2nd Q: Lesson 2: Absolute vs Relative Dating

Geologists use two main methods to determine when events occurred:

To analyze the exact ages of rocks and fossils, scientists analyze isotopes of radioactive elements.

Atoms of the same element that have a similar number of protons but a different number of neutrons.

is how unstable atoms become stable over time — and this process is what scientists use in absolute dating to determine the age of rocks and fossils.

is a method used to determine the age of once-living things—like plants, animals, or humans—by measuring the amount of carbon-14 (C-14) they contain.

Carbon dating is mainly useful for materials up to __________ years old

It is used to determine whether an object or event is older or younger than other objects or events. Sedimentary rocks are useful in relative dating because it can preserve fossils.

The branch of geology that studies rock layers (strata) and their formation.

a Danish scientist often called the “Father Stratigraphy” He made important contributions to our understanding of how rock layers (strata) and developed the method of stratigraphy.

New rock layers are always deposited on top of existing rock layers. In an undisturbed sequence, older rocks lie at the bottom.

All rock layers are originally laid down (deposited) horizontally and can later be deformed.

Rock layers extend laterally, or out to the sides. Erosion may have worn away some of the rock, but layers on either side of eroded areas will still “match up.”

If rock fragments also known as inclusions are found inside a magma or another rock, the inclusions are older than the surrounding rock.

When a fault or igneous intrusion cuts through other rocks, it must be younger than the rocks it cuts.