![]() ![]() An image with a more complete timescale is also available, as is more information and references about geologic time scales. SCIENCE Travel Through Deep Time With This Interactive Earth Explore key moments in Earth’s transformative history as continents drift and climate fluctuates over 4.6 billion years Victoria. The scale is broken in the Precambrian because this period is extremely long in duration (it extends from 545 million years ago to over 4.5 billion years ago). The time scale is depicted in its traditional form with oldest at the bottom, and youngest at the top the present day is at the zero mark. ![]() This geologic time scale is based upon data from Harland et al., (1990) and Gradstein and Ogg, (1996). We have a million hypotheses of why this happened, but absolutely none of them are scientific at the moment, Professor Collins says. Absolute time measurements can therefore be used to calibrate the relative time scale, producing an integrated geologic or "geochronologic" time scale that combines both types of data, as is depicted here. The geologic timeline (also called the geologic time scale) is a system of measurement commonly used by earth scientists. It’s only in the last billion years of the Earth’s 4.5-billion-year history that life worked out how to form cells, combine them, and make complicated creatures. Absolute time is the measurement taken from the same rocks to determine the amount of time that has expired. ![]() Relative time is the physical subdivision of the rocks found in the Earth's geology and the time and order of events they represent. "Lunchtime" occurs after "morning" and before "suppertime", but its position in time and its duration can also be measured in hours and minutes, just like the Jurassic Period occurs after the Triassic Period, and before the Cretaceous Period, and spans the time from about 205 million years ago to about 142 million years ago. The two types of geologic time are analogous to the difference between "lunchtime" ("relative time") and the numerical time on a clock, like 12:00pm to 1:00pm ("absolute time"). ![]()
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