There is always more pressure and higher temperature under the Earth's surface. In the root of a mountain chain or a volcano these forces will be enough to change shape of the strata and the minerals it is made of. Sedimentary rock which has been near such forces often looks as if a giant had twisted it and heated it over a fire. Examples of metamorphic rock:
The recrystallisation of minerals after heating generally causes the destruction of any fossils the rocks might have contained. These rocks are formed when igneous or sedimentary rocks are subjected to extreme heat and pressure as result they undergo a complete change in their form and characteristics. Such form rocks are called metamorphic rocks.
Regional metamorphism, or dynamic metamorphism, occurs in great masses of rock. Rocks can be metamorphosed just by being at great depths below the Earth's surface. There they get high temperatures and the great weight of the rock layers above.
Much of the lower continental crust is metamorphic, except for recent igneous intrusions. Horizontal tectonic movements such as the collision of continents create orogenic belts. High temperature, pressures and deformation occurs along these belts. If the metamorphosed rocks are later uplifted and exposed by erosion, they are seen as long belts or other large areas at the surface.
Contact metamorphism occurs when magma is injected into the surrounding solid rock (country rock). The changes that occur are greatest where the magma comes into contact with the rock. The temperatures were highest there and decreased with distance from it.
Metamorphic minerals are those that form only at the high temperatures and pressures of metamorphism. These minerals, known as index minerals, include sillimanite, kyanite, staurolite, andalusite, and some garnet.
Other minerals, such as olivines, pyroxenes, amphiboles, micas, feldspars, and quartz may be found in metamorphic rocks. They are not necessarily the result of the process of metamorphism. These minerals formed during the crystallization of igneous rocks. They are stable at high temperatures and pressures and may remain chemically unchanged during the metamorphic process.
Extrusion
Extrusive means to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. This is opposed to intrusive rock formation, in which magma does not reach the surface.
Extruded when talking about an artificial material like soft metals like aluminium, plastic or glass means that it is pushed out of a nozzle when the material is in a soft state. The shape of the nozzle will vary depending on the shape required in the finished product
Intrusion
An intrusion is magma (melted rock) which cools and becomes solid under the Earth's surface. It occurs when there are lines of weakness such as faults, joints, or bedding planes in the crust. Then magma enters these lines of weakness. By contrast, an extrusion is magma which cools into rock above the surface of the crust. Both intrusive and extrusive rocks are classed as igneous rocks.
The process of forming intrusive rocks may take millions of years. As the rock slowly cools into a solid, the different parts of the magma crystallize into minerals. The crystals are usually larger than in extrusive rocks. Many mountain ranges, such as the Sierra Nevada in California, are formed mostly by intrusive rock. Often they are huge granite (or related rock) formations.
Intrusions vary widely, from mountain range sized batholiths to thin vein-like fracture fillings. When exposed by erosion, these cores called batholiths may occupy huge areas of Earth's surface. Large bodies of magma that solidify underground before they reach the surface of the crust are called plutons.
Intrusive structures may go between bedding planes of earlier 'country' rock. A sill is an intrusion which makes a table along bedding planes. A dyke is an intrusion which moves up, crossing older strata.
Radiation pressure
Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. If absorbed, the pressure is the energy flux density divided by the speed of light. If the radiation is totally reflected, the radiation pressure is doubled. This happens because the waves that make up electromagnetic radiation carry momentum with them and pass that momentum on when they reach a surface.
A Crookes radiometer appears to demonstrate the pressure of light, but instead it demonstrate the energy that light brings to a surface. The black side of each paddle absorbs most of the light's energy an causes the air near that surface to have a higher pressure. So, while a Crookes radiometer turns because of pressure, it is air pressure caused by the heat energy that light brings to the device.
The solar radiation at Earth's distance from the Sun has an energy flux density of 1370 W/m, and more than half of this energy reaches surface. A calculation shows that this value of the flux would cause on an absorbing surface to experience 4.6 µPa of radiation pressure. A convenient way to compare the Sun's energy flux and radiation pressure is to imagine the pressure and energy deposited on one square meter:
To understand how small a micro-newton is, convert calculate how much mass you need on Earth to get that force using formula_3:
The difference between the energy flux and the pressure is like the difference between the heat coming through a large window and the weight of a very small mosquito.
Kirkwood gap
Kirkwood gaps are areas of the asteroid belt where asteroids are unusually scarce, as seen in the . They are caused by orbital resonances with Jupiter.
The gaps were first noticed in 1857 by Daniel Kirkwood, who also correctly explained their origin in the orbital resonances with Jupiter while a professor at Jefferson College in Canonsburg, Pennsylvania.
Ca-Al-rich inclusions
Ca-Al-rich inclusions (CAIs) are centimeter-sized light-coloured calcium and aluminium rich inclusions found in carbonaceous chondrites. CAIs contains high-temperature minerals and are among the first solids which solidified from the cooling protoplanetary disk. CAIs were formed at much higher temperatures than the associated chondrules, and may have survived many high-temperature events, whereas most chondrules are the product of a single transient melting event.
The isotopic anomalies of CAIs give valuable clues about the solar system's formation, suggesting that the solar nebula collapsed shortly after a nearby supernova. Radiometric dating shows that the CAIs formed about 2 million years before the chondrules formed.
Eucrite
Eucrites are achondritic stony meteorites that originate from the surface of the asteroid 4 Vesta, and as such are part of the HED meteorite group. They are the most common achondrite group with well over 100 distinct finds at present.
Eucrites consist of basaltic rock from the crust of 4 Vesta. They are mostly made up of Ca-poor pyroxene, pigeonite, and Ca-rich plagioclase (anorthite).
Eucrites are named from a Greek word meaning "easily distinguished".
81P/Wild
Comet 81P/Wild, also known as Wild 2, is a comet named after Swiss astronomer Paul Wild (pronounced "Vilt"), who discovered it in 1978.
It is believed that for most of its 4.5 billion-year lifetime, Wild 2 had a more distant and circular orbit. In 1974, it passed within only about one million kilometers of the planet Jupiter, whose strong gravitational pull altered the comet's orbit and brought it into the inner solar system. Its orbital period changed from 40 years to about 6 years, and its perihelion is now about 1.59 AU (astronomical unit).
Barrel (weapons)