Geological time

Earth’s history of 4.6 billions of years spans from Earth’s formation through the beginning of plate tectonics to the many active geological processes today. We will only be able to understand Earth’s evolution if we can place these geological processes in chronological order.

Many different dating methods exist. Some provide relative ages, while others provide absolute ages. The most commonly used absolute dating methods are based on the radioactive decay of chemical elements.

Parent nuclides decay to form daughter products. When we know how quickly this decay process occurs, the parent-daughter relationship will give us the time elapsed after a certain geological event, such as a volcanic eruption, the formation of an ore body, or the break-up of a continent. These methods are commonly referred to as geochronological methods. Thermochronological methods are related to this and provide information on the temperature history. Temperature increases with depth in the Earth, and knowledge of the temperature history of a rock provides information about how much erosion has taken place, how deep it was buried, and the potential for oil and gas in a particular geological formation.

Paleomagnetism and mineral magnetic data from igneous and sedimentary rocks and unconsolidated sediments enable us to reconstruct the direction, polarity and intensity of the past Earth's geomagnetic field. From these data we can reconstruct a continent's journey through geological time and determine the ages of rocks and geological events.

In the NGU labs we apply a range of dating techniques to determine ages which are then used in our mapping and research activities.