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Volcanoes and Earthquakes7 Articles
Check articles you have read:
Volcanoes: Magma Rising - Volcanic Eruptions532 words
Earthquakes: Tremors from Below - A Tsunami in the Pacific307 words
Earthquakes: Tremors from Below - How Do Scientists Study Earthquakes?241 words
Earthquakes: Tremors from Below - What Causes the Earth to Shake?183 words
Volcanoes: Magma Rising – Mt. Pelée Erupts503 words
Volcanoes: Magma Rising - Studying Volcanoes287 words
Volcanoes: Magma Rising - Volcanic EruptionsT his text is pro vided co urtesy o f OLo g y, the American Museum o f Natural Histo ry’s website fo r kids.
What Causes Volcanoes to Erupt?
Earth’s crust, or outer shell, is broken into big pieces called tectonic plates. These plates fit together like a
puzzle. They are moving very slowly all the time, as slow as fingernails grow! When the edges of the plates
meet, plates can collide, separate, or grind against each other.
Illustration Credit: AMNH
Tectonic Plate Boundaries
Nearly every Caribbean island has its own active volcano. That’s because these islands lie above subduction
zones, where one tectonic plate sinks, or subducts, beneath another.
Find Out How Subduction Causes Volcanoes to Form
Illustration Credit: AMNH
1. When an oceanic plate collides with a continental plate, it sinks into the mantle below.
2. As the oceanic plate sinks, fluid is squeezed out of it.
harden and fall to the ground, accumulatingaround the vent in a cone shape. The lava islow in silica, so the lava is runny. High gaslevels make for the explosive eruptions thatsend lava flying. Cinder cones typically form atthe beginning of eruptions, and lava flowfollows.
The most explosive eruptions come fromstratovolcanoes, like the Augustine Volcano inAlaska. When they erupt, stratovolcanoes blowhuge columns of gas and ash into the air thatcan collapse in hot, fast-moving clouds calledpyroclastic flows.
Photo Credit: Courtesy of Nula666, WikiCommons
A shield volcano, like Mauna Kea in Hawaii,has gentle slopes formed by oozing, runnylava. The magma is low in silica and low in gas,so it doesn’t erupt explosively.
A lava dome, like the one of Chaitén Volcano inChile, forms when thick lava oozes from avent, piles up, and cools into a steep mound.The lava is thick because it’s high in silica, andit oozes instead of explodes because it’s low ingas. Sometimes lava domes form afterexplosive eruptions.
Earthquakes: Tremors from Below - How Do ScientistsStudy Earthquakes?
T his text is pro vided co urtesy o f OLo g y, the American Museum o f Natural Histo ry’s website fo r kids.
Around five million people are affected by earthquakes every year — so it’s not surprising that people want to
know when the next big one will hit. But earthquakes are unpredictable. That’s because there’s no way to tell
exactly when the rocks will snap from stress that builds up as the plates move. So what can scientists do? They
calculate the probability that an earthquake will occur at a particular location.
Explore Some of the Tools that Scientists Use to Measure,Record, and Study Earth’s Movements
Scientists use the Global Positioning System(GPS) to monitor day-to-day platemovements. GPS satellites orbiting Earthsend radar signals to receivers on theground.
With GPS receivers like this one, scientistscan use GPS data to measure tiny platemovements along fault lines. GPS also helpsthem measure plate movement after anearthquake.
Seismometers measure the seismic activity,or shaking, in Earth’s crust. Today, networksof hundreds of seismometers are at workaround the world. They measure more than100,000 earthquakes every year!
A seismogram is a recording of anearthquake’s intensity. The greater the peakson the graph, the greater the shaking — andthe greater the shaking, the greater theearthquake’s magnitude.
When an undersea earthquake occurs, scientists use computer models to predict whether a tsunami will occur.
The model can forecast the wave’s speed, direction, and height as it approaches land. Local authorities can then
warn communities that might be in danger.
Earthquakes: Tremors from Below - How Do Scientists Study Earthquakes?
News of the disaster horrified the world. Geologists were drawn to
Martinique to understand the science behind the tragedy. The American
Museum of Natural History sent geologist Edmund Hovey.
Take a look at what Edmund Hovey saw and collected.
Once a vibrant city, Saint-Pierre, as Hovey foundit, was now a smoldering ruin with barely a brickleft standing. “Even photographs do not conveyan adequate idea of what has happened,” wroteHovey.
Volcanoes: Magma Rising - Studying VolcanoesT his text is pro vided co urtesy o f OLo g y, the American Museum o f Natural Histo ry’s website fo r kids.
How Do Scientists Study Volcanoes?
Around the world, there are about 1,500 active volcanoes. Active volcanoes are those that have erupted in the
past, and could erupt again. About twenty are probably erupting right now.
These days, eruptions rarely come as a surprise. Scientists are keeping a watchful eye on active volcanoes. They
want to find out if magma is rising beneath a volcano — a sign that it could erupt. The goal? Reduce the risk to
humans who live near them.
Nearly every Caribbean island has its own active volcano. That’s because these islands lie above subduction
zones, where one tectontic plate sinks, or subducts, beneath another.
Check Out Some of the Tools that Scientists Use to Monitor Volcanoes
The Global Positioning System (GPS) and satellite radartechnology can signal if rising magma is causing a volcano’sshape to change. Satellites bounce radar signals off avolcano’s surface and compare images over time to detectsmall changes in the mountain’s shape.
This portable monitoring station is called a “spider.” Spidersare dropped into an active volcano’s crater and transmitseismic data to geologists about the movement of magmainside.
Some volcanoes erupt explosively,like opening a shaken soda bottle,because their magma is full of gases.Other volcanoes erupt gently, likeboiling milk spilling over the sides of apot, because their magma has fewergases. An "active" volcano eruptedrecently or might erupt soon. A"dormant" or sleeping volcano hasbeen quiet for a long time, but mayerupt again someday. An "extinct"volcano has not erupted for over10,000 years.
Making RocksT his text is pro vided co urtesy o f OLo g y, the American Museum o f Natural Histo ry’s website fo r kids.
Hi, I'm Jim Webster. I'm an Earth scientist at the American Museum of Natural History and I
study volcanoes.
Some volcanoes slowly ooze magma like a thick stew that overflows on a hot stove. The ones I
study explode with immense power.
Like most scientists who study volcanoes, I visit them to get a closer
look and collect rock samples. But my real research happens in the
lab. I'm interested in where all the action starts—way down below the volcano in the
magma chamber, where gas-rich magma collects. As you can imagine, it's way too
deep and hot to actually go there. One way I can get a close-up look is by recreating
the conditions of a magma chamber in my lab. If I can do this, I can understand what it
is about magma that makes some volcanoes so explosive.
Introduction
Before we get started in the lab, there are a few things to know about volcanoes.
Magma is hot, melted rock found inside the Earth. It collects deep under a volcano in
an area called a magma chamber. Over time, magma and gases like water vapor and
carbon dioxide build up in the magma chamber. When the pressure becomes too great, a volcano will erupt.
Illustration Credit: Eric Hamilton
You can think of a magma chamberas a bottle of soda. The soda is likethe magma and the fizz representsall the gases in the magma. Whenthe cap is on, the fizz is under a lot ofpressure, but it is dissolved in themagma.
Illustration Credit: Eric Hamilton
When you crack open the sodabottle, the pressure is released, orsuddenly lowered. As the gases tryto come out of the soda, bubbles areformed. As soon as bubbles form,they want to escape the liquid. Thiscauses an explosion.
In the same way, when a crack opens up above the magma chamber, the magma bursts out in an eruption. When
My scientific assistant ChristineTappen does most of the work to getthe samples ready. She also helps toanalyze them.
Step 2: Examine the Rocks in the Lab
Now I return to the lab to study the pumice. This is where my research really begins!
These rocks formed over thousands of years under extreme temperatures and pressures. My goal is to figure
out exactly how they formed. To do this, I'm going to crush a piece of pumice and try to re-create it in the lab. I
have to learn as much as I can about the rock before I begin.
I'm most interested in two parts of the pumice: volcanic glass and melt inclusions.
Photo Credit: AMNH
Volcanic glass is magma that cooledquickly after it erupted. It has thesame composition as the originalmagma, minus gases that escaped.
Photo Credit: AMNH
Down in the magma chamber,sometimes drops of melt, or magma,get trapped inside minerals as theygrow. When the magma erupts andcools, these melt inclusions remainintact and preserve droplets of theoriginal magma, including the gases.
To begin, we prepare the samples.
To get a closer look, we cut a rock into thin slices or crush it and separate the grains. Then we mount the
samples on glass slides.
Then, we examine them.
We're looking for rock samples with minerals that contain melt inclusions. These
can only be seen with a powerful microscope because they are smaller than a grain of
sand. We also use more powerful instruments to measure the amount of and types of
gases in the samples.
Now I know a lot about the pumice. I'm ready to begin my experiments.
Step 3: Make a Mini-Magma Chamber
What was it l ike deep in the magma chamber when the pumice formed? What was the