What is a timeline? Objective Students will be able to construct a timeline. Students will begin to comprehend the magnitude of geologic time. Background The Earth is about 4.5 billion years old, a number too large for people to conceptualize. If we were to shrink the Earth down to the size of a basketball and compress those 4.5 billion years into a few hours we would be able to observe radical changes. Continents would race around the globe, sink beneath the sea, rise up again, smash into other continents, build mountains, and erode back into the sea. Volcanoes would continually erupt and the Duration: 90 Minutes.