Mauna Loa
Mauna Kea
Copyright © 2020
by Ralph F. Couey
Data from USGS
and Hawai'i Volcano Observatory
I thought it might be a good opportunity to take some time off from the current unhappiness and discuss something completely different.
Over the Holidays last year, we had most of our family in Hawai'i to help celebrate our son's retirement after 23 years in the Navy. It was a joyous time, especially since the last time we all got together was for our granddaughters funeral.
We spent the first week on the island of Hawai'i, locally called simply "the Big Island." One of the things we did was to visit Hawai'i Volcanoes National Park. Now, I've seen pictures of a volcano and it's usually a typical cone shape with steep sides and a caldera at the top. I had seen two of them, Mammoth in California and Rainier outside of Seattle. But I was never as impressed and awe-struck as the day we drove along the southeast coast of the Big Island. We had stopped at an overlook to take some pictures of a beautiful deep blue and generously white-capped Pacific Ocean (the winds were really howling that day). After a few minutes, I turned around and beheld an awesome sight.
There before me were three of the five volcanoes on the island. Since the slopes are very clean, it was very easy to take in the incredible size of them. Not that I was able to fully wrap my head around them, mind you. It's one thing to think of a volcano, another to look at pictures, but to see them in person was mind-blowing. To my left, Mauna Loa rose into a flawless blue sky, capped by snow. To my right, further away, Mauna Kea poked it's similarly white cap above the immediate horizon. We had just driven by Kilauea, south of the highway, a lower peak, but still massive in size.
All of the Hawii'an Islands chain were created by volcanic action. There is an active hot spot over which the earth's crust floats in a generally northwest direction. The Big Island is not only the youngest, it is also the largest of the eight main islands. There are five volcanoes that not only make up the island, but actually made the island. Of the five, Kohala is the only one that is extinct. Mauna Kea and Hualalai are termed "dormant," which is to say not erupting now, but will again at some indeterminate time in the future. By indeterminate, that means it could be next month or a thousand years from now. But astronomers were confident enough to establish the Mauna Kea observatory complex, which, due to it's altitude, has provided unprecedented "seeing" and a host of ground-breaking deep space discoveries. Mauna Loa and Kilauea are considered active. Kilauea was actively erupting from 1983 through 2018. Mauna Loa, according to USGS has been erupting for some 700,000 years, and was last spewing lava in the spring of 1984.
The statistics on the two largest, Mauna Loa and Mauna Kea are astounding. Most people think the tallest mountain in the world is Everest in the Himalayas. Incorrect, grasshopper. Both Hawai'ian peaks have significant height above sea level, but like glaciers, a lot of their mass lies invisible beneath the waves.
Mauna Loa rises 13,680 above sea level. To that, you must add another 16,400 feet to the ocean floor. On top of that (or perhaps more accurately, "on bottom of that") Mauna Loa's incredible weight has caused it to sink five miles below the ocean floor. Adding all those numbers together, the total height of this mountain is some 56,000 feet, a little over 10.6 miles high. Everest rises 29,029, a "paltry" 5.5 miles.
Mauna Kea's summit sits at 13,085 feet above the Pacific. An additional 19,697 feet go from sea level to the ocean floor. Like it's neighbor, it is also sunk into the ocean floor for some four miles, so the total height of Mauna Kea from its true base to the summit is 54,520 feet, or just over ten miles.
Because Mauna Loa and Kilauea are still active, the two have produced enough lava to add some 1,600 acres to the island since the mid-1980's. Lava flows during that time have destroyed numerous communities which were established by some highly unethical developers in the 60's and 70's, who somehow never got around to telling the buyers that they would be living in the crosshairs of active volcanoes. My wife's parents got suckered in to that deal, and own a couple of acres, currently sitting under about 22 feet of lava. Since then, the USGS has established hazard zones around the island, according to the risk of lava inundation.
On this map, "9" is the safest, "1" (outlined in red) is the most dangerous. Now, a person can still build in the dangerous areas, but no bank will grant a mortgage and no insurance company will issue coverage to any dwelling in those high-risk zones. Still, real estate prices being what they are in Hawai'i, there are a few who choose to roll the dice. Cruising any of the real estate websites, you can easily tell. If the price of a house is affordable, then it lies in a high-risk zone.
Mauna Loa in the Hawai'ian language translates to "Long Mountain," no doubt suggested by its size and shape. Mauna Kea has been thought to mean "White Mountain," thanks to it's nearly year-round snow cap. But more recent scholarship has corrected the name to be a shortened version of "Mauna a Wakea." Wakea is the name of the Hawai'ian Sky Father, so the name means "Mountain of the Sky Father." Very evocative.
Geologic time spans are, of course, hard to really grasp for ordinary humans, but are instructive nonetheless. On Hawai'i, the oldest volcano is Kohala, the one extinct of the five, is over a million years old, occupying the far norther peninsula of the island. Mauna Kea is the next oldest at around a million years. Mauna Loa is estimated to be between 300,000 and 600,000 years old. Hualalai is next, about 300,00 years old. Kilauea is the "kid" of the bunch, only between 200,000 and 280,000 years young. In a preview of coming attractions, there is another volcano named Lo'ihi currently rises 3,200 feet below the ocean's surface and is expected to break above the waves in the next 1,000 to 100,000 years. Probably still too early to buy land there, though.
As mentioned before, the Hawai'ian Hotspot is responsible not only for creating the main islands, but also a long string of islets and seamounts stretching almost all the way to Russia. You might remember a couple, Sand and Eastern Islands which make up the atoll we more familiarly know as Midway. As long as the hotspot remains active, the slow drift of the Pacific Plate will create more Hawai'ian Islands over the next 10 million years or so. As an illustration of the age differences, the northernmost island of Kauai is about five million years old. The southernmost, the Big Island is less than a tenth of that age. The aforementioned Midway is about 28 million years old. You can look on Google Maps and see the entire chain, including some names like Necker, La Perouse, Laysan, Lisianski, French Frigate Shoals, all uninhabited, uninhabitable impossibly remote places, all less than a few acres above water.
But eruptions are not the only thing people here think about. Volcanoes generate earthquakes, some uncomfortably large in magnitude, always followed by a period of breath-holding until the scientists assure us that no lava is flowing. Also, on the southeast flank of Kilauea is a stretch of land about the size of Manhattan (New York, not Kansas) called the Hilina Slump. This piece of land has been slipping down the side of Kilauea for some time. A large slip of 26 feet accompanied a magnitude 7.2 earthquake in November 1975, which generated a 47-foot tsunami. That event has been fodder for an entire generation of apocalyptic pseudo-science writers who wildly described the mega tsunami that would be generated if the entire chunk slid into the sea. But two things will keep the odds of that happening very low. You see, previous landslides going back to a time long before humans have created a shelf-like structure that has been shown to support the slumping land mass. Also, the growth of the previously-discussed natal island Lo'ihi also helps push back against a possible collapse. So, rest easy. The numerous natural disaster scenarios threatening the poor, put-upon Southern California coast won't include this one.
Thinking about geologic time spans can make a human feel really small and insignificant, not to mention powerless. Tens of millions of years after humans go extinct (and we eventually will), new Hawai'ian Islands will continue to be created as the Pacific Plate continues to drift along, home to whatever land and aquatic species come to live there. If you possess any intellectual processes at all, you cannot help but be awed by looking at, and thinking about volcanoes, and how fragile our hold on history actually is.
Because despite our long domination as the most successful form of life on on this planet, once we are gone, all the natural geological processes will continue to change the geography. Earth, you see, will get along just fine without us.
Oh, come on. At least I got through an entire post without mention of one word about the Pandemic.
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