Subspecies. 1  H. c. charithonia, Ecuador. 2  H. c. simulator, Jamaica. 3  H. c. bassleri, Colombia. 4  H. c. churchi, Haiti. 5  H. c. tuckeri, Florida. 6  H. c. vazquezae, Mexico. 7  H. c. ramsdeni, Cuba. 8  H. c. antiquus, St. Kitts, Antigua.
This is the cell, a current develops as hot liquid rises and cooler liquid sinks. All liquids do this weather air, water, or molten rock. In a pot, the liquid is water, the heat source is the stove burner. In the earth the mantle is the liquid, the heat source is the core.Cells develop in different areas due to variations in the mantle.here cool material is sinking between two cells you have a subduction margin form, the asthenosphere is dragged down and with it the plate forming subduction zones. In the odd occasion you might have a hot spot. I describe this as somethng like a welding torch burning through a plate of steel.
The pore spaces (known as vesicles) in pumice are a clue to how it forms. The vesicles are actually gas bubbles that were trapped in the rock during the rapid cooling of a gas-rich frothy magma. The material cools so quickly that atoms in the melt are not able to arrange themselves into a crystalline structure. Thus, pumice is an amorphous volcanic glass known as a  mineraloid .