LONDON — As volcanic ash cast a shadow over millions of lives, Londoners and other city dwellers across Europe were treated to a rare spectacle of nature: Pristine, blue skies brighter than any in recent memory.

U.S. President Barack Obama joins Martha Coakley

Volcanic cloud over Europe highlights vulnerabilities of interwoven world

Volcanic cloud casts pall over interwoven world

Volcanic ash spreading slowly over northern Europe and Russia; no telling how far it will go

Volcanic ash spreads high over Europe, Russia

Seismic activity drops after day of shallow quakes at Alaska volcano Mount Redoubt

Earthquake activity lessens below Alaska volcano

Alaska volcano could be waking up, as seismic swarm occurs near summit of Mount Redoubt

Swarm of small quakes occurring at Alaska volcano

Alaska volcano could be waking up, small earthquakes occurring near summit

Small earthquakes occurring on Alaska volcano

Iceland volcano draws hikers, tourists despite lava flow and opening of second fissure

Iceland volcano draws hikers despite lava flow

Swedish tourist falls into active volcano crater on Bali; rescuers try to recover body

Tourist falls into active volcano crater on Bali

Scientists fear larger volcanic eruption in Iceland could bring global consequences

Iceland’s eruptions could have global consequences

Scientists to fly over Icelandic volcano to evaluate eruption; flights return to normal

Scientists to evaluate Icelandic volcano eruption

Volcano erupts in Iceland, hundreds evacuated; scientists wary of larger eruption

Iceland fears 2nd, even larger volcanic eruption

Volcano erupts in Iceland, hundreds evacuated, air travel disrupted

Air travel to Iceland disrupted by volcano

Volcano erupts in Iceland, first at Eyjafjallajokull glacier since 1820s; US flights diverted

Volcano erupts in Iceland; US flights diverted

Volcano erupts in Iceland, first at Eyjafjallajokull glacier since 1820s; hundreds evacuated

Volcano erupts in Iceland, hundreds evacuated

Volcano erupts in southern Iceland; hundreds evacuated

Volcano erupts in southern Iceland

REYKJAVIK, Iceland — Authorities evacuated hundreds of people after a volcano erupted beneath a glacier in southern Iceland, Iceland’s civil protection agency said Sunday.