Relative dating of rock layers epg updating service list
This format is useful, but it tends to conceal the immense span of time, over 85 percent of Earth's history, within the Precambrian.
To see the entire geologic time scale drawn to scale so you can see the divisions of time in their correct proportions, click here.
This image from Lake Mead NRA shows a sequence of sedimentary rock layers.
The oldest layers, Cambrian (570-505 million years ago) are at the base, with younger layers piled on top.
Concealed within the rocks that make up the Earth's crust lies evidence of over 4.5 billion years of time.
The written record of human history, measured in decades and centuries, is but a blink of an eye when compared with this vast span of time.
This time scale, from the Decade of North American Geology, is widely used in North America.
Students not only want to know how old a fossil is, but they want to know how that age was determined.Our app works best with the latest versions of the browsers listed below If you're using an outdated or unsupported browser, some features may not work properly.Microsoft no longer supports Internet Explorer (IE) so it isn't included in the list below.The older layers are lower 'relative' to the younger layers.Long before scientists had developed the technology necessary to assign ages in terms of number of years before the present, they were able to develop a 'relative' geologic time scale.