This week, in honor of Halloween, we're presenting two classic stories about facing fears for science.

Part 1: As a newly minted PhD student in geology, Erik Klemetti starts to question his decisions when Aucanquilcha, a 20,000-foot volcano in Chile, proves difficult to tame.

Part 2: Explorer George Kourounis finds himself growing increasingly anxious as he prepares to enter a fiery sinkhole known as the “Doorway to Hell.”

Erik Klemetti is an associate professor of Geosciences and volcanologist at Denison University. He works on volcanoes all over the planet, from Chile to New Zealand to the Cascades of Oregon and California. His research focuses on how crystals record the events inside a volcano before and between eruptions. For the past 9 years, he’s been teaching all the “hard rock” classes at Denison. He also writes for Discover Magazine. His blog, Rocky Planet, have been running since Fall 2017. Before that, he wrote Eruptions, a blog about volcanoes, for Wired Science for 9 years. You can also find him on Twitter (@eruptionsblog), variously tweeting about volcanoes, baseball (mostly Red Sox and Mariners) and his love of punk.

George Kourounis is a renowned global explorer and storm chaser who specializes in documenting extreme forces of nature including: tornadoes, hurricanes, volcanoes, deserts, caves, avalanches and more. He is an Explorer In Residence for The Royal Canadian Geographical Society, served as the Chairman of the Explorers Club Canadian Chapter, and has received several awards and medals for his efforts. He frequently finds himself driving into the eye of fierce storms, or descending ropes into actively erupting volcanic craters, often while hosting television programs including “Angry Planet” and others. He has given five TEDx talks, and has addressed the United Nations Environmental Emergencies Forum. George’s expeditions have taken him to over 80 countries on all seven continents to such far-flung places as: Madagascar, Turkmenistan, Vanuatu, Greenland, North Korea, Myanmar, and Antarctica.

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