Relative dating for geological purposes validating strong passwords perl
On other solid-surfaced worlds -- which I'll call "planets" for brevity, even though I'm including moons and asteroids -- we haven't yet found a single fossil.
Something else must serve to establish a relative time sequence. Earth is an unusual planet in that it doesn't have very many impact craters -- they've mostly been obliterated by active geology.
Major boundaries in Earth's time scale happen when there were major extinction events that wiped certain kinds of fossils out of the fossil record.
This is called the chronostratigraphic time scale -- that is, the division of time (the "chrono-" part) according to the relative position in the rock record (that's "stratigraphy").
That's why geologic time is usually diagramed in tall columnar diagrams like this.Venus, Io, Europa, Titan, and Triton have a similar problem.On almost all the other solid-surfaced planets in the solar system, impact craters are everywhere. We use craters to establish relative age dates in two ways.The more fossils you find at a location, the more you can fine-tune the relative age of this layer versus that layer.Of course, this only works for rocks that contain abundant fossils.
When you talk about the Precambrian, Paleozoic, Mesozoic, and Cenozoic on Earth, or the Noachian, Hesperian, and Amazonian for Mars, these are all relative ages.