How are volcanoes and earthquakes related? | Volcano World | Oregon State University
The shifting rock in an earthquake causes shock waves—called seismic waves— to . there is a direct relationship between the borders of the world's tectonic plates and the geographic . Earthquakes and Volcanoes (Houghton Mifflin, ). A secondary school revision resource for AQA GCSE Chemistry about the Earth's core, mantle, crust and tectonic plates. Some, but not all, earthquakes are related to volcanoes. For example, most earthquakes are along the edges of tectonic plates. This is where most volcanoes .
But why do they happen? The Earth's surface is formed of massive slabs of rock called plates. These plates, also called tectonic plates, are always moving. Sometimes they just slide past one another. At other times they actually collide with one another. Plate movement causes the buildup of tremendous quantities of energy in the rock. When the energy is released, it produces vibrations that travel through the rock, leading to earthquakes.
During earthquakes, faultsor giant cracks, are produced by the pressure of the moving rock. Earthquakes and volcanoes occur along the edges of the plates. P waves alternately compress and expand the rock through which they pass and vibrate in the same direction in which the waves travel. S waves vibrate at right angles to the direction of wave travel.
The speed of S waves is always less than that of P waves. By comparing the arrival times of both P waves and S waves at seismological observatories, scientists can determine the location of an earthquake many thousands of miles away. They are named Love and Rayleigh waves, after the scientists who identified them.
Because of their larger amplitude, surface waves are responsible for much of the destructive shaking that occurs far from the epicenter. Surface waves, which travel more slowly than body waves, are the most powerful shock waves. In addition to the ground movements, other surface effects include changes in the flow of groundwater, landslides, and mudflows.
Earthquakes can do significant damage to buildings, bridges, pipelines, railways, embankments, dams, and other structures. Underwater earthquakes can cause giant waves called tsunamis.
Tectonic Plates, Earthquakes, and Volcanoes | PBS LearningMedia
Violent shaking of the seafloor produces waves that spread over the ocean surface in ever-widening circles. In deep water a tsunami can travel as fast as miles kilometers per hour.
By the time a tsunami reaches shore, it has gained tremendous size and power, reaching heights as great as feet 30 meters. Tsunamis can be catastrophic, with the potential to wipe out coastal settlements. Library of Congress, Washington, D. Earthquakes also can lead to devastating fires. Fire produced the greatest property loss following the San Francisco earthquake, when blocks in the city center burned uncontrollably for three days.
Fire also followed the Tokyo earthquake, causing much damage and hardship for the citizens. A seismograph records the pattern of shock waves caused by an earthquake. Seismographs are equipped with electromagnetic sensors that translate ground motions into electrical changes, which are processed and recorded by the instrument. A record produced by a seismograph on a display screen or paper printout is called a seismogram.
Displayed by permission of The Regents of the University of California. Most seismographs use a pendulum. As the ground moves during an earthquake, so does the pendulum. The seismograph records the motion of the pendulum relative to the motion of the ground. Early mechanical seismographs had a heavy pendulum and recorded the wave patterns by scratching a line on a revolving drum of paper.
Later instruments used a mirror that was moved by the motion of the pendulum; light reflected by the mirror traced the wave patterns onto photosensitive paper wrapped on a drum. Technological developments in electronics have given rise to the higher-precision pendulum seismographs that are widely used today.
Volcanoes and Earthquakes
In these instruments an electric current produced by the motion of the pendulum is passed through electronic circuitry to amplify and digitize the ground motion for more exact readings. The strength of an earthquake may be measured either by the amount of damage done or through calculations using various instrument readings.What Is An Earthquake? - The Dr. Binocs Show - Educational Videos For Kids
The Modified Mercalli Intensity Scale is commonly used to determine the amount of destruction caused by an earthquake. It defines 12 levels of earthquake strength. The Richter Magnitude Scale is based upon the amount of energy released by the rock movements. An earthquake with a Richter magnitude of 2 is about the smallest earthquake that can be felt by humans without instrumental assistance.
An increase of one magnitude step corresponds roughly to an increase of 30 times the amount of energy released as seismic waves. Thus, the energy of the great Alaska earthquake, which had a magnitude of 8.
Rather, it released more thantimes as much energy as one of magnitude 4. However, the Richter scale underestimates the relative size of very large earthquakes. The moment magnitude scale, which takes into account the amount and nature of fault slippage, provides a more consistent measure.
The moment magnitude of the great Alaska earthquake is 9. Several other magnitude scales also are in use. The belts coincide with the more recently formed mountain ranges and with belts of volcanic activity.
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One earthquake belt circles the Pacific Ocean along the mountainous west coasts of North and South America and runs through the island areas of Asia. It is estimated that 80 percent of the energy presently released in earthquakes comes from this belt, which is called the Circum-Pacific Belt or the Ring of Fire. A second, less active belt passes between Europe and North Africa in the Mediterranean region.
The eruption of Mount St. Helens in was caused in part by a lava dome shifting to allow explosive gas and steam to escape from inside the mountain.
Volcanoes and earthquakes
What is the difference between lava and magma? Magma is liquid rock inside a volcano.
Lava is liquid rock magma that flows out of a volcano. Fresh lava glows red hot to white hot as it flows.
Why does lava take a long time to cool down? Lava cools slowly because lava is a poor conductor of heat. Lava flows slow down and thicken as they harden. What is a pyroclastic flow? A pyroclastic flow is a fluidized mixture of solid to semi-solid fragments and hot, expanding gases that flows down the sides of a volcano.
These awesome features are heavier-than-air emulsions that move much like a snow avalanche, except that they are fiercely hot, contain toxic gases, and move at phenomenal, hurricane-force speeds. They are the most deadly of all volcanic phenomena. A lahar is a type of mudflow or debris flow composed of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley.
It is very dangerous because it's consistency and the way it acts is very much like cement. It is liquid when it's moving, but when it stops, it solidifies. This can cause just as much devastation as lava itself. Pumice is a light, porous volcanic rock that forms during explosive eruptions.
It resembles a sponge because it consists of a network of gas bubbles frozen amidst fragile volcanic glass and minerals. All types of magma basalt, andesite, dacite, and rhyolite will form pumice.
What is the largest active volcano? The world's largest, active volcano is Mauna Loa in Hawaii, where famous coffee is grown in the rich volcanic soils. Mauna Loa is 13, feet above sea level.
From its base below sea level to its summit, Mauna Loa is taller than Mount Everest. What is the Ring of Fire? The Pacific Ring of Fire is an area of frequent earthquakes and volcanic eruptions encircling the basin of the Pacific Ocean.
When did Mount St. On May 18,Mount St. It's located in southwestern Washington State in the Cascade Range. The blast was heard as far away as Montana, Idaho, Canada and California.
Click Here for more info on Mount St. What are some other notable volcano eruptions? Krakatoa was a dormant volcano in Indonesia, which awakened and produced one of the biggest volcanic eruptions in So massive was the eruption that the sound of it was heard as far away as Australia.
The Krakatoa eruption created a huge amount of ash cloud which covered the Earth and reduced global temperatures for 5 years! A total of 40, people died in that explosion and an entire chain of the volcanic island was destroyed. Mount Pelee was a dormant volcano situated in the Caribbean island of Martinique.
Init erupted in a massive horizontal explosion sending huge clouds of ash released towards the nearby town of Saint-Pierre. The side of the volcano exploded and lava flowed straight into the town, killing 30, people in a matter of minutes.
It is regarded as one of the biggest and most devastating volcanic eruptions of the 20th century, a benchmark for future eruptions. Mount Fujiyama, also popularly known as Mount Fuji, is an active volcano which last erupted in It is incidentally the tallest mountain in Japan.