Note: This was originally going to be an earthcache, but I couldn't find enough unique information about the geology of this particular cinder cone, so I have turned it into a traditional cache. I'll keep the information here, but you don't need to answer any questions - just sign the log!
The volcano-looking cinder cone you can see here, along with the associated lava flow to the south are the most recent bits of evidence of the extensive volcanism of Cedar Mountain. Geologists believe that much of this lava rock is very young - not young compared to a human life span, but young in geologic terms. Much of the lava did not come from a central volcano but welled up from cracks and fissures in the earth’s surface.
A cinder cone is a steep cone-shapped hill of volcanic debris that accumulate around and downwind from a volcanic vent. The rock fragments, often called cinders or scoria, are glassy and contain numerous gas bubbles "frozen" into place as magma exploded into the air and then quickly cooled. Cinder cones range in size from tens to hundreds of meters tall. Cinder cones are made of pyroclastic material. Many cinder cones have a bowl-shaped crater at the top.
Lava flows are usually erupted by cinder cones, either through a breach on one side of the crater or from a vent located on a flank. If the crater is fully breached, the remaining walls form an amphitheatre or horseshoe shape around the vent. Lava rarely flows from the top (except as a fountain) because the loose cinders are not cemented together and are too weak to support the pressure exerted by molten rock as it rises toward the surface through a central vent.
There are two general resulting surface types from lava flows. One type called Aa (see image) creates a surface that is jagged, rough and blocky in appearance. These come from very hot and gas-rich lava with abundant iron & magnesium. Pahoehoe (see image) lava flow surfaces are more smooth with a glassy or sometimes ropey appearance. These flows are produced from lava that is cooler, gas-poor, and has high levels of silicon, sodium and potassium. The flow is sluggish and resembles thick honey. Aa & Pahoehoe are Hawaiian terms, and an easy way to remember the difference is this: If you were to walk over Aa rock with bare feet, it would not feel too good and you would be saying to yourself "Ahh, aahh...".
Information adapted from Wikipedia & Volcanoes: The Nature of Volcanoes