Noun. 1. prefrontal cortex-the anterior part of the frontal lobe. prefrontal lobe. cerebral cortex, cerebral mantle, cortex, pallium-the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum. lobe - (anatomy) a somewhat rounded subdivision of a bodily organ or part; ear lobe.refrontal lobe. cerebral cortex, cerebral mantle, cortex, pallium-the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum. lobe - (anatomy) a somewhat rounded subdivision of a bodily organ or part; ear lobe.
1. igneous rocks: formed by the cooling and hardening of magma (molten rock) from inside Earth. 2. sedimentary rocks: formed by the compaction and cementing of layers of sediment (rock fragments, plant and animal remains, minerals from water) 3. metamorphic rocks: formed by the effect of heat and pressure on other rocks. *Earthâs crust is made-up primarily of igneous rocks.
Sedimentary rock is one of the three main rock groups (along with igneous and metamorphic rocks) and is formed in three main waysâby the deposition of the weathered remains of other rocks (known as clastic sedimentary rocks); by the deposition of the results of biogenic activity; and by precipitation from solution.ther examples include stromatolites, and the flint nodules found in chalk (which is itself a biogenic sedimentary rock, a form of limestone). Precipitate sedimentary rocks. Precipitate sedimentary rocks form when mineral solutions, such as sea water, evaporate.