Kilauea in Hawai’i—safely visiting an active volcano
Kilauea grabbed the attention of the media and the public when it began a new eruption on May 4, 2018. This is normal business for one of the most active (maybe THE most active) volcanoes on Earth. The Big Island of Hawai’i is located on top of a hot spot that is providing the fuel for continuing volcanic activity—imagine a huge candle deep in the Earth that is causing rock to melt and travel to the surface to be erupted as lava. As the Pacific plate has moved northwest, new volcanoes have developed to the southeast—five million years ago, the island of Kauai was located over the hot spot and since then it has moved off the hot spot and new islands have been successively built. Today, a new volcano (Loihi) is building up on the seafloor and will be the next island to emerge from the sea—but not in our lifetimes!
In 1983, eruptions began along the East Rift Zone on Kilauea volcano and have been continuous since then. Most of the flows have emanated from the Pu’u O’o vent located just west of the area shown on the map below. Since 1983, many acres of new land have been added to the island, where flows have buried roads and homes located in this south-eastern-most part of the island. The current eruption is just the latest in a series of eruptions—the map below shows older flows and the fissures (red numbers) that have been opening in and near the housing development of Leilani Estates. A series of earthquakes caused by magma moving upward heralded the new eruptions.
Hawaiian-type lavas produce shield volcanoes. Unlike the classic Fuji-style cone-shaped, steep-sided strata (or composite) volcanoes, Hawaiian-type volcanoes have very gentle slopes and are much less discernible in the landscape. Although volcanoes on the Big Island reach nearly 14,000 feet (>4000 meters) in elevation, visitors sometimes don’t realize that these vast features are volcanoes—in fact, all of the islands of Hawaii were constructed by volcanic eruptions of basaltic-type lava. The photo below shows the flank of Kohala volcano, the least active volcano located on the northwest end of the Big Island. Older flows on the west side of the island, even those that erupted around 100 years old, still appear fresh because there is less rain on this side to create soil and grow plants.
The good news about Hawaiian-style volcanoes is that you can usually visit this type of active volcano without danger. Unlike strata volcanoes that tend to erupt catastrophically—with blasts that can spew material hundreds of miles inside the atmosphere and over vast distances—shield volcanoes tend to erupt with relatively well-behaved lava flows. For example, visitors to Hawai’i Volcanoes National Park typically drive down the Chain of Craters Road to where they can see lava flowing into the sea or walk a short distance up the slope to see the flowing lava. The eruption in May 2018 is a different story, however, and the national park is mainly closed as scientists monitor what is going to happen next. In the southeast part of the island, new fissures continue to open, hot lava is fountaining (i.e., spewing upward, not just flowing on the surface) along the fissures, and roads and houses are being buried by advancing flows. Another dangerous part of the eruptions is the release of sulphur dioxide gas that can form a type of toxic air pollution.
Although Kilauea has been continually active, the places where actively flowing lava can be seen changes daily. When we visited in February 2018, lava was being emitted from the Pu’u O’o vent but, although it has sometimes flowed all the way to the sea, it was not flowing very far from the vent. The photo below is taken in the direction of the pali (the slope along the East Rift Zone) where we could see the red lava glow when we started hiking before dawn. Jay is looking dispirited because after hours of hiking we still had not reached the flow and it was time to turn back.
Nevertheless, we enjoyed looking at the vast variety of textures and flow types as we walked over the plain of lava that had all flowed southward toward the coast during the past several years.
On the way down the Chain of Craters road, between the Hawai’i Volcanoes National Park Visitors Center and where the road ends because the flows have covered it, there are trails that take visitors across many interesting lava features. The trail to Mauna Ulu crater goes across a 1974 flow, where plants are just starting to get a foot hold. Here Jay stands on the contact between pahoehoe (ropy) flows and a’a (blocky) flows. The composition is the same (basalt), but the pahoehoe forms when the basalt flow is warm and pasty and can wrinkle into smooth, glassy, rope-like ridges; if the moving flow becomes too viscous, the surface of the lava breaks up into a jumble of sharp, angular fragments that are not fun to walk on!
Although the lava was not flowing very much from the Pu’u O’o vent, the lava lake in the crater at the Kilauea summit was very active. Smoke from the lava lake was visible from along the Halema’uma’u trail that ventures down over the lip of the Kilauea summit caldera and was particularly spectacular at night, when the red colors of lava could be seen from the Jagger Museum, located along the road that rims the Kilauea Caldera. The lava is not visible now, however, because the lava lake level has continued to drop—yet more smoke is billowing from the crater. Scientists are concerned that pressure is building up and that huge boulders could be catastrophically erupted into the atmosphere.
We stayed a few nights near the Kapoho tide pools at the south-eastern-most point of the Big Island (labeled Vacationland Hawaii on the East Rift Zone map above). People vacationing there now would have to evacuate, so we’re glad we visited a few months ago. The tide pools were a good place to see another famous feature of Hawai’i—beautiful tropical fish. This photo shows yellow tangs and a parrot fish (called Uhu in Hawai’i).
After visiting the active volcanoes in the southern part of Hawai’i, we stayed on a mango farm very close to Kealakekua Bay, shown in the photo below. Today this stunningly beautiful spot is popular for kayaking and snorkeling, but it has a tragic history. It was formed by a geologic catastrophe, when the western flank of Mauna Loa volcano slid into the ocean as a giant landslide about 120,000 years ago. Luckily, no people were living in the region at that time. People were occupying the island when the English explorer Captain John Cook and his men arrived in 1778. Although Cook was first mistaken for a god, he was killed on the north side of the bay about a year later, when the native people became angered and suspicious that he was not their favored god. A monument to Captain Cook was erected at the north end of the bay near where he was killed.
On the south side of Kealakekua Bay is Hikiau Heiau—a laukini (temple) where human sacrifices were made. Here Captain Cook was first worshipped as the returning god Lono. It’s a beautiful place to ponder the history of the island, from its geologic origins to its occupation by the native Hawai’ians to the changes wrought by European conquest and the subsequent tourist invasion.
Of course, the other big attraction for tourists is the stunning white sand beaches formed by pieces of coral that get broken apart by wave action. The good news is that even when Kilauea is spewing off, it’s still safe to visit the west side of the island and enjoy swimming, snorkeling, boogie boarding, and eating fresh ocean fish.
For more information about the current state of eruptions at Kilauea Volcano, see the National Park web site (https://www.nps.gov/index.htm) or the U.S. Geological Survey web site (https://volcanoes.usgs.gov/volcanoes/kilauea/geo_hist_summary.html).