1. 6.5 Time Marches On Pages 151-155 12-16-14

2.  Rock layers form oldest on the bottom first, newest on top, so as you go down you go back in time.

3.  Geologic Column is an ideal sequence of rock layers that contain all the known fossils and rock formation on Earth arranged from oldest to youngest.

4.  Geologic Time Scale: divides Earth’s 4.6 billion year history into distinct intervals of time.

5.  Eons are the largest divisions of time.  Eons are divided into four eras.  Eras are divided into periods.  Some periods are divided into epochs.

6.  4.6 billion years ago – 3.8 billion years ago  The only rocks that scientists have found from this eon are meteorites and rocks from the moon.

7.  3.8 billion years ago – 2.5 billion years ago  The earliest known rocks on Earth formed during this eon.

8.  2.5 billion years ago – 540 million years ago  The first organisms with well-developed cells appeared during this eon.

9.  540 million years ago – present  The rock and fossil record mainly represents the Phanerozoic eon.  This is the eon in which we live.

10.  The Phanerozoic Eon is divided into three eras and spans 540 mya to present.

11.  “Old life” from 540 to 248 mya and the first era that is well represented by fossils.  Beginning with no land organisms ending with as mass extinction of the amphibians and insects that had moved onto the land.

12.  “Middle-Life” from 248-65 mya, the age of the reptiles.  Dinosaurs dominated the Earth and birds and small mammals began to evolve, ending with 50% of all species becoming extinct.

13.  “Recent Life” mya to the present.  We live in the Cenozoic era, and other mammals are abundant.  Many mammals that once lived in this era are now extinct.

14.  Humans appear in the last second!

16.  The Colorado River has cut the canyon exposing rock layers that represent nearly 2 billion years of geologic time.

17.  Extends the geologic time scale  Include Zion Canyon and Bryce Canyon

19.  OUT: What future event will mark the end of the Cenozoic era?