The term "Grand Staircase" refers to a sequence of sedimentary rock layers that form a massive "staircase" between Bryce Canyon and the Grand Canyon. Each canyon's cliff edge acts as a giant step displaying the earth's geologic history and its layers. As one moves down the geologic column, each successive rock layer is older than the previous one. The oldest exposed formation in Bryce Canyon is the youngest remaining layer in Zion Canyon. Likewise, the floor of Zion Canyon is Kaibab Formation, which is the same formation one stands on at the Grand Canyon's rim. As one stands at the South Rim looking into the depths of the grandest canyon of them all, one is witnessing some 2 billion years of geologic history.

Your Guide to the National Parks by Michael J. Oswald

Over what could be as little as a few million years, the turbulent waters of the Colorado River carved out the Grand Canyon. Cutting down about 5,900 ft (1,800 m) through sedimentary rock layers of the uplifted Colorado Plateau, it has revealed a glimpse of Earth history that extends back about 1.8 billion years into the depths of Precambrian time.

Prehistoric Life

Tusayan Ruin is a remnant of a small village of about 30 people who lived here from 25 to 30 years in the late 1100s. The architecture was typical for that period. Pueblo architecture varied according to availability of local materials. Here, builders used limestone blocks held together with mud. The name "Tusayan" was the Spanish name for this geographic area and was given to the ruin by archeologists who excavated the site in 1930.

The museum description

This circular row of stones outlines a kiva (ceremonial room). Usually kivas were built underground, but the Kaibab Limestone in this region prevented digging very deep. Sometime during the occupation of the pueblo, this kiva burned. Rather than rebuild it here, another kiva was built nearby to replace it.

The museum description