Younger than the rock it intrudes into
The constituent time segments are epochs and periods, which are further divided into ages.
They had little competition from other land dwellers
Deformation
meteorite collision
Uniformitarianism
Based on the popular theory that the dinosaurs went extinct due to the impact of a large asteroid, scientists think that the asteroid caused large amounts of debris to fly into the atmosphere, blocking out the sun. This caused global temperatures to drop, thus freezing the plants. In addition, without the sun the plants could not carry on photosynthesis, which caused them to die.
The folding or tilting of rocks, followed by renewed deposition, has to occur to create an angular unconformity.
It enlarges continental landmasses and forms mountains along the edges of continents.
The boundaries of history of eras are marked by great worldwide changes in continental coastline