Our planet has experienced six ice ages in the last billion years. The first two at about 800 and 600 million years ago may have covered all or most of the earth in ice and is referred to as the “Snowball Earth.” The most recent Pleistocene ice age, perhaps not done, involved over 16 glacial cooling and warming events over the past 2.5 million years.

Geologist James Lawford Anderson of the Department of Earth and Environment at Boston University will speak on Wednesday, November 30 from 7 – 8:30 at the Hunnewell Building of the Arnold Arboretum, 125 Arborway, about various ice ages, today’s climate, and end his lecture with Boston’s glacially-influenced earthquake problem. $5, free for Arnold Arboretum members and students. Register at www.my.arboretum.harvard.edu or call 617-384-5277. Image from www.air-worldwide.com.