If you had the chance to go skiing or hiking during the holiday period, did you ever stop and wonder where the rocks that form our planet’s magnificent mountain ranges come from? While some of the rocks covering the earth’s land surface were created by volcanic eruptions, up to 73% originated in the oceans in a relatively slow but perpetual process called sedimentation1. Sedimentation is the accumulation of biological detritus and particles like gravel, sand and clay, which themselves originate from the slow breakdown (erosion) of continental rocks, at the seabed. Over millions of years, the accumulated sediments form thick layers, which become buried and consolidated to form sedimentary rocks. As the tectonic plates of the earth collide, these buried rock layers get pushed up to form mountain ranges and the process of erosion and sedimentation starts anew.
Sedimentation takes place across the entire ocean and other bodies of water but the rate at which sediments accumulate differs greatly from place to place. While in the deep ocean, far away from the continents, the sediment accumulation rate is no more than a few millimetres per hundreds of years2, coastal regions have higher rates up to several centimetres per year. Accumulation rates are especially high near the mouths of rivers which transport large amounts of sediments from the hinterland to the sea. Knowledge on the sediment accumulation rates in a specific area is important for the maintenance of shipping lanes and the stability of offshore constructions like wind farms or oil platforms.
The map of the week features the seabed sediment accumulation rates at different locations in European waters. The rates were determined by careful dating of the sediment or estimated from acoustic-seismic and sediment core data.
The data in this map were provided by EMODnet Geology.