Question

1. according to the diagram, all of geologic time is divided into four large units called eras. list the four eras in order from the one that is most recent to the one that occurred farthest back in time.

__________ (most recent)
__________
__________
__________ (farthest back in time)

1. which of the eras lasted for the longest period of time? __________

how long did it last? __________

1. which era covers the shortest length of geologic time? __________
2. what time era do we live in? ________ when did it start? ________
3. when did the mesozoic era begin? ________ when did it end? ________

how long did it last? ________ what type of animal lived only during the mesozoic era? ________

Explanation:

1. Geologic eras ordered from most recent to oldest follow the standard geologic time scale.
2. The Precambrian is the longest era, spanning most of Earth's early history.
3. The Cenozoic is the shortest era, representing the most recent period of Earth's history.
4. Humans currently live in the Cenozoic Era, which began after the mass extinction of dinosaurs.
5. The Mesozoic Era is known as the "age of dinosaurs," with defined start/end dates and duration calculated by subtracting the start from end year.

Answer:

1.

• Cenozoic (most recent)
• Mesozoic
• Paleozoic
• Precambrian (farthest back in time)

2.

• Precambrian
• ~4 billion years (from ~4.6 billion years ago to ~541 million years ago)

1. Cenozoic

4.

• Cenozoic
• ~66 million years ago

5.

• ~252 million years ago
• ~66 million years ago
• ~186 million years (252 - 66 = 186)
• Dinosaurs (non-avian dinosaurs)