Lava low degree of polymerization and high temperature favors chemical diffusion, so it is common to see large, well-formed phenocrysts within mafic lavas. Basalt lavas tend to produce low-profile shield volcanoes or "flood basalt fields", because the fluidal lava flows for long distances from the vent. The thickness of a basalt lava, particularly on a low slope, may be much greater than the thickness of the moving lava flow at any one time, because basalt lavas may "inflate" by supply of lava beneath a solidified crust. Most basalt lavas are of "ʻAʻā" or "pāhoehoe" types, rather than block lavas. Underwater, they
Lava bear Alfred Bayne. As late as 1981, scientist were being asked to identify small bear tracks in the Fort Rock area to determine if they were made by lava bears. Today, it is accepted that lava bears are actually common American black bears. It is also generally acknowledged that all of the animals that were killed or captured between 1917 and 1934 were either black bear cubs or small adults stunted from malnutrition. In 1924, Bend Senior High School selected the lava bear as the school’s sports mascot. The mascot was chosen shortly after a living bear was exhibited in Bend.