Igneous rock is created in the issue of volcanic activity. The process starts with the volcano becoming active because of tectonic plate pressure, which causes magma to expand during eruptions. Once hot magma is on the surface, it streams down the volcano and turns into lava.
Ash, molten, and dust are thrown away after an eruption (Mattern, 2006). After a while, the molten rock starts cooling down and, as a result, the igneous rocks are formed. Over time, these rocks gradually break apart because of weathering and erosion until break totally apart. Smaller rocks reach the foot of the mountain and turn into sediments. Later, the sediments are faded away by wind and water (Mattern, 2006).
The sediment rocks start accumulating in rivers, seas, and oceans. They move further down as the continuous pressure influences the rocks. The rocks are heated up as soon as they move further down to the Earth surface. As the temperature increases, the rocks undergo significant transformation without melting.
Extreme temperatures modify the rocks that later begin melting between 1000 and 2400 degrees F turning them into magma (Mattern, 2006). The newly created magma flows under the Earth’s mantle. The molten rock is gathered under the volcano and remains inside the magma chamber until the next eruption. This is the end of the igneous rock cycle.
There is a distinction between extrusive and intrusive igneous rocks. Extrusive igneous rocks originate from volcanic activity and occur at the surface of lava that expands in sheets, cools down and hardens (Rafferty, 2011). Extrusive igneous rocks are made up of molten stuff ejected from vents because of gaseous explosions. In contrast, intrusive rocks are remnants of shallow bodies left on volcanic necks.
Rocks can be changed mechanically by a range of deformation processes. The force imposed on a rock can deform it. Such forces involve confining and internal pore pressure, temperature, loading rate, and time. Under the influence of stress, rock experiences alterations in terms of shape, dimension, and volume (Rafferty, 2011).
Stresses, or deformation, can be axial – for instance, simple compressions, or directional tensions – or shear, like hydrostatic compression (Rafferty, 2011). Stress is often associated with directional stress and shear stress and pressure refers to hydrostatic compression. In case stress imposed on rocks are insignificant, the strains is called elastic. Permanent or inelastic stain occurs when stresses are more intense.
There are various types of volcano depending on their structure, location, and shape. These are shield volcanoes, composite volcanoes, cinder cones, and lava domes (Monroe & Wicander, 2011). Shield volcanoes resemble the shield surface that lies on the ground. These types of volcano are composed of mafic lava having low viscosity (Monroe & Wicander, 2011). While flowing outside, lava forms thin layers of low temperature.
Shield volcano usually belonged to the Hawaiian type of volcanoes and they do not constitute danger to humans because of magma flows out a little on surface. Composite volcanoes look like symmetrical, steep-sided cones build up of chancing layers of lava, cinders, blocks, and volcanic ash.
They rise up to 8.000 above the base level (Monroe & Wicander, 2011). Composite volcanoes have a crater with a central vent. The conduit system of composite volcanoes is the most important feature because magma rises deep from the Earth’s mantle. Mount Fuji, Mount Cotopaxi, Mount Hood and others are among the most popular volcanoes in the world.
Cinder cones possess the simplest volcanic structures because they consist of particles of lava that is ejected from one vent. There is a cinder cone located in Paricutin, a village in Mexico (Monroe & Wicander, 2011). Finally, lava domes are created by insignificant masses lava that does not flow at great distance because of high viscosity (Monroe & Wicander, 2011). Volcanic domes usually appear within the crates of composite volcanoes. Katmai Volcano is the example of such type of volcano.
Earthquakes occur as a result of fluctuation of energy in the mantle, which produces seismic waves. The latter influences type, size, and frequency of earthquake occurrence. Usually, earthquakes occur in seismic belts, on place boundaries where such processes as divergence, convergence take place.
Scientists distinguish between S-waves and P-waves causing earthquakes (Monroe & Wicander, 2011). Thus, P-waves move at much higher speed than S-waves and, therefore, seismograph can identify this type of wave first. S-waves arrive later, but they identify the intensity of the earthquake (Monroe & Wicander, 2011). These waves are also valuable for defining the distance between the place of earthquake and the seismograph.
They also allow the seismologists to define the epicenter of the earthquakes. Usually, earthquakes are measure by means of a 5-grade scale where the fifth level defines the depth of damages. Intensity and magnitude are two parameters that are used to measure the strength of an earthquake. Most of the evaluations are based on the intensity feature. The strongest areas of damage are imposed on areas with soil structure whereas solid breaks are the least damaged.
References
Mattern, J. (2006). Igneous Rocks and the Rock Cycle. US: The Rosen Publishing Group.
Monroe, J.S., & Wicander, R. (2011). The Changing Earth: Exploring Geology and Evolution. US: Cengage Learning.
Rafferty, P. J. (2011). Rocks. US: The Rosen Publishing Groups.