• colonization of the Americas by European explorers and settlers
• invention of the telephone by Alexander Graham Bell
• signing of the Declaration of Independence in the United States
• construction of the Great Wall of China
Event that
Event that
occurred billions
occurred
or millions of years thousands of years
ago
ago
Event that occurred decades ago
carbon dioxide levels reach their highest levels on record
• oxygen builds up in Earth's atmosphere
:: the last Ice Age ended
1 answer