The northern flank of the mountain was bulging outward at a rate of more than one meter per day as magma built up inside. By May 18, 1980, the volcano could withstand the pressure no longer. The side of St Helens collapsed in an immense landslide, unleashing the largest explosive eruption in US recorded history.
Amid all the destruction, however, the blast stimulated unheralded interest in eruptions and sparked many careers in volcanology. One of the biggest insights was the lateral blast that occurred when the landslide unroofed the volcano’s highly pressurised magma dome. Before that eruption, scientists had never witnessed the violence of a sideways eruption.
Volcanologists identified distinctive rounded knolls, or hummocks, left behind by the avalanche that started the eruption. Researchers realised that similar deposits elsewhere must have formed in the same way, when the flank of a volcano collapsed. Since 1980, volcanologists have found at least 200 similar deposits worldwide, such as those at Mount Galunggung in Indonesia and at Unzen and Bandai in Japan.
The eruption allowed petrologists to decipher “volcano plumbing,” by using the erupted rock to determine the depth and temperature of the magma reservoir and how quickly magma rose to the surface. The 1980 eruption was not the first time Mount St Helens had lost its top. About 2,500 years ago, the volcano collapsed in another flank failure, and then rebuilt itself over the following 150 years. In September 2004, magma that had lingered underground since the 1980s, began erupting and forming a new dome inside the mountain’s crater. The series of dome-building eruptions continued until January 2008, reconstructing about seven per cent of what was lost in 1980.
Janet Fang,Nature News

Morrocan species linked to Cambrian era
Ever since their discovery in 1909, the spectacular Burgess Shale outcrops in the Canadian Rockies have presented scientists with a cornucopia of evidence for the “explosion” of complex, multicellular life beginning 550 million years ago.
The fossils, all new to science, were at first seen as little more than amazing curiosities from a time when life, except for bacteria and algae, was confined to the sea – and what is now Canada was just south of the Equator. In the last half century, however, paleontologists recognised that the Burgess Shale exemplified the radiation of diverse life forms unlike anything in earlier time.
Here was evolution in action, organisms over time responding to changing fortunes through natural experimentation in new body forms and different ecological niches.
But the fossil record then goes dark: The Cambrian-period innovations in life appeared to have few clear descendants. Many scientists thought that the likely explanation for this mysterious disappearance was that a major extinction had wiped out much of the distinctive Cambrian life.

Not everyone was convinced, however, and now a trove of 480 million-year-old fossils in Morocco appears to strike a blow to the idea of a major extinction.
The international team of scientists who discovered the 1,500 fossils reports in the journal Nature that the large number of “exceptionally preserved” Moroccan species exhibits apparently strong links to Cambrian species known from fossil beds in China, Greenland and, most notably, the Burgess Shale.  
The discovery team’s principal scientist and lead author of the journal article was Peter Van Roy, a Belgian paleontologist.
John Noble Wilford
NYT News Service

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