1. Lesson 4 – Geological Timescale

2.  The Grand Record  The largest defined unit of time is eons. Eons are divided into eras, which are in turn divided into periods, epochs and ages.  Geological Time Record is in your data booklet on page 4.  Geological Time Scale is broken into 4 major era’s that show major shifts in the fossil record. You are responsible for knowing the major events that occur in these :  Precambrian, Paleozoic, Mesozoic, Cenozoic  Look at page 312 for more info.

3.  The geologic time scale is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth.  Evidence from radiometric dating indicates that the Earth is about 4.570 billion years old. The geological or deep time of Earth's past has been organized into various units according to events which took place in each period. Different spans of time on the time scale are usually delimited by major geological or paleontological events, such as mass extinctions.

5. Palezoic Era  Followed the Precambrian. Before now, mostly bacteria and worms…  First major event was the Cambrian Explosion!  Oxygen levels now reaching adequate levels to support life.  Signals a wide-variety of animals, insects in the fossil record.  About 20 million years in length (short time… relative)  Many of the organisms living today share common ancestors found in the fossil record from the Cambrian explosion.

6. Cambrian Explosion  Sudden appearance of fauna  Fauna – all the animal life in a particular region.  Some of the organisms that appeared  Arthropods with an exoskeleton  Crustaceans  Vertebrates and invertebrates (backbone)

7.  Some of the best evidence from the Cambrian Explosion is from the _____________________________________ ________________________ found in British Columbia. More on this can be found on p. 333 of your textbook.  Shale - Shale is a clay stone that splits into layers. Shale is usually soft and does not crop out unless harder rock protects it. Video

8.  BEFORE WE CAN TALK ABOUT WHAT HAPPENS NEXT WE HAVE TO TALK ABOUT PLATE TECTONICS… BECAUSE THE CONTINENTS MOVE!