Geologic Time - Short Lecture 7 Notes 1G03 Relative Dating: events are arranged in order of occurrence but it does not tell the actual age of the event. Key principles include: ● Law of Superposition: as regards the geological strata, the oldest ones are always at the bottom provided they have not been shifted by tectonic force at some time in the past. ● Principle of Original Horizontality: Originally, sediment layers are in the horizontal plane due to the forces exerted by the deposits that create a homogenous layer on the base of the new layer of deposit. ● Cross-Cutting Relationships: The feature which cuts another is generally younger than the feature that has been cut. ● Faunal Succession: The fossil organisms are thereby suppositional to shift one after the other in a definite and recognizable manner. Absolute Dating: the absolute dating gives an actual date or even a range of the age in calendar years for layers of rocks or fossils. Methods include: ● Radiometric Dating: Uses the amount of currently existing radioactive isotopes like carbon-14 to calculate age. ● Dendrochronology: Application of tree ring in dating events and changes in the environment. ● Thermoluminescence: Measures the total radiation dose that is received by a material to the dated objects. Evolution of Earth's Landscapes ● Over millions of years, Earth's landscapes have undergone significant transformations due to various geological processes: 1. Plate Tectonics: Continental drift and sea floor spreading is a phenomenon that leads to the changes in the continents and ocean floor. 2. Weathering and Erosion: Quarrying erodes down rocks and minerals and dismantles them sculpt landscapes. 3. Volcanism: Creation of new geoforms as a result of eruptions of volcanoes. 4. Glaciation: Glaciers are engaged in the process of creating and contouring valleys and mountains. - The rocks bear a lot of information about the various ages that have passed and the activities that have taken place, the same activities that are bound to happen in future.