Geoff Mackley is an extreme filmmaker, tackling typhoons in Korea and chasing cyclones in Samoa. Volcanoes are his favorite. He recently returned to Mt. Marum, an active volcano in Vanuatu, to film climbers getting closer to lava than humans have before. Here team member Drew Bristol, after rappelling into the crater, poses as lava churns behind him. Watch the full story on "Nightline." (Bradley Ambrose)