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 form from melted rock, called magma. On the surface of the Earth, igneous rocks usually occur in a cooled state, except where molten rock is erupting from an active volcano.Magma that flows out onto the Earth's surface is called lava. Rocks that crystallize quickly from cooling lava at or near the Earth's surface are called volcanic rocks-no surprise.gneous rocks form from melted rock, called magma. On the surface of the Earth, igneous rocks usually occur in a cooled state, except where molten rock is erupting from an active volcano.