Tag Archives: Volcanoes

Sailboats in the harbor

These sailboats were moored in Kawaihae Harbor, with Hualalai volcano in the background.

There is a small boat harbor on the other side of that rock breakwater. It opened in 2014 built after 20-plus years of studies and considerations and general hand-wringing. But since it only has room for a limited number of boats, some still retain their moorages in the port’s main harbor.

Road across the flow

Road across the flow

I’ve posted about my January visit to Pohoiki here, here, and here. The reason I was able to make that visit is because the county finally put a temporary road over one of the flows that cut off that part of the island.

One of the features of lava flows is that they don’t uniformly erase everything in their path. Sometimes they flow around areas. Sometimes they stop and a new flow emerges to one side. Sometimes a flow blocks one side of an area and a different flow blocks the other side.

The 2018 Kilauea eruption was no different in this regard. Some houses escaped destruction, but became inaccessible by road. Pohoiki was one of those places, until the new road was completed.

Things move at a leisurely pace in Hawaii and one might think the delay in building the road was due to this, but in this case, the county had good reason to wait. The simple reason is that they had to wait for the lava to cool down. It took several months for the lava to cool enough to make it practical to build a road over the flow. Even then it would not have been safe to cut through the flow and build the road at its former level.

How quickly the lava cools depends on many things including hot hot it was to begin with and how deep the flow is. It can take many months before the lava at the heart of a flow cools down enough to solidify and not present a danger.

For those interested in what happened during that 2018 eruption, the PBS show, NOVA, broadcast an episode titled ‘Kīlauea: Hawaiʻi on Fire.’ It’s about 50 minutes long and has a bit of a dramatic ‘will anyone survive’ tone in places, but I found it very informative. It might be available at https://www.pbs.org/wgbh/nova/, but if not you can see it here.

Pu’u O’o vent

Pu'u O'o vent

Pu'u O'o vent and steamPu'u O'o vent from aboveThis week’s Sunday Stills challenge theme is ‘Time.’ (See more responses here.) I had a couple of thoughts about this. The first is that the state of Hawaii is a kind of geologic timepiece. The Hawaiian islands exist because a magma source known as the Hawaii hotspot generates volcanic activity. This creates underwater seamounts that eventually break the surface to form new islands. Such a process is currently taking place with Lōʻihi Seamount, off the southeast coast of the Big Island. It’s about 3,000 feet below the surface but, if it continues its present activity, it will rise above sea level in another 10,000 to 100,000 years.

But if Hawaii is on a volcanic hotspot, why doesn’t it produce one volcano that just gets bigger and bigger? Well, the tectonic plate on which Hawaii sits is in constant motion to the northwest. So the volcanic activity generates an island, but as the plate moves, that island edges away from its creative source and the volcanic activity ceases. What happens then is that the winds and waves begin a long process of erosion until that island is reduced to an atoll and finally disappears below the ocean’s surface. We’re not talking months here. We’re talking millions of years for this process to take place.

Look at a map and you’ll see this chain of Hawaiian Islands stretching away to the northwest, the islands or atolls becoming progressively smaller until they disappear and return to being below-surface seamounts. And while I say this is a slow process, it can also be speedy. In October of this year, Hurricane Walaka ripped through the French Frigate Shoals, part of the northwest Hawaiian chain. Its passage completely removed the second largest island in the group, East Island, from the map. Researchers had been working there before the hurricane struck. After its passage, it was gone (more info here).

So Hawaii is an example of the geologic passage of time. But there’s another aspect of our view of time that is illustrated here. The photos are of Kilauea’s Pu’u O’o vent. Kilauea is one of the planet’s most active volcanoes and the Pu’u O’o vent had been more-or-less continuously active since 1983. Then, in May of this year, the activity in this vent, and in the summit vent at Halema’uma’u Crater, ceased. The magma drained from these places and traveled down the east rift zone of the volcano before emerging in a residential subdivision, Leilani Estates, in the southeast corner of the island. This new eruption produced a lava flow that reached the ocean, destroying more than 700 structures en route, but adding hundreds of acres to the Big Island coastline.

What’s the time aspect of this? Well, it’s part of the geologic time process noted above. But there’s another way of looking at it. Kilauea has been erupting so long and so regularly that it’s been a little bit taken for granted. “Oh, lava’s flowing into the ocean? You know, I’m really busy right now. I’ll catch it later.” “The summit vent is spilling onto Halema’uma’u Crater’s floor? I’ll check that out next time I’m down that way.”

I consider myself fortunate that I got to see the firehose of lava entering the sea after a cliff collapse (here). Next day, following another cliff collapse, it was no longer visible. And in April of this year I went down to see the summit lava lake (here) bubbling up to the crater floor and visible from Jagger Museum. Two weeks later, the level had dropped a thousand feet. It continued to fall.

I might never see these things again in my lifetime, but at the time, there seemed to be lots of time to visit. But even events happening in a long, geologic timeframe might occur in the space of a week, a day, even an hour. It’s a reminder to me that each moment is something fleeting, perhaps something special, something to pay attention to.

These photos are of Pu’u O’o vent in late September of this year. No lava is visible in the vent, but it’s still hot enough that rainfall generates steam, which is what’s visible here. It was quite dramatic to pass over this vent, which for 35 years has pumped lava out onto the surrounding landscape.

Pu'u O'o vent steam

Going to the Moon or Mars?

HI-SEAS site on Mauna Loa

HI-SEAS access road on Mauna LoaSitting at around 8,200 feet on the northern slope of Mauna Loa, is the HI-SEAS (Hawai’i Space Exploration Analog and Simulation) site. The dome is where a crew of volunteers stays, simulating what could face a similar crew living on Mars. The terrain has similarities to Mars, the crew can only go outside in space suits, and communications are delayed by 20 minutes as they would be in real transmissions between Earth and Mars.

Currently, I believe the dome is empty. The last mission, scheduled to run for eight months from February 15, 2018 through October 15, 2018, was canceled after a few days because of some kind of accident, the details of which were never released.

The photo on the left shows the approach road to the HI-SEAS site with a near full moon above. Public access to the site is not allowed for obvious reasons, but I do think it would be great fun to dress the kids up as little green Martians and take them trick or treating there. Imagine being inside the dome when there’s a knock on the door.

For more information about HI-SEAS, go to hi-seas.org/.

A’a and pahoehoe lava

A'a and pahoehoe lava

This photo shows the two main types of lava found on the Big Island. On the left is pahoehoe lava and to the right, a’a lava. They’re noticeably different. Pahoehoe lava is typically rounded and smoother, and the height of the flow is quite modest. A’a flows are characterized by a rough, clinker surface and the flow height is greater. Both types of lava can be produced by the same eruption and even in the same flow, depending on conditions.

Pahoehoe flows occur when lava is hot and fluid. Typically, pahoehoe flows result from an eruption that outputs lava at a lower rate, has a lower flow rate and a slower moving flow front. The slower movement of the flow allows a skin to form on the surface and this insulates the lava within. The flow is actually made up of a large number of ‘toes.’ Each toe flows for a short time, a matter of minutes. When it stops, the lava inside causes the toe to expand until the skin cracks and releases a new toe.

A’a flows are more viscous, but with a higher flow rate and faster flow front. The lava in the center of the flow is very dense with a layer of rough clinker on top. As the flow advances, the front tumbles over itself breaking into more rough pieces.

It’s easy to see from the photo that walking is much easier over pahoehoe lava than a’a lava. That’s when it’s cooled of course. When it’s red hot and flowing, it’s best not to get too close.

This flow was on the north side of Mauna Loa, looking across to Mauna Kea.

For a more thorough description of the difference between a’a and pahoehoe lava, go to http://volcano.oregonstate.edu/book/export/html/131