Time Scale Vocabulary Eon: the largest division of geologic time, comprising two or more eras. Era: a period of time marked by distinctive character, events, etc. Period: a rather large interval of time that is meaningful in the life of a person, in history, etc., because of its particular characteristics: Epoch: the beginning of a distinctive period in the history of anything:

Open the link to view another time line http://leonids

And it begins

4600 million years ago: Earth Forms ~ 4.6 Billion Years Ago – collisions in the giant discs-haped cloud of material that also formed sun. ~ Gravity pulling gas and dust together made small planetesimals.

Objects collided repeatedly gradually getting bigger….building planets

4500 millon years ago The moon forms Most widely accepted theory is formation right after Earth. An object the size of mars struck Earth. This planet is Theia. It was partially absorbed by Earth. Large portion of debris sprayed out, gravity pulled debris into orbit around Earth in a ring Moon formed as clumps of debris grew together. Rock samples gathered by astronauts support this “Giant Impact Hypothesis”

Theiaa Earth

The Moon The same material that formed Earth also formed the Moon. Because of this there are traces of water found on the moon. For every 1 ton of lunar surface, will hold 32 oz of water. This opens up possibilities to retrieve water from new source.

Debris from Earth and Theia

Why is the moon not like us….. ~ Small to know metallic core ~ Could not hold atmosphere because there is no magnetic field. ~ With no atmosphere, the terrain is constantly being bombarded with solar winds - radiation

3800 The Late Heavy Bombardment Ends Comet and asteroid bombardment peppered all the planets. Many craters developed on the moon. These are not visible on the Earth because of tectonic plate movement erased all evidence over time…… But this is how water came to our planet.

2400 Early Life: Oxygen Enters the atmosphere Early Bacterial life introduced Oxygen being produced in water. Dissolved into iron rich ocean water, when water becomes full of oxygen, it begins to form an atmospheric layer around Earth.

650 Snowball Earth Entirely or wholly covered in ice pole to tropics. Pre-Cambrian – possible for this to have occurred more than once Life could only cling on in ice-free refuges, or where sunlight can penetrate to photosynthesis.

545 Life Explodes Cambrian – life more abundant and diverse. Fossils in pre-cambrian rocks are simple like bacteria. More complex soft bodied creatures Cambrian rocks show large number of different types of animals many with hard shells.