Absolute age dating — 3. Geological time scale — 4. Geological maps. It may surprise you to learn that geologists were able to determine much of the history of the Earth and its life without knowing anything about the actual ages of the rocks that they studied.
Earth Science: Geologic Ages and Dating Techniques
1. Relative age dating | Digital Atlas of Ancient Life
Something that we hope you have learned from these lessons and from your own life experience is that the laws of nature never change. They are the same today as they were billions of years ago. Geologists always use present-day processes to interpret the past. If you find a fossil of a fish in a dry terrestrial environment did the fish flop around on land? Did the rock form in water and then move?
5 Key Principles of Relative Dating in Geology
Stratigraphic Superposition Picture on left: In places where layers of rocks are contorted, the relative ages of the layers may be difficult to determine. View near Copiapo, Chile. At the close of the 18th century, careful studies by scientists showed that rocks had diverse origins. Some rock layers, containing clearly identifiable fossil remains of fish and other forms of aquatic animal and plant life, originally formed in the ocean. Other layers, consisting of sand grains winnowed clean by the pounding surf, obviously formed as beach deposits that marked the shorelines of ancient seas.
While true, fossils are buried with plenty of clues that allow us to reconstruct their history. In , in Ethiopia's Afar region, our research team discovered a rare fossil jawbone belonging to our genus, Homo. To solve the mystery of when this human ancestor lived on Earth, we looked to nearby volcanic ash layers for answers. Working in this part of Ethiopia is quite the adventure.