Explain how Earth has changed over geologic time. Explain how geologists determine the absolute age of rocks. Explain how geologists determine the relative age of rocks. Describe the Law of Superposition. Explain how fossils can be used to date rocks.

Explain how Earth has changed over geologic time?

Eath has changed significantly over the geological time scale both physically and compositionally. Physically, what we see today is different than what was, for example, 335 million years ago. At that time, Earth had only one major continent called Pangaea. But then, the continent started breaking apart and pieces of landmass moved to different directions leading to the formation of 7 continents which we see today.

Secondly, the composition of Earth's material, both within the Earth and in the atmosphere has been changed. Many of the elements were not there when Earth was formed but formed later due to physical and chemical changes. In the context of elemental composition, most of Earth's elements are formed later such as iron. However, there are still some elements such as Uranium are present in the same form, when Earth was formed. Accordingly, many compounds are formed due to weathering and other processes that were not there before.

Explain how geologists determine the absolute age of rocks?

Geologists measure the age of rocks via age dating procedure. Further, there are two types of age dating namely absolute dating and relative dating. They are often studied in the discipline called stratigraphy. In stratigraphy, the layering of Earth is studied. Older layers are deposited below the newer layers. In these layers, some of the elements are radioactive whose half-life is known to scientists. So, they can easily trace back when this layer would have been formed. In absolute dating, geologists can estimate the exact age of the rock, however, in relative dating, geologists cannot exactly tell the age of the rock but can tell that this rock must have been developed between this and that age.

Describe the Law of Superposition?

The law of superposition says that the younger layer of rocks is always on top of the older layer, which is below the younger layer. This is because of the natural deposition process. The deposition of sediments takes place in each age. Newer material will come later so it will be on top of the layer. These studies come in the field of stratigraphy.

Explain how fossils can be used to date rocks?

Fossils are proxy to learn the age of rocks. Precisely, if we manage to learn that an "organism A" was only present during the "age X" only, then anywhere in the world, if we found the fossil of that organism, the layer age will be the same. For example, dinosaurs lived the Earth's biosphere 252 million years ago to about 66 million years ago. Therefore, if we found the fossils of dinosaurs, we are sure that the age of that particular rock or sediment layer is between 252 million years ago to about 66 million years ago. To understand the age of fossil more precisely, we can conduct further dating experiments based on isotopes or radioactive materials.