for Ikon

Igneous Rocks Intrusions and Volcanoes

Igneous rocks are associated with molten material. This material can be from the mantel or

melted crust material. Texture, iron content and silica content determine the type of igneous rock. The

texture determines the cooling temperature. Rapid cooling gives small to no crystal formation. This

means that the rock formed on the surface. The main minerals for igneous rocks are quartz, feldspar,

mica pyroxene amphibole and olivine. Mantel rock will have mainly olivine, and pyroxene. Melted

crustal rock has large amounts of quartz in it. Texture is a clue to the environment, internal (intrusive) or

external (extrusive). This was known for 200 years and later confirmed with the developing of polarizing

microscope and the careful grinding of a rock thin section (ground rock so thin light can pass through it).

Texture is created by cooling temperatures. Ions in hot magma have too much energy to bond together

and form a crystal. As cooling proceeds the ions lose energy and can then form crystals. Pressure will

also help in this since it forces ions together regardless of the heat energy. If the cooling proceeds slowly

as in intrusive material you have large crystals, if ejected into the surface you get small crystals or no

crystals.

Intrusive rocks are coarse textured (phanorytic.) These rocks

have slow cooling regimes cooling over thousands and thousands of

years in the crust of our planet. The heat is held in by the overlaying

rock. Elephant rocks in Missouri are a perfect example of such a rock.

This is an igneous intrusive body injected into the crust over a billion of

years ago.

Extrusive rocks have different types of appearances, one composed of

fine grained aphenitic another by glassy (no crystals) rocks. These categories

are dependent on how they erupted from the volcanoes. Lavas have a range

of appearances dependent on their chemical make-up and temperature.

Pyroclastic formation is characterized by violent

eruption with lava thrown into high into the air. If

the material is ejected rapidly and cools rapidly it forms volcanic glass- mineral

free since amorphous. Pumice is a form of igneous rock that forms from

volcanic glass with air pockets or vesicles. These vesicles are formed by the

degassing of the molten material (CO2, H2O, etc.). Volcanic ash is composed of

fragmented rocks, lavas and/or volcanic glass. It is thrown high in the air and

smaller fragments will travel around the globe. Bombs have a range of shapes and made up of solidified

lava. They are tossed into the air and fall along the sides of the volcanic cone. The last two are scoria and

pumice. These are gas filed lava. Pumice (to the left) is so light that it floats.

There is one more texture, a mixed texture indicating two different cooling regimes. This is

called porphyritic texture or porphyry. Here a slow cooling regime starts and

large visible crystals form. These are then there is a volcanic eruption before

more large crystals can grow and this gives us the two different crystal types.

Igneous material is also classified by chemical content. We break the material into four types according

to the proportion of silicate minerals. Specific minerals form at specific temperatures. Minerals with a

high proportion of iron and magnesium and calcium compared to silica form this group and are called

mafic from magnesium. The mafic and felsic mineral suites are on page 112 in your book. The feldspar

group is divided into potassium rich (orthoclase), sodium rich plagioclase and calcium rich plagioclase.

The last two the sodium and the calcium are end the

members of a solid solution where the plagioclase

formula is NaAlSi3O8;CaAl2Si2O8. The more calcium in

the plagioclase the more mafic the forming rock and

the higher the melting temperature to the right is an

example of these mixture. The more sodium, the more

felsic the magma melt and the lighter the igneous

rock( look at the chart on page 113).

Mafic Rocks a have large amounts of olivine

and pyroxenes giving the rocks their characteristic dark

colors. There may be a small to moderate amount of

calcium plagioclase. The lava form of this is called basalt. There are several areas of sheets of basalt such

the Columbian Plateau along the Columbia River in Washington. India as an even larger area, the Deccan

Traps, where kilometers thick layers of basalt contributed to the Cretaceous extinction event and

another in Siberia with an area as large if not larger also associated with an extinction event (Permian).

There is another mafic rock form. This form is called ultra-mafic. The mineral suite is primarily

made up of olivine with a small amount of pyroxene. This is the material that makes up the upper

mantel. The basalt upwelling at the spreading centers formed the ocean crust.

Felsic Rocks are poor in iron and magnesium. They are also poor in calcium. These rocks tend to

be light in color and one of the most abundant intrusive igneous rocks. They contain approximately 70%

silica and are abundant in quartz and orthoclase feldspar with some

sodium feldspar (albeit minerals). The intrusive form of this igneous

rock is Granite, the extrusive form is Rhyolite. These rocks can appear

as light brown, salt and pepper, pink, or orange or in some cases

almost purple (Missouri rhyolite). The Picture on the left is an image

of this rhyolite. Notice that it is porphyritic.

Between

the end members

of these two rock

types are the rocks

that are called the

intermediate.

These rocks have

less silica then the

Labradorite- tectosilicate

- Ca(50-70%) Na(50-30%) (Al, Si)AlSi2 O8

felsic and more than the mafic. They have some quartz, micas and may have some pyroxene. They may

also have amphiboles. The intermediate is divided into granodiorite and diorite. Granodiortite is

very difficult to differentiate from granite. This is done by looking at difference in the percentages of

quartz, orthoclase and sodium plagioclase. We will then only talk about diorite and its extrusive form

andesite. This material has a mineral suite with pyroxene like mafic and calcium plagioclase but it also

has amphiboles, micas, a mix of the sodium/calcium plagioclase minerals and some quartz. The variation

in the amount of silica gives its melt a variety of properties that can swing from one extreme to another.

The last is the composition factor impacting the melting is the chemical formula. The more mafic the

melt, the higher the melting temperature for mineral formation and mafic melts are characterized by

less silica in the melt and more iron and magnesium. Conversely the more felsic the melt represented by

more silica, the lower the melting temperature.

` We know from seismic waves that the Earth is solid until we reach the liquid outer core. Where

does the magma come from? While we are

still working on this question we do know

some factors that impact the temperature at

which this solid will melt. One of the big ones

is pressure. Most of these solids are at such a

high temperature that they should have

melted. The pressure prevents this by

preventing atoms from moving apart thereby

keeping it a solid. The only way to overcome

this is an even greater temperature. Water

content also impacts this. Water enters the

system at convergent plate boundaries and by

water circulating naturally close to a magma

body (think Yellowstone geysers).

The last is the composition factor

impacting the melting is the chemical formula. The more mafic the melt, the higher the melting

temperature for mineral formation and mafic melts are characterized by less silica in the melt and more

iron and magnesium. Conversely the more felsic the melt represented by more silica, the lower the

melting temperature.

Looking more closely at temperature it was found that a magma chamber only undergoes partial

melting. This partial melt is determined by the temperature of the chamber and the mineral

composition of the magma. Only certain minerals will melt at a given temperature. It is like the new

"lava cake" desert. The cake turned solid at one temperature but the temperature wasn't low enough

for the chocolate center to turn solid. As water enters the melt this temperature will lower for many of

the minerals and there will be a more complete melt. We geologist use this information to determine

how different kinds of magma form in different regions of the Earth's interior. Since magma is formed

from rock in which only the minerals with the lowest temperature melts.

As you go deeper into the Earth the pressure increases. This increase in pressure (as mentioned

earlier) increases the melting temperature. Because of the convection currents mantel material will

move to an area of lesser pressure in the region of the spreading centers. This allows for the

decompression melting of the mantel creating the basalt of our seafloor.

Water impacts the behavior on the melting temperatures. The impact of large amounts of water

on melting temperatures can be seen with the mineral albite which melts at 1000 o C. When water is

added to the melt drops to 800 o C. Water is present as a gas and dissolves into the molten albite. There is

a rule to explain this. This states that if you dissolve one material into another lowers the melting

temperature of the solution. It also impacts the melting temperature of mixture of other sedimentary

and other rocks .These rocks are often water rich and will melt.

Magma chambers are formed by the change in density as material is heated. The magmatic

material will rise through and upward. Being fluid the partial melt moves up through the pores and

boundaries of surrounding rock. As the drops of molten material rises they can coalesce into larger

bodies. It also cam melt the host rock forming magma chambers or cavities in the lithosphere.

Magmatic differentiation can partially account for the different types of igneous rock found on

this planet. In the chamber as it cools high temperature mineral will form. This will remove more iron,

magnesium and calcium/silica tetrahedrons creating the ultramafic and mafic material. This leaves

behind more silicate tetrahedrons per cation so more high temperature minerals that are silica rich and

felsic form. These only form, though, as the melt cools. The process is called fractional crystallization

and gives different minerals in the same chamber. By studying the Bowin's Reaction Series (bottom of

last page)you can predict a magma temperature by the minerals present.

The diagram to the left demonstrates magmatic differentiation and fractional crystallization. The initial

minerals that come out of the melt are more rich in iron and magnesium. As they crystalize out then

remove these cations leaving behind a progressively more silica rich melt. By the time there is later

crystallization the magma body has cooled and the excess silica gives you the minerals found on the

lower portion of the Bowin’ s reaction series.

While magmatic differentiation and fractional crystallization explains how there are different

minerals in a magmatic intrusion it doesn't answer the questions of where did all of the granite come

from. Granite is one of the most common igneous continental rocks. The idea rose of a complicated

process that had both partial melting giving basaltic magma at the spreading centers followed by the

formation of intermediate andisitic magma with the mixing of basaltic magma and sedimentary rocks at

ocean-ocean convergent plate boundaries while the melting of igneous, metamorphic and continental

crust at ocean-continental convergent plate boundaries might melt to produce granite if magmas.

Igneous intrusions take

place as the rising magma intrudes

into the country rock. They wedge

open the overlying rock as the

magma lifts up the overlying rock in

extension. This lifting up and

fracturing cam be seen with the

formation of rifts and is presently happening in the Basin and Range of our own west. The

magma can then intrude into these fractures.

As the body rises by breaking off the overlying rocks which may or may not melt into the

chamber. If the rock pieces melt they will change the composition of the melt in that region. If they

don't melt they remain as xenoliths in the magma that can be seen when the material cools and is

exposed by weathering.

The structures

that form by these process

are called Plutons and can

be from one cubic

kilometer to hundreds of

kilometers in size. The

largest of these plutons is

called a Batholith. These

large structures make up

not a single mountains but entire chains of mountains such as the Sierra Nevada Mountains. Smaller

plutons are called stocks and laccoliths are often the size of a single mountain.

Material that squeezes through the cracks from these bodies can cut across the country rock

making dikes. These magma bodies can also create their own cracks from the pressure they exert as

they rise. These are not a linear structure as they appear in a road cut but are actually a three

dimensional structure or can invade the country rock and spread along it in a horizontal structure called

a sill. You can view a dike here in Missouri at the Silver Mines State Park and on State Highway 72 on the

way to Arcadia.

The last features associated with igneous bodies are hydrothermal

veins. This can also be seen in sedimentary and metamorphic rocks. These can

be as small as millimeters or as large as a km in size. These veins can be in the

form of hydrothermal solutions often with quartz and valuable minerals

dissolved in it. These originate as water that permeates the country rock

(ground water) and forms into hydrothermal If they cool quickly they form

small crystals forming a sheet like tabular structure. These veins are an

important source of metallic ores.

Magmas form at two types of plate boundaries, the mid-oceanic ridges, where there is

divergence. The other plate boundary where magma is common is at the convergent plate boundaries.

There is another major source of magma, the mantle plumes. This are not associated with plate

boundaries and are the result of partial melting and form near the core-mantle boundary.

At the mid-oceanic ridge there is a decompression melt which then seeps up the fissures at the

divergent plate boundaries. The magma forms pillow lava of basalt. These columns of basalt are cut by

dykes cutting into the basalt country rock. Below this is the magma chamber. In the magma chamber

magmatic differentiation takes place with the olivine and pyroxenes precipitate out to form a peridotite

layer. Adjacent to the magma chamber is a layer of gabbro. The gabbro layer is adjacent to the hotter

magma layer becoming metamorphosed. Above the basalt layer is layers of sediment and sedimentary

rocks. These form the Ophiolite Suites on land. This appears when to plates move so fast that the

ocean

plate is

forced

on and

over the

lighter

continental crust. As the plates move further from the magma more gabbro forms. The areas of

subduction are another area in which magma makes its way to the surface. The composition of the

magmas are dependent on what is being subducted. With this form of magma there is fluid induced

melting. The water in the subducting oceanic crust decreases the melting temperature of the overlaying

mantel material (peridotite rich) and the basaltic crust. There is also a portion of sediment that is left on

this subducting oceanic crust. This material has a very low melting temperature and melts readily.

The composition of these magmas should be basaltic considering they are formed from the

basaltic oceanic crust and the peridotite layer but there is a lot of variation. This variation comes from

the amount of accumulated sediment and sedimentary rock that is incorporated. As the magma rises up

and through the overlaying lithosphere there is also the effect of fractional crystallization giving an

increasingly more silica rich melt. When the oceanic crust is subducted beneath a continental crust felsic

rock melts and contribute to this melt. The different compositions of these melts and the amount of

gases present have a major impact in the eruption style of the volcanoes that are formed in this area.

The last type of "magma factories" is the mantle plume. They originate in the mantle itself and is

thought as a mechanism for cooling the core. It forms a

column of nucleated rock that rises up through the rest of the

mantel in the shape of a diapere. When it reaches the

lithosphere this flattens out and undergoes a decompression

melt forming the magma and the models predict large scale of

eruptions that can last millions of years such as the Deccan Traps

in India and the Siberian Traps in Russia. While the models

predict millions of years eruptions this is often not the case.

This plume is often postulated to be fixed with the

overlaying plate moving over it giving a string of volcanoes from the same magma chamber but of

different ages. While this is often true there are other plumes that are geographically stable such as the

one in Iceland and the Azores off of the coast of Africa.

While plumes can either form flood basalts or strings of volcanoes the volcanic composition can

very. The plume material itself is basalt with high temperature minerals containing a high iron and

magnesium content and low silica content when they appear below a continent other process can take

place. The underlying basalt magma can melt the continental rock; both the granite and the sedimentary

rocks creating a more felsic melt with high silica content.

Volcanic Eruptions

Basaltic lavas are mafic in composition (high iron,

magnesium and calcium) with the lowest of all magma

compositions. The eruption temperatures from these lavas are high,

anywhere from 1000 to 1200 o C (1832-2192

o F). This lava has the

fastest downhill speed (62 mph) on a steep slope due to this high

temperature and low silica content.

This gives three different basaltic lava appearances. The

high temperature fast moving is called

pahoehoe a Hawaiian word. This gives

a ropey appearance to the lava field. As

the lava cools a skin forms over the

flow with hot lava continues to flow

beneath. As the lava cools and slows

the "aa" forms. This forms a thick

skin that breaks as it flows giving an angular blocky appearance. The last form that basaltic lava forms is

pillow lava. This lava captures air as the lava flows over itself moving forward. This form develops as the

magma erupts under water. This forms a bulbous form that resembles "pillows".

Andesitic lavas from the andesitic magmas have a higher silica content than the basaltic lava this

means that the minerals formed at this lava is made up of lower temperature minerals, no olivine. This

decreases the speed and distance of the flows. Their flows are stick forming blocky with few or no air

vesicles. They seldom get beyond the intermediate area of the volcano itself.

Rhyolite lavas are the highest in silica content (over 68%). The minerals are low temperature in

nature and the silicate minerals are high in sodium and potassium. The temperature of this lava is

600-800 o C (1,112-1,472

o F). This lava seldom leaves the crater and moves 10 times slower than basaltic

flows.

Volcanic eruptions are not always in the form of lavas. If water comes into contact with hot, gas

charged magma you can have a phreatic or steam explosion. One of the largest in history involved the

island Krakatau. This eruption started from an andesite chamber. The volcanic islands magma chamber

had emptied and collapsed (caldera formation) and sea water poured in triggering a violent phreatic

explosion that sent a major tsunami into much Indonesia as well as sending ash and debris travelled

over water onto the adjacent island of

Sumatra.

Pyroclastic flows and debris form

when water and gases come out of the

magma.

Pressure in

the magma

chamber

will keep

these

volatiles

from escaping. When the pressure drops

during an eruption the gases come out of solution. This can form an explosive eruption. This will shatter

pahoehoe aa

Pillow Lava

the overlaying rock and also form gas charged fragments in the air.

Pyroclastics or tephra have different sizes and these different sizes have different names: 1. ash,

2. lapelli, 3. agglutinates, 4. bombs and 5. blocks The smallest is the volcanic ash and are less than 2 mm

in size and are usually glass in nature. If you have larger blobs different things are formed. Blocks can are

greater than 64 mm in size and are formed from angular

solid rocks from the plugs in the volcano itself. Bombs are

greater than 64 mm but are formed from molten magma

and can have different shapes. Agglutinates form either

cinders (scoria) or pumice depending on are 2-64 mm in

size and are formed from smaller vesicular blobs. Pumice

is formed from volcanic glass and the air filling the vesicles.

Pumice is characterized by being able to float on water.

The caldera eruption takes place when the magma

chamber partially empties itself and triggers a collapse of

the unsupported material (roof of the chamber). This

then triggers a cataclysmic eruption with the pieces forcing

upward and out with much of the remaining magma in the

camber. The volcano doesn't present a cone at this stage

but a large valley ringed by the edges of the former magma

chamber. Calder eruptions can take place with any volcano

but are common with volcanoes such as Yellowstone and

stratovolcanoes.

Volcanic

processes- The

anatomy of a volcano can vary depending on the volcano

type. The common features for all volcanoes include a magma

chamber and a transport mechanism. The magma chamber

which lies in the crust portion of the lithosphere. The

chamber is filled by rising magma from the asthenosphere or

by the melting of the overlying rock by the rising magma.

Next is the transport mechanism. This can be in the form of a

central vent and side vents or from a fracture or fissure

through the overlaying rocks and into the magma chamber.

If there is

magmatic

eruption from a vent system you then get these volcanic

features. The most common is the volcanic cone. The overall

shape of this structure is dependent on the eruption type

and the magma type. Craters are a bowel shaped pit at the

Pumice

summit of the volcanic cone. This is over type

volcanic central vent. Another structure is the

volcanic dome. This structure is associated with a

more felsic magma and can act as a plug to the

central vent trapping magma and gas beneath

them. Here the pressure will increase until there is

an explosion.

The last feature is the caldera. Here the magma has

escaped at such a rapid rate that the chamber can

no longer support the overlaying rock. This rock

then collapses into the chamber. This often leads to

an even more violent eruption as the remaining

melted material is expelled from the chamber. The picture on the left is the famous Crater Lake in

Oregon. It is a 6 mile wide caldera that formed after the volcano Mt. Mazamo erupted over 7,000 years

ago. The volcano in the center (Wizard Island) formed much later.

Volcano Types

Fissure volcanos are characterized by large lava fields that latter form plateaus. They are

basaltic in nature and have little to no gas. If gases are present then you will see other volcanic forms

associated with them. Massive flood basalts

from fissure volcanoes have been linked to at

least one extinction event, the Permian and

possible another, the Cretaceous. There have

been many smaller flood basalts from fissures,

one of these is the Columbia Plateau in

Washington and Oregon. Other examples of

fissure volcanism are the massive spreading

centers at the divergent plate boundaries.

Shield volcanoes have a melt with

gases as well as basalt magma. There is a central vent as well as side vents. The temperature and speed

of flow gives the shape of this

volcano. The initial lava is pahoehoe.

This gives the gentle angle of the

shield near the central vent. As the

lava cools it forms aa and has a

steeper angle along the sides of the

volcano giving it the characteristic

shield shape. These volcanoes are

common in areas of divergence as well as oceanic hot

spots such as Hawaii and the Galapagos islands. There are

often fissures and side vents opening up on the sides of the

shields.

Stratovolcanoes form from two different types of

eruptions. You have an alternation of pyroclastics and lava.

This is due to the characteristics of the intermediate melt.

When there is a high gas content combined with a silica

rich melt (more felsic minerals such as sodium plagioclase,

micas and quartz) you have an explosive eruption

and the cone that forms is of rock fragments and

assumes a steep angle. This material can be

covered in a subsequent by lava when the melt is

more basaltic in nature having less silica in it. This

melt would have more high temperature

minerals, plagioclases with more calcium and less

sodium, pyroxenes and little mica. This coats the

rock fragments and maintains the steep angle of

the cone. These volcanoes are seen along

convergent plate boundaries such as the Andes,

the Cascades, Japan and the Aleutians.

The last volcanic cone is the cinder-cone. This is made up by solid fragments builds up into a

cone, this allows for a steep angled cone. These have a small central vent and the magma is gas charged.

These can form on the flanks of shield volcanoes and stratovolcanoes. Once the gases have been

expelled from the magma a side vent often

opens and lava flows out. These volcanoes

erupt only once then their vent seals with cold

magma.

There are multiple hazards with a

volcanic eruption but while we have heard of

many of these hazards such as lava and

massive explosions. VOG or volcanic “smog” is seldom

looked at. Volcanic gases vary in composition. Two of

the most common gases are CO2 and H2O. The amount

of CO2 is 0.25 gigatons a year. Large eruptions can have

profound effects on global warming. Other gases

include H2O. Other toxic gases include: HCL

(hydrochloric acid), HF (hydrofluoric acid), CO (carbon

monoxide) SO2 (sulfur dioxide) and H2S (hydrogen

sulfide). The sulfur compounds will interact

with water to form sulfuric acid. The

picture to the right shows the gases exiting

Kilauea’s central vent. These acidic gases

cause widespread devastation to plant and

animal life on both land and in the sea. This

gas is reportedly equivalent to over a pack

of cigarettes a day. To complicate things if

the sulfur compounds enter the upper

atmosphere the droplets from the acid

they form reflects sunlight and causes

widespread cooling. The eruption of

Tambora caused a year without summer in 1815 and widespread starvation. The eruption of Toba

approximately seventy thousand years ago is credited with a ten year volcanic winter and 1,000 years

of cooling. We are overdue for such an eruption from Yellowstone and Long Valley volcanoes in the

United States.

Ash is a pyroclastic product. It is small enough in size that it and can travel miles away (smaller

particles go worldwide) from the source. Ash clogs the stomata of plants

preventing the exchange of gases and suffocating the plants. Ash is rock and

volcanic glass shards. When animals breathe in ash it enters the lungs and

damaging the alveoli. Exposure can and often does prematurely age these lungs.

This material can also turn into a concrete like material and suffocate people

and animals. Both ash and pumice adds weight to structures roofs. This weight

can collapse buildings. One more problem with the ash is the impact

on engines. These can get clogged by the ash and stop working. Jet

engines are very susceptible to the ash and are the reason that jets are

routed around or cancelled when there are ash clouds. The picture on

the right shows layers of ash from Mt. St. Helens. This is a record of

not just the 1980’s eruption of many past eruptions.

Another hazard is the lahar. This is a mud flow is a mixture

of volcanic debris and water. The water can be from melting

glaciers as in Mt. St. Helens, or rain fall as in Mt. Pinatubo’s

eruption. This mud flow can cover landscapes to hundreds of feet

deep, destroys bridges and homes. With speeds up to

10-60miles/hour a lahar can be linked to thousands of deaths. They

travel along existing water ways onto floodplains.

The deadliest hazard of them all is the pyroclastic flows and surges. Both of these are a mixture

of ash and toxic gases with temperatures as high as 1,000 °C (1,830 °F). Their speed is controlled by the

slope of the volcano (steeper slope more speed) 700 km/h (450 mph). These are normally caused by

the eruption column collapse. There are two layers,

the basal layer will hug close to the ground and

contains larger courser material. The upper layer is

the extremely hot ash plume mixed with the toxic

gases. There is mixing of the cold atmosphere and

the hot gases due to the turbulence causing

expansion and convection.

The pyroclastic surge has less material and

more gas making it act differently than the flow.

Lacking the courser material makes the surge more turbulent and it can rise over ridges and hill crest

while flows are more constrained.

The first thing that I will talk about in predicting volcanic eruptions is what constitutes an active

volcano. If there has been an eruption in the last 10,000 years the volcano or volcanic field it is active.

After saying this there are exception to this rule. These are volcanoes that haven’t had an eruption in

over 10,000 years. They are called active if they have indication of an active magma chamber beneath

them such as thermal features (hot springs, geysers and mud pots), magmatic gases (sulfur gases, and

CO2) and seismic activity. Two examples of ancient volcanoes that haven’t erupted in thousands of

years are Long Valley and Yellowstone.

To predict the eruption you monitor the region for the

things that indicate activity. The first can be seismicity. There is

a type of earthquake called the harmonic tremor that indicates

magma entering a chamber. The seismogram to the right shows

Mt. St. Helens harmonic tremors prior to eruption. Below is a

seismogram supposedly shows Yellowstone with harmonic

tremors during 2008.

You also look for an

increase in the release of magmatic

gases such as CO2 and H2S and SO2.

Both Long Valley and Yellowstone shows such an increase.

Another indication of an impending eruption is ground deformation. This is normally measured

by a tilt meter and indicated magma moving upward towards the vent. Below is a false color map

showing not one bulge in Yellowstone but two.

With magma moving upward closer to the

surface you will also find an increase in surface

temperatures. In 2002 the Norris Geyser Basin (arrow

on the left) ground temperature rose to the

temperature to the temperature of boiling water.

I have been using both Long Valley and

Yellowstone as examples of earthquake prediction for

several reasons. The most obvious is that they both

have all of the eruption indicators but haven’t

erupted. The second reason is what such an eruption

from these volcanoes would mean to mankind.

The image to the right shows the extent

of Yellowstone’s last eruption. The area

stripped of vegetation is the area where

large amounts of ash would be deposited.

This ash deposit impacts the continental

United States as far east as Louisiana and

as far south as far as Mexico. This region

is the bread basket of the world as well as

the United States. So famine would

fallow. It would propel sulfuric acid and

ash into the stratosphere leading to a

global winter for 10 years. The last time there was an eruption close to this magnitude (Toba ~74,000

years ago) there where many extinctions and close extinctions. The current theory is that the population

of the Earth was reduced to 1,000 humans.