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 are commonly classified by their composition and texture. Most are composed of the eight most abundant elements in the Earth's crust. Because of the dominance of oxygen and silicon in the crust, igneous rocks are mostly made up of silicate minerals.These silicates can be generally divided into light and dark silicates.lements Abundant in Igneous Rock. Eight elements make up about 98% by weight of most magmas from which igneous rocks are made. Click on any element for further details. The dominance of oxygen and silicon in the Earth's crust gaurantees that most igneous rocks are made up of silicate minerals.