The Big Island of Hawai'i is home to the largest volcano in the world: Mauna Loa is a massive shield volcano whose gentle slopes start at the deep ocean floor of the mid-Pacific and rise majestically up to almost 14,000 feet above sea level! It's name literally means "long mountain", for obvious reasons. The slope is so slight that at first glance it appears very unimpressive, like a low hill. This is a classic shield volcano, looking like a warrior's shield lying flat against the ground. As you give the mountain a second look, and maybe try hiking up a bit of it, you gain a new respect - it's huge! It is also fairly active. The last eruption was in 1984 and lava almost flowed through Hilo. Kilauea is but a mosquito bite on Mauna Loa's eastern slopes. In fact, it was postulated that Kilauea was just a vent on a Mauna Loa rift zone. But when both volcanoes were in simultaneous eruption in 1984, without any effect on each other, that idea was dispelled. Another little tidbit: the volume of lava erupted in one day during a Mauna Loa eruption is roughly equivalent to what Kilauea erupts in a year of continuous activity!

To Mauna Loa's immediate north lies another massive volcano, Mauna Kea. Mauna Kea is much older and no longer active. It has a more pronounced slope, and is marked by cinder cones. It rises slightly higher above sea level than Mauna Loa, and the summit is usually covered with snow. (Yes, some people actually ski or snowboard up there, but there are no facilities...)

Also atop Mauna Kea are a cluster of astonomy observatories. The summit is almost always clear, and ideally suited for gazing into the heavens. I've only been to the summit once, when a bunch of us decided to drive up (there is a well-maintained dirt road). The winds were howling at about 70 MPH, making it difficult to stand, and of course we weren't quite prepared with cold-weather gear (who brings gloves to Hawai'i?). But the sunset scene was incredible. Looking east you could see the mountain's shadow against the clouds, and to the west the dark form of East Maui volcano looms on the horizon.

Kilauea and Mauna Loa are not the only active volcanoes on the Big Island. Hualalai, situated on the central western side of the island, last erupted in 1801, and is responsible for extensive lava flows around the Kona airport. It has steeper slopes than Mauna Loa, and as a result lava may flow very quickly from an eruption down towards Kailua-Kona. I was fortunate enough to accompany several HVO scientists on a road-trip to the summit of Hualalai for some field work. Since a large portion of the mountain is privately owned, we had to obtain special permission. A few hours of 4WD jostling and a flat tire later, and we were near the top. We had fantastic views of both Mauna Kea and Mauna Loa to the east from atop Hualalai, and were able to check out some intense geologic formations (such as the enormous pit crater shown in the photo to the left - notice our truck parked along the left edge!).