What does granite change into

Sometimes magma forces its way up to the surface through a vent such as a volcano and spills onto the surface. This happened near Flagstaff, Arizona at Sunset Crater less than 1, years ago. Once magma comes out onto the surface of the earth it is called lava, and it cools rapidly at the surface.

Extrusive igneous rocks can be distinguished by their small crystal sizes. In all extrusive igneous rock, it is nearly impossible to detect crystals without the aid of a microscope.

The faster the rock cools, the smaller the crystals. Some extrusive igneous rocks cool so quickly that they have a glassy texture. Common extrusive igneous rocks are: andesite, basalt, dacite, pumice, rhyolite, and obsidian. Intrusive igneous rocks solidify over a period of thousands of years.

This slow cooling rate allows better development of mineral crystals. Intrusive igneous rocks will have eye visible crystals and will appear coarse-grained.

Igneous intrusive rocks eventually will become exposed at the surface of the earth by erosion of the overlying material. Common intrusive igneous rocks are: granite, diorite, gabbro, and peridotite.

The La Sal Mountains were formed by widespread igneous activity that began about 40 million years ago. Caldera explosions erupted thousands of cubic miles of volcanic rocks from several locations. Volcanoes spewed ash and lava. For 20 million years these extrusive volcanic rocks smoothed the landscape, filling depressions with accumulations of ash, flows, and debris literally miles thick.

These mostly pastel-colored extrusive rocks still blanket much of the high areas of central and southwestern Utah. Not all of the molten rising igneous material erupted as volcanic rocks; some material, along with its mineral-bearing fluids, congealed in the earth's crust.

Several of these intruded masses having been exposed by erosion or encountered out by exploration drilling became great mining districts, such as at Alta, Brighton, Bingham, Park City, and Cedar City. In the Colorado Plateau, bodies of intrusive rocks domed the overlying sedimentary rocks to form the Abajo and Henry Mountains as well as the La Sal Mountains.

NOTE: This paragraph on laccoliths borrowed from here. Rocks which have undergone these sorts of changes are called metamorphic rocks. Agents of Matamorphosis. The three primary agents which metamorphose rock are temperature, pressure, and fluids.

High temperatures can change rock by changing the structure of the minerals which make up the rocks; changing the structure of the minerals changes them into new minerals remember the definition of a mineral. This increase in temperature with increase in depth is called the geotherm. Intrusions Another source of high temperatures inside the Earth is magma intruding cooler rock. These temperature increases are localized near the intrusion, but also metamorphose rock this is called contact metamorphism.

Pressure or more properly, stress can also change rock. There are two main kinds I want you to know about: Confining Pressure Pressure due to the weight of overlying rock. This kind of pressure is roughly the same in all directions this is like water pressure when scuba diving , and is the kind which compacts rock during diagenesis.

Confining pressure changes rock by compaction and by changing the crystal structure of minerals from relatively open forms to more densely-packed forms.

One mineral which does this is olivine, which changes from olivine isolated silica tetrahedra to spinel a much more tightly-bonded structure to perovskite a still more highly compressed structure.

This kind of pressure is usually due to tectonic forces. It changes rocks by changing the structure of minerals and by changing the orientation of mineral grains, particularly platy minerals like mica or clay. Fluids which metamorphose rock are not pore fluids remaining from when sedimentary rocks were deposited. Instead, they come from two main sources: hydrothermal fluids from magmatic intrusions and dehydration of minerals, like clay, which contain water in their structures hydrous minerals.

Whatever the source, fluids contain ions dissolved from other rock or from their original source. As fluids percolate through rocks, they can exchange ions with the existing minerals and thus change the chemical makeup of those minerals.

The other way fluids change minerals is by hydrating minerals which previously did not contain water. Either way, fluids change the chemical makeup of minerals, turning them into new minerals, which changes the rocks which were made of the previous minerals. This process of change by fluids is called metasomatism. Types of Rock Metamorphism.

Some kinds of metamorphism: Burial Bury rocks deeply enough and they will warm up and change. This form of metamorphism is found anywhere where sediments and rocks are buried deeply, and should strike you as being pretty similar to diagenesis, which we discussed last time.

The line between diagenesis and burial metamorphism is fuzzy. Regional Caused by widespread moderate-to-high temperatures and pressures, as opposed to localized changes along faults or near magmatic intrusions. You find this type of metamorphism in mountain building regions and near subduction zone volcanism. Contact Caused by high temperatures near magmatic intrusions.

Found in volcanic regions subduction zones, hot spots and mountain building zones. Cataclastic Caused by grinding along fault zones. Found along major faults like the San Andreas Fault in California , in mountain building zones, and in deformation regions associated with subduction zones. Hydrothermal Caused by hot fluids percolating through rocks.

Found anywhere where hot fluids can percolate through rocks, notably along mid-ocean ridges. Metamorphic Rocks and Rock Textures. Three major texture and rock types for metamorphic rocks that you need to know: Foliated Rocks Characterized by parallel planes formed through directed pressure and preferred growth orientations of certain platy minerals. Two common kinds are schist and gneiss, which have been used in a great many really bad geological puns.

Non-foliated Rocks Don't have those planes, usually because they are made of mineral grains which are cubic or spherical, and therefore have no preferred orientation.

Two common examples are marble and amphibolites. Deformational Caused by cataclastic metamorphism. The most common rock of this kind is called a mylonite; there is a big mylonite belt in the mountains south of Palm Springs, CA. Metamorphic Grade. Geologists who study metamorphic rocks have come up with the concept of metamorphic grade to describe how 'metamorphosed' a rock is. More specific distinctions can be made through lab experiments in which various kinds of rocks are squeezed and heated up and the changes observed.

Through this kind of work, geologists have found a set of index minerals , which are common minerals which form under particular combinations of pressure and temperature.

Armed with knowledge from these experiments, field geologists can go out and make maps of mineral location to determine how metamorphism is distributed over large regions of rocks.

Metamorphic Facies. Don Mac. Feb 15, Explanation: Granites at the surface are exposed to weathering in which they break down into mostly quartz and feldspars. Related questions What is beach erosion? How does ice cause erosion? How does erosion happen? What are the river processes of erosion, transportation, and deposition? Rocks are made up of different types of minerals that harden and form crystalline structures. Three examples of rocks that have the same primary composition, but vary in classification and appearance are gneiss, granite and sandstone.

Gneiss is a metamorphic rock, granite is an igneous rock and sandstone is a sedimentary rock. These rocks primarily consist of quartz, feldspar and mica. All rocks undergo a series of processes called the rock cycle, where one type of rock changes into another. The mineral constituents that create these rocks get recycled over time.