Why a Mormon Mega-Temple is Being Dug-Up

Quick Overview

The largest Mormon temple in the world, the Salt Lake City Temple, is undergoing a massive $2 billion retrofit project involving base isolation technology to protect it from potential major earthquakes, which experts estimate have a 57% probability of magnitude 6 or greater in the next 50 years.

Key Points: The retrofit project to save the Salt Lake City Temple is estimated to cost $2 billion US and involves decoupling the structure from ground motion using base isolation. The temple took over 40 years to construct, completed over 130 years ago, featuring walls up to 9 ft thick and built from granite and quartz monzenite. Geologists estimate a 57% probability of at least one earthquake of magnitude 6 or greater in the next 50 years, comparable in devastation to the 1994 LA earthquake. The base isolation system will allow up to 1.5 m of horizontal movement during seismic activity by installing 98 base isolators, each weighing 8,000 kilos, beneath the structure. Construction involved extensive underpinning techniques, including micro piles and consolidation grouting, before installing a new concrete foundation with over 423 km worth of post-tensioned cables. The renovation is delayed, pushing completion to 2026 (with reopening in 2027), as teams are also reinforcing walls and spires while adding more space for ritual baptisms and increasing seating. Salt Lake City's unique urban plan, established by Brigham Young, featured exceptionally large 200x200 m blocks and wide streets, which helped the city adapt to the automobile and supported the temple's historic role as the city's anchor.

Context: The video examines the critical seismic retrofit of the Salt Lake City Temple, the largest temple belonging to The Church of Jesus Christ of Latter-day Saints, which was completed over 130 years ago. This undertaking is necessary because the temple was not designed to withstand earthquakes, and the Wasatch fault runs through the valley, presenting a significant risk of damaging seismic events, prompting the church to undertake a major, costly preservation effort mirroring seismic strengthening done on other historic structures like Christ Church Cathedral in New Zealand.