Final answer:
Changes in magnetic polarity are used in magnetostratigraphy to date fossils absolutely by correlating paleomagnetic properties with the Geomagnetic Polarity Time Scale. Thermoluminescence is another absolute dating technique that requires high-temperature events to reset the radioactive elements within the material. These methods provide a precise age compared to relative dating techniques.
Step-by-step explanation:
We use changes in magnetic polarity, a method known as magnetostratigraphy, to check the absolute dates assigned to fossils. This involves the study of paleomagnetic properties in sediment cores, which can be correlated to known changes in Earth's magnetic field to determine the sediment's depositional age. The orientation of magnetic minerals in igneous rocks aligns with Earth's magnetic field when they crystallize, a concept that applies to sediments as they are deposited.
Magnetic reversals are well documented on the Geomagnetic Polarity Time Scale (GPTS), which can be used to match the polarity found in sediment layers with known periods of normal and reversed polarity. Whenever the sediment or the fossils within them are exposed to a high-temperature event like volcanic activity, scientists can also apply other absolute dating techniques such as thermoluminescence to find out when the radioactive elements within the material were last reheated.
Relative dating can also be used to understand the sequence of events but does not provide numerical ages. Therefore, absolute dating, which includes techniques that estimate the actual number of years, is more precise and allows us to place fossils within the context of Earth's history in terms of millions or even billions of years.