Accessibility Even if plenty of water is provided, there may be other limits to its use, such as the time taken for people to travel and queue to collect it. If it takes more than 30 minutes to collect water, the amount they will collect will reduce (see Figure 9.4).
. See also Geologic(al) time scale (below). Geologic(al) time scale: a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth.
Scientists have put together the geologic time scale to describe the order and duration of major events on Earth for the last 4 1 â 2 billion years. Some examples of events listed on the geologic time scale include the first appearance of plant life on Earth, the first appearance of animals on Earth, the formation of Earth's mountains, and the extinction of the dinosaurs.