Easy Chair Crater

Cinder cones are a very common type of volcano. They are relatively small and composed of basalt, a dark fluid lava that is relatively rich in iron and magnesium. The basalt is also scoriaceous (frothy), as the magma is typically gas-rich. The eruption starts out as fire fountains, with frothy basalt cinders falling out around the vent to build up into a cone. Other material is usually incorporated into the ascending magma, so that big crystals and even bits of the surrounding rock (the “country rock”) are also ejected with the cinders. Occasionally a large blob of lava, a so-called “bomb,” will be thrown out as well. Commonly the very last eruptive activity is a flow of basalt lava that pushes its way out the base of the cone through the loose cinders. Paricutín in Mexico [link: https://www.atlasobscura.com/places/paricutin-volcano], which erupted in the 20th century, is a modern example.

Although not completely symmetric, due to the vagaries of the winds blowing the cinders around, cinder cones are usually not markedly asymmetric, and are usually “one-off” events to boot. Easy Chair Crater is unusual, however, in its markedly asymmetric form; it is not just oval but has the northeast rim some 550 feet higher, which gives it the “easy chair” form.

This seems to be a case where a second eruption did occur almost on top of the original one. The older crater is the higher part to the northeast, while the younger is the lower part to the southeast.