how well the flu vaccine is matched to flu viruses that are causing illness. Over a period of 31 seasons between 1976 and 2007, estimates of flu-associated deaths in the United States range from a low of about 3,000 to a high of about 49,000 people.
metamorphic rocks form from heat and pressure changing the original or parent rock into a completely new rock the parent rock can be either sedimentary igneous or even another metamorphic rock the word metamorphic comes from greek and means to change form the diagram above shows you how the rocks on earth have been changed continually over time from one rock type to another
Classification of Metamorphic Rocks. TEXTURES Textures of metamorphic rocks fall into two broad groups, FOLIATED and NON-FOLIATED. Foliation is produced in a rock by the parallel alignment of platy minerals (e.g., muscovite, biotite, chlorite), needle-like minerals (e.g., hornblende), or tabular minerals (e.g., feldspars). This parallel alignment causes the rock to split easily into thin layers or sheets. Foliation is common in aphanitic as well as phaneritic metamorphic rocks. Some foliated rocks are also banded. Banding means that the rock consists of alternating, thin layers (typically 1 mm to 1 cm) of two different mineral compositions. Normally, the two types of layers have the same kinds of minerals, but in different proportions, giving the rock a striped appearance. Banding, by itself, defines a foliation.