Geology is the study of the Earth’s composition, structure, processes, and history. It is one of the major Earth sciences, which examine questions relating to the planet Earth. This node will look briefly at some of the major branches of geology: mineralogy, petrology, palaeontology, plate tectonics, geophysics, geochemistry, and planetary and marine geology.
Structure of the Earth
The Earth is made of three main layers: the crust, mantle, and core. The outer solid crust surrounds the mantle, and is between 3 and 6.8 miles thick under the oceans, and 12 to 40 miles thick under the continents.
The mantle makes up the majority of the Earth’s volume and mass, and consists of molten rock 1,802 miles thick.
The Earth’s core is 2,200 miles thick, and is composed mainly of iron, partly liquid and partly solid.
Mineralogy
Mineralogy attempts to describe the
crystal structure,
chemistry, and physical properties of
minerals, including their creation and destruction. Geologists look at certain features of minerals known as
cleavage,
colour,
crystal shape,
fracture,
hardness,
specific gravity,
streak, and
striations.
Petrology
Petrology studies
rocks, which are aggregates of minerals, and the conditions they form in. Petrology focuses its attention on the three types of rocks:
igneous,
metamorphic and
sedimentary rocks.
Paleontology
Paleontology is the study of ancient life on earth, based on
fossils. Physical
anthropology also examines
human fossils and their evolution.
Plate tectonics
The theory of
plate tectonics states that the
lithosphere is divided into plates which interact with each other and float around the planed on the
asthenosphere. This helps explain
continental drift and the
Ring of Fire, which is marked by frequent
earthquakes and
volcanoes.
Geophysics
Geophysics is the science of physics as it applies to geology, and includes the measurement of
seismic movements,
geodesy,
gravity,
magnetism,
electricity,
electromagnetism, and radioactivity.
Geochemistry
In a similar way,
geochemistry is the science of chemistry as it applies to geology. It looks at absolute and relative abundances of the chemical
elements and their
isotopes in the Earth, and also the chemical changes that accompany geologic processes.
Planetary geology
Planetary geology, as its name suggests, involves the study of planets and moons other than the Earth itself, for instance,
Mars,
Venus, and the moons of
Saturn and
Jupiter. Planetary geologists place great emphasis on the results of space probes to provide information.
Marine geology
Marine geology looks in particular at ocean floors and coastlines, and uses geophysics, geochemistry, sedimentology and paleontology to aid its research. Its studies also have links with oceanography and plate tectonics.
Sources:
Hutchison Encyclopedia, Research Machines plc, 2004
New York Public Library Science Desk Reference, Stonesong Press Inc, 1995
Minerals, Rocks, and Fossils, Reed International Books Ltd, 1974