintage camera in the other.
In addition to the excitement of active lava, there were several smoldering, gaseous holes in the pahoehoe, as well. Gas fuming beneath the hardened pahoehoe escapes through many fractures and faults, and ultimately surfaces through these holes.
March 9, 2003 Chain of Craters Road Lava Flow: After spending a day exploring in and around the Kilauea crater, we wanted to come back for one last look at active lava before we had to leave the VNP.
We were greeted by a much faster moving flow than what we’d seen before. This new flow was a few hundred feet west of the March 7 flow, and had branched into two flows at about right angles to each other. Here we saw the process by which shelly pahoehoe forms: as the lava moved toward us, a thin layer at the top of the flow cooled with the atmosphere, forming a semi-hardened surface that surrounded the nose of the lava. As the pressure inside this shell increased, a weak point along the surface ruptured, and quick moving lava belched out, causing the parent digit to deflate slightly. This is a continuous trend as the lava moves toward the ocean.
|This guy’s getting ready to blow! When the pressure
inside the hardened crust is great enough,
part of the skin tears and…
|Bam! Lava comes pouring out!|
We stayed at the flows for about an hour, during which time some of the lava advanced more than thirty feet. Thom, apparently unaware that geologists aren’t immune to the effects of fire, displayed his bravery by pulling from the flow a glob of fresh lava with his rock hammer. Quickly, he cooled the lava with some water, and almost instantly the lava began to solidify. Hoping to get an authentic VNP trophy, Jen was quick to comment: “Technically, Thom, you made that. It doesn’t belong to the park.” Of course, Thom being the responsible man that he is, returned the new rock to the flow. Slowly, the rock was enveloped by the flow, like a protective mother cradling her child.