The Pale Blue Dot

There are two things the earth has in rather sharp contrast with the other planets:

• Active Geology which keeps the surface young
• Life (intelligent?)

Undoubtedly the Earth was heavily impacted at the same time the moon was but its surface has been completely reworked since then so there is no evidence for this event.

On average, the current surface of the earth is 500 million years old

The Earth's Surface is kept young by Plate Tectonics and what follows is a primer on how this basic machine works:

Plate Tectonics:

Plate Tectonics means that the crust of the earth is divided into large connected units, all of which are moving relative to one another and colliding with one another in various ways. The idea of Plate Tectonics was first published by the German geologist, Alfred Wegener in 1915 but this theory was largely ridiculed until magnetic mapping of the ocean floor was done in the late 50's. This history of the acceptance of this theory is summarized here .

Summary of Evidence for Plate Tectonics:

• The continents appear that they could fit together like a Jigsaw Puzzle. Just a coincidence?

• Similar fossil records are found in Brazil and North Africa could just mean that the climates and hence vegetation and animal life were similar

• Similar rock types are seen in Brazil and North Africa this is much harder to explain away especially if the ages of the rock types are similar.

• Sea Floor Spreading Magnetic mapping of the ocean floor revealed a history of polarity reversals that formed a mirror image about the Mid-Atlantic Ridge.
  

  This indicates that the floor of the Atlantic Ocean is created at the mid Atlantic ridge due to crustal separation. As magma issues forth and solidifies, it records the orientation of the earth's magnetic field at the time of solidification. These newly formed rocks are then carried either East or West of the Mid-Ocean ridge. The floor of the Atlantic Ocean is thus an Age sequence with newly formed rock appearing at the Mid Atlantic Ridge and the oldest rocks being at the North American and European Coastlines. The time of transport from the mid Atlantic ridge to these coastlines is about 210 million years which indicates a total sea floor motion of about 1.5 inches per year.

Now it is recognized that the surface of the earth can be divided up into roughly 10--12 large scale plates and perhaps a number of smaller ones as in the case of the Pacific Northwest

Plate Tectonics Continued
The basic premise is that 180 million to 200 million years ago, the entire land mass of the Earth was in fact connected. This connected land mass is known as Pangea and is thought to have looked like this:

Over time the plates drifted apart and individual continents gained their identity.

Ultimately leading to the current network of individual plates:

Break up of Pangea

This idea of connected land masses goes a long way in observing various strong similarities in fossil characteristics in now quite disparate locations: