The yarn number is the length in yards of one pound of the yarn, divided by 1600. Symbol Nar. This is the same as the weight in ounces of 100 yards. So one pound of number 1 run yarn is 1600 yards long, one pound of number 2 run yarn is 3200 yards long, and so on.
As with most other volcanoes in the Cascade Range, Mount St. Helens is a large eruptive cone consisting of lava rock interlayered with ash, pumice, and other deposits. The mountain includes layers of basalt and andesite through which several domes of dacite lava have erupted.
OVERVIEW. The 1980 eruption of Mt. St. Helens is the most studied volcanic eruption of the twentieth century. Although most people were unaware of the potential for such a violent display of volcanism in the contiguous U.S., volcanologists were keenly aware of the potential danger.onths before it erupted, the U.S. Geological Survey (USGS) established a base of operations at Vancouver, Washington to monitor the volcano. On May 18, survey volcanologist David Johnston was camping on Coldwater Ridge, only a few miles north of Mt. St. Helens.