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Classroom Rock Collection A comprehensive collection of 36 different sedimentary, metamorphic and igneous rocks.
So, you just arrived for your first day of Geology grad school. Welcome to the next 2-10 years of your life! Your program may be a major research department with 40 faculty members, or a small liberal arts schools with a little-used MS degree.
It's Still a Good Time to Be a Geologist!
Definition of Geology: Geology is the study of the Earth, the materials of which it is made, the structure of those materials, and the processes acting upon them.
About USGS The USGS is a science organization that provides impartial information on the health of our ecosystems and environment, the natural hazards that threaten us, the natural resources we rely on, the impacts of climate and land-use change, and the core science systems that help us provide timely, relevant, and useable information. Mission
Travis Gibson Hydrological Technician “Working as a student for the USGS is an excellent way for anybody interested in working in a science field to “get their foot in the door“”
Every year in the United States, natural hazard events threaten lives and livelihoods, resulting in deaths and billions of dollars in damage. The USGS works with many partners to monitor, assess, and conduct targeted research on a wide range of natural hazards so that policymakers and the public have the understanding they need to enhance preparedness, response and resilience. In 2010, the USGS realigned its organizational structure around the missions identified in the USGS Science Strategy .
Geology (from the Greek γῆ, gê , "earth" and λόγος, logos , "study") is the science comprising the study of solid Earth , the rocks of which it is composed, and the processes by which they change. Geology can also refer generally to the study of the solid features of any celestial body (such as the geology of the Moon or Mars ). Geology gives insight into the history of the Earth , as it provides the primary evidence for plate tectonics , the evolutionary history of life , and past climates .
This clock representation shows some of the major units of geological time and definitive events of Earth history. The Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga ( billion years ago). [ 1 ] Other subdivisions reflect the evolution of life; the Archean and Proterozoic are both eons, the Palaeozoic, Mesozoic and Cenozoic are eras of the Phanerozoic eon. The two million year Quaternary period, the time of recognizable humans, is too small to be visible at this scale. The geologic time scale is a system of chronological measurement that relates stratigraphy to time, and is used by geologists , paleontologists , and other earth scientists to describe the timing and relationships between events that have occurred throughout Earth's history .
"Rocks", "Stone", and "The Stone" redirect here. For other uses, see Rock (disambiguation) , Stone (disambiguation) , and The Stone (disambiguation) , respectively. In geology , a rock is a naturally occurring solid aggregate of one or more minerals or mineraloids . For example, the common rock, granite , is a combination of the quartz , feldspar and biotite minerals.
The rock cycle is a fundamental concept in geology that describes the dynamic transitions through geologic time among the three main rock types: sedimentary , metamorphic , and igneous . As the diagram to the right illustrates, each of the types of rocks are altered or destroyed when it is forced out of its equilibrium conditions. An igneous rock such as basalt may break down and dissolve when exposed to the atmosphere , or melt as it is subducted under a continent . Due to the driving forces of the rock cycle, plate tectonics and the water cycle , rocks do not remain in equilibrium and are forced to change as they encounter new environments. The rock cycle is an illustration that explains how the three rock types are related to each other, and how processes change from one type to another over time. [ edit ] Historical development
Igneous rock (derived from the Latin word ignis meaning fire) is one of the three main rock types , the others being sedimentary and metamorphic rock . Igneous rock is formed through the cooling and solidification of magma or lava . Igneous rock may form with or without crystallization , either below the surface as intrusive ( plutonic ) rocks or on the surface as extrusive ( volcanic ) rocks. This magma can be derived from partial melts of pre-existing rocks in either a planet 's mantle or crust . Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Over 700 types of igneous rocks have been described, most of them having formed beneath the surface of Earth 's crust.
Middle Triassic marginal marine sequence of siltstones (below) and limestones (above), Virgin Formation, southwestern Utah , USA Sedimentary rocks are types of rock that are formed by the deposition of material at the Earth 's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles ( detritus ) to settle and accumulate or minerals to precipitate from a solution . Particles that form a sedimentary rock by accumulating are called sediment .
Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism , which means "change in form". The original rock ( protolith ) is subjected to heat (temperatures greater than 150 to 200 °C) and pressure (1500 bars), [ 1 ] causing profound physical and/or chemical change. The protolith may be sedimentary rock , igneous rock or another older metamorphic rock. Metamorphic rocks make up a large part of the Earth 's crust and are classified by texture and by chemical and mineral assemblage ( metamorphic facies ). They may be formed simply by being deep beneath the Earth's surface, subjected to high temperatures and the great pressure of the rock layers above it. They can form from tectonic processes such as continental collisions, which cause horizontal pressure, friction and distortion.