Incredible, wonderful, mysterious Kilauea Volcano, Hawaii

by Donald B. MacGowan

Kilauea erupting at Halema'uma'u Crater, Hawaii Volcanoes National Park: Graphic from Photo by Donald B MacGowan

There are many wondrous, enigmatic and fascinating attractions on the Big Island of Hawaii, some better known than others, many out of the way and generally off the beaten track. Tour Guide Hawaii has produced an encyclopedic collection of the most up-to-date information, presented as short GPS-cued videos, in an app downloadable to iPhone and iPod Touch that covers the entire Big Island, highlighting the popular and the uncrowded, the famous and the secluded, the adventurous and the relaxing.

Kilauea lava flow from Kupaianaha Vent, Hawaii: Photo Courtesy of Big Island Air

Kilauea Volcano

Although it is the most active volcano on earth, many visitors to Hawaii Volcanoes National Park standing on the very summit of Kilauea Volcano often stare and wonder “Where’s the volcano?” Nestled snugly up against Mauna Loa, and not as vertically spectacular as either this near neighbor or Mauna Kea, Kilauea doesn’t even appear to be a bump on the landscape from the usual viewpoints. Even though it doesn’t standout visually, Kilauea is one of the most intriguing and fascinating volcanoes on earth…let’s just take a quick look at some of the reasons why.

The Kilauea eruption at Halema'uma'u Crater from Jagger Museum at night: Photo by Donald B MacGowan

Comprising the entire southeastern portion of Hawaii Island, Kilauea Volcano is not only currently the world’s most active volcano, it is also the home of the fire-goddess Pele. Early geologists believed Kilauea was merely a satellite vent of Mauna Loa, as it lies directly on that mountain’s southern slopes. However, Kilauea is now recognized as its own, distinct, volcano which has its own, separate, magma source and unique plumbing.

Looking over the shield of Kilauea, at some of the 760 billion tons of lava Mau Loa o Mauna Ulu, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

Presenting the classic “Hawaiian Shield Volcano” shape, a basic oval with low, shallow slope angles, volume-wise Kilauea is one of the the world’s most massive mountains. Standing 1240 meters (4080) above sea level, the above-ocean part of the volcano is about 80 km (50 miles) long and 32 km, (20 miles) wide, along an axis trending roughly southwest to northeast. However, like all the other Hawaiian volcanoes, the great majority of its vast bulk lies below the sea, about 5.5 km (18,000 feet) deep here, making Kilauea’s true base-to-summit height about 7 km (23,000 ft).

A lava flow from Kilauea blocks the highway at Kalapana Hawaii: Photo by Donald B MacGowan

Sometimes vying with Mts. Aetna and Stromboli for the title of “most active volcano on earth”, Kilauea has been erupting continuously since January 1983; between then and June 2009, nearly 700 acres of new land was created on Hawaii Island by Kilauea lava flows. As the time scale of human lives and human tragedy are so much shorter than geologic time scales, and thus human memories of past disasters grow dim rather rapidly, this volcanic growth has come at quite a cost because people insist on building villages, towns and roads on this highly active landscape. In recent decades, the towns of Kapoho (in 1960), Kalapana (in 1990), and Kaimu (in 1990) have all been burned, buried and destroyed by Kilauea, and now are seemingly all but abandoned except by a few hardy souls. Although popularly thought to be rather tame with fairly peaceable eruptions, Kilauea in the past has had its fair share of explosive, violent, phreatomagmatic eruptions, spewing great quantities of ash as well.

The summit of Kilauea Volcano with the much more massive Mauna Loa looming in the background, Hawaii Volcanoes National Park: Photo by Donnie MacGowan

Kilauea owes its peculiar shape to two long rift systems, the currently active East Rift and the Southwest Rift. These rifts are comprised of huge, deep fractures through the bulk of the mountain. Magma rises from deep below the volcano to a pool just below the summit caldera, then flows through internal plumbing down either rift, causing flank eruptions at vents down-rift. These flank eruptions greatly enhance Kilauea’s exaggerated elongate shape. In recent times, many more eruptions have occurred along the East Rift, than the Southwest Rift.

A patch of sunlight illuminates the nearly 1400 feet of throw on the Holei Pali fault scarp, Hawaii Volcanoes National Park: Photo by Donnie MacGowan

The orientation of these rifts is controlled by the geography of Mauna Loa and Kilauea, as well as by gravity. Because the north side of Kilauea is well buttressed by the huge mass of Mauna Loa and the unsupported south side slopes-off into the sea, the very mass of Kilauea is pulling it down slope, into the sea. Indeed, the sub-sea, southern slope of Kilauea is a vast, hummocky field of debris from enormous landslides. Above sea level, this slumping activity is evidenced by the several, sub-parallel ridges (or “Pali”, in Hawaiian) on the southern flank. With throws of much as 430 meters (1400 feet), these faults represent the massive fracturing of the volcano’s southern flank and the subsequent slumping of these giant blocks down slope. A drive down the Holei Pali along Chain of Craters Road will quickly demonstrate the magnitude of seaward movement as Kilauea erupts, slumps and grows.

The Kilauea Iki Crater, within the much more massive Kilauea Caldera, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

Seaward slumping is exacerbated by the volcanic activity itself; as Kilauea fills with magma, it swells and slumps southward, producing massive earthquakes and landslides. The slumping, however, also exacerbates the volcanic activity. By opening-up new voids in Kilauea’s internal plumbing, the slumping allows injection of even more magmatic material into Kilauea, which then causes more earthquakes and more slumping. Essentially spreading under its own enormous weight, the synergy between magma injection and slumping allows Kilauea to grow both by eruption of, and intrusion of, magma.

A pahoehoe lava flow sizzles into the sea at La'epuki on Kilauea Volcano, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

The supply of magma to the volcano is fairly consistent at 1.8 cubic km (1.0 cubic miles) per year, however forty to fifty per cent of the melt never makes its way to the surface. Called “endogenous growth”, nearly half the growth of Kilauea can be attributed to magma cooling and solidifying below ground, in the growing voids opened by the synergistic magma injection and seaward slumping of the mountain.

Looking out over Kilauea Caldera from the back porch of Volcano House, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

Conjoined on its northern flank by the vastly larger Mauna Loa, Kilauea doesn’t appear to the casual observer to have a true summit. However, the summit region, around which Crater Rim Drive circles, is comprised of a larger collapse crater (Kilauea Caldera), which contains three smaller collapse craters (Halema’uma’u, Keanakako’i and Kilauea Iki Craters). Collapse craters, such as here and those along Chain of Craters Road, are formed when magma is withdrawn from a reservoir during an eruption, and the suddenly unsupported land above simply collapses into the void. As you look out over the enormous cavity formed by Kilauea Caldera, imagine the immensity of the eruptive event that left enough of a void in the magma chamber to allow this huge crater to form.

Offerings to the Goddess Pele at Halema'uma'u Crater in Kilauea Caldera, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

Kilauea’s large magma pool lies just below the summit region, somewhat south of Halema’uma’u Crater, at a depth of about 1.5-5 km (1-3 miles). Forming a magma reservoir several kilometers wide, it acts as central storage for the entire summit-rift magma plumbing system. Partial melting in the mantle at a depth of 40-60 km (52-30 miles) produces magma which rises through the earth and pools within a couple kilometers or so of the surface, and which then flows almost immediately to the site of eruption (summit or flank), having very little residence time within the volcano itself. This “open door to the mantle” feature is a fairly unique to Kilauea Volcano.

Pu'u O'o Vent on Kilauea in Hawaii Volcanoes National Park: Photo by Shannon Walker

Based on eruptive patterns in recorded history, Kilauea has been observed to follow three shifting modes of eruptive behavior. The first mode involves explosive volcanism at Kilauea’s summit. This activity contributed to the formation of past and present calderas in the summit area as well as having showered Ka’u with a cover of cinder and ash. The second mode is continuous effusive eruptive activity at the summit. This mode is typified by features such as the former lava lake at the summit which was present well into historic times, and events such as voluminous outpouring of lava from several summit vents. This mode tends to fill-in summit calderas and produce a landscape of broad, coalescing shields atop the various vents. The third mode of eruption is the continuous flank eruption, as seen today on the East Rift at vents such as Pu’u O’o and Kupaianaha.

A view into the vent at Kupaianaha on Kilauea Volcano, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

These modes are derived from observation of the volcano’s activity only during modern times, and almost certainly Kilauea’s behavior over geologic time must be much more complex. Rather than a view of the evolution of Kilauea Volcano, these modes may serve more as template through which to view what the volcano is capable of doing. It has been observed that periods of volcanic quiescence, or of small eruptions which shift location from summit to flank, may herald a shift in these eruptive modes. Further, it has been suggested based on recent observations that large, south-flank earthquakes initiating magma intrusion can greatly alter eruptive modes.

Kilauea eruption at Halema'uma'u Crater from Steaming Bluff, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

So, now that we understand a little of the mystery and complexity of Kilauea Volcano, where is the best place to see it from? For starters, one cannot beat the view off the back porch of Volcano House in Hawaii Volcanoes National Park, which encompasses much of Kilauea Caldera and Halema’uma’u Crater. Although currently closed between Jagger Museum and the intersection with Chain of Craters Road because of the ongoing eruption in Halema’uma’u Crater, the portion of Crater Rim Drive which is open provides a unique view of the volcano in a scenic loop around the entire summit region. Of particular interest are the stops at Steaming Bluff, Jagger Museum, Halema’uma’u Crater (closed), Southwest Rift Zone (closed), Keanakako’i Crater (closed), and Kilauea Iki Crater Overlook.

Looking at the trail across Kilauea Iki Crater, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

Driving across the summit dome and down to the slump-block cliffs on Hilina Pali Road takes you on a fabulous backcountry exploration from a nether-world of volcanic destruction and to lush, tropical dryland forest and savanna. Hikes along Devastation Trail, through Kilauea Iki Crater and out to the caldera overlook at Waldron Ledge give fabulous insight to Kilauea Volcano and are particularly beautiful as well as fascinating, and fairly easy for those in reasonable physical condition.

View down the slump blocks that comprise the Hilina Pali, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

Aside from the summit region, the Chain of Craters Road travels through the most interesting geography of Kilauea, including lava flows from numerous recent eruptions. Although everywhere fascinating, stops at Pauahi Crater, Mauna Ulu and Muliwai O Pele are almost mandatory. As mentioned earlier, this drive gives stark perspective on the slump blocks and the slippage of Kilauea’s south flank toward the sea. Stops at Kealakomo Overlook, Halona Kahakai, Alanui Kahiko and Holei Pali illustrate the vast nature of the slow creep of Kilauea’s southern flank down-slope. A stop to see the amazing, ancient petroglyphs at Pu’u Loa Petroglyph Field provides a moving, human connection to the peoples of the past, the awe and respect they had for this Goddess and her mountain home. The end of Chain of Craters Road gives way to a playground of geological landscapes, booming sea cliffs and ancient villages, as well as providing the jumping-off point for hikes to see the flowing lava, when it is flowing within the Park boundaries.

The eruption of Kilauea at Halema'uma'u from Jagger Museum, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

A complete guide to exploring Hawaii Volcanoes National Park can be found here; you should plan to spend the better part of a full day in the park—unless you’ve been here before, it will be the most interesting place you’ve ever been to yet. Viewing the flowing lava, the spectacle of the earth remaking herself, is one of the most moving, soul-filling, surprisingly emotional experiences you can have. The current eruption in Halema’uma’u Crater, although it hasn’t yet produced any lava flows, is best viewed from the Jagger Museum; at times of peak activity, it is most spectacular when viewed after dark. Guides to Lava Viewing in the Park and at the County of Hawaii Lava Viewing platform east in Puna at Waikupanaha can be found here and here respectively. A general outline of the volcanoes of Hawaii Island is presented here, a brief discussion on the differences between a’a and pahoehoe lavas can be found here, and an overview geologic history of the Hawaiian Islands can be found here.

A hiker watches lava from Kilauea Volcano flow into the ocean at Hawaii Volcanoes National Park: Photo by Donnie MacGowan

Perhaps no other volcano in the world, certainly no active volcano, is so easy to explore, to touch, to experience. If you come to see Kilauea, home of the Goddess Pele, be sure to give yourself a lot of time—you’ll be more captivated than you expect; certainly you’ve never experienced anything like this before. Come, explore, enjoy, stand at her door and breath the breath of the Fire Goddess.

The plume from littoral explosions where lava from Kilauea Volcano enters the sea at Waikupanaha, Hawaii: Photo by Donald B MacGowan

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Aerial view of the Mauna Ulu Crater, Kilauea Volcano, Hawaii: Photo by Donald B MacGowan

For more information on traveling to Hawaii in general and on touring the Big Island in particular, please also visit www.tourguidehawaii.com and www.tourguidehawaii.blogspot.com.

All media copyright 2010 by Donald B. MacGowan. All rights reserved.

The steam cloud at Waikupanaha where lava fro,m Kilauea meets the sea, Hawaii: Photo by Donald B MacGowan

The County of Hawaii Lava Viewing Platform at Waikupanaha, Hawaii: Photo by Donald B MacGowan

Aerial view of Pu'u O'o Vent on Kilauea, Hawaii Volcanoes National Park: Photo by Shannon Walker

Looking down into Kilauea Caldera from Waldron Ledge, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

A’a and Pahoehoe Lavas of Hawaii

by Donald B. MacGowan

The Mauna Ulu A'a and Pahoehoe Lava Flows at Alanui Kahiko, Hawaii Volcanoes National Park: Graphic from Photo by Donnie MacGowan

There are many wondrous, enigmatic and fascinating attractions on the Big Island of Hawaii, some better known than others, many out of the way and generally off the beaten track. Tour Guide Hawaii has produced an encyclopedic collection of the most up-to-date information, presented as short GPS-cued videos, in an app downloadable to iPhone and iPod Touch that covers the entire Big Island, highlighting the popular and the uncrowded, the famous and the secluded, the adventurous and the relaxing.

Pahoehoe flow at night on Kilauea, Hawaii Volcanoes National Park: Photo Courtesy of Big Island Air

Pahoehoe, A’a, Pele’s Tears and Pele’s Hair

It is obvious to even the most causal observer that various lava formations and lava fields of Hawaii display two distinctly different types of lava flows. Some flows are very smooth, with obvious, well-preserved flow structures, looking almost like poured taffy that has hardened. Others appear more clunky, clinkery and jagged like a field of sharp boulders and cobbles. These two unique rock types result from two distinctly different types of lava flows, Pahoehoe and A’a.

Pahoehoe lava flow, showing well-developed flow structures at La'epuki, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

The onomatopoetic word “pahoehoe” flows across your tongue in the same fashion that pahoehoe lava flows down the volcano. Gelatinous and smooth, it looks a bit like small waves with bulbous, lobate “toes” at the front of the flow. As the advancing lobe cools, a thin crust forms on its surface. This crust is expanded and broken by the pressure of lava flowing in behind, in a continually advancing flow. A distinctive breaking-glass sound is made when that cooling crust fractures, which can be disorienting and surprising at first.

A flowing field of pahoehoe lava, note the intense orange glow just under the chilled surface, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

The Hawaiian word “pahoehoe” means “to paddle a canoe vigorously” or “well stirred” and indeed, pahoehoe lava has the look of water being furiously paddled by canoeists, or indeed, of well-stirred poi. These highly fluid pahoehoe flows form from the hottest lava with high dissolved fluid content. As the lava cools and de-gasses, the second kind of flow, a’a lava, is formed from it.

An a'a lava flow, piled up on a pahoehoe flow in front of Pu'u Huluhulu, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

A’a flows travel along as a dense mass of highly viscous lava covered in sharp, broken shards called clinkers. Like a tractor tread, a’a clinkers fall off the advancing front of the flow and are buried as the flow moves forward over them, sounding for all the world like a herd of wild bulls has run amok in the world’s largest china shop.

The Kuamo'o Battlefield, near Kailua Kona Hawaii is an example of a Hawaiian battle that was fought on an a'a flow. Note the large Hawaiian tombs made of a'a: Photo by Donald B MacGowan

A’a lava, which cools to great piles of razor sharp clinkers, has given rise to the myth that its name derives from Hawaiian’s walking across the cooled a’a barefoot, wincing and saying “Ah! Ah!” with every cringing step. In fact, the word “a’a” in Hawaiian not only means “to blaze or glow” but also “to dare or challenge”. It is a testament to the toughness of Hawaiian warriors that when choosing the site for a battle field, inevitably they chose to fight on an a’a field—using the razor sharp a’a strewn along the landscape as a weapon in and of itself.

An a'a lava flow engulfs pahoehoe lava flow at Alanui Kahiko, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

Flows generally emerge from the volcano as pahoehoe and change to a’a as they cool and de-gas or as they are subjected to stress and strain forces. It is especially common to find pahoehoe flows changing to a’a in the midst of a steep drop over a cliff, or when butted-up against an impediment to flow. Like the cucumber becoming a pickle, once pahoehoe turns to a’a, in can never turn back into pahoehoe.

Littoral explosions cause lava to splatter out into the blowing wind where Pele's Tears and Pele's Hair can form, Waikupanaha, Hawaii: Photo by Donald B MacGowan

Where fire fountains and geysers of lava occur, Pele’s hair and Pele’s tears will form. Pele’s hair are thin, fiber-like strands of basalt glass pulled and spun from the lava fountain by the blowing wind,. Pele’s tears are the droplet-sized, cooled splashes of basalt glass that from from showering, spraying lava.

Pele's Hair from Kilauea Volcano, Hawaii Photo by Donald B MacGowan

All media copyright 2010 by Donald B. MacGowan. All rights reserved.

Pele's Tears from Kilauea Volcano, Hawaii: Photo by Donald B MacGowan

The best of Tour Guide Hawaii’s free content about traveling to, and exploring, the Big island, can be found here.

For more information on traveling to Hawaii in general and on touring the Big Island in particular, please also visit www.tourguidehawaii.com and www.tourguidehawaii.blogspot.com.

All media copyright 2010 by Donald B. MacGowan. All rights reserved.

Pahoehoe lava flowing on Kilauea Volcano, Hawaii, showing large-scale flow structures: Photo Courtesy of Big Island Air

The Volcanoes of Hawaii Island: Mahukona, Kohala, Mauna Kea, Hualalai, Mauna Loa

by Donald B. MacGowan

Hikers pause to look over the summit from Mauna Loa from the summit of Mauna Kea, Hawaii Graphic From Photo by Donald B MacGowan

There are many wondrous, enigmatic and fascinating attractions on the Big Island of Hawaii, some better known than others, many out of the way and generally off the beaten track. Tour Guide Hawaii has produced an encyclopedic collection of the most up-to-date information, presented as short GPS-cued videos, in an app downloadable to iPhone and iPod Touch that covers the entire Big Island, highlighting the popular and the uncrowded, the famous and the secluded, the adventurous and the relaxing.

A view from the summit of Hualalai to Mauna Loa Hawaii Photo by Donald B MacGowan

The Volcanoes of Hawaii Island

The Hawaiian Archipelago, part of the Hawaiian Island-Emperor Seamount chain, is the most isolated island group earth and is comprised entirely of volcanic islands and their fringing reefs.  The archipelago was formed as one of the Earth’s great tectonic plates, the Pacific Plate, moved steadily northwest over a stationary plume of molten material welling up from the Earth’s mantle, called a “hot spot”.

Fumes bellow from skylights in an active lava tube on Kilauea Volcano, Hawaii Photo by Kelly Kuchman

Creating a chain of volcanic islands that, today, stretches from the Aleutian Islands to the Big Island of Hawaii, this hotspot gave rise to at least 129 separate volcanoes in the past 86 million years.  There are 19 islands and atolls, and dozens of separate islets, seamounts, reefs and shoals in the Hawaiian Island portion of this chain, stretching from Kure Atoll to Hawaii Island (please go here for a complete discussion of the geologic history of the Hawaiian Islands).

Halema'uma'u Crater and Eruption on Kilauea, Hawaii Photo by Donnie MacGowan

Hawai’i is the youngest island in the Archipelago and first began forming about a million years ago as volcanic vents opened above the mantle “hot spot” on the ocean bottom and molten lava began pouring onto the sea floor. Over the centuries, the making of the Big Island as we know it today eventually entailed the growth and conjoining of six separate volcanoes, building all the way up from the seafloor, some 18,000 feet below the ocean’s surface.  These volcanoes, from northwest to southeast, are named Mahukona, Kohala, Mauna Kea, Hualalai, Mauna Loa and Kilauea, and become younger as one moves north to south.

Lava Flowing Into the Sea at Waikupanaha, Hawaii Photo by Donald B MacGowan

Mahukona Volcano, just off the Big Island’s northwest coast, was the first volcano to start forming. Now submerged beneath the surface of the ocean because it is sinking into the Earth’s crust under its own vast weight, Mahukona is no longer visible.  As the Pacific Plate slowly continued moving northwestward over the hotspot, the location of the rising magma moved relatively southeastward, and through time the rest of the Big Island volcanoes formed along that path.

Kohala Mountain from the slopes of Mauna Kea Photo by Donald B MacGowan

After Mahukona, Kohala Volcano, the precursor to today’s Kohala Mountain, erupted next.  As Kohala Volcano emerged from the sea and joined with Mahukona, a much larger Big Island began forming. With continued movement of the Pacific Plate, the center of volcanism migrated on to Mauna Kea and Hualalai, the middle-aged volcanoes, and finally on to Mauna Loa and Kilauea, which are the youngest volcanoes on the island.  Over the geologically short time of several hundred thousand years, these volcanoes erupted thousands of thin flows which spread over, and built upon, older flows; each volcano growing until it finally emerged from the sea. As time went on, lava flows from one volcano began to overlap flows from other, nearby volcanoes and eventually the peaks coalesced into a single island, the Big Island.

Lava from Kilauea flows into the sea at La'epuki, Hawaii Photo by Donald B MacGowan

In geologically recent times, a new volcano, Lo’ihi, began forming about 18 miles off the southeast coast of the Big Island.  In time, Loihi may join its mass with that of Kilauea, again changing the size and shape of the Big Island.  It is estimated that Lo’ihi, whose summit lies approximately 3,178 feet below the surface of the ocean today, will begin to protrude above the surface in about 10,000 years.

Hualalai Volcano from Saddle Road, Hawaii Photo by Donald B MacGowan

Currently, the remnants of Mahukona and Kohala volcanoes are completely extinct; Hualalai and Mauna Kea are considered dormant and Mauna Loa, Kilauea and Loihi are still very active.   This means that eruptions of Mahukona and Kohala are not at all likely. Eruptions of Mauna Kea and Hualalai are probable at some time in the future, though the major phase of mountain building is over for these volcanoes.  Movement of the Pacific Plate has moved both Hualalai and Mauna Kea off the hot spot so only remnants of liquid magma reside beneath them. These late-stage, mature Hawaiian volcanoes experience violent, explosive eruptions which are spectacular but comparatively small, volume-wise.  Late-stage Hawaiian volcanic eruptions are characterized by crater-forming explosions, tephra-cone building and ash ejecting events.

Mauna Loa from Bird Park in Hawaii Volcanoes National Park: Photo by Donald B MacGowan

Mauna Loa and Kilauea are both considered active volcanoes. Although inflation and dilation events are common on the summit of Mauna Loa, it has not erupted since 1984; Mauna Loa could, however, erupt at any time.  Since 1833 when accurate records began to be kept, there have been 33 eruptions of Mauna Loa, making it one of the most active volcanoes on earth.  Its name means “long mountain”, and Mauna Loa is capable of erupting huge amounts of lava in a very short time, dwarfing the current output of Kilauea.  The most massive mountain on earth, this prolific effusion of molten rock accounts for Mauna Loa’s vast bulk.

Kilauea eruption in Halema'uma'u Crater at night, Hawaii Volcanoes National Park: Photo by Donald B MacGowan

Kilauea, once believed to be a mere satellite vent on Mauna Loa, is known to be a separate and distinct volcano with its own, geologically separate magma chamber and subterranean plumbing. Nearly half a million years old, Kilauea’s most recent eruption has been continuous since 1983 making it currently the world’s most active volcano. Indeed, between 1983 and 2009 about 700 acres of new land were produced by lava flows from Kilauea.  Articles on how to see the active lava flows on Kilauea can be found here and here. A detailed guide to enjoying Hawaii Volcanoes National Park, featuring Kilauea and Mauna Loa Volcanoes can be found here.

Kilauea buried the town of Kalapana in the early 1990s and formed Kaimu Black, Hawaii: Photo by Donald B MacGowan

Because the time-scale of human experience is virtually instantaneous compared to the aeons-long march of geologic history, there is continuing human drama, a tension, between short-sighted humans attempting to establish roads, villages and towns, and the ongoing geologic processes of the landscapes they choose to inhabit.  In very recent decades, the towns of Kapoho, Kalapana and Kaimu have been inundated, destroyed and buried by Kilauea Volcano (please see a related article on the death and rebirth of Kalapana, here).  As more people move to Hawaii, more such drama is inevitable.

Mauna Loa floats above the fields of Kohala, Hawaii Photo by Donald B MacGowan

The evolution of Hawaiian volcanoes continues even after the major phase of eruptive activity subsides. There are great differences, obvious to even the most casual observer, between the elongated, fluted ridge-like shape of Kohala Mountain and the lower angled slopes of Mauna Loa and Kilauea.  Likewise, steep-sided Mauna Kea has a greatly different physical aspect than does gently-sloped, shield-shaped Mauna Loa.  These differences are accounted for by the differences in their relative ages, and thus eruptive and erosive stages.

The steeper, crater-poked slopes of Hualalai indicate it has moved on to the later stages of volcanism Photo by Donald B MacGowan

Remembering that the angle of repose of Hawaiian lava is about 6 degrees, the shield-shaped, gentle slopes of Mauna Loa and Kilauea reflect the fact that they are quite young and are still in the shield-building stage, being built-up by successive flows of highly fluid lava.  The much steeper flanks of Hualalai and Mauna Kea volcanoes are due to the late-stage, explosive eruptions, to erosion and to ashfall which piles up much more steeply than the flowing lava.  The fluted ridges of Kohala volcano result from the deep dissection of the once shield-shaped slopes of the original volcano by streams and surface flow of water.  The distinctive steep valleys and great cliffs seen on the north and east sides of Kohala Volcano result from later process of normal faulting and giant landslides (see further discussion in an article about Waipi’o Valley, here).

Glacial cirques and moraines along the Mauna Kea summit ridge, Hawaii: Photo by Donnie MacGowan

Another process, operative in the geologically recent past, has served to shape the slopes of the volcanoes of the Big Island, at least those which are or great height.  Glaciers covered the summit of Mauna Kea (and possibly Mauna Loa) three times between 200,000 and 13,000 years ago, leaving behind many glacial features such as cirques, u-shaped valleys and scoured bedrock; surviving into the present is a remnant rock glacier near the summit of Mauna Kea (a related article on the summit of Mauna Kea and the Hawaiian Snow Goddess, Poliahu, can be found here; details on exploring Mauna Kea can be found here).  Any evidence on Mauna Loa of ice-age glaciers has been covered by recent eruptions.

Kohala Volcano is subsiding, cut by enormous valleys and giant cliff-forming landslides, Hawaii: Photo by Donald B MacGowan

Simultaneously with the ongoing eruptions and island building, due to their enormous mass, the great volcanoes of the Hawaiian Chain begin to subside into the oceanic crust.  After the majority of eruptions cease, with cooling and with a great amount of time, they eventually disappear beneath the surface of the sea completely, as Mahukona Volcano already has.

Originally carved above sea level, these 500-year old petroglyphs at Keauhou today are awash due to subsidence of Hualalai Volcano: Photo by Donald B MacGowan

Today, the Big Island of Hawai’i comprises more than twice the area of all the other Hawaiian Islands combined.  It’s size is not anomalous, however, considering the geologic history of the archipelago. All the other Hawaiian Islands experienced the same pattern of volcanic eruption, growth and coalescence, as well as the gradual subsidence and submersion that Hawaii Island has, and thus at one time may have been as large as the Big Island.  Indeed, geologists have demonstrated that Maui at one time formed a single landmass, known as Maui Nui or “Big Maui”, with the islands of Lana’i, Moloka’i, and Kaho’olawe.  Continued subsidence submerged the larger landmass, leaving the four, smaller islands above the ocean surface. Ultimately, this will happen to the Big Island, as well.

Looking from Mauna Kea summit to Mauna Loa, Hawaii: Photo by Donald B MacGowan

The relentless movement of the Pacific Plate carries it, with the all the islands piggy-backed, inexorably northward to the Aleutian Trench, where it is subducted underneath the North American Plate, melted, and recycled as volcanic material in the Aleutian Island volcanoes.  The Emperor Seamounts are currently undergoing such destruction, and, the evolution of the Hawaiian-Emperor Chain is such that, eventually this fate also awaits the Big Island…but not for tens of millions of years.

Magical Sunset at the lava ocean entry at Waikupanaha, Hawaii Photo by Donald B MacGowan

Given the ephemeral nature of this precious island, this geologic certainty should serve to make us love and treasure the Big Island more deeply, as well as to spur us to protect and preserve it more completely.

Silent sunset descends upon Hawaii Island at Kahalu'u Beach: Photo by Donald B MacGowan

The best of Tour Guide Hawaii’s free content about traveling to, and exploring, the Big island, can be found here.

Near the summit of Kohala Mountain, Photo by Donnie MacGowan

For more information on traveling to Hawaii in general and on touring the Big Island in particular, please also visit www.tourguidehawaii.com and www.tourguidehawaii.blogspot.com.

All media copyright 2010 by Donald B. MacGowan. All rights reserved.

Full moon over Mauna Kea, Hawaii Photo by Donald B MacGowan

A Quick Geologic History of the Hawaiian Islands

by Donald B. MacGowan

Visitors Watch the Halema'uma'u eruption of Kilauea at Hawaii Volcanoes National Park Graphic from Photo by Donald B MacGowan

There are many wondrous, enigmatic and fascinating attractions on the Big Island of Hawaii, some better known than others, many out of the way and generally off the beaten track. Tour Guide Hawaii has produced an encyclopedic collection of the most up-to-date information, presented as short GPS-cued videos, in an app downloadable to iPhone and iPod Touch that covers the entire Big Island, highlighting the popular and the uncrowded, the famous and the secluded, the adventurous and the relaxing.

Aerial view of Pu'u O'o Vent on Kilauea, Hawaii Volcanoes National Park Photo by Shannon Walker

The Geologic History of the Hawaiian Islands

The Hawaiian Islands, part of a much longer chain of oceanic islands and seamounts called the Hawaiian-Emperor Chain, is comprised of 8 principal islands and 124 islets, shoals, atolls, seamounts and banks, all volcanic in origin.  The Hawaiian Islands proper extend from Kure Atoll in the mid-Pacific, trending southeast to Hawaii Island (the Big Island) and Lo’ihi submarine volcano.  The eight major islands of the Hawaiian chain are named, from northwest to southeast, Ni’ihau, Kauai, O`ahu, Moloka`i, Lana`i, Kaho`olawe, Maui, and Hawai`i. Unraveling the geologic history of the Hawaiian Islands provides a fascinating glimpse into structures and process occurring deep within our Earth.  To understand how the Hawaiian Islands were formed, let’s review a bit about the nature of our planet.

Kilauea Lava Stream, Hawaii Photo courtesy of Big Island Air

Layered like an onion, our seeming solid earth is actually a heaving mass composed of various solid, partially-molten, semi-plastic and liquid layers.  The solid crust (or lithosphere), which covers the entire surface of the earth, seems strong and robust but is, in fact, quite thin and malleable.  About the same thickness relative to the rest of the planet as an onion skin is to an onion, the Earth’s silica-rich crust more or less floats upon a much thicker, partially molten, more iron and magnesium-rich, semi-plastic layer of much hotter material called the “mantle”.  Below the mantle are the liquid outer core and the solid inner core of the Earth.

Halema'uma'u Crater and eruption on Kilauea, Hawaii: Photo by Donnie MacGowan

Earth’s crust comes in basically two varieties, oceanic crust which is quite thin (only 5-7 km thick) and continental crust, which is much thicker than oceanic crust (up to 200 km thick).  Oceanic crust is composed almost wholly of an effusive volcanic rock type called “basalt”, its intrusive volcanic, subsurface equivalent called “gabbro” and a thin covering of sediment. The continental crust, which underlies the seven continents and the more massive islands, and upon which most human activity takes place, on the other hand, is composed not only of basalt and gabbro, but all the other rock types as well.  Continental crust is much less dense than oceanic crust, being much more silica-rich, and therefore is more buoyant on the mantle.  This, in part, accounts for its relative thickness and higher elevation compared to the denser, thinner oceanic crust.

Lava from Kilauea flows into the sea at La'epuki, Hawaii: Photo by Donald B MacGowan

The Earth’s crust is further divided-up into various distinct pieces, called “tectonic plates”, all moving relative to each other. Plates are composed almost wholly of either oceanic or continental crustal material. These plates “float” on the semi-plastic mantle, and are carried along by currents on the mantle’s surface. Mantle currents are caused by various physical process of heat transport within the mantle.   Think of a pot of boiling soup; the point of the boil in the soup is analogous to the heat transfer in the mantle and the skim of chilled soup riding around on the surface is analogous to the moving tectonic plates carried on top of the mantle.

Hikers pause to look over at the summit of Mauna Loa From the summit of Mauna Kea, Hawaii: Photo by Donald B MacGowan

Interactions along the edges of these plates, whether slipping past each other (such as along the San Andreas Fault), one riding up over another (such as beneath the Himalayan Mountains), or one being subducted beneath the other (such as along the western edge of North America), accounts for much of the earthquake, mountain-building and volcanic activity seen on the surface of the earth, and plate margins are certainly the most geologically active places on earth.

Kilauea eruption in Halema'uma'u Crater at night Hawaii Volcanoes National Park: Photo by Donald B MacGowan

Occasionally, exceptions to this generality occur, and the Hawaiian Islands are one such spectacular exception. To understand the forces and process which shape the Hawaiian Islands, we must look a little closer at the origin and movement of the crust and the structure of the mantle.  Happily, we need only concern ourselves with oceanic crust in general and the Pacific Plate in particular, as well as one, singular feature of the mantle.

Skylight at Kupaianaha Vent, Kilauea Volcano Hawaii: Photo by Donald B MacGowan

Oceanic crust is continually created by volcanic action along giant ridges which run generally north-south down the middle of the ocean basins.  The hot liquid magma at the ridges is much less dense than the surrounding, cold crustal rocks, and so “floats” these ridges and the still hot, newly-formed oceanic crust, up above the surrounding ocean basin, thus forming the ridge.  As volcanic eruptions along these ridges add hot, new material to the edge of the oceanic plates, the mass of new material drives the older oceanic crust away from the ridge, down both sides of it.  As the new material cools and becomes less dense, it sinks and further drives the crust away from the ridges.

Lava Flowing Into the Sea at Waikupanaha, Hawaii Photo by Donald B MacGowan

Called “Mid-Ocean Ridge Spreading”, this process can be likened to a conveyor belt where new crust is created at the mid-ocean ridge, and is driven along by buoyancy and gravity, farther and farther away from the ridge until the plate’s leading edge interacts in some way with another tectonic plate.  Thus we see that the floors of the ocean basins, all around the world, are in constant, relative motion.  The Pacific Plate, upon which the Hawaiian Islands are built, has been moving at a rate of about 3.9 inches per year to the northwest, relative to other plate motions, for about the last 42 million years.

Sunset on Haleakala from Kiholo, Hawaii Photo by Donnie MacGowan

But what causes the enormous volcanoes that comprise the Hawaiian Archipelago to form in the middle of the ocean basin?  As mentioned above, the mantle is far from uniform either compositionally, thermally or in terms of the processes controlling its internal motions.  There are places on the earth where, for a variety of reasons, hot and buoyant mantle plumes rise above the general surface of the mantle, into the crust, carrying great amounts of heat and semi-liquid material quite near the earth’s surface.  Called “Hot Spots”, extreme volcanism can result from these thermal plumes.  The volcanic fields at Yellowstone in North America are one such example of this “hot spot magmatism”; the Hawaiian Islands are yet another.

The heavily-dissected mountains of Kauai completely obscure the original shield shape of the volcano Photo by Donald B MacGowan

The Hawaiian Hot Spot has caused the creation of at least 129 volcanoes on the ocean floor, the center of volcanism on the Pacific Plate continually migrating across the plate as it travels over the hot spot. Of these 129 volcanoes, 123 are extinct, three are dormant and three are active.  At first, the trend of volcanoes was almost due north-south.  Then, somewhere between 41 and 43 million years ago the relative motion between the Pacific Plate and the hot spot changed, becoming more northwesterly; this caused a sharp bend in the line of island-forming volcanoes.

Aerial view of Pu'u O'o vent on Kilauea Volcano, Hawaii Volcanoes National Park Photo by Donald B MacGowan

Although all were formed by the same, continuing tectono-volcanic processes, two island groups are named from this bent line of islands, atolls and seamounts.  North of the bend are the Emperor Seamounts, a long chain of islands, seamounts, atolls and reefs trending steeply southeast to northwest between Abbot Seamount in the mid-Pacific and Meiji Seamount near the Aleutian Trench.  South of the bend are the Hawaiian Islands, trending from the active volcanism at the Big Island and Loihi Volcano today, gently northwest to Kure Atoll in the mid-Pacific. Movement of the Pacific Plate over the hotspot is such that Midway and Kure Atolls were where the Big Island is now, directly over the hot spot, about 30 million years ago.

The steep sides of Mt. Rainier in Washington result from its relatively high-silica, viscous lava Photo by Donald B MacGowan

The chemical composition of the Hawaiian magmas plays a central role in determining the physical form of the Hawaiian Islands.  All crustal rocks are formed of minerals composed of aluminum and silicon oxides with varying amounts of iron, magnesium, sodium, calcium, potassium and other elements stirred in.  In lava, silica tends to polymerize and greatly increase the viscosity of the melt—thus silica-rich lavas are fairly “sticky”, forming slow moving lava flows that pile-up into steep volcanoes which are typified by explosive eruptions. Silica-poor melts, on the other hand, because they are not so polymerized, form very fluid lavas that flow quickly and easily, forming gently-sloped volcanoes typified by relatively quiescent eruptions.  Remember the key words here are: “relatively quiescent”.

Mauna Loa floats above the fields of Kohala, Hawaii Photo by Donald B MacGowan

One glance at the profile of the Hawaiian volcanoes is enough to convince us that the lavas must be very silica poor, since they are very gently-sloped and the eruptions relatively peaceable; certainly civilized enough so that the casual viewer may approach them quite closely in relative safety.  Compare these with the very steep-sided, highly explosive eruptions of volcanoes like Mt. St. Helens, which is comprised of lava much more intermediate in silica composition, or the smoking hole in the ground that is the Yellowstone volcanic field, left by a massively explosive, very silica rich (and very, very viscous) lava erupting.

Layered basalts in Waimea Canyon on Kauai show the structure of the Island, flow upon flow: Photo by Donald B MacGowan

The rocks formed when the lava from Hawaiian volcanoes hardens are called “basalt”.  Although you hear the term “lava rock” used by laymen, it is a nonsensical word geologically and the registered trademark of a commercial product.  Commonly misapplied, it makes even less sense than the equivalent of using the term “water solid” instead of “ice”. The name “basalt” denotes both the silica-poor composition, as well as the fact that it was erupted onto, and it has cooled at, the Earth’s surface.  When lavas cool within a magma chamber before being erupted onto the surface, they are called an “intrusive volcanic” rock; intrusive volcanic rocks formed from lavas of basalt-like composition are called “gabbros”.  There are a few rocks in the Hawaiian islands of differing composition and texture than basalt and gabbro, but they are unimportant to this discussion.

The classic, low-angle shield shape of Mauna Loa seen from Hilo, Hawaii Photo by Donald B MacGowan

The angle of repose, which is controlled by the viscosity of the melt, is about 6 degrees for Hawaiian basalts. Melt viscosity is a function of its temperature, silica content and fluid composition.   Hawaiian basalts are very fluid because of the low silica content and high eruptive temperature (in excess of 1100 degrees C); this low viscosity accounts for low angle, “shield shape” of Hawaiian volcanoes.

Kohala Volcano is dissected by several major fault-bounded valleys, further obscuring its original shield shape Photo by Donald B MacGowan

As soon as the Hawaiian volcano forms, other forces begin to act upon it, affecting the general “shield shape” of the volcano: tides and waves attack the edges, rivers and streams begin to dissect the shield into ridges.  As time goes on, erosion from surface water flow produces fluting along those ridges.  Great landslides produce enormous cliffs; faulting produces huge valleys and collapse produces enormous craters and calderas.  Further, the later stage of Hawaiian volcanism is typified by increasing violence, which makes deep explosion craters, steep-sided cinder cones and steeply sloped, but easily eroded, ash deposits.

Stream erosion dissects the shield volcanoes into valley and knife-like ridges Photo by Donnie MacGowan

To look at the volcanoes of Hawaii starting in the southeast at Kilauea and Mauna Loa and moving northwest, one can see this evolution quite clearly.  Kilauea and Mauna Loa, being quite young, are still broad and shallow-sloped, basically the classic shield-shape.  Mauna Kea and Hualalai are obviously more mature, showing steeper slopes, a reflection of greater ashfall and greater erosion, as well as pocked with explosion craters and cinder cones.  Moving father along, Kohala Mountain is so deeply eroded and festooned with long, fluted ridges as well as cut by enormous canyons, that it is almost unrecognizable as a shield volcano.  And so it continues as one proceeds north through the older islands and the more highly eroded mountains; the original shield shape of the volcanoes become more and more obscured by deeper and deeper erosion.  By the time one gets to the famous and spectacular Na Pali Cliffs of Kaua’i, all that is left of the original volcano are the deeply fluted, now almost knife-like, ridges.

Ancient Petroglyph, Keauhou Historic District, Hawaii Photo by Donald B MacGowan

The great mass of these volcanoes causes them to begin to sink back into the mantle.  This is evident on even relatively young volcanoes.  For instance, on the slopes of Hualalai Volcano on the Big Island, along the shore at Keauhou, numerous petroglyphs commemorating the famous victory of King Lonoikamakahiki of Hawaii over King Kamalalawalu of Maui were carved in the rock around the end of the 16^th century.  Although when they were originally carved they stood above sea level, in the intervening four centuries, the island has sunk sufficiently that they are now mostly awash in the sea and submerged at high tide.

Glacial cirque and terminal moraine on Mauna Kea, Hawaii Photo by Donald B MacGowan

Another process, operative in the geologically recent past, has served to shape the slopes of the Hawaiian volcanoes, at least those which are or great height.  Glaciers covered the summit of Mauna Kea (and possibly Mauna Loa and Haleakala) three times between 200,000 and 13,000 years ago, leaving behind many glacial features such as cirques, u-shaped valleys and scoured bedrock; surviving into the present is a remnant rock glacier near the summit of Mauna Kea.

Valleys and Ridges of the Famous Na Pali Coast, Kauai Photo by Donald B MacGowan

The complex interaction of volcano growth, coalescing of various volcanoes forming a single island and the eventual subsidence of the volcanoes into the crust determines the shape and size of the individual Hawaiian Islands through time.  Today, the youngest islands are largest and the oldest islands, generally, are the smallest…this trend continues throughout the Hawaii Island/Emperor Seamount chain.

Lava flows from Kilauea to the sea at Waikupanaha, Hawaii Photo by Donald B MacGowan

In the case of the Big Island, even though the first volcano to form, Mahukona, has completely subsided below sea level, the Big Island still comprises more than twice the area of all the other Hawaiian Islands combined, due to the large number of volcanic peaks forming it. However, through their history, all the Hawaiian Islands will experience the same pattern of growth, coalescence, subsidence and submersion, and so may have been much larger at one time.

Haleakala from Kohala, Hawaii Photo by Donald B MacGowan

Maui, today comprised only of the remnant peaks of Haleakala and the West Maui Mountains, at one time formed a single giant landmass with the islands of Lana’i, Moloka’i, and Kaho’olawe.  As the continual northwest movement of the Pacific Plate carried Maui away from the Hawaiian hot spot, continued subsidence submerged the larger landmass, known as Maui Nui, or “Big Maui”, into the oceanic crust, leaving only these four, very much smaller, islands above the surface today.

Superstition to Science, Pu'u Weiku Summit, Mauna Kea Photo by Donald B. MacGowan

In fact, Kaua’i, Ni’ihau and O’ahu all represent the tiny remnants of once much larger landmasses that are actively subsiding into the oceanic crust.  Tracing the Hawaiian Archipelago to the northwest, and thus to very much older islands, we see this evolution continue as the great volcanoes are completely submerged below the surface leaving only the fringing coral reefs and a tiny remnant island above sea level, such as we see at Laysan Atoll and Midway Island. Continuing along through the chain to the Emperor Seamounts, not even that much is left as all traces of these islands, once proud and beautiful like the Hawaiian Islands today, become totally submerged beneath the surface of the ocean.

Alpen Glow on Hualalai Volcano and Sunset on Kailua Kona Hawaii: Photo by Donald B MacGowan

Add to this mental picture the fact that the Pacific Plate relentlessly drives northwestward, carrying all the Hawaiian-Emperor Chain with it, northward to the Aleutian Trench, where it is subducted and destroyed beneath the North American Plate.  Eventually, in the far-distant future, this fate awaits all these beautiful, precious islands.  Such is the ephemeral nature of the Hawaiian Islands, and this vision of their very delicate and temporary nature should make us respect and wonder at their splendor and beauty, all the more.  And increase our desire to protect and preserve them.

To see the new iPhone/iPod Touch App, please visit http://www.tourguidehawaii.com/iphone.html.

The steeper, crater-poked slopes of Hualalai indicate it has moved on to the later stages of volcanism Photo by Donald B MacGowan

The best of Tour Guide Hawaii’s free content about traveling to, and exploring, the Big island, can be found here.

For more information on traveling to Hawaii in general and on touring the Big Island in particular, please also visit www.tourguidehawaii.com and www.tourguidehawaii.blogspot.com.

Watching Lava Pour Into the Sea at Waikupanaha, Hawaii Photo by Donald B MacGowan

All media copyright 2010 by Donald B. MacGowan. All rights reserved.

Lava ocean entry, Waikupanaha, Hawaii: Graphic from Photo by Donnie MacGowan