Volcanoes, with their dramatic eruptions and varied forms, sculpt landscapes and reveal dynamic forces beneath Earth’s surface. SP Crater in Arizona represents one such compelling volcanic formation, offering clear insights into a specific category of volcanic activity.
Unveiling SP Crater
SP Crater is a prominent volcanic feature located approximately 25 miles north of Flagstaff, Arizona. It resides within the vast San Francisco Volcanic Field, encompassing more than 600 volcanoes that have erupted over the past 6 million years. SP Crater stands out as a relatively young and exceptionally well-preserved formation within this expansive field. Its distinct morphology makes it a notable landmark in the high desert landscape.
Defining the Cinder Cone Volcano
A cinder cone, also known as a scoria cone, is a steep, conical hill built from loose pyroclastic fragments. These fragments, such as volcanic ash, cinders, and scoria, are ejected during explosive eruptions from a single, typically cylindrical vent. As gas-charged lava is blown into the air, it breaks into small pieces that solidify and fall around the vent, forming a cone. Cinder cones commonly exhibit symmetrical shapes with steep slopes, usually between 30 and 40 degrees, and often feature a bowl-shaped crater at their summit. Composed of porous, basaltic to andesitic material, these volcanoes are generally smaller, typically ranging from tens to a few hundred meters in height.
SP Crater’s Cinder Cone Features
SP Crater exemplifies the characteristics of a cinder cone volcano. Its symmetrical conical shape, rising about 820 feet (250 meters) above the surrounding terrain, is a classic representation of this volcanic type. The cone’s slopes, composed of loose cinders and scoria, maintain a consistent steepness from the accumulation of ejected volcanic fragments. At its summit, SP Crater features a well-defined, bowl-shaped crater, characteristic of cinder cones formed from a single vent. The structure is remarkably preserved, partly due to an agglutinate rim that helps protect its form.
The Distinctive “SP” Lava Flow
SP Crater is notable for a dark lava flow that extends from its base. This flow stretches for approximately 4 to 4.3 miles (6 to 7 kilometers) to the north, creating a striking contrast against the lighter desert floor. When viewed from above, the lava flow exhibits a distinctive “S” or “P” shape, which is believed to be the origin of the volcano’s abbreviated name. This basaltic lava, characterized by its low resistance to flow, emerged from a vent near the cone’s base, likely after the main cinder cone formation. The eruption occurred thousands of years ago, with estimates placing its age around 5,500 to 70,000 years old, and it retains a pristine surface texture.