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Week 2 Volcanoes
Can we use the heat from Yellowstone for energy?
Geothermal energy, heat energy from the earth's interior, is used to generate electricity in a variety of places
throughout the world. Although Yellowstone and its surroundings are a significant geothermal resource, the
Park itself is off limits to development. Because geothermal developments often cause a decrease in flow of
nearby hot springs and other geothermal features, it is questionable whether anyone could get permission to
develop geothermal energy in the region outside the park.
There are other natural heat sources in the United States that are being used for geothermal energy.
Typically, hot water or steam is tapped from a deep reservoir through a geothermal drillhole. The fluid is then
expanded through a turbine to generate electricity. In California, there are about 4 to 5 GW of electricity
generated at power plants at The Geysers, Salton Sea, Coso, Casa Diablo and other geothermal systems.
This is enough to provide energy for several million people. There are also power plants in Nevada, Utah,
and Hawaii. Geothermal power is also used in many others countries. TheGeothermal Education Office has
a good website with lots of information about geothermal energy, its uses, and the output of different
geothermal systems. The U. S. Geological Survey also has an educational and well-illustrated booklet on
geothermal energy.
Can you release some of the pressure at Yellowstone by drilling into the volcano?
No. Scientists agree that drilling into a volcano would be of questionable usefulness. Not withstanding the
enormous expense and technological difficulties in drilling through hot, mushy rock, drilling is unlikely to
have much effect. At near magmatic temperatures and pressures, any hole would rapidly become sealed by
minerals crystallizing from the natural fluids that are present at those depths.
Could a large Yellowstone eruption significantly change weather patterns?
If another catastrophic caldera-forming Yellowstone eruption were to occur, it quite likely would alter global
weather patterns and have enormous effects on human activity, especially agricultural production, for many
years. In fact, the relatively small 1991 eruption of Mt. Pinatubo in the Philippines was shown to have
temporarily, yet measurably, changed global temperatures. Scientists, however, at this time do not have the
predictive ability to determine specific consequences or durations of possible global impacts from such large
eruptions.
Could the Yellowstone volcano have an eruption that is not catastrophic?
Yes. Over the past 640,000 years since the last giant eruption at Yellowstone, approximately 80 relatively
nonexplosive eruptions have occurred and produced primarily lava flows. This would be the most likely kind
of future eruption. If such an event were to occur today, there would be much disruption of activities in
Yellowstone National Park, but in all likelihood few lives would be threatened. The most recent volcanic
eruption at Yellowstone, a lava flow on the Pitchstone Plateau, occurred 70,000 years ago.
How fast is the hotspot moving under Yellowstone?
Actually, the source of the hotspot is more or less stationary at depth within the Earth, and the North
America plate moves southwest across it. The average rate of movement of the plate in the Yellowstone
area for the last 16.5 million years has been about 4.6 centimeters annually. However, if shorter time
intervals are analyzed, the plate can be inferred to have moved about 6.1 centimeters per year from 16.5
million years ago until about 8 million years ago, then slowed to 3.3 centimeters a year for the past 8 million
years.
How hot is Yellowstone?
Yellowstone is a plateau high in the Rocky Mountains, and is snowbound for over six months per year. The
mean annual temperature is 2.2°C, barely above the freezing point of water. However, Yellowstone is also
an active geothermal area with hot springs emerging at ~92°C (the boiling point of water at Yellowstone's
mean altitude) and steam vents reported as high as 135°C. Only about 0.3% of the park's terrain is thermal
ground, so most places are no hotter than anywhere else in the Rockies.
In some of Yellowstone's thermal areas, heat flow is over 100 watts per square meter, about 50 times that of
Yellowstone's average and ~2000 times that of average North American terrain. This enormous heat flow is
derived from the molten rock or magma in the crust beneath the caldera, which ultimately is generated by
the Yellowstone Hot Spot, a partly molten region of the Earth's mantle hundreds of kilometers beneath the
surface.
How is heat released in Yellowstone?
Earth's heat is released in Yellowstone by two main processes, conduction and convection:
1. Conduction is the movement of heat from hotter material to colder material. A common example of
conduction is when heat from a stove is transferred through the bottom of a coffee pot to the liquid inside.
Conduction in Yellowstone helps transfer heat from deep within Earth to shallower depths. Of the heat
released from the ground at Yellowstone, about 25% is by conduction.
2. Convection is heat transported by hot material in motion, such as hot water or magma. Convection
happens inside a coffee pot when heat is carried to the top of the liquid in the pot by hot water that rises
buoyantly from the heated bottom because it is less dense than overlying cooler water. As the water boils,
the rise of the hotter water and the compensating fall of cooler water from the top forms what is called a
convection cell. Convection of molten rock helps carry heat up through the Yellowstone caldera. Near the
surface, convection of hot ground water drives geysers, hot springs, and fumaroles. Convection accounts for
roughly 75% of the heat released from the ground at Yellowstone.
How large is the magma chamber that is currently under Yellowstone?
The magma chamber is believed to be about 40 by 80 kilometers across, similar in size to the overlying
Yellowstone caldera. The top of the chamber is about 8 km deep and the bottom is around 16 km deep.
However, the chamber is not completely filled with fluid magma. It contains a partial melt, meaning that only
a portion of the rock is molten (about 10 to 30%); the rest of the material is solid but, of course, remains hot.
The method that scientists use to discern this information is similar to medical CT scans that bounce X-rays
through the human body to make three-dimensional pictures of internal tissue. In an analogous manner, a
method called seismic tomography uses hundreds of seismograms to measure the speed of seismic waves
from earthquakes and small, intentional dynamite explosions--data that allow geophysicists to make 3-D
pictures of structures within the Earth. Scientists compare these seismic velocities, and infer the composition
from deviations of these from average, thermally undisturbed values.
How many caldera-forming eruptions have occurred from the long-lived hotspot that is currently
beneath Yellowstone?
Many eruptive units found along the path of the Yellowstone hotspot have been dated, but only a few of
them represent large caldera-forming eruptions. At least five volcanic fields centered on large caldera
complexes have been identified. Some of these caldera complexes erupted climatically more than once;
probably 15 to 20 caldera-forming eruptions have occurred along the hotspot as it left a trail from western
Idaho to Yellowstone within the past 16.5 million years.
How many giant eruptions have occurred in the Yellowstone National Park region and how large
were they?
Volcanic activity began in the Yellowstone National Park region a little before about 2 million years ago.
Molten rock (magma) rising from deep within the Earth produced three cataclysmic eruptions. The first
caldera-forming eruption occurred about 2.1 million years ago. The eruptive blast removed so much magma
from its subsurface storage reservoir that the ground above it collapsed into the magma chamber and left a
gigantic depression in the ground- a hole larger than the state of Rhode Island. The huge crater, known as
a caldera, measured as much as 80 kilometers long, 65 kilometers wide, and hundreds of meters deep,
extending from outside of Yellowstone National Park into the central area of the Park (Figure 1).
Later, activity shifted to a smaller region within the Island Park area of eastern Idaho, just southwest of
Yellowstone National Park, and produced another large caldera-forming eruption 1.3 million years ago.
Subsequent activity has been focused within the area of the National Park, and another huge eruption
640,000 years ago formed the Yellowstone caldera as we now see it.
The three caldera-forming eruptions, respectively, were about 2,500, 280, and 1,000 times larger than the
May 18, 1980 eruption of Mt. St. Helens in Washington State. Together, the three catastrophic eruptions
expelled enough ash and lava to fill the Grand Canyon.
In addition to the three climactic eruptions, activity associated with each of the three caldera cycles
produced dozens or even hundreds of smaller eruptions that produced both lava and pyroclastic materials.
What are potential geologic hazards at Yellowstone other than volcanic eruptions?
The heat and geologic forces fueling the massive Yellowstone volcano affect the park in many ways.
Yellowstone's many geysers, hot springs, steam vents, and mudpots are evidence of the heat and geologic
forces. These hydrothermal (hot water) features are mostly benign, but can rarely be the sites of violent
steam explosions and pose a hydrothermal hazard. Earthquakes, another example of active geologic forces,
are quite common in Yellowstone, with 1,000 to 3,000 occurring annually. Most of these are quite small,
although significant earthquakes have shaken Yellowstone, such as the 1959 magnitude 7.5 Hebgen Lake
quake, the largest historical earthquake in the intermountain region, and the 1975 magnitude 6.1 quake near
Norris Geyser Basin. The many earthquakes and steam explosions in the past 10,000 years at Yellowstone
have not led to volcanic eruptions.
What are the main monitoring instruments of the Yellowstone Volcano Observatory?
Activity leading to a possibly impending volcanic eruption or a large earthquake can be evaluated using the
modern seismic and GPS networks of YVO. The instruments are designed to provide information in near
real time using modern digital instrumentation and internet and telephone links.
What is Yellowstone’s caldera?
Let’s start with some background information. The Earth is made of three layers: the core at the
center, surrounded by the mantle, and then the crust.
Millions of years ago, a source of immense heat known as a hotspot formed in the Earth’s
mantle below what today is Yellowstone. Roughly 600,000 years ago, the hotspot pushed a
large plume of magma toward the Earth’s surface. This caused the crust to jut upward. Bob
Smith, a seismologist at the University of Utah, described the phenomenon to Fox News like this.
“This crustal magma body is a little dimple that creates the uplift.It’s like putting your finger under
a rubber membrane and pushing it up and the sides expand,” he said.
The pressure on the surface finally gave way when cracks formed around the plume’s edges.
When the surface could no longer withstand the pressure there was a massive explosion of
magma, emptying more than one hundred cubic miles below the surface of molten rock. With
nothing beneath the surface to hold it up, the crust caved in.
A caldera is that volcanic depression that occurs when a magma reserve is emptied, the “caved
in,” typically round in shape, section. The Yellowstone caldera is 35 miles wide and 50 miles
long, although a recent study suggests the caldera is larger than previously thought.
Watch Creation of Yellowstone
http://www.history.com/topics/us-states/montana/videos/creation-of-yellowstone-nationalpark?m=528e394da93ae&s=undefined&f=1&free=false
Monitoring Volcano Ground Deformation
Changes at the Surface Tell us about the Subsurface
Ground deformation (swelling, subsidence, or cracking) is measured with a variety of techniques, including Electronic
Distance Meters (EDM), the Global Positioning System (GPS), precise leveling surveys, strainmeters, and tiltmeters.
EDMs use lasers to accurately measure changes in distance between benchmarks (fixed points) with repeated
measurements. GPS makes use of satellites orbiting the Earth to determine and track the locations of points.
Strainmeters and tiltmeters are used to monitor subtle changes in shape of the ground surface. For more information,
please see Monitoring Volcano Ground Deformation in our Activity Section.
Changes to the surface of a volcano (volcano deformation) can provide clues about what is happening
deep below the surface. Most volcano deformation can only be detected and measured with precise
surveying techniques. The Volcano Hazards Program has installed networks of sensitive deformation
instruments around volcanoes to monitor changes over time. These instruments, along with satellite-based
technologies help us to better understand the volcanoes we watch and allow us to provide eruption
warnings.
GPS
Mapping individual ground locations Earth-orbiting satellites.
InSAR
Mapping ground deformation of large areas using radar images
from Earth-orbiting satellites.
Tilt
Measuring tiny changes in the slope angle or "tilt" of the
ground.
EDM
Measuring the distance between benchmarks placed on a
volcano tens to thousands of meters apart.
Got a Tummy Ache?
How are volcanic gases measured?
Watch this video
http://app.discoveryeducation.com/player/view/assetGuid/84BA3BA7-D2C3-4531-ABD00924E6B0093F
Instruments to measure sulfur dioxide and carbon dioxide can be mounted in aircraft to determine the quantity of gas
being emitted on a daily basis. Such instruments can also be used in a ground-based mode. An instrument that detects
carbon dioxide can be installed on a volcano and configured to send data continuously via radio to an observatory.
Sulfur dioxide in volcanic clouds can also be measured from space with instruments aboard satellites.
Activity:
Fill a balloon with 1/8 tsp of baking soda. Fill a test tube ¼ full. Gently place the balloon on to
the test tube without spilling the baking soda into the tube. Once balloon is sealed over the test
tube, lift up the end gently and empty the baking soda into the test tube - shake and fill.
What happened? Why did this happen?
How could you determine what type of gas is emitted and how could you measure how much?
What does this have to do with modern day science and detecting a volcano before eruption?
Watch this video:
http://app.discoveryeducation.com/player/view/assetGuid/84BA3BA7-D2C3-4531-ABD0-0924E6B0093F
Monitoring Volcanic Gases
Monitoring Volcanic Gases: the driving force of eruptions
Scientists have long recognized that gases dissolved in magma provide the driving force of volcanic eruptions, but only
recently have new techniques permitted routine measurement of different types of volcanic gases released into the
atmosphere. Sulfurous volcanic gas and visible steam are usually the first things people notice when they visit an active
volcano, for example Mount St. Helens pictured here. A number of other gases also escape sight unseen into the
atmosphere through hot fumaroles, active vents, and porous ground surfaces. The gases escape as magma rises toward
the surface, when it erupts, and even as it cools and crystallizes below ground.
A primary objective in gas monitoring is to determine changes in the release of certain gases from a volcano,
chiefly carbon dioxide and sulfur dioxide. Such changes can be used with other monitoring information to provide
eruption warnings and to improve our understanding of how volcanoes work. In recent years, we have directed
increased attention toward volcanic gas emissions because of the newly appreciated hazards they sometimes pose and
their effects on the Earth's atmosphere and climate.
The challenge of studying volcanic gas emissions
Gases released by most volcanoes are difficult to sample and measure on a regular basis, especially when a volcano becomes restless.
Direct sampling of gas requires that scientists visit a hot fumarole or an active vent, usually high on a volcano's flank or within its summit crater.
At some volcanoes, gases discharge directly into crater lakes. The remote location of these sampling sites, intense and often hazardous fumes,
frequent bad weather, and the potential for sudden eruptions can make regular gas sampling sometimes impossible and dangerous.
Measuring gases remotely is possible but requires ideal weather and the availability of suitable aircraft or a network of roads around a
volcano. Consistent and favorable wind conditions are needed to carry gases from vents and fissures to where they can be measured. In some
cases, automated on-site gas monitoring is feasible. Under corrosive conditions, only a few sensors are available, however, for continuously
recording the concentrations of specific gases.
Scientists face yet another challenge--acid gases, like SO2, easily dissolve in water. Thus, volcanoes with abundant surface or subsurface
water can prevent scientists from measuring the emission of acid gases as magma rises toward the surface and even after explosive eruptions.
Because CO2 is is less likely to be masked by the presence of water, measuring it when a volcano first becomes restless and between eruptions
may be important for determining whether significant magma degassing is occurring.
Lahar in a jar
Hydrologic Monitoring of Volcanoes
Watch this video:
https://www.youtube.com/watch?v=5x5tZAHEoRU
Watch this video:
http://app.discoveryeducation.com/player/view/assetGuid/699A0208-67B2-437E-BA3A4A39A6871CD8
What is lahar?
Why does volcanic activity often lead to high rates of erosion and sedimentation?
What types of problems could occur after a volcano?
How can lahar be measured and/or stopped?
Field observations by experienced volcanologists go hand in hand with more sophisticated equipment and techniques to
form a complete system for monitoring volcanoes. Field observations may include water temperature and pH (acidity)
measurements, or observations of ground cracking and new areas of avalanching rocks. An experienced observer can
integrate many different types of data on the spot and design simple measurements to further assess the significance of
volcanic unrest. There is no substitute for well-trained, experienced observers when trying to figure out how a volcano
will behave.
Rivers route lahars and deliver sediment
Photograph by K. Scott on June 24, 1990
When water combines with loose rocks and sediment in river valleys to form a flood or lahar, large areas downstream from a volcano can be buried with water
and sediment several meters thick. Scientists monitoring an active volcano face the critical challenge of detecting a potentially dangerous lahar in real time so
that a warning can be issued by public officials to people downstream.
An even more difficult and less obvious challenge for scientists, however, comes in the weeks and years after an eruption that significantly alters a volcano's
watersheds--monitoring the long-term threat of sediment transport and increased flooding. For example, annual sediment yields following the explosive 1980
eruption of Mount St. Helens were as much as 500 times greater than typical background level. After 20 years, the average annual suspended-sediment yield in
the Toutle River downstream from the 1980 landslide deposit was still 100 times above typical background level.
Why is this a potential problem? Such high sediment yields often cause river channels leading away from an active volcano to gradually fill with new, loose
sediment. As such channels partially fill with sediment, their capacity to convey water within their banks is reduced, which commonly results in more frequent
flooding during periods of intense rainfall. The experience at Mount St. Helens, and more recently with 1991 eruption of Mount Pinatubo in the Philippines,
shows that effective mitigation measures must remain functional for decades following a major volcanic disturbance in order to reduce the likelihood of
flooding.
Hot Lava
Watch Video:
https://www.youtube.com/watch?v=aU5NtZUePk8
What are the three main volcanoes?
There are three main types of volcano - composite or strato, shield and dome.
Composite Volcanoes
Composite volcanoes, sometimes known as strato volcanoes, are steep sided cones formed from layers of ash
and [lava] flows. The eruptions from these volcanoes may be a pyroclastic flow rather than a flow of lava. A
pyroclastic flow is a superheated mixture of hot steam, ash, rock and dust. A pyroclastic flow can travel down the
side of a volcano at very high speeds with temperatures over 400 degrees celsius. Composite volcanoes can rise
over 8000 feet.
A simple cross section through a composite volcano
When composite volcanoes erupt they are explosive and pose a threat to nearby life and property.Eruptions are
explosive due to the thick, highly viscous lava that is produced by composite cone volcanoes. This viscous lava
has a lot to do with why they are shaped the way they are. The thick lava cannot travel far down the slope of the
volcano before it cools.
Composite volcanoes are usually found at destructive plate margins. Examples of composite volcanoes include
Mount Fuji (Japan), Mount St Helens (USA) and Mount Pinatubo (Philippines).
Shield Volcanoes
Shield volcanoes are low with gently sloping sides and are formed from layers of lava. Eruptions are typically nonexplosive. Shield volcanoes produce fast flowing fluid [lava] that can flow for many miles. Eruptions tend to be
frequent but relatively gentle. Although these eruptions destroy property, death or injury to humans rarely occurs.
A simple cross section through a shield volcano
Shield volcanoes are usually found at constructive boundaries and sometimes at volcanic hotspots. Examples of
shield volcanoes include Mount Kilauea and Maunaloa on Hawaii.
The video below shows a lava flow from Mount Kilauea.
Dome (Acid Lava Cones)
Acid [lava] is much thicker than [lava] which flows from shield volcanoes. Dome volcanoes have much steeper
sides than shield volcanoes. This is because the lava is thick and sticky. It cannot flow very far before ot cools and
hardens. An example is Puy de Dome in the Auvergne region of France which last erupted over 1 million years
ago.