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.
Most of these eruptions resulted in the building up of the lava dome on Mount St. Helens' summit crater. In 2005 however, Mount St. Helens erupted a 36,000 foot (11,000 m) plume of ash and steam. A minor earthquake accompanied this event. Since these events ash and steam have been visible on the mountain several times in recent years.