Elizabeth Clare Prophet, the retired leader of the Summit Lighthouse and the Church Universal and Triumphant, a New Age religion, who called on her followers in the late 1980s to prepare for nuclear Armageddon, died Thursday at her home in Bozeman, Mont. She was 70. The cause was Alzheimer’s disease, said her daughter Erin.

Prophet took over the leadership of the Summit Lighthouse in 1973 on the death of her husband, Mark Prophet. He had founded the organization in 1958 to spread a message combining elements of Christianity, Buddhism, Hinduism and Theosophy.

In 1975, she founded the Church Universal and Triumphant, a formal religion with ceremonies and sacraments, extending the work of the Lighthouse. The religion’s teachings were derived from divine messages believed to be transmitted by the Ascended Masters, a pantheon of mystic saints and sages, among them Jesus and the Theosophist master El Morya. Its worldwide membership was once estimated at 30,000 to 50,000.

In the late 1980s, Prophet issued warnings of an impending nuclear strike by the Soviet Union against the United States. More than 2,000 of her followers left their homes and gathered at the church’s compound near Corwin Springs, Mont., near the northern edge of Yellowstone National Park. There they began stockpiling weapons, food and clothing in underground bomb shelters.

Mounting tensions with local residents subsided when the predicted attack did not occur. At the same time, a looming face-off with the U.S. government was averted when church leaders agreed not to store weapons in return for a reinstatement of the church’s tax-exempt status, which had been revoked in 1987.