A Flight Around the World's Highest Mountains: Mauna Kea and Mauna Loa

Mountains that make their own weather can be frustrating because...they make their own weather. High mountains in the path of consistent winds force air masses upwards, causing the water vapor within to condense, forming clouds and as often as not, rain. This is especially true around the tallest mountains on the planet.

I'm not talking about Mt. Everest in the Himalayas. It's tall of course, just over 29,000 feet above sea level. But if one measures from the base of the mountain on the sea floor, Mauna Loa and Mauna Kea on the Big Island of Hawai'i are around 32,000 feet high (Mauna Kea edges out Mauna Loa by about 120 feet). The two giants are nearly 14,000 feet above sea level, and they rise in the middle of the northeast Trade Winds of the Pacific Ocean. They are often clear for a few minutes in the early morning, but the clouds can build quickly, obscuring the view. During our field studies trip in 2016, we had been exploring for five days before the students even saw Mauna Loa at all.

I've been privileged to visit the Hawaiian Islands eight times now, and that means there've been a few chances to see the great shield volcanoes from above as I've arrived or departed from the islands, but none of them was like the scene that presented itself to me this morning. We had an early flight, and for once I was on the correct side of the plane (for the record, on flights out of Hilo you want to be on the left side of the plane). There were just a few clouds on the northeast side, but we flew through them and soon the entire north flank of Mauna Kea was spread out below.

These mountains are astoundingly big. They formed from hundreds of thousands of eruptions of non-viscous (easily flowing) streams of basaltic lava generated at a "hot spot" in the earth's mantle hundreds of miles beneath the surface. The outer lithosphere of the earth slides over the hot spot, carrying earlier-formed volcanoes to the northwest. Kauai, Maui, and Oahu were all once large shield volcanoes like Mauna Kea and Mauna Loa, but they have subsided and erosion has ripped into their flanks. Mauna Kea and Mauna Loa will eventually suffer the same fate, and in fact Mauna Kea hasn't erupted in several thousand years (a number of very expensive telescope dot its summit). Mauna Loa is still highly active, having erupted in 1984. I wouldn't be shocked if it erupted again tomorrow (which would be the karma of just having left the island).

Perhaps my favorite shot of all, the north flank of Mauna Kea

These mountains aren't just fascinating as geological entities. They are also biological refuges. There are hundreds if not thousands of rare and endemic species of plants and animals in the forests on the flanks of the mountains. There are few environments like these on the planet, a slope that climbs from beaches to tropical rainforests, temperate rainforests, high deserts, and alpine slopes. One can see from the patchwork of cleared forests on the flanks of the volcanoes that we have severely affected these unique environments in order to raise cattle and goats. Many species, especially birds, have been lost, and other are barely hanging on.

Three gigantic shields in one picture, Mauna Kea on the left, Mauna Loa in the center, and Hualapai on the right.

It was a fascinating flight around the summits of the world's highest mountains!

The Hawai'i That Was: Watching the Destruction of the Islands in Real Time

The Big Island volcanoes of Mauna Kea (left) and Mauna Loa (right), as seen from the summit of Haleakala on Maui

Geologists have at their fingertips the closest thing to a working time machine that exists on planet Earth. We can't travel to the past, of course, but we can decipher past happenings by working out the sequence of geological events. But with the Hawaiian Islands, we have a different kind of time machine. We can predict the future of the Big Island.

The Hawaiian Islands are an example of an active hot spot, an enigmatic place in the Earth's mantle that is much hotter than surrounding regions. The hot spots produce tremendous amounts of basaltic lava that erupt onto the ocean floor, and the constant eruptions result in the formation of the gigantic shields like Mauna Loa and Mauna Kea (top picture). Since the asthenosphere (solid upper mantle and crust) is in constant lateral motion, the volcanoes that grow on the hot spots are carried off, and ultimately become inactive. The former hot spot volcanoes don't end with Kauai and Ni'ihau. There are submerged former islands on the Pacific Ocean floor that extend all the way to the Aleutian Islands in Alaska. In the history of these islands and former islands we see the future of the Big Island of Hawai'i. It will be a history of destruction and loss.

Haleakala on the island of Maui

The Big Island is larger than all of the other main Hawaiian Islands combined. As has been mentioned in the previous posts on the the Hawai'i That Was, the island is composed of five distinct shield volcanoes, Kilauea, Mauna Loa, Mauna Kea, Hualalai, and Kohala. As one flies to Kaua'i, as we did during our recent trip, we passed each of these smaller islands, some well known, others not. They include popular Maui and Molokai, as well as Lana'i and Kaho'olawe.

Maui (above) includes two shield volcanoes, the immense Haleakala (10,023 ft - 3,055 m), and the lesser known West Maui volcano (5,788 ft - 1,764 m). A low valley separates the two volcanoes. Some might ask why there are only two volcanoes and not five, like on the Big Island. Why, indeed?

South side of Moloka'i

Moloka'i is likewise made up of two volcanoes, although the linear nature of the island hardly suggests any kind of volcano shape at all. The entire north side of the island is one continuous high cliff that originated when the half of the volcano slid into the sea in a gigantic debris avalanche. Another island composed of two volcanoes. Why is that?

North side of Moloka'i (I haven't been there so we have an aerial photo instead).

The island of Lana'i is what remains of a single volcano. The uninhabited island of Kaho'olawe is likewise the remains of an isolated shield. So what's with all of these small islands composed of one or two volcanoes, instead of a large single island like the Big Island of Hawai'i? An answer is to be found with a map of the islands that also shows the submarine geology

Lana'i

The four islands, Maui, Moloka'i, Lana'i, and Kaho'olawe, are spaced about as far apart from each other as the peaks on the Big Island. The intervening seas are very shallow, and one soon realizes that Mau'i and the other islands were in fact once a single island similar in size to the Big Island. The islands have been sinking slowly as they press down on the underlying crust and mantle. They were interconnected as recently as the last ice age.

So, on our flight from the Big Island to Kaua'i, we see the future of the Big Island of Hawai'i. As the volcanoes subside (measurements at Hilo suggest about an inch per decade), the single island will become a series of isolated islands. Erosion will tear away at their flanks, and gigantic avalanches will tear away large portions, spreading the debris across the deep ocean floor. What's nice about this? The degraded and eroded masses of rock in the islands of Hawai'i have turned out to be some of the most beautiful landscapes on the planet! In the next post, we'll arrive at the most eroded island of all, Kaua'i (our recent trip only covered the two islands; I may take up an exploration of Oahu and Maui later on).

The Hawai'i That Was: The Beginning of All Things, (Ba)salt of the Earth

There are lots of places that are associated with a particular kind of rock. There's the granite of the Sierra Nevada, or the sandstone of Zion National Park. Geologists think Franciscan graywacke sandstone when someone mentions the California Coast Ranges. But nearly every mainland location is really made of a variety of different rocks. That's not the case with the Hawaiian Islands. There is but one rock. It comes in many guises, but it is compositionally the same thing: basalt.

A pahoehoe flow from Kilauea from 2004. The flow was only a few days old and looks silver because of a thin layer of volcanic glass that degrades and falls away within weeks or months.

That's the starting point of our journey through The Hawai'i That Was. Hawai'i began as basalt, and until the eroded rocks are covered by coral reefs, that's all there will be, the basalt or the weathered components of the basalt. Every island in the chain began as a series of sterile tracts of the black volcanic rock.

That's not to say that basalt in Hawai'i is everywhere the same. It originates in the same place, as a "partial melt" magma deep in the Earth's mantle at a (probable) hot spot. Magma results from the melting of rocks, but rocks are made of different kinds of crystals, and different crystals melt at different temperatures. So a partially melted magma will be made of the minerals that melt at slightly lower temperatures. In the case of Hawai'i, the original rock, peridotite (or related rock like dunite), is composed primarily of olivine and a few other minerals, but the partial melt produces a rock composed of pyroxene, calcium-rich plagioclase and lesser amounts of olivine. Two kinds of lava, not easily distinguished in the field, are found in Hawaii: a sodium-depleted tholeiitic basalt (early-stage eruptions), and a sodium-rich alkali basalt (late-stage eruptions). At times, the magma will bring bits of peridotite to the surface as clots in the lava like the one in the picture below. These clots are called xenoliths ("alien rocks").

A mantle xenolith in basalt. The green mineral is olivine (it weathers to red iron oxide quickly in the moist climate of Hawai'i)

Olivine is a semi-precious gemstone, and is occasionally visible as phenocrysts in the basalt. Given the name, it's not hard to guess that the stone is green in color. Hawai'i hosts one of the few green sand beaches to be found anywhere on the planet (which we visited; the story will come in a follow-up blog).

Olivine phenocrysts in vesicular (holey) basalt at Pu'ohonua o Honaunau National Historical Park

Eruptions of basalt can vary in temperature, gas content, water content and other factors. Depending on the circumstances of the eruption, basalt can take the form of a pahoehoe flow (see the second picture above) where the surface is smooth or ropy looking. It can also take a rough and blocky aspect like the one in the picture below called an a'a flow (believe it or not students misspell this word sometimes). Lava flowing into the sea can explode into sand-sized particles (forming black-sand beaches), or pillow-shaped lobes called (not surprisingly) pillow lavas.

Explosive eruptions of basalt are fairly rare on Hawai'i, but they do happen. The rapidly cooling lava may not even form crystals, forming a glass instead. The glass can take the form of a gold-colored basaltic pumice (below), a spongy material with the consistency of styrofoam.

Basaltic pumice at the Lyman Museum in Hilo

One of the oddest materials to result from a basaltic eruption happens when molten lava flies through the air trailing long thin strands of glass called Pele's Hair. The strands are so delicate it's amazing they can be found at all, much less in bunches like the sample below from the Lyman Museum in Hilo. I've only found single strands out in the wilds.

Pele's Hair at the Lyman Museum in Hilo

Larger chunks of molten lava can twist during flight into so-called lava bombs. In the picture below, the sample is lying in a bed of cinders, the smaller bits of explosive eruptions. Take some serious advice here: if you collect lava bombs in Hawai'i and you are going through airport security, and they ask what you have in your luggage, DO NOT use the word "bomb". The results are not happy or convenient, based on a true story (thankfully not mine; I have plenty of lava bombs from California).

Basalt is the beginning of all that is in the Hawaiian Islands. The islands began as thousands upon thousands of lava flows, the soils on which plants and animals survive are derived from the weathering of basalt, and the platform on which coral reefs later grow at the end of the island's existence is basalt. Basalt forms the base on which all travels took place and basalt was the building stone of choice (the only choice).

The Mamalahoa Trail, that stretches from Kona to Puako. It was built in the 1800s.

The islands started as sterile basalt, but as the saying goes, "life finds a way". Certain native ferns and trees are able to colonize the rock even in the absence of anything resembling soil. In the picture below, native 'Ohi'a trees are growing in basalt that erupted in 1959. Barring any more eruptions (a risky proposition in this particular spot on Kilauea), this will be a rainforest in a few centuries.

Native 'Ohi'a trees growing in a recent basalt flow in the interior of the Kilauea Iki crater, which erupted in 1959.

It was June 1st. Although Mrs. Geotripper and I had been on the islands for nearly a week doing some reconnaissance, the students were now arriving at the airport, and we were gathering our class together. Our exploration of the Hawai'i That Was had reached the starting gate.

The Hawai'i That Was: A New Blog Series

Source: http://www.noaanews.noaa.gov/stories2006/s2644b.htm

There's a rock in the sea about 500 miles northwest of Honolulu. It's about as far removed from the beaches and high-rises of Waikiki as any place on Earth can be. It's called Pūhāhonu (Gardner Pinnacles to Europeans), a part of the Papahānaumokuākea (Northwestern Hawaiian Islands) Marine National Monument, established by presidential proclamation in 2006. The land amounts to an entire six acres, and reaches a height of 170 feet. The island was discovered by a whaling ship, the Maro, in 1820, but I suspect that it was known to the ancient Hawaiians. They had enough navigating skill to realize that other islands lay beyond Kaua'i and Niihau.

The rocks were erupted about 12.3 million years ago. The island covered more than 900 square miles, based on the present size of the remaining shallow coral reefs, but it may have rivaled the Big Island in size before underwater landslides ate away at the flanks. The height of the volcano can't be easily estimated, but it would have been at least thousands of feet high, maybe much more.

Why is an obscure rock in the middle of the ocean showing up on a blog about Hawai'i? It's just this: it was Hawai'i. Twelve million years ago, the Gardner Pinnacles sat astride the hot spot that is forming the Hawaiian Islands, and it was the "Big Island". But no longer; today it is the last island in the Hawaiian chain that exposes any volcanic rock. An island that once rivaled the Big Island is now a bit of rock that will be gone in a few thousand years. An island that once provided home to thousands of plant species has just one, a Portulaca species. An island that once provided home to thousands of arthropod and other invertebrate species now has a few dozen. The rest of the species are extinct. Dozens of unique species of birds once lived here, only to go extinct as their territory shrunk and disappeared beneath the waves. A dozen or so seabird species live on the island today. It's a Hawai'i that once was.

There are many ways to describe a Hawai'i that "once was". I just spent three weeks on two of the islands, Hawai'i itself and Kaua'i, touring the geology and archaeology of this unique landscape. If we seemed to be avoiding Oahu and Honolulu, it was true. There is so little of any of the original Hawai'i to be found on the coastal strip of Waikiki. None of the native plants, or animals, or for that matter, precious little rock (Diamond Head being a prominent exception). But exploring the corners where far fewer tourists go, we had a chance to see something of the Hawai'i that existed before the arrival of the European explorers and missionaries, and even before the arrival of the Polynesian people (and the Menehune). That's the Hawai'i I'm hoping to introduce you to over the next few weeks. I hope you enjoy it!

What Lies Beneath Yellowstone? Yosemite, of course!

Upper Yosemite Falls, 1,250 feet high. Taken together the three components of Yosemite Falls amount to the fifth or seventh highest waterfall on the planet, at 1,425 feet (depending on who is measuring).

Okay, it's more fair to ask "what lies beneath Mt. Rainier or Crater Lake?". Yellowstone National Park sits atop a continental hot spot, and the plume of hot material will either explode out in a violent rhyolite tuff eruption, or cool deep underground into a granitic pluton. And Yosemite National Park exposes a great deal of granitic rock. But the origin of the granite at Yosemite is more related to arc magmatism, the formation of volcanic and plutonic rock as a plate of oceanic lithosphere sinks into the mantle beneath the edge of a continent. That's what is happening today in the Cascades, and it's what formed the famous volcanoes of that range: Rainier, Hood, St. Helens, Crater Lake, and more than a dozen others.

Lower Yosemite Falls, 320 feet high. Note the people for scale.

In a way, today's post is a sneak preview of the ending portion of my certain blog series on "Driving Through the Most Dangerous Plate Boundary in the World". The Franciscan subduction zone that was active during the Mesozoic Era was responsible for forming the Sierra Nevada batholith (batholith is a term for large bodies of magma, or a combination of numerous plutons in a region). The neat thing one can consider when visiting a Sierra Nevada park like Yosemite is that not only are you standing on the underside of former volcanoes and calderas, but you can also imagine the dinosaurs that once tromped around on the slopes of said volcanoes (we have even found fossils of a few of them, down in the sediments of the Great Valley)!

The Cathedral Rocks. Bridalveil Falls lie hidden on the other side.

I was in the valley again on Saturday, working through the onerous chore of dragging students around on a geology field trip. Somebody has to do it, after all. Buses can only stop in a couple of places around the valley floor, so we got off the bus and used the valley tram system to make a series of appointments at several spots in the valley to discuss the very cool geology.

The Middle Brother slide, from 1987. It is the largest slide in Yosemite's recorded history

Given a choice, I usually fore-go the tram in favor of walking to the appointment spots. It's not that I don't like the trams; they make a big difference in traffic congestion on the valley floor (you think it's crowded today? Imagine all the people on the trams in individual vehicles...). But because the trams make around thirty stops while traveling the loop of 8 or 9 miles, I can progress as fast or faster on foot. So I hoofed it from Yosemite Lodge to Happy Isles, a distance of about four miles. I had an hour and twenty minutes to get there, and I arrived with not a second to spare. But I saw marvelous sights along the way!

Yosemite Falls was at what may be the best flow it will have all year (top two photos). The drought left the park with 5% of its normal snowpack, and much or most of the ice is already flowing down the creeks and rivers. The falls will be dry in early summer.

I walked south from Yosemite Lodge where I had some very nice views of the Cathedral Rocks and the Middle Brothers Slide. The slide took place in 1987, and was the largest slope failure in Yosemite's recorded history, with over a million tons of rock.

Washington Column, the Royal Arches, and Clouds Rest

Washington Column, the Royal Arches, and Clouds Rest make for an awesomely steep gorge from the perspective of Swinging Bridge. The Bridge doesn't swing anymore, darn it! But it makes a nice platform for viewing Yosemite Falls and Yosemite Point from some distance away. The Merced River should be a bit more riotous at this time of year.

Yosemite Falls and the Merced River from Swinging Bridge

I added one small new section of trail to my experience this day. The Yosemite Loop trail travels the length of the valley on both sides, and I have walked most of it, but the section from the chapel to the LeConte Memorial Building was new to me. Despite the dry conditions, the forest floor was green and bursting with small white flowers.

From the south side of the valley, Washington Column stands as a bold cliff like the prow of a mighty battleship. It is shaped by joint fissures, large vertical cracks formed when the rock was exposed by erosion and expanded. North Dome, high above the Column, was formed by a similar process called exfoliation, where the rock expanded outwards, breaking off slabs that are parallel to the surface of the rock. The process tends to form domes all across the Sierra without the action of glacial erosion. The slabs formed by exfoliation can be dangerous to humans. In 1996, a slab the size of a football field came off the valley rim near Glacier Point, and collapsed on the valley floor near Happy Isles. The rocks killed one person and severely injured another. I was racing to the appointment at Happy Isles to show the students the site.

It was a beautiful day on the valley floor, and it was the first time some of my students had ever visited the park. That is one of the great privileges I have as a teacher of geology, introducing them to such a wonderful place, and providing an in-depth story explaining how the place came to exist. And dinosaurs!