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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

Making Rocks1242 words

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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


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.

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3. The fluid flows up into the mantle rock above and changes its chemistry, causing it to melt. This forms magma

(molten rock).

4. The magma rises and collects in chambers within the crust.

5. As magma fills the chamber, pressure grows. If the pressure gets high enough, the magma can break through

the crust and spew out in a volcanic eruption. Most explosive volcanoes occur above subduction zones.

Why Are Some Volcanoes So Explosive?

“Mt. Pelée was incredibly explosive. It’s like twisting off the top of a soda bottle!”

JIM WEBSTER, volcanologist Photo Credit: AMNH

It’s all a matter of chemistry. The way a volcano erupts depends on the amount of gas and silica (a molecule of

silicon oxygen) in the magma below. Magma with lots of silica is thick and gooey, while magma low in silica is

thin and runny. And in magma with lots of gas, bubbles form as it rises. The more bubbles that form, the more

explosive the eruption!

Mt. Pelée was the most explosive type of volcano: it was high in silica and high in gas. This type of volcano is

called a stratovolcano.

Explore How Different Shapes of Volcanoes Have Different Kinds of Eruption

Photo Credit: © USGS

A cinder cone volcano, like Tavurvur in PapuaNew Guinea, forms when erupted fragments


Volcanoes: Magma Rising - Volcanic Eruptions


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.

Volcanoes: Magma Rising - Volcanic Eruptions


Earthquakes: Tremors from Below - A Tsunami in thePacific

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.

Earthquakes are happening all the time. Most are so small that people don’t even feel them. But some can be

very powerful. If they occur near towns and cities, they can make buildings and bridges sway or even collapse.

Earthquakes can also occur along the seafloor and cause it to move. And if the quake is powerful enough, it can

trigger waves that travel across the ocean. These waves grow taller as they approach land, becoming a tsunami.

Tsunamis can have devastating effects on people.

A Tsunami Sweeps the South Pacific


On the morning of September 29, 2009, a strong undersea earthquake occurred near the Samoan island chain in

the South Pacific. It happened as children were getting ready for school and adults were dressing for work.

“The ground shook from side to side and then swayed as if one was sitting on a boat on the water.”

- TSUNAMI SURVIVOR, recalling the earthquake before the wave

When the shaking stopped, people noticed the sea was rough and bubbly. Then it

drained rapidly away from the shore. Within minutes, a tsunami swept over the

islands. In some places, its height reached around 40 feet (12 meters). The

earthquake had triggered the tsunami.

Coming Together

SHOW_AUTO_COPYRIGHT© 2015 American Museum of Natural History. All rights reserved. Used by PermissionamnhEarthquakes: Tremors from Below - A Tsunami in the Pacific


Tsunami evacuation sign PhotoCredit: AMNH

Photo Credit: AMNH

The people of Samoa helped each other rebuild homes and lives. They also held

ceremonies to strengthen the connections within their community.

One ritual is for the leaders to pass a cup of the ceremonial

drink called áva. The daughter of a high chief prepares áva by mixing pepper roots in

a wooden bowl. During the ceremony, áva is passed around the group in a communal

cup. Before drinking, each person pours a few drops on the ground, returning the áva

to the earth.

Photo Credit: AMNH

Photo Credit: © Philippe Meunier/Tahititatou.com

Earthquakes: Tremors from Below - A Tsunami in the Pacific


Earthquakes: Tremors from Below - How Do ScientistsStudy Earthquakes?


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.

SHOW_AUTO_COPYRIGHT© 2015 American Museum of Natural History. All rights reserved. Used by PermissionamnhEarthquakes: Tremors from Below - How Do Scientists Study Earthquakes?


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?


Earthquakes: Tremors from Below - What Causes theEarth to Shake?


Tsunamis like the one in Samoa are triggered by large undersea earthquakes. To understand how tsunamis

form, let’s first take a look at what causes earthquakes. Most earthquakes happen at the edges of tectonic

plates, the big pieces of Earth’s crust that make up its outer shell . These plates fit together like a puzzle, but

they are always moving very slowly, about one or two inches per year. Where the edges of the plates meet,

three things can happen. Plates can collide, separate, or grind against each other. The movement between two

plates can trigger earthquakes.

When Plates CollideWhen plates collide, sometimes one plate sinks, or subducts, below another one.

This can trigger an earthquake. When earthquakes cause the ocean floor to move, the

water moves, too. Columns of water travel across the ocean and grow taller as they

approach land, becoming a tsunami.

When Plates GrindWhen the edge of one plate grinds against another, it sometimes gets stuck and

pressure builds up. When it finally breaks loose, rocks break, releasing energy in the

form of a seismic wave, or earthquake.

SHOW_AUTO_COPYRIGHT© 2015 American Museum of Natural History. All rights reserved. Used by PermissionamnhEarthquakes: Tremors from Below - What Causes the Earth to Shake?


Volcanoes: Magma Rising - Mt. Pelee EruptsT 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.

Some volcanoes explode with the force of an atomic bomb. Others spill rivers of gently flowing lava.

What causes volcanoes to erupt? How do scientists study them? Let’s explore one of the most powerful,

destructive volcanic eruptions in history.

The city of St. Pierre with Mt. Pelée in the distance

More than a century ago, the city of Saint-Pierre was known as the Paris of the Caribbean. Located on the island

of Martinique, Saint-Pierre was a center of trade in rum, sugar, cocoa, and coffee. Its boulevards were lined with

beautiful homes and shops.

But in the spring of 1902, all of that changed…

SHOW_AUTO_COPYRIGHT© 2016 American Museum of Natural History. All rights reserved. Used by PermissionamnhVolcanoes: Magma Rising - Mt. Pelee Erupts


On the morning of May 8, the nearby volcano Mt. Pelée exploded in a burst. A swirling cloud of hot gas, ash, and

rocks, called a pyroclastic flow, rushed down the mountainside at 480 kilometers per hour (300 mph). It burned

everything in its path, including the town of Saint-Pierre and nearly all the ships in the harbor. Within two

minutes, close to 30,000 people were dead.

A Disaster Unfolds: 1902

“No one ever thought of fearing the volcano, which all thought to be

extinct… the people wandered about by thousands, never dreaming that

there was any danger.”

- J. CHATENAY, a Saint-Pierre resident who moved away before the

eruption

At the time, people living on the islands of Martinique and St. Vincent

underestimated the risks of living near volcanoes. They had ignored

signals that the volcanoes were still active.

Timeline of the Eruption

April 23: Earthquakes shake dishes from shelves in Saint-Pierre.

April 24: Fine ash from Mt. Pelée falls for two hours on a town nearby.

May 2: A column of ash and fumes rises nearly 3 kilometers (2 miles) above

the mountain. An inch of ash covers Saint-Pierre.

May 5: A mudflow from Mt. Pelée kills 23 people north of the city. Fifteen

minutes later, a small tsunami reaches Saint- Pierre.

May 6: Mt. Pelée spews columns of gas and ash, and flings huge molten

rocks in the air.

May 7: Mt. Soufrière, a volcano 120 kilometers (75 miles) north on the island

of St. Vincent, erupts, and a boiling mudflow of steam and ash kills 1,565

people.

May 8: Mt. Pelée explodes, destroying the town of Saint-Pierre.

May 20: A second eruption covers the now desolate town of Saint-Pierre.

May 31: The volcano’s dome rises nearly 300 meters (1,000 feet). A spine, called the “Needle of Pelée,” juts

above it. Within a couple of months, the needle collapses.

Volcanoes: Magma Rising - Mt. Pelee Erupts


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.

Rue Victor Hugo after the eruption





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

Photo Credit: © NASA

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.

SHOW_AUTO_COPYRIGHT© 2016 American Museum of Natural History. All rights reserved. Used by PermissionamnhVolcanoes: Magma Rising - Studying Volcanoes


Photo Credit: © AMNH

Thermal imaging reveals where Mt. Etna is warming under thesurface.

Photo Credit: © AMNH

Scientists observe a wall of digital monitors that constantlyrelay Mt. Etna’s vital signs.

“We now know much more about how volcanoes work. We have learned more about gases, the relationship

between seismic activity and magma movement, [and] even how gas can open the rock and provide a pathway

for magma to flow. So we’re better able to issue warnings that a volcano will erupt.”

Photo Credit: AMNH

JIM WEBSTER, volcanologist

Volcanoes: Magma Rising - Studying Volcanoes


Photo Credit: Courtesy of AMNH

Courtesy of USGS

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

SHOW_AUTO_COPYRIGHT© 2016 American Museum of Natural History. All rights reserved. Used by Permissionamnh Making Rocks


a volcano is explosive, we know there were lots of gases dissolved in the magma.

I want to find out how various gases behave in magma at different temperatures and pressures. When do the

gases dissolve in magma? How are the gases released? When do they cause an explosive eruption?

My goal is to understand, and even predict, explosive volcanic eruptions. This could protect the 500 million

people across the planet who live near active volcanoes!

Step 1: Visit Volcanoes and Collect Rocks

I may do most of my work in the lab, but my research starts in the field, at actual volcanoes. I study two

volcanoes: Mount Vesuvius in Italy and Mount St. Augustine in Alaska. Both these volcanoes erupted explosively

many times. They're both found above subduction zones, places where the edge of one tectonic plate is sinking

underneath another.

Photo Credit: AMNH

The explosion of Mount Vesuvius inA.D. 79 buried the cities of Pompeiiand Herculaneum with mud and ash.

Photo Credit: AMNH

Mount St. Augustine is part of theRing of Fire, a chain of volcanoescircling the Pacific Ocean. It haserupted twice since 1969.

I hope to discover what makes these types of volcanoes explosive.

Photo Credit: AMNH

I start by collecting pumice, a light rock filled with holes like a sponge. Pumice forms from explosive eruptions.

The lava flows during these eruptions are foamy from all the gas. The frothy liquid cools very quickly. When it

hardens, the bubbles in the lava become holes in the solid rock. In fact, there are so many holes that pieces of

pumice actually float on water!

Making Rocks


Photo Credit: AMNH

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

temperature? What was the pressure?

Making Rocks


Photo Credit: AMNH

We experiment with different conditions until we have re-created the same rock. Then, we will know more

about what it was like deep inside the magma chamber, before the volcano erupted.

FIRST, we prepare a mini-magma chamber

We combine all of the ingredients needed to make our own rock.

• We crush some of the pumice we collected into a fine powder.

• This goes into a tiny gold capsule, with some gas we added.

• Then, we seal it tight so the gas does not escape.

SECOND, we turn it into magma...and make a rock!

We put our capsule, or mini-magma chamber, under some pretty extreme conditions.

Photo Credit: AMNH

• We heat the sample to about 800 degrees C (1500 degrees F.) That's about three times hotter than your oven

gets.

• We set the pressure to about 2000 bars. This is equal to the pressure exerted by the Earth about 4 1/2 miles

deep.

• After the machine runs for several days, we shut it off so the magma cools quickly and hardens into glass.

THIRD, we analyze our new rock.

If it has the same amount of gas as the original rock, we know we chose the right temperature and pressure. If

not, we try again.

It can take many experiments to discover the same conditions as the original magma chamber. But, every time

that we do it, we are learning more about what makes volcanoes explode.

Making Rocks


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Volcanoes and Earthquakes - ed-MAGIC-ation · Volcanoes: Magma Rising - Volcanic Eruptions 532 words Earthquakes: Tremors from Below - A Tsunami in the Pacific 307 words ... “The