Scientists use the geologic time scale to illustrate the order in which events on Earth have happened. ... They used relative dating to divide Earth's past in several chunks of time when similar organisms were on Earth. Later, scientists used absolute dating to determine the actual number of years ago that events happened.
Earth and its atmosphere are continuously altered. Plate tectonics shift the continents, raise mountains and move the ocean floor while processes not fully understood alter the climate. Such constant change has characterized Earth since its beginning some 4.5 billion years ago.
Water is something that is dependent on amongst living things. Without the water cycle, there wouldn't be a source of water and living things wouldn't be able to survive.
