Essay On Plate Tectonics: Earthquakes, Volcanoes, Mountain Belt

Introduction

It is currently apparent that most of what we observe on the surface of the earth and at shallow depths below the surface is related to one way or the other to plate tectonics. The plate tectonics theory started with an assumption and had to be proven with concrete evidences before being entirely accepted by the global scientific community. (Earth Observatory of Singapore, n.d. para. 1). Practically, all of the major land forming processes (exogenic or endogenic) that ensue on the earth's surface are related to plate tectonics. Seismic activity, volcanism, and mountain building are three of the most remarkable surface processes related to tectonic activity. Correspondingly, numerous other processes such as metamorphism and sedimentary rock formation, are either related directly or indirectly to plate tectonics.
Geologically, Japan and the surrounding islands bestride four major tectonic plates: the Pacific plate; the continental North America plate; the Eurasia plate; and the Philippine Sea plate. The Pacific plate subducts into the mantle, beneath the regions of Hokkaido and northern Honshu. Farther south, the subducted Pacific plate extends beneath the volcanic islands along the eastern margin of the Philippine Sea plate. Scientific observations reveal that this 2,200 km-long zone of subduction of the Pacific Ocean plate is responsible for the formation of the Ogasawara and Japan trenches. According to the USGS, the Pacific plate also formed the Circumpacific island arcs. (2015. Para.1).In the same way, the Philippine Sea plate subducts beneath the Ryukyu Islands and the Nansei-Shoto trench. These subduction zones situated at the Japanese island arcs are geologically intricate and produce numerous earthquakes from manifold sources. Deformations of the overriding plates generate superficial crustal quakes. On the other hand, slips at the interface of the plates causes inter-plate earthquakes that range from the base of the trench to depths of 40 to 60 km. (USGS, 2015. Para. 2).
1. Earthquake event: M6.2 - 15km N of Omachi, Japan

Image as retrieved from

2. Volcano event: M2.9 - 73km NNW of Redoubt Volcano, Alaska
As shown in the interactive diagram below, the Aleutian arc extends from the eastern Gulf of Alaska into the Kamchatka Peninsula in the west. Scientific information is further revealed that the arc marks the zone where the Pacific Ocean plate subducts into the mantle beneath the continental North America plate (USGS, n.d. para. 1).
Image as retrieved from (USGS, n.d.)
This subduction process occasioned the generation of the Aleutian Islands and the deep offshore Aleutian Trench. Divided into three regions: the central, western, and central areas. The Aleutian arc, as the name implies, is curved. The curvature is attributed to the westward shift of relative plate gesticulation from trench-normal in the eastern part to trench-parallel in the western zone. (USGS, n.d. para 2). The westbound variations in seismic activity, volcanism, and the overriding plate composition further magnifies the curvature effect of the arc.
3. Mountain belt event: The Himalayas
Ordinarily known as the “roof of the world”, the Himalayas host Mt. Everest at 8,848 meters above sea level – the highest peaks on Earth (Egger, 2003. Para. 1) The mystery of the Himalayas is compounded by the fact that the rock that caps Mt. Everest is limestone. Limestone is a type of rock formed beneath warm, shallow seas and is composed predominantly of fossilized marine creatures. For an inordinate length of time, geologists struggled to explain how the remains of marine organisms could exist at the crest of a mountain range. The quest for that answer led to the theory of Continental Drift by Wegener in 1924 (Egger, 2003. Para. 4).

Image as retrieved from (USGS, 1999)

However, scientific advancement led to the evolution of Wegener’s theory to Plate tectonics. Stretching for over 2,900 km between the Indian-Tibetan borders, this colossal mountain ranges began to form around 50 million years ago. Its formation occurred when two large landmasses, India, and Eurasia, driven by plate movement, collided (USGS, 1999. Para. 1). Because both these continental landmasses exhibit the same rock density, the pressure of the impacting plates could only be relieved by thrusting upwards. The thrusting up process further warps the collision zone and forms the jagged Himalayan peaks.
Geological information reveals that following the breakup of Pangaea about 200 million years ago, and the Indian sub-continent began to forge northward. Ultimately, India rammed into Asia about 40 to 50 million years ago, and its northward advance slowed by about half. The resultant collision and associated decrease in the rate of plate movement marked the beginning of the rapid uplift of the Himalayas (USGS, 1999. Para. 2).
Geological events are inherent parts of the natural disturbance regimes in voluminous natural ecosystems. But then again they need to be well-thought-out as threats if a species or habitat is impaired from other threats and has lost its resilience and is accordingly vulnerable to the disturbance. Geologic hazards are responsible for the significant loss of life and destruction of property. Scientific data shows that in the twentieth century over a million people globally have been killed by earthquakes alone. Additionally, the value of the asset wrecked by earthquakes, volcanoes, and related disasters amounts to scores of billions of dollars (USGS, 2013. Para. 1). Global subduction zones are sliding slowly on the earth's mantle, slips under continental plates forming trenches. Friction at this zones produces excessive stress and an increase in temperature. As a result, the subducted rock melts and expands, causing added stress and upward movement of the magma. The magma then reaches the surface as lava and erupts to form volcanoes. The crustal rocks in turn respond to the stresses by breaking and moving. Consequently, the crust above the subduction zone is demarcated by volcanoes and active faults. Movement along the faults causes earthquakes. These areas of volcanism and earthquakes, involving several plates and trenches and their extensions, virtually encircles the Pacific Ocean. The region geologically known as the "Ring of Fire." These geologic hazards - earthquakes, volcanic eruptions and the landslides and tsunamis they induce impacts significantly on the surface of the earth.
In the light of the above threats posed by geological hazards, earth scientists work with multiple partners to assess and monitor research on a broad range of natural hazards. These professionals then disseminate their findings and response mechanisms so that policymakers and the public have the understanding they need to enhance preparedness, intervention, and resilience. For instance, in 2010, the USGS realigned its organizational structure around the Natural Hazards Mission Area. The mission area includes a number of earth science programs geared towards disaster preparedness. The areas include Earthquake Hazards, Marine Geology, and Global Seismographic Network. These programs, enable the USGS to provides timely alerts and warnings of geologic hazards to the public.(USGS, 2013. Para. 2)
In sum, plate tectonics is arguably the most significant geologic revolution of the 20th Century. Through it, Earth scientists acknowledge that the earth’s surface is covered with mobile tectonic plates that move around the earth. In this motion, plates move apart while others move together. At the same time, some just slide by each other. Therefore, the most critical concept about plate tectonics is that it’s an all-encompassing theory that explains almost everything humans observe on the surface of the earth and at greater depth.

References

Earth Observatory of Singapore. (n.d.). Brief history of the plate tectonics theory | Tectonics | Earth Observatory of Singapore. Retrieved February 19, 2015, from http://www.earthobservatory.sg/faq-on-earth-sciences/brief-history-plate-tectonics-theory
Egger, A. (2003). Visionlearning | Earth Science | Plates, Plate Boundaries, and Driving Forces. Retrieved February 19, 2015, from http://www.visionlearning.com/en/library/Earth-Science/6/Plates-Plate-Boundaries-and-Driving-Forces/66
U.S. Geological Survey: Natural Hazards. (n.d.). Retrieved from http://www.usgs.gov/natural_hazards/
Unites States Geological Survey - USGS. (2014, September 15). Understanding plate motions [This Dynamic Earth, USGS]. Retrieved February 19, 2015, from http://pubs.usgs.gov/gip/dynamic/understanding.html
USGS. (1999, May 5). The Himalayas [This Dynamic Earth, USGS]. Retrieved February 19, 2015, from http://pubs.usgs.gov/gip/dynamic/himalaya.html
USGS. (2013, September 11). U.S. Geological Survey: Natural Hazards. Retrieved February 19, 2015, from http://www.usgs.gov/natural_hazards/
USGS. (2015, February 19). M6.2 - 15km N of Omachi, Japan (BETA) 2014-11-22 13:08:18 UTC. Retrieved February 19, 2015, from http://comcat.cr.usgs.gov/earthquakes/eventpage/usb000syza#summary
USGS. (n.d.). M2.9 - 73km NNW of Redoubt Volcano, Alaska. Retrieved February 19, 2015, from http://earthquake.usgs.gov/earthquakes/eventpage/ak11508947#general_map