Moenkopi Formation mudstone and sandstone

About 237 million years ago theMoenkopi Formation rocks were deposited in a coastal plain that covered what is now northern Arizona and surrounding states. The plain ended at the shoreline of a sea in Utah. Seasonal stream beds crossing that plain deposited thick sheets of sand. Over millions of years, “another 10,000 feet of Mesozoic sedimentary rocks accumulated.”

Quote and details from Stone Landmarks,Flagstaff’s Geology and Historic Building Stones

A lava flow and black cinders in the San Francisco volcanic field.

Exposed Moenkopi sandstone with overlaying cinders

All of these sedimentary layers have been warped, twisted and eroded, ending up being uplifted by molten lava between 70 million and 30 million years ago as a huge chunk of thick crust. This was the origin of the Colorado Plateau, a 130000 square-mile block.  In time, that molten base began to erupt in the San Francisco volcanic field, creating thousands of cinder cones, long lava flows, the stratovolcano known as San Francisco Mountain, and lava domes like Mount Elden near present day Flagstaff. Volcanic activity continued, with the most recent eruption occurring in AD 1064. At that time, the Sinaguan people found that the loose cinders made a good mulch for growing crops, and they created Wupatki. They used the red Moenkopi sandstone exposed in the area along with Kaibab limestone and black basalt from the volcanic field to build substantial buildings.

Wupatki and the surrounding Moenkopi sandstone building material

Wupatki was built directly on the exposed layers of Moenkopi.

Centuries later, when the railroads necessitated the creation of the town of Flagstaff, the buildings were made of wood.  However, over the years the citizens learned the same lesson that many cities of the day learned, as fires consumed the town.  When reconstructed, the materials of choice were identical to those of the ancients, Moenkopi sandstone, Kaibab Formation limestone and volcanic basalt.

The Babbitt Brothers Building was constructed in 1888 of Moenkopi sandstone.

The landmark Coconino County Courthouse was constructed in 1895 of “Arizona Red” Moenkopi sandstone.

The Bank Hotel 1886

The Bank Hotel is built of a combination of local sandstones of different colors.

The David Babbitt Building was built in 1907 of split-faced blocks of volcanic rock.

The Raymond Building was built in 1911.

The Raymond building uses carved Moenkopi sandstone.

The ornate 1906 wall that used to surround the grand home of Charles J. Babbitt, which was destroyed by fire. Wall is 265 million year old limestone.

The Nativity Chapel was built in 1929 of basalt chunks collected by parishioners from local lava flows.

New offices occupy Flagstaff’s old Ice House, built in 1946 of limestone filled with impressions or molds of fossilized shells.

Molds and casts of fossilized clams, snails, brachiopods and sea urchins are found in the limestone chunks of which the old Ice House was built.

Used copies of the Stone Landmarks are available for purchase at various booksellers.  Photos are my own.