5-1 Earthquakes and Volcanoes

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Michael East 10 February 2024 PHY103 Earthquakes and Volcanoes When it comes to earthquakes, earthquakes are a sudden release of energy in the earth’s crust, this causes the ground to violently shake. They occur due to the movement of tectonic plates along fault lines. Earthquakes themselves are common around the world with many of them being recorded each year. A vast majority of the earthquakes that happen tend to go unnoticed, however the larger ones are much more violent and often cause very significant damage. When we talk about the types of earthquake waves and seismographs, the waves include the primary waves, secondary waves, and the surface waves. A seismograph is an instrument used to record the motion of the ground during an earthquake which analyzes the time difference between the primary and the secondary waves at different seismograph stations. This is how we determine where the epicenter of an earthquake was. With the intensity versus magnitude of earthquakes, the intensity is measured by the effects the people and structures in an area were felt. When assessing this you would use the Modified Mercalli Intensity Scale. When you are talking about the magnitude of an earthquake, this quantifies the amount of energy that was released by an earthquake, this is all measured on the Richter scale or a moment magnitude scale. The magnitude of an earthquake provides the standard measure for comparing multiple earthquakes. The types of faults are divergent faults, transform faults, and convergent boundaries. A transform fault occurs where the plates would slide past each other, a divergent boundary is often associated with the separation of plates. When talking about convergent

boundaries, this is the collision or the subduction of plates. Typically, these faults are linked to the plate tectonic boundaries. Earthquakes can cause death and damage in a lot of different ways. Some of these ways are the ground itself shaking and the ground splitting. Theres many other ways that devastation can be caused by earthquakes, like landslides, tsunamis, and liquefaction. A few things that can be done to change the impact of earthquakes is the preparedness, the infrastructure design, and the density of the population in the area. As of right now globally, most of the regions prone to earthquakes are the Pacific Ring of Fire, the Mid-Atlantic Ridge, and the Alpide Belt. Around the United States, you have states like California and Alaska that are prone to earthquakes and the New Madrid seismic zone. Other regions that are at a smaller risk but still at a risk are the west coast, the intermountain west, and the central and eastern regions of the United States. Volcanoes are an opening on the earths crust that releases magma, volcanic ash, and gases. Volcanoes tend to occur by magma rising from hot spots and erupting as lava through the cracks in the earths surface. Volcanoes are classified as either active, dormant, and extinct. When you talk about active volcanoes, they have recently erupted and are very likely to do so again. Dormant volcanoes haven’t erupted in a very long time but are expected to do so in the future. With extinct volcanoes, it seems very unlikely that they well erupt again in the near future. The amount of volcanoes in the world is a very difficult thing to quantify because it solely depends on how you define a volcano. However, besides the continuous volcanoes that are on the ocean floor, the Global Volcanism Program with the Smithsonian Institution has estimated that there are around 1500 potential active volcanoes. The different types of volcanoes are cinder cones, stratovolcanoes or composite volcanoes, shield volcanoes, and lava domes are some of the volcano types. Cinder cones are round or oval in shape and consist of lava shards that were

thrown into the air to form a vent. Quite typically they occur from eruptions of pyroclastic material that ends up building up around the vent. Cinder cones typically only tend to erupt once. When we talk about Composite volcanoes, or Stratovolcanoes for common term, They are very steep volcanoes that are made up of numerous layers of volcanic rock. Usually they are formed from high-viscosity lava, some ash, and rock fragments. Usually, they’re tall conical mountains that are made of alternating layers of lava flows and other ejected materials. Now shield volcanoes are gradual slopes created by basaltic lava flows, and these volcanoes have an oval or shield-shaped center. These types of volcanoes are formed by an eruption of low-viscosity lava which can tend to travel far from the vent. Shield volcanoes don’t tend to detonate. When talking about lava domes, they are created when a lava flow is too thick to flow and builds up a steep- sided mound close to the volcanoes vent. All volcanoes are unique in size, the style of the eruption, and the type of magma. The properties of a magma are determined by its chemical makeup, which affects how easily it flows and how rapidly the eruptions occur. The explosivity of a volcano is influenced by the gas content of a volcano and the speed of the eruption. Whether it be on land or in the ocean, tectonic plate boundaries are home to most of the planets volcanoes. Volcanes that are on land develop when one of the tectonic plates slide beneath the other. This is known as a subduction. The divergent and convergent plates are two plate boundaries that are frequently linked to volcanic eruptions. A divergent border causes the separation of tectonic plates. With this, shallow earthquakes and volcanic activity are the result. One of the plates subduct beneath the other at a convergent plate boundary, this causes a series of earthquakes and a line of volcanoes on the overriding plate. A hotspot is another spot where volcanic activity is common. A hot spot is a place where a rising plume of heated mantle can create a volcano at the surface. A line of volcanoes may form on top of the plate traveling above the hotspot. The type of

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volcano that develops in each of these environments depends on many variables. Some of them being the composition of the magma, the pace of the eruption and the gas content. Volcanic risks are volcanic processes that have the potential to harm or destroy property, human life, or the environment itself. Some of the dangers include landslides, poisonous gases, ash fall, pumice falls, lava flows and pyroclastic flows. A stream of molten rock is called a lava flow, and this comes from an erupting volcanic vent. Everything that a lava flow encounters is destroyed, this includes structures and the environment. Volcanic ash is dangerous as well, it can prevent air travel, it can damage buildings, it can taint water supplies, and it can cause respiratory issues. A Pyroclastic flow is a cloud of hot gas and volcanic materials that moves very quickly, they can reach speeds of up to 700 km/h (or 450mph). They will literally decimate everything in its path and are extremely dangerous. When volcanoes deposit pumice particles, this is called pumice falls. Pumice is a light-colored volcanic rock that is created when lava rapidly cools. Infrastructure can be damaged by pumice. During volcanic eruptions, gases like sulfur dioxide, carbon dioxide, and hydrogen sulfide are released into the atmosphere. These gases are harmful to both the environment and humans. When a volcanoes slope becomes unstable, this can lead to landslides and these are very dangerous and harmful to buildings. There aren’t any active volcanoes near me in Jacksonville, North Carolina. Reading up on it, there aren’t any active volcanoes in North Carolina at all. The only volcanoes in North Carolina at all are all extinct and reading up on it they all were last active about half a billion years ago. It is a major challenge to try and foresee where a major volcanic eruption might happen in our world or in the United States as a matter of fact. However there are several volcanoes that are active and are watched for any indication of activity or impending eruptions. The volcano hazard program of the United States Geological Survey monitors many active volcanoes around the country. Some of the

dangers that can come from a volcanic eruption tends to depends on several different factors, this includes the type of volcano, the makeup of the magma, and the rate of the eruption. Like we talked about before, some of the danges of volcanic eruptions include pyroclastic flows, lava flows, ash fall, pumice, poisonous gas, and landslides. Most volcanic activity can be linked to the boundaries of tectonic plates and the majority of these volcanoes are located all along the Pacific Ring of Fire. The Pacific Ring of Fire is a horseshoe shaped region where many tectonic plates converge around the Pacific Ocean. Subduction is forcing one plate under another at certain plate borders. Volcanoes can result from magma rising to the surface. British Geological Survey 1998 - 2019 (c)UKRI http://www.bgs.ac.uk mailto:www- bgs@bgs.ac.uk. (n.d.). What is the difference between magnitude and intensity? . British Geological Survey Seismology Monitoring Page. https://www.earthquakes.bgs.ac.uk/education/faqs/faq17.html#:~:text=Magnitude%20is %20a%20measure%20of,distance%20from%20the%20earthquake%20epicentre. DiNome, W. G. (n.d.). Volcanoes . NCpedia. https://www.ncpedia.org/volcanoes#:~:text=There %20are%20no%20known%20active,geologic%20instability%20on%20the%20coast. Encyclopædia Britannica, inc. (2023, December 23). Richter scale . Encyclopædia Britannica. https://www.britannica.com/science/Richter-scale Government of Canada, N. R. C. (2019a, March 1). Government of Canada / gouvernement du Canada . Government of Canada, Natural Resources Canada, Canadian Hazards Information Service. https://chis.nrcan.gc.ca/volcano-volcan/volcano-volcan-en.php Government of Canada, N. R. C. (2019b, March 1). Government of Canada / gouvernement du Canada . Government of Canada, Natural Resources Canada, Canadian Hazards Information Service. https://chis.nrcan.gc.ca/volcano-volcan/volcano-volcan-en.php How volcanoes form . British Geological Survey. (2021, June 23). https://www.bgs.ac.uk/discovering-geology/earth-hazards/volcanoes/how-volcanoes-form- 2/#:~:text=At%20constructive%20plate%20boundaries%2C%20the,setting%3B%20one %20example%20is%20Iceland. Lava flows destroy everything in their path . Lava flows destroy everything in their path | U.S. Geological Survey. (n.d.). https://www.usgs.gov/programs/VHP/lava-flows-destroy- everything-their-path

Pumice . Minerals Education Coalition. (2017, April 28). https://mineralseducationcoalition.org/minerals-database/pumice/#:~:text=Pumice%20is %20a%20type%20of,with%20tiny%20bubbles%20of%20gas. Pyroclastic flow . Education. (n.d.). https://education.nationalgeographic.org/resource/pyroclastic-flow/ Seismometers, seismographs, seismograms - what’s the difference? how do they work? Seismometers, seismographs, seismograms - what’s the difference? How do they work? | U.S. Geological Survey. (n.d.). https://www.usgs.gov/faqs/seismometers-seismographs- seismograms-whats-difference-how-do-they-work#:~:text=Seismographs%20are %20instruments%20used%20to,part%20of%20a%20seismographic%20network. U.S. Department of the Interior. (n.d.-a). Types of volcanoes . National Parks Service. https://www.nps.gov/subjects/volcanoes/types-of-volcanoes.htm U.S. Department of the Interior. (n.d.-b). Types of volcanoes . National Parks Service. https://www.nps.gov/subjects/volcanoes/types-of-volcanoes.htm#:~:text=The%20most %20well%2Dknown%20types,stratovolcanoes)%2C%20and%20shield%20volcanoes. US Department of Commerce, N. O. and A. A. (2014, July 8). What is a hotspot volcano? . Ocean Exploration Facts: NOAA Office of Ocean Exploration and Research. https://oceanexplorer.noaa.gov/facts/volcanic-hotspot.html#:~:text=In%20geology%2C %20a%20hotspot%20is,atop%20the%20Pacific%20tectonic%20plate. What is a fault and what are the different types? . What is a fault and what are the different types? | U.S. Geological Survey. (n.d.). https://www.usgs.gov/faqs/what-a-fault-and-what-are- different-types

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