Pyroclastic rocks are the product of explosive volcanism. They are often felsic (high in silica). Pyroclastic rocks are often the result of volcanic debris, such as ash, bombs and tephra, and other volcanic ejecta.henocrysts are crystals that are larger than the matrix and are identifiable with the unaided eye. Rhomb porphyry is an example with large rhomb shaped phenocrysts embedded in a very fine grained matrix. Volcanic rocks often have a vesicular texture caused by voids left by volatiles trapped in the molten lava.
July 9, 2014. Frozen sperm must be stored in extremely cold temperatures (-196 F), but in order to ensure that the fewest possible sperm are damaged, the freezing must be gradual. Generally, the following procedure is followed:
It takes approximately 72 days for sperm to mature in the body. During the last 14 days of this process, the sperm are very much alive and swimming. They are alive a long time prior to leaving a manâs body. During freezing, sperm are cooled to a very low sub zero temperature (minus 196 degrees Centigrade). At that temperature, all biological activity is effectively stopped.