Basics of polymyalgia rheumatica. Polymyalgia rheumatica (PMR) is a disorder that causes stiffness and aching that begins in the neck, shoulder and hip areas. It is not known whether it is a disease of the joints muscles or arteries.However it is thought that inflammation in these areas leads to pain and stiffness.Incidence.olymyalgia rheumatica (PMR) is a disorder that causes stiffness and aching that begins in the neck, shoulder and hip areas. It is not known whether it is a disease of the joints muscles or arteries. However it is thought that inflammation in these areas leads to pain and stiffness. Incidence.
There are two main types of volcanic eruptions: Explosive and Nonexplosive eruptions.he types of volcanic eruptions are magmatic, phreatomagmatic, and phreatic. For a description of each type and different styles of each, refer to the link below.
Volcanoes and Volcanic Eruptions. Magmas and Lava. Since volcanic eruptions are caused by magma (a mixture of liquid rock, crystals, and dissolved gas) expelled onto the Earth's surface, we'll first review the characteristics of magma that we covered previously. Three basic types of magma: Mafic or Basaltic-- SiO2 45-55 wt%, high in Fe, Mg, Ca, low in K, Na.