So we expect that the description of the velocities of molecules in a gas will in fact be the most probable distribution, since we are dealing with particle numbers in the range of Avogadro's number. But this most probable distribution (the Maxwell-Boltzmann distribution) is subject to constraints, namely that the number of particles is constant and that the total energy is constant (conservation of energy).
The oldest rocks are metamorphic gneisses which are to be found on Inishtrahull, several miles off Malin Head in Co. Donegal, and elsewhere in the north-west. They originally formed as igneous rocks 1750-1780 million years ago.
Igneous Rocks. Igneous Rocks are rocks that have crystallized from molten rock, or magma. Magma is generated in the subsurface where it may solidify to form a plutonic rock, such as granite. The magma may also rise to the surface and erupt out of a volcano or volcanic fissure to form a volcanic rock, such as basalt.Igneous rock composition. Magma has a range of composition that is dominated by the elements silicon and oxygen, or silica (SiO 2).agma is generated in the subsurface where it may solidify to form a plutonic rock, such as granite. The magma may also rise to the surface and erupt out of a volcano or volcanic fissure to form a volcanic rock, such as basalt.