The earth is over 4.5 billion years old1 while humans are estimated to only have been around for the last 3.8 million years2 and recorded history only goes back to about 6 thousand years3. In order to learn about the majority of earth’s history and the evolution of life, geologist look for clues in the rocks that make up our planet.
Igneous or magmatic rocks form by solidification of magma derived from the earth’s interior, which reaches the surface in volcanoes and at the mid-oceanic ridges. Along these ridges, the earth’s tectonic plates slowly move away from each other, causing the rocks at the ocean floor to gradually become older away from the mid-ocean ridges. In contrast, sedimentary rocks form through the gradual accumulation of sediment particles like gravel, sand and clay as well as shells and other biological debris in the earth’s ocean, seas, lakes and rivers. Over time, these rock layers pile up, recording the earth’s history and the evolution of life within the particles and fossils they contain.
The description of the successions of rock layers is called stratigraphy. Based on the stratigraphy of the earth, geologists have subdivided its history in a system of hierarchical time periods known as the Geological Time Scale. The primary division of geological time are the “eons”, which are further subdivided into “eras” (e.g. the Mesozoic era also known as the age of the dinosaurs), “periods”, “epochs” and “ages”. Time periods at the “age” level are commonly named after a place on earth where rocks of this age were first discovered or are very common. This map of the week features the stratigraphy of the European sea-floor at the age level. Have a look and discover the age of the rocks at your nearest coast, you may be able to find dinosaurs or other fossils.
The data in this map were provided by EMODnet Geology.