Mountains have been built and eroded, continents and oceans have moved great distances, and the Earth has fluctuated from being extremely cold and almost completely covered with ice to being very warm and ice-free.These changes typically occur so slowly that they are barely detectable over the span of a human life, yet even at this instant, the Earth's surface is moving and changing.
The topic covered was stratigraphy and relative dating, so we covered many key geological concepts including the principle of unifominitarianism, cross-cutting relationships, original horrzontality, and the principle of superposition.
Just as when they were deposited, the strata are mostly horizontal (principle of original horizontality).
The layers of rock at the base of the canyon were deposited first, and are thus older than the layers of rock exposed at the top (principle of superposition).
Numerical ages estimate the date of a geological event and can sometimes reveal quite precisely when a fossil species existed in time.
Third, magnetism in rocks can be used to estimate the age of a fossil site.