Geologists define an ice age as a period when more of the Earth’s surface was covered by larger ice sheets than in modern times, or when cool temperatures endured for extended periods of time, allowing the polar ice to advance into lower, more temperate latitudes. The last ice age event, which ended about 12,000 years ago, is referred to as the “Ice Age” or the “Great Ice Age”—both usually capitalized—a time when ice covered nearly 32 percent of the land and 30 percent of the oceans.