Volcanoes played key role in ancient ice age.

• Position: Eruptions

The pivotal role that volcanoes played in a deadly ice age 450,000,000 years ago has been discovered by researchers from Pennsylvania State University, University Park. Perhaps ironically, these volcanoes first caused global warming--by releasing massive amounts of carbon dioxide into the atmosphere. When they stopped erupting, Earth's climate was thrown off-balance, and an ice age began. The discovery underscores the importance of carbon in Earth's climate today.

Previously, scientists linked this same ice age to the rise of the Appalachian Mountains. As the exposed rock weathered, chemical reactions pulled carbon from Earth's atmosphere, causing a global cooling which ultimately killed two-thirds of all species on the planet. Now, researchers have discovered the other half of the story: giant volcanoes that formed during the closing of the proto-Atlantic Ocean--known as the lapetus Ocean --set the stage for the rise of the Appalachians and the ice age that followed. This is the first evidence that a decrease in carbon from volcanic degassing--combined with continued weathering of the Appalachians--caused the long-enigmatic glaciation and extinction in the Ordovician period, explains Lee Kump, professor of geosciences.

Here is the picture the researchers have assembled: 460,000,000 years ago, during the Ordovician, volcanoes along the margin of what is now the Atlantic Ocean spewed massive amounts of carbon dioxide into the atmosphere, turning the world into a hothouse. Lava from those volcanoes eventually collided with North America to form the...