Two Apollo 15 crew members, riding a Lunar Roving Vehicle (LRV) simulator, participate in geology training at the Cinder Lake crater field in Arizona.

Before the Apollo astronauts set foot on the moon, they underwent a routine of rigorous training in order to prepare themselves for the mission. While much of the training took place inside classrooms, simulators and at testing facilities, NASA also gave the astronauts hands-on experience in geology and taught them how to collect geological specimens by taking them out on field trips.

To make their training as realistic as possible, the crew trained at sites on Earth that was geologically and topographically similar to the moon. The Sea of Tranquillity, where the Apollo 11 Lunar Module was scheduled to land, is a large basaltic plain formed by ancient volcanoes. Such a volcanic field in Arizona was chosen as the training ground, but before training could begin NASA decided to alter it so that the landscape was more moon-like.

In the summer of 1967, two year before the planned touch down, NASA selected a 500 foot square site northeast of Flagstaff, near the famous San Francisco peaks and just south of the Sunset Crater volcano, and proceeded to sculpt the landscape so that it resembled the lunar terrain. The engineers dug into the basaltic rock, planted explosives and blew them up to create craters. The amount of explosives used and the depth to which they were buried were carefully calculated in order to create craters of precise dimension. Over the course of four months, they blasted 143 craters between five and forty feet in diameter.

The distribution and size of the craters were not arbitrarily chosen. They were produced at 1:1 scale to duplicate a small area of the proposed landing site. This area became known as the Cinder Lake Crater Field.

Crater field (left) and the Apollo 11 landing site (right)

Later, NASA created another, much larger crater field, this one made to replicate not only the size but also the specific age of lunar craters. The aim was to allow the astronauts to practice describing the type and age of geological formations they encountered. The second site measured 1,200 feet square and contained 354 craters. To create the second crater field, several sets of explosions were detonated and the sequence of blasts were designed to create craters with overlapping ejecta blankets to simulate craters of different ages.

Once Cinder Lake was transformed into a crate field, the astronauts began testing their equipment, knowledge and skills on the ground. Although the site was created for the Apollo 11 landing, it was the crew of Apollo 15 who trained on the Crater Field first, because their mission was focused primarily on geology. In addition to geology training, the crater fields were used to help map potential paths across the lunar landscape. Slopes of the craters were used to test the lunar modules and the rovers. The last training took place in 1972 for Apollo 17, the final of the Apollo mission.

Now fifty years later, much of the craters have eroded away, with only the largest craters distinguishable.

First crater field

Second crater field