history of earth

Question 1

eon

Answer 1

longest time unit, measured in billions of years

Question 2

era

Answer 2

measured in hundreds of millions of years

Question 3

period

Answer 3

measured in tens of millions of years

Question 4

epoch

Answer 4

measured in millions of years

Question 5

hadeon eon

Answer 5

happened 4.6 billion years ago to 4 billion years ago. during this eon, the earth formed the solar nebula.

Question 6

archeon eon

Answer 6

happened 4 billion years ago to 2.5 billion years. the early earth cooled, oceans formed, and the first continents emerged.

Question 7

proterozoic eon

Answer 7

happened 2.5 billion years ago to 541 million years ago. oxygen levels in the atmosphere increased significantly due to photosynthesizing organisms.

Question 8

phanerozoic eon

Answer 8

happened 541 million years ago to the present time. this eon is marked by the proliferation of life and the appearance of visible (phanerozoic) life forms.

Question 9

paleozoic era

Answer 9

happened 541 million years ago to 252 million years ago. characterized by the cambrian explosion, a rapid diversification of life.

Question 10

mesozoic era

Answer 10

happened 252 million years ago to 66 million years ago. often called the “age of the dinosaurs”, as they dominated the land.

Question 11

the end of mesozoic era

Answer 11

the mesozoic era ended with the cretaceous-paleogene extinction event, leading to the death of the dinosaurs.

Question 12

cenezoic era

Answer 12

happened 66 million years ago until the present time. characterized by the rise of mammals and the evolution of modern ecosystems

Question 13

epoch within cenezoic era

Answer 13

the pleistocene epoch is known for ice ages and the emergences of homo sapiens (modern humans)

Question 14

the three eras of the phanerozoic eon

Answer 14

paleozic, mesozoic, and ceneozoic