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.
Chemical sedimentary rocks form when minerals that are dissolved in water become deposited as solids. See miore below. Classification of clastic sedimentary rocks is done according to the size of the sediments that make up the rock. The following table contains the major groups of clastic sedimentary rocks with their characteristics: Chemical sedimentary rocks form from dissolved minerals that are precipitated or separated from water.