Mount's Etna's busy pace produces enough lava each year to fill Chicago's Willis Tower (the former Sears Tower), a 2012 study found.Whether it's a few fast-flowing lava flows or a fiery fountain, the volcano's outbursts have been a constant companion for Sicilians for more than 2,000 years.Yet geoscientists are still trying to figure out why Etna erupts so frequently, and in so many different ways.Nearly every kind of eruption has appeared at Etna over the millennia — quiet lava streams, sputtering fire fountains and even deadly pyroclastic flows, the superheated mix of ash, lava fragments and gases that race down steep volcanic slopes.The volcano erupted again this past weekend, tossing lava bombs that looked like fireworks from afar.The blast from Etna's New Southeast Crater is the latest in a string of spectacular eruptions.
Critical to these dating methods is the assumption that there was no radiogenic argon ( Hualalai basalt, Hawaii (AD 1800-1801) 1.6±0.16 Ma; 1.41±0.08 Ma Mt. Stromboli, Italy, volcanic bomb (September 23, 1963) 2.4±2 Ma Mt.
Why does the lava dome provide an opportunity to test the accuracy of radioisotope dating? First, radioisotope dating methods can be used mainly on volcanic (igneous) rock, such as dacite.
(Fossil-bearing sedimentary rock cannot be directly dated radioisotopically.) Second, the date of formation of the dacite is known.
It is composed of a volcanic rock called dacite and appears to an observer in the crater as a huge steaming mound of dark, blocky rubble. Helens is the third dome to form since the 1980 eruption, the first two having been blasted away by subsequent eruptions.
The current dome started to form after the volcano's last explosive eruption on October 17, 1980.