Mauna Loa, if you don't know, is the largest volcano on Earth, and second in the Solar System only to Olympus Mons on Mars. It is estimated to have a volume of 18,000 cubic miles of rock (75,000 km³), that is, 375 times the size of Mount Hood, enough to fill the Grand Canyon 18 times over, and more than the entire Sierra Nevada range. It achieves this great volume by being not only incredibly tall (almost 56,000 feet [17 km] from the ocean floor), but incredibly flat. The overall slope of the mountain doesn't exceed 12°, which, despite its great height, makes it rather hard to see when you're directly on it. From Hilo, Mauna Loa just looks like a big hill, while Mauna Kea (which is only 120 feet [36 m] taller than it) looks like a looming mountain. The name Mauna Loa means “Long Mountain” in Hawaiian, and as I quickly discovered, it could not be more appropriate.
We got out of Hilo a bit late, and the fact that the road from the Saddle road up to the Mauna Loa Observatories is a big pot-hole-y mess meant we didn't arrive at the 11,000 foot mark until 8:40 AM, at which point we left the car and began hiking [edit from the future: how funny that by 2017 the road would be entirely paved, and an easier drive than Mauna Kea]. Now, being the over-prepared nerd that I am I had taken the opportunity beforehand to thoroughly inspect our route on Google Earth, so that I would have at the very least a mental map in case I couldn't get reception, or the weather suddenly turned nasty and we couldn't navigate. The smooth slope of Mauna Loa actually makes it somewhat difficult to determine which way is mauka (uphill, away from the sea) or makai (downhill, seaward) in places.
Anyway, on Google Earth there was a very clearly defined route traveling up the mountain via several switch backs that petered out just below the rim of North Pit, a small secondary crater on the edge of the summit caldera, which is named Mokuʻāweoweo. (Mokuʻāweoweo is an absolutely huge crater, 1.5 miles wide and 3 miles long. North Pit is small only in comparison, and is probably a mile in diameter.) I naturally assumed that this was the “6 mile trail” mentioned on several websites, and that it would be a fairly simple matter to just walk up the nice, gentle slope of Mauna Loa's flank.
Since no one else was showing any signs of navigation, I assumed the position (aided by the fact that I had excellent reception [and access to Google Maps] the entire way up) and bravely led the group up the fork of the trail that led up the mountain, rather than the mysterious fork that appeared to continue on around the mountain. Or, rather, I pointed the way out to the group and huffed and puffed along behind them in the thin atmosphere. Along the way I turned around long enough to snap the following picture of Mauna Loa in the early morning light:
|Mauna Kea in all its glory. So pretty...|
|Observatories on Mauna Kea, and the line marking the extent of glaciation.|
Anyway, we continued on our merry oxygen-deprived way for an hour. Then two. Then another. And another. Finally, after five hours of almost non-stop walking, at long last we we reached the edge of North Pit. Oh, and did I mention that the clouds came in and started dropping sleet on us (yes, sleet) about noon?
Trying to get out of the constant light sleet I clamored down the edge of North Pit, found a slight outcropping of the crater rim, and proceeded to eat the small lunch I had brought with me. It was quite exciting to be sitting on the frozen surface of a vast lava sea, knowing that the volcano had been active a mere twenty-eight years earlier, and that a vast magma chamber lurked only a little less than two miles below my feet. I was able to put together the following panorama while I was sitting there.
Edit (3/17/18): I redid the panorama using Hugin, but you can still see the original by mousing over the image.
This picture was taken in a rare five-minute period when the sun broke through the clouds. Off in the distance, just below the far wall of North Pit you can see steam rising from the floor of the crater. (Probably from rain landing on rocks heated by the sun I hasten to add, not because they were being heated by magma underneath!) Further off you can see through the break in the wall of Mokuʻāweoweo, and even see the highest part of the crater rim near the center of the image.
By this time, it was already 2 in the afternoon, the sleet was switching to rain and back again and showing no signs of letting up, and we still had to walk down, so after eating a woefully late lunch we started the trek back down. I was happy when we got low enough for the sleet to stop, until it was replaced by rain. That morning I had made the decision to wear my (lighter, non-water-proof) fleece in favor of my (heavier, water-proof) coat, so everything I had very slowly began to moisten as we walked down. That actually turned out to be a blessing in disguise, because my damp clothes kept me from overheating and kept my body temperature just about perfect the entire way down. Thankfully the rain never got heavier than a light drizzle.
Three hours after we left the summit we finally staggered back to car, whereupon we had another hour-and-a-half drive back to civilization. I haven't heard of any lasting injuries, but we were all stiff and sore for the next few days.
Mauna Loa is an absolutely fascinating mountain, especially when you compare it with its near sibling Mauna Kea. The lava on Mauna Loa is obviously much newer and fresher than on Mauna Kea, where most lava flows have been covered by either cinder, glacial deposits, or vegetation. (There are some places near Mauna Kea's summit where you can see the exposed flows, usually deeply scarred from the glaciers they erupted under.) On Mauna Loa, lava flows stand out stark and fresh. They also weather to a different color; while old lava on Mauna Kea oxidizes to a reddish-brown color, Mauna Loa's lava goes more for a straight brown. It's very neat to be driving through a patch of black lava, probably less than a hundred years old, and come across a small kīpuka of much older brown lava that didn't get covered in the middle of it. There is a lot of older lava on Mauna Loa (take a look at the picture below for some) and it's fascinating to think about what Mauna Kea must have looked like before it began its post-shield phase and covered everything with a layer of cinder. Alternatively, it's really cool to imagine Mauna Loa after it enters its post-shield phase and starts erupting cinder and cinder cones all over.
|A fairly old lava flow on Mauna Loa's flank.|
Note how the lava is starting to crumble and flake off.
Now that I know where the trail really is, I wouldn't mind going back some day (hopefully one with better weather) and trying again for the summit. Because despite the discomfort and days of soreness, there's something incredibly cool about standing on an active volcano so far removed from sea level and civilization.
I'm going to close this post by linking to a chapter from a book called Life in Hawaii by Titus Coan, an early American missionary. He describes Mauna Loa's great eruption of 1855-56 that came within a few miles of destroying Hilo. He describes ascending to over 12,000 feet to find the source of the eruption, watching it for many days, trying to cross it in full flood (!!!), and a whole bunch of other incredibly nifty observations about it. It's a long read, but I suspect that once you start you won't be able to stop reading it. Here it is: The Eruption of 1855.