Classifying Rocks
Rocks are classified to make it easier on people to identify them in the future. This can be done by a numerous amount of ways. Each rock type has their own specific ways, but there are two distinct characteristics that apply to all. These are texture and composition. These two, along with many others helps to classify igneous, sedimentary, and metamorphic rocks.
Igneous rocks are classified first by texture. This is broken down mainly into grain size. First there are intrusive, or plutonic igneous rocks. These types of rocks cool within the crust and forms large, visible crystals. The opposite would be extrusive, or volcanic rocks. These cool at the surface rapidly, forming small grains. A combination of the two would be porphyritic, large grains in an aphanitic, or extrusive matrix. Secondly, composition is used to classify igneous rocks. There are four types, ultramafic, mafic, intermediate, and felsic. Ultramafic rocks are very dark and contain and extreme amount of iron and magnesium. Mafic rocks are also dark in color; they too contain high iron and magnesium amounts. An example would be olivine, or pyroxene. Intermediate igneous rocks are made from silica and plagioclase. They tend to be grays and browns in color. Finally, felsic socks are light in color and contains high amounts of silica. Quartz and potassium feldspar are examples of felsic igneous rocks. Other types of rocks are classified similarly.
Sedimentary rocks form...
Quartzite is a non-foliated metamorphic rock. This rock is intrusive and forms when exposed to extreme amounts of heat and pressure. Over a billion years ago, there was an ocean where Kamiak Butte is. This ocean floor was made of sand, as time went on oceans receded and the exposed sand underwent processes that turned it into sandstone – or as we learned in class the process of lithification. Years later, this sandstone would morph into the quartzite that is present now.2
Shown in the picture above is volcanic extrusive igneous rock known as andesite. They were imported here to Laguna Beach to help minimize erosion (Merton Hill, p. 10-11). Extrusive Igneous rocks are formed on Earths surface due to lava quickly cooling or mixing with different materials such as ash or cinders from an eruption. There are two different types of extrusive igneous rocks; Plutonic and Volcanic. Andesite is known for being gray in color and being made up of very coarse grainy textures, which make it much harder to break down than sedimentary rocks. Unlike loose gravel and other sediments igneous rocks are known for being able to slow down seismic waves from earthquakes which cause less damage to surface structures.
and Metamorphic rocks can be found. There are also a lot of crusted plates, and violent
Basalt is a commonly occurring igneous rock. More specifically however, Basalt falls under the category of Mafic Rocks. Mafic rocks have a poor Silica content, approximately 50% (Charles, Diane, Lisa, 2010) and contain high concentrations of metal oxides. Basalt is a fine grained rock containing predominantly ferromagnesian minerals, followed by plagioclase feldspar. The colour of Basalt ranges from dark grey to black and is relatively featureless. See Fig 1.
“Table rock is a conglomerate composed of olivine, augite, andesine, labrodorite, magnetite, hematite, apatite and orthopyroxine. Table rock is a geologist’s classroom as the lava caps display irregular column jointing and uneven displacement” (Lorenz, 1970).
The rock coquina is originally a sedimentary rock. Sedimentary rocks are made up of sediments. The sediments are formed by the mechanical or chemical activities of the natural activities like running water, blowing wind, glaciers etc. this which causes disintegration and decomposition of the pre-existing rocks. The products of decay are transported to some depositional sites by the natural agencies, where they get deposited and with subsequent compaction form sedimentary rocks (Hefferan, O’Brien, 2010). . The sedimentary rocks usually accumulate under a great variety of conditions. This shows the variation in rock, chemical structure as well as in texture. Weathering is the most important process that operates in the formation of sedimentary rocks. Weathering takes place by three methods as: mechanical disintegration, rock decomposition, and biological weathering. Mechanical disintegration is due to frost action, thermal expansion and contraction, aided with gravitational forces. Due to mechanical disintegration, the reduction of size and desegregation of rocks takes place. Chemical weathering is the use of the chemical elements of the atmosphere such as moisture, carbon dioxide, and oxygen (Hefferan, O’Brien, 2010). . This depends on the composition of the rock and the size of the particles that make up them. Biological weathering is a form of weathering caused by growth of roots and burrowing of animals. The environment of a sedimentary rock can show the deposition the quality and quantity of the deposition is affected. Sedi¬mentary rocks differ from environment to environment. These environments include the continental environments such as estuarine, lacustrine (fresh and salt water), deltaic, glacial. Anothe...
Many meteorites have been discovered over the years which, in many cases, can give an insight into the creation of the universe. All these meteorites can be grouped together by looking at the various characteristics they have in common, such as the structures of the different meteorites and the isotopic properties of the meteorites. When trying to classify meteorites, they are generally identified as one of the three main groups of meteorites: Iron, Stony and Stony-iron. Each group has its own properties which makes them unique to one another. These groups can be divided further more into smaller groups.
As discussed above, there are different varieties of gypsum (five basic forms); there is alabaster, satin spar, selenite, rock gypsum, and gypsite. Alabaster is fine-grained, satin spar is very fibrous, selenite is transparent (the more gemstone looking version of gypsum), rock gypsum is the most
This particular sample of granite is phaneritic in texture as described by its visible crystals. The rate at which the rocks cool determines the size of the crystals, in this case, a steady cooling rate produces larger crystals (“Characteristics of Igneous Rocks” n.d). The rate at which rocks cool is also related to the temperature of cooling which determines a rocks mineral composition (“Characteristics of Igneous Rocks” n.d). A low cooling temperature yields rocks with higher amounts of potassium, aluminum, and silicon (“Characteristics of Igneous Rocks” n.d). This is evident by the abundance of potassium feldspar, which also makes granite a felsic
As one of the most popular music genres, rock music has grown and expanded to incorporate many styles throughout the years. A rock band usually consists of a vocalist, an acoustic drum kit played with a strong beat, usually a back beat, and features electric and acoustic guitars. From its beginnings in the late 1950s and early 1960s until the present day, rock has changed styles seemingly every decade as new bands become popular because of their unique style of music. Throughout the years rock has influenced our culture and helped shape the world we live in today.
The Rock Cycle The Rock Cycle is a group of changes. Igneous rock can change into
Obsidian is considered to be naturally occurring volcanic glass. It is also called black lava glass. It can come in a variety of colors, such as yellow, red, greenish- brown, purple, as well as blueish green. However black and grey are the most common. It is a transparent stone with a translucent or opaque vitreous luster. It may have a iridescent sheen, caused by inclusions. These inclusions can also cause them to be called a different variety. Some of the varieties are snowflake obsidian, sheen obsidian, mahogany, rainbow, and apache tears. Obsidian is caused when volcanic lava cools so quickly that minerals do not have tie to form crystals. They are a type of glass, with a mohs hardness of 5- 5.5 and a specific
Crystalline silica may be of several distinct types. Quartz, a form of silica and the most common mineral in the earth's crust, is associated with many types of rock. Other types of silica include cristobalite and tridymite.
First order relief features are tectonic plates and are the largest in special extent. Two types of plates; continental plates and Oceanic plates. These are differentiated by their rock and mineral composition. Continental plates are lighter in density and are composed of granitic rock materials rich in silica and aluminum. The oceanic plates are made up of dense, basaltic rock composed of silica and magnesium.
There are two types of Igneous rocks. The first is intrusive, which is when the magma slowly cools beneath the earths surface. Because the magma is cooling slowly it allows the rocks end result to form crystal- like pigments. Examples of intrusive igneous rocks are Diorite, Gabbro, Granite, Pegmatite, and Periodotite. All of these rocks are course and grainy. The other type is an extrusive Igneous rock. This lava erupts onto the surface of the earth and cools rapidly also forming crystals, the lava cools so fast that at times it allows the rocks to form as clear-like glass. Examples of these rocks are Andesite, Basalt, Obsidian, Pumice, Rhyolite, Scoria,