Rabbi Avraham Feldman stands in front of an erupting volcano, reciting a blessing. Located an hour outside of Iceland's capital city, Reykjavík, Fagradalsfjall spews orange lava like a pot of boiling water left too long on the stove. Rivers of molten magma ooze through crevices in the black igneous rock, blanketing the surrounding valley as clouds of steam and ash dissipate into the air. As the volcano gurgles behind him, Feldman casually holds up his phone to film a short video. With his eyes squinting into the sun from behind wire-framed glasses, he slowly and patiently explains the meaning of...