Ambrym is a large basaltic volcano with a 12-km-wide caldera. It is not only one of the most active volcanoes of Vanuatu, but also in the world. Ambrym’s caldera is a wide, impressive moon-like landscape containing an ash plain, cut by innumerable erosion gullies and containing several active craters and recent lava flows.
The caldera is believed to have formed during a major plinian eruption with dacitic pyroclastic flows about 1900 years ago. Activity after the caldera formation was concentrated around two vents that have become large complex craters called Marum and Benbow. Often, both Marum and Benbow (as well as other craters) contain small lava lakes, which occasionally erupt lava flows onto the caldera floor, or even exit the caldera through erosion gaps.
To capture close-up footage of this lava lake on the Pacific island of Vanuatu, Geoff Mackley and his colleagues had to brave excruciating heat and some rather precarious-looking abseiling.
You can see more incredible shots at Mackley’s website.