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This may not look very impressive in this photo, but this pit crater near the summit of Hualalai is quite remarkable, with high vertical sides and many lava flows exposed in the walls. In the background we can see one of the flows from Hualalai that reached the coast.


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Because it does not have a shallow magma chamber (the volcano erupts too infrequently for the magma to stay molten), when it does erupt Hualalai brings very fluid lava to the surface very quickly from appreciable depth. The 1801 eruption brought big olivine nodules to the surface that were dropped on the ground around the vent as soon as the velocity fell. Here we see just part of the deposit formed by these olivine nodules.


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A closer look at the Hualalai olivine nodules helps scientists calculate how quickly the magma had to reach the surface in order to avoid these nodules falling through the ascending magma as it was erupted. We estimate that the ascent rate was more than 2 meters per second, which doesn't sound very fast until one considers the total volume of lava moving at this speed. The 1801 eruption produced flows that reached the coast in only a few hours, so that if a similar eruption were to occur today, much of the Kailua-Kona area could be at great risk due to the lack of warning of the advancing flow.

From here you can continue on to Stop 14 on the ground, or you can pick another point from the Big Island Virtual Field Trip page.