SEDIMENTARY ROCKS ARE FORMED BY THE ACCUMULATION and consolidation of sediments. There are three main types of sedimentary rock. Clastic sedimentary rocks, such as breccia or sandstone, are formed from other rocks that have been broken down into fragments by weathering, which have then been transported and deposited elsewhere. Organic sedimentary rocks—for example, coal—are derived from plant and animal remains. Chemical sedimentary rocks are formed by chemical processes. For example, rock salt is formed when salt dissolved in water is deposited as the water evaporates. Sedimentary rocks are laid down in layers, called beds or strata. Each new layer is laid down horizontally over older ones. There are usually some gaps in the sequence, called unconformities. These represent periods in which no new sediments were being laid down, or when earlier sedimentary layers were raised above sea level and eroded away.
Sedimentary rocks
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GEOLOGY AND GEOGRAPHY AND METEOROLOGY
published on 5:45 AM
SEDIMENTARY ROCKS ARE FORMED BY THE ACCUMULATION and consolidation of sediments. There are three main types of sedimentary rock. Clastic sedimentary rocks, such as breccia or sandstone, are formed from other rocks that have been broken down into fragments by weathering, which have then been transported and deposited elsewhere. Organic sedimentary rocks—for example, coal—are derived from plant and animal remains. Chemical sedimentary rocks are formed by chemical processes. For example, rock salt is formed when salt dissolved in water is deposited as the water evaporates. Sedimentary rocks are laid down in layers, called beds or strata. Each new layer is laid down horizontally over older ones. There are usually some gaps in the sequence, called unconformities. These represent periods in which no new sediments were being laid down, or when earlier sedimentary layers were raised above sea level and eroded away.
