A short dictionary of terms used in this blog. 

Earth science (also known as geoscience, the geosciences or the Earth Sciences), is an all-embracing term for the sciences related to the planet Earth. It is arguably a special case in planetary science, the Earth being the only known life-bearing planet. There are both reductionist and holistic approaches to Earth science. The major historic disciplines use physics, geology, geography, meteorology, mathematics, chemistry and biology to build a quantitative understanding of the principal areas or spheres of the Earth system.

Geology (from Greek: γη, gê, "earth"; and λόγος, logos, knowledge, "speech" lit. to talk about the earth) is the science and study of the solid matter that constitutes the Earth. Encompassing such things as rocks, soil, and gemstones, geology studies the composition, structure, physical properties, history, and the processes that shape Earth's components.

Petrology (from Greek: πέτρα, petra, rock; and λόγος, logos, knowledge, "speech") is a field of geology that focuses on the study of rocks and the conditions on which they form. The word lithology once was approximately synonymous with petrography, but today lithology is essentially a subdivision of petrology focusing on macroscopic hand-sample or outcrop-scale description of rocks. There are three branches of petrology, corresponding to the three types of rocks: igneous, metamorphic, and sedimentary. Petrology utilizes the classical fields of mineralogy, petrography, optical mineralogy, and chemical analyses to describe the composition and texture of rocks. Modern petrologists also include the principles of geochemistry and geophysics through the studies of geochemical trends and cycles and the use of thermodynamic data and experiments to better understand the origins of rocks.

Mineralogy is an Earth Science focused around the chemistry, crystal structure, and physical (including optical) properties of minerals. In short, The study of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.

A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties. A rock, by comparison, is an aggregate of minerals and need not have a specific chemical composition. Minerals range in composition from pure elements and simple salts to very complex silicates with thousands of known forms. There are over 4000 known types of minerals. 

Paleontology, palaeontology or palæontology (from Greek: παλαιό (palaeo), "old, ancient"; όν (on), "being"; and logos, knowledge, "speech") is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised faeces (coprolites), palynomorphs and chemical residues. Studies of prehistoric hominins, their culture and their behaviour are the purview of two other disciplines, archaeology and paleoanthropology. (But the exact divisions between the different sciences varies from country to country). Many people confuse archaeology with paleontology and vise versa.

Ma (as in 435 Ma for example) means Mega anno. Millions of years. Ga means Giga anno. Billions of years.