On January 14, 1993, a team of scientists descended into the crater of Galeras, a restless Andean volcano in southern Colombia, for a day of field research. As the group slowly moved across the rocky moonscape of the caldera near the heart of the volcano, Galeras erupted, its crater exploding in a barrage of burning rocks and glowing shrapnel. Nine men died instantly, their bodies torn apart by the blast. While others watched helplessly from the rim, Colombian geologist Marta Calvache raced into the rumbling crater, praying to find survivors. This was Calvache's second volcanic disaster in less than a decade. In 1985 Calvache was part of a group of Colombia's brightest young scientists that had been studying activity at Nevado del Ruiz, a volcano three hundred miles north of Galeras. They had warned of the dire consequences of an eruption for months, but their fledgling coalition lacked the resources and muscle to implement a plan of action or sway public opinion. When Nevado del Ruiz erupted suddenly in November 1985, it wiped the city of Armero off the face of the earth and killed more than twenty-three thousand people -- one of the worst natural disasters of the twentieth century.No Apparent Danger links the characters and events of these two eruptions to tell a riveting story of scientific tragedy and human heroism. In the aftermath of Nevado del Ruiz, volcanologists from all over the world came to Galeras -- some to ensure that such horrors woul