Geology (from Greek γη- (ge-, "the earth") and λογος ("logos", "word", "reason")) is the science and study of the solid matter of a celestial body, its composition, structure, physical properties, history and the processes that shape it. In this book, the term Geology will apply to the Earth in particular.
Geology can be split into two main branches: historical and physical. Historical geology attempts to understand the origins, composition, systems and changes of the Earth.
Geology is the study of the things that make up Earth. Geologists have used geology to find out many things about Earth, such as that it is about 4.6 billion years old.
According to the widely accepted Big Bang theory, the Universe began at some point in space and time around 13,700,000,000 years ago, as evidenced by the Doppler effectobserved in all stars and a 3 degree Kelvin background radiation observed elsewhere.
- In about 10E-43 seconds, physics became defined and gravity separated from other forces. The Universe was 10E32 K in temperature.
- At 10E-35 seconds, the Universe expanded to the size of a softball and the strong nuclear force separated. Energy turned into quarks and electrons and their anti-matter counterparts. The temperature was 1027 K.
- At 10E-6 seconds, quarks began to bind into protons and neutrons; matter and antimatter destroyed each other and the balance turned out to be in favor of matter. The Universe was about the size of our solar system and 1013 K hot.
- 1 second after its inception, the electromagnetic and weak nuclear forces appeared as the Universe cooled to 109 K.
- 3 minutes later, protons and neutrons fused into nuclei.
- After 100,000 years, the electrons and the nuclei came together to form atoms; photons separated from matter and there was light.
- In the next 1,000,000,000 years the Universe became clumpy as galaxies began to take shape.
- Ever since then, the Universe has cooled down to 3 K, galaxies have developed, generations of stars have passed, creating heavier elements, and life has appeared. Our galaxy, the Milky Way, contains about 200,000,000,000 stars and lies 1 million light years from its nearest neighbor.
- The solar system was formed around 4,600,000,000 years ago as dust collapsed into the protostar that was to become the Sun, and into planetesimals orbiting it. The inner planets, from Mercury to Mars, are solid because the solar winds have driven gases away and have a core; the outer planets are larger and consist of gas.
Plate Tectonics is a theory that almost all of the world's scientists believe is true. It involves tectonic plates: puzzle-like formations under the Earth's crust that are floating on a layer of magma called the mantle. The mantle is a layer of the earth. The crust is another, it is what we live on. Tectonic plates are part of a layer called the lithosphere. The lithosphere floats on a section of the upper mantle called the asthenosphere. The asthenosphere is a place where hot magma swirls in a convection current. This current causes the movement of the tectonic plates.
Tectonic plates are constantly moving around, colliding, and drifting apart. Sometimes one plate slides under the other. This is called subduction. Divergence means that two plates are sliding apart, and convergence is the opposite. Transform is when the edges of two plates slide along each other. When plates collide, it can cause earthquakes and tsunamis. Volcanoes, however, are more commonly caused by subduction, because when two plates part it allows the magma in the mantle to burst forth.