Download The Vesuvius Science Lab Training Packet

The Vesuvius Science Lab
Training Packet
One Day In Pompeii
November 9th, 2013 to April 27th, 2014
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Vesuvius Science Lab Logistics
● This is a wait-for-relief station with two tables. If one person has a wait-for-relief station
during the next block, one other person can remain to keep the Lab open until the next
volunteers arrive.
● When the Lab is closed, all materials should remain in the cabinet. The cabinet should
be locked with the padlock. The combination for this lock is 1269.
● The tables have cloth table covers. Please leave the covers on the tables at all times. Do
not put them in the cabinet.
● A QR code (2D barcode) will be in the cabinet along with the other materials. Please put
it out on one of the tables in its “table tent.” If guests use a QR code reader on their
smartphone to scan it, they will be directed to a web-based pdf document with
take-home activities relating to Pompeii. It will also give them a code (just say
“Vesuvius Science Lab”) for a 10% discount at the main Sci Store (not the Pompeii Gift
Shop)
Brief Background of Pompeii and Vesuvius
In the first century CE (common era--a term used by historians and archaeologists),
Pompeii had about 20,000 inhabitants, making it one of the largest cities in the Roman Empire.
It was situated about 5 miles from Mount Vesuvius in a portion of Italy called Compania.
The summit crater of Mt. Vesuvius
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Many historical accounts acknowledged Vesuvius’ odd appearance, even comparing it to
Mount Etna, an active volcano in Sicily. But as it had been dormant for 800 years, no one
foresaw the impending danger. No one understood that the frequent tremors in the area were
caused by pressure building beneath the ground.
In 62 CE, a huge earthquake devastated the area, destroying buildings and roads in
Pompeii and all the nearby towns. Many people fled the area and swore never to return, while
others chose to remain and rebuild. The following quote from Seneca, a prominent philosopher
of the time, clearly conveys to a modern reader some of the scientific misconceptions of the
age.
“Let us stop listening to people who have abandoned Campania and who have
moved out after this catastrophe, saying they will never again return to the region. . . For
we are wrong if we think that any part of the earth’s surface is safe and immune from
this risk [earthquakes]. Everywhere is subject to the same laws: nature conceived nothing
to be unmoveable [sic]. Things collapse at different times: just as in cities different
houses collapse at different moments, so on the earth’s surface flaws make themselves
apparent at different times.”
While many people still believed that this type of natural disaster was caused by the
wrath of the gods, even the most scientific minds lacked adequate explanations. In the nearly
2000 years separating us, the fields of geology and plate tectonics have evolved enormously.
Today, we have a far clearer understanding of the mechanics of these phenomena.
Timeline of Eruption and Burial of Pompeii
Day 1: August 24th
9-10:00 am
Eruption begins with a small explosion, depositing a thin layer of ash on Pompeii.
1:00 pm
First eruption phase begins with a massive explosion and the emission of a huge
eruption cloud.
1:30 pm
Fallout of ash, pumice, and other material begins to rain on Pompeii.
5:30 pm
Approximately 2 feet of ash and stone have accumulated on streets and roofs. So
much pumice has gathered on roofs that buildings begin to collapse.
Day 2: August 25th
12:00 am
Eruption cloud reaches about 20 miles in height. First story doors and windows are
completely blocked by fallout.
1:00 am
Second eruption phase begins, eruption cloud begins to collapse.
1-2:00 am
Pyroclastic surges (waves of superheated ash and gas) 1 and 2 overwhelm
Herculaneum, Oplontis, and Boscoreale.
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2-6:30 am
6:30 am
7:30 am
8:00 am
Pumice fall decreases, many people attempt to flee.
Surge 3 reaches Pompeii’s town walls, anyone in outlying buildings suffocates.
Pompeii lays approximately 9 feet under pumice, ash, and debris.
Surges 4 and 5 overwhelm Pompeii and neighboring cities, killing any remaining
people.
Surge 6 adds two more feet of debris and ash. Pompeii ends under nearly 12 feet of
pumice, ash, and debris.
The darker regions of this map indicate where most of the volcanic ash and pumice landed.
Herculaneum
Pompeii wasn’t the only city affected by the volcanic eruption, though less is known about
many of the others. The other town that has been studied extensively is Herculaneum. A little over a
mile from Vesuvius, Herculaneum was much closer to the volcano when it erupted. The conditions
experienced there were consequently quite different. While Pompeii was buried in ash and small
pumice stones (called lapilli) which helped to preserve bodies in great detail, Herculaneum was hit
by extremely hot clouds of gas around 400-500 degrees Celsius. At this temperature, flesh is
incinerated, leaving only bones. However, this heat did help to preserve other organic materials like
wood, grains, cloth, and papyrus by carbonizing them, providing a very different piece of the
archaeological puzzle.
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Geology
Goal: Visitors will learn about the formation of volcanic rock and what these rocks can tell us about
the geological past of both Pompeii and the earth. Moreover, visitors will examine the role of plate
tectonics in the formation and eruption of Mount Vesuvius and other volcanoes.
Background Information
What is Geology?
Geology is the study of the earth, both physical (“what it is made of”) and historical (“how it was
made”). One of the main sources of information we have about the formation of the earth are the
rocks that we walk on, build with, and marvel at from all around the world. This part of the packet will
provide a brief overview of how we can use geology to understand the Vesuvian eruption of 79 CE.
Composition of the earth
The earth is made of many different types of materials that are layered from the very center to the
outer shell. The earth is 7908 1 miles in diameter and is a dynamic system.
(Above) A diagram of the earth’s interior layers. The semicircle on the left is to scale.
1
All measurements given in miles will have variation at different places within and on the Earth.
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At the very center of our planet is the core, a dense sphere with a radius of 2164 miles, larger than the
planet Mars. This center core comprises about ⅙ of the earth’s volume and ⅓ of its mass, and can
reach temperatures of 5000°C.
Interior Layers of the Earth
Miles (depth)
Kilometers
Layer Name
Behavior
0–37
0–60
Lithosphere
Solid
0–22
0–35
...Crust
“Brittle” Solid
22–37
35–60
...Uppermost part of mantle
Solid
22–1,790
35–2,890
Mantle
Liquid
60–430
100–700
...Asthenosphere
Liquid
1,790–3,160
2,890–5,150
Outer core
Liquid
3,160–3,954
5,150–6,360
Inner core
Solid
The core can be further separated into two layers. The inner core is a solid mass with a 794 mile radius
made mostly iron and nickel. And the outer core, also a solid layer but 1370 miles thick, behaves more
like a liquid over long periods of geologic time. The great pressures and temperatures of the core are
what drive the geological processes of the planet.
The next layer out from the earth’s core is the mantle, the thickest single layer of the planet’s
interior measures 1768 miles. The mantle is composed of oxygen, silicon, magnesium, aluminum and
other lighter-than-iron elements that behave like a very viscous liquid over long periods of time. This
layer is also very hot; 500 to 4,000°C from edge to center.
The asthenosphere is a part of the outer mantle that is about 370 miles thick, although the lower
boundary is not well defined. The asthenosphere behaves like a viscous liquid in response to stress.
This layer is particularly significant because the convective flow of materials within is responsible for
the motion of Earth’s tectonic plates.
The outermost layer of our planet is the crust, a 22 mile thick layer of solid, “brittle” rock. The crust
has both oceanic and continental sections, with oceanic crust only averaging about 3 to 6 miles in
thickness.
The crust, along with the uppermost solid portion of the mantle, is known as the lithosphere. This
layer, 37 miles thick, excludes the asthenosphere but extends into the mantle. The lithosphere
behaves like a solid over long periods of geologic time and is the layer that comprises the earth’s
tectonic plates.
How do we know about these layers?
Seismic activity, such as earthquakes, do not only cause the ground to shake, but also the interior of
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the planet. Various types of seismic waves (e.g. P waves, S waves) reflect, refract, accelerate,
decelerate, and are obscured by the interior layers of the planet, all of which have different
densities, depths, and viscosities. Based on how the seismic waves behave, geologists can infer the
interior composition of the Earth.
(Above) A cross section of the earth, showing how seismic waves travel differently through the interior layers.
Waves marked with a “K” means they have travelled through the core.
Plate Tectonics
As mentioned above, the lithosphere is the 37 mile thick layer of the Earth that is divided into large
segments known as plates. The hot layers of the mantle below the lithosphere are what drive the
motion of the plates across the surface of the Earth.
Plates move gradually over the course of years, some just a few millimeters every year. The largest
plate is the Pacific, which is almost entirely under the Pacific Ocean. Plates move in specific ways.
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(Above) Illustrations of Divergent, Convergent, and Transform plate boundaries.
A divergent boundary occurs where plates move apart. As two diverging plates move away from one
another, molten rock rises from the asthenosphere and cools; this occurs mostly under the ocean and
is known as sea-floor spreading. But a divergence can also occur within a continent, causing the crust
to fragment and eventually sink into the continental gap, creating a rift. It is thought that the
supercontinent of Pangea may have separated into today’s continents in this manner.
A convergent boundary occurs where plates move together. The collision forces the denser plate
(typically, the oceanic plate) of lithosphere downward into the asthenosphere; this is known as
subduction. During subduction, the sinking plate begins to melt, resulting in the production of lowerdensity magma, the molten liquid form of rock. This magma can rise, build pressure, and penetrate
the crust, creating a volcano on land or at sea (see image below).
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A transform boundary occurs where plates slide past one another without the production or
destruction of crust. It is typical for the fault lines of transform boundaries to parallel the direction of
the plate motion. A good example of a transform fault would be the San Andreas fault (pictured
below) in California, which separates the North American plate from the Pacific plate.
Volcanoes
While almost everyone knows what a volcano is, there is a technical definition for this natural
phenomenon. A volcano is an opening in the crust of the Earth (or other planetary body) that allows
magma to rise from a lower chamber and erupt as lava, gas, and ash from a central crater. All of this
hot, coarse, suffocating material that erupts from a volcano is known as pyroclastic material.
As the volcano forms, the hot and less-dense magma rises from a magma chamber in the
lithosphere, through a rocky vent, to the upper crater on the surface. The volcanic craters can be
massive, and those that exceed 1 kilometer in diameter are known as calderas. Volcanoes come in
many shapes and sizes and can be classified according to three main types.
A shield volcano (see image below) forms when fluid lava is extruded from the Earth with little
release of other pyroclastic material, taking the shape of a broad, low angle structure (their name
comes from the resemblance to a shield). The outpouring of fluid lava onto the ground is known as an
effusive eruption. The islands of Hawaii are shield volcanoes that began on the ocean floor.
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A cinder cone (see image below) is a steep, conical hill of volcanic fragments that accumulate around
and downwind from a vent. The rock fragments, often called cinders or scoria, are glassy and contain
numerous gas bubbles “frozen” into place as magma exploded into the air and then cooled quickly.
These volcanoes are usually smaller, less than 300 meters in height, and frequently occur in groups. A
cinder cone can generate an explosive eruption, characterized by gas-driven explosions that propels
lava and pyroclasts.
Lastly, a stratovolcano (see image below), also known as a composite cone, is formed when relatively
viscous lava and pyroclastic material flow from the vent alternately and intermittently, resulting in a
buildup of alternating or mixed material. A stratovolcano typically consists of many separate vents,
some of which may have erupted cinder cones and domes on the volcano's flanks.
Mount Vesuvius is considered to be a stratovolcano, one that explosively erupted in 79 CE with great
violence and destruction. However, not all volcanoes are as large or result in as explosive an
eruption.
The Volcanic Explosivity Index (VEI) is a description of the relative size or magnitude of explosive
volcanic eruptions. It is a 0-to-8 index of increasing explosivity. Each increase in number represents
an increase around a factor of ten. The VEI uses several factors to assign a number, including volume
of erupted pyroclastic material, height of the eruption column, and duration in hours. Mount
Vesuvius and Mount Saint Helens both classified as 5, Plinian, on the VEI.
The Plinian distinction is called such as Pliny the Younger documented one of the few historical
accounts of the 79 CE eruption of Mount Vesuvius.
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The Volcanic Explosivity Index
Classification
Description
Plume
Frequency
Tropospheric
injection
Stratospheric
injection
0 Hawaiian
Effusive
< 100 m
constant
negligible
none
1 Hawaiian / Strombolian
Gentle
100m–1km
daily
minor
none
2 Strombolian / Vulcanian Explosive
1–5 km
weekly
moderate
none
3 Vulcanian / Peléan
Severe
3–15 km
months
substantial
possible
4 Peléan / Plinian
Cataclysmic 10–25 km
≥ 1 yr
substantial
definite
5 Plinian
Paroxysmal
20–35 km
≥ 10 yrs
substantial
significant
6 Plinian / Ultra-Plinian
Huge
> 30 km
≥ 100 yrs
substantial
substantial
7 Ultra-Plinian
Colossal
> 40 km
≥ 1k yrs
substantial
substantial
8 Supervolcanic
Catastrophic > 50 km
≥ 10k yrs
substantial
substantial
So what formed Mount Vesuvius?
Mount Vesuvius formed in the same way as many volcanoes; due to the collision of an oceanic plate
with a continental plate. The oceanic African plate, being of greater density, is sliding under the
continental Eurasian plate, creating a subduction zone. The subduction of the African plate under the
Eurasian plate creates slab windows under Italy, one in particular under the Pompeii region. The slab
window allows hot asthenosphere magma to rise through the crust, which created Mount Vesuvius
over the course of thousands of years. Mount Vesuvius is classified as a Stratovolcano.
(Above left) An image of Italy illustrating the Eurasian and African plates. The African plate is being subducted.
(Above right) A cross section of the AB line from the map. The Slab Window allows hot magma to rise.
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Rocks vs Minerals
Many times, the words rock and mineral are used interchangeably; but in fact, rocks and minerals
have unique distinctions.
A mineral is one constituent part of a rock. Minerals are inorganic solids (non-carbon based) with a
specific internal structure and chemical composition. Silicon, calcium, magnesium, and iron are some
examples of the internal atoms that make a mineral. The internal structure of some minerals can be
inferred if they form a crystal, a collection of atoms that are arranged in a uniform pattern.
(Above left) A rendering of the microscopic view of halite, a sodium (small) and chlorine (large) based mineral.
(Above right) A macroscopic view of an actual halite crystal. Note the cubic shape.
What is commonly referred to as a rock is actually an aggregate of one or more minerals, one which
does not have an orderly arrangement outside of the minerals that comprise it. One example would
be a piece of sandstone (rock) that is actually made of microscopic minerals of quartz.
(Above left) A piece of quartz-based sandstone. (Above right) A quartz crystal.
Types of Rocks
Rocks come in many shapes, sizes, colors, and textures, and can be classified into three main types;
igneous, sedimentary, and metamorphic.
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Igneous rock forms when molten magma cools and
solidifies. This process is known as crystallization.
When magma exits the Earth and the contained
gasses escape, it is known as lava. There are many
types of igneous rock that form in different ways.
Igneous rock that forms when lava solidifies is
known as extrusive, or volcanic, rock (this type of
rock is of particular importance to our Vesuvius
Science Lab). If the internal magma does not reach
the surface and crystallizes within the Earth, it is
known as intrusive, or plutonic, rock.
Here are some features of igneous rock that are
worth discussing:
● Minerals within the magma or lava can group together, creating a speckled look to the rock.
● Different sized minerals indicate how quickly or slowly the rock cooled. The bigger the
minerals, the longer they had to move together while the rock was still warm.
● If the magma cools with gases still trapped inside, the rock can form with internal holes.
These holes are known as vesicles, and are the remnants of the gas that was trapped in the
rock.
● If the rock has cooled very quickly, the minerals and atoms may not have time to form any
regular crystal structure. This can result in a glassy appearance, which can break to create
rounded and sharp conchoidal fractures.
Sedimentary rock forms when other types of rock
join together. Any rock type can be weathered, or
broken down by air or water, turning it into
sediment. As the sediment deposits itself onto
ocean or river beds, it will undergo lithification, a
process that involves compaction and cementation
of the sediment. This generates layers of new rock
that can accumulate over thousands or millions of
years. Given the way sedimentary rock forms, it is
also the only type of rock in which fossils are found.
Some features of sedimentary rock worth noticing include:
● A grainy or sandy appearance. This is the sediment that has been cemented together.
● Individual rocks or stones, aside from sediment, can become “trapped” within the rock.
Larger pieces of rock (not individual minerals) can be cemented in place, as well.
● The sedimentary rock can crumble easily, or grains of sand can be worn off by simply rubbing
the rock.
● Deposits of fossils, including bones, leaf imprints, shells or microscopic fauna, can be seen in
some sedimentary rock.
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Lastly, metamorphic rock forms when other types of
rock are subjected to great heat and pressure within
the Earth, transforming them into new rock. Pressure
on metamorphic rock can exert stress that squeezes
the rock, or shear that deforms the rock on a given
plane. Metamorphic rocks can also be layered or
banded; this is known as foliation. Layers that are
compacted and break off cleanly create cleavage. A
flakey plate-like appearance of minerals within
metamorphic rock is known as schistosity.
Here are some features to look for in metamorphic rocks:
● A banded or layered appearance within the rock (unlike the pattern in sedimentary rock) that
resembles a mashing of minerals; this is due to stress and shear.
● Metamorphic rocks can exhibit layers that break along precise planes; this breaking is known
as cleavage.
● Bands of colored minerals can also appear to wave and twist. Once again, this is due to the
stress and shear exerted upon the rock.
● A more homogenous rock can be metamorphosed to form a subtle mineral pattern with veins
of color coursing through the rock.
Rocks form in many different ways and can change via different physical processes. The rock cycle is a
good way to understand how rocks change from one form to another.
Melting can form any type of rock into
magma, which will then cool to form new
igneous rock. Weathering can also take
any type of rock and turn it into
sediments, which can then compact and
cement to form sedimentary rock. Heat
and pressure make metamorphic rock out
of igneous or sedimentary rock.
It is important to note that the rock cycle is not a
unidirectional process where one type of rock
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always form the next type. Rather, the rock cycle is a set of processes that manifest to create new
rocks of all three types from within and above the earth’s interior.
Activities
Activity #1: Plate Tectonics
At the lab will be model tectonic plates for the visitors to manipulate and experiment with. These
models have slanted edges and are flexible; they are designed to simulate the movement of the
tectonic plates.
As previously discussed in the packet, Earth’s tectonic plates can move at a Convergent, Divergent, or
Transform Boundary. These models are most useful when discussing Convergent or Transform
Boundaries.
● Have visitors slide the plates into one another with the slanted edges meeting each other
flush. What do they notice? What type of boundary is this?
● Have visitors slide the plates into one another with the edges of the slants colliding. What
happens then?
● Have visitors hold the sides of the plates such they they rub past one another. Can they be
slid easily? What type of boundary would this be?
Activity #2: Observing Rocks
Different types of rocks are provided for visitors to examine and discuss. An important part of this
activity is to allow visitors to examine the rocks using their own observation skills. As a facilitator,
your use of open ended questions can guide the conversation.
*** This should not be a rock naming activity, but a way for visitors to understand, based on their
observations, how rocks form and what they tell us about the inner workings of the earth.
Visitors will be able to see and feel the rocks, pick them up, and comparing them. Here are some
questions to start your conversation:
● Which rocks seem interesting? Which ones do you like?
● What did you find interesting about this rock in particular?
● Maybe you liked the spots on that rock on the left. But some of the other rocks have spots
too. How are they similar/different?
● Tell me more about similarities/differences you see in these rocks.
● How could we group these rocks together? How/why did you group them that way?
● How would you describe some of these other rocks, the ones you didn’t pick? Tell me more!
Once the visitor has found some rocks or specific features interesting, present them with some more
questions. This time, you can focus on specifics:
● How would you describe this rock?
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●
●
●
●
Describe the types of shapes and colors you see.
What do you mean by the texture of the rock?
What do you mean by layers?
Tell me more!
All of these questions can guide the visitor to the type (i.e. igneous, sedimentary, metamorphic) of
the rock they are examining and how it formed. Feel free to present more questions, or provide
more detail to visitors that are particularly interested in geology.
Also provided at this station is a vial of volcanic ash from the May 18th, 1980 Mount Saint Helens
eruption. Visitors will be able to examine the ash through the vial. Some questions to ask:
● What do you see? Does this look like anything you’ve seen before?
● Is it fine or chunky? What color is it?
● How much of this ash do you think gets spewed into the air?
*** The vial of volcanic ash SHOULD NOT BE OPENED as it can easily spill or aerate. Although fine,
volcanic ash is very coarse and can be
damaging to the lungs, nasal passages,
trachea, and eyes.
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Archaeology
Goals: Visitors will learn why Pompeii is such an important archaeological site and the science behind
why it was so remarkably well preserved.
Background Information:
What is archaeology? What exactly do archaeologists do?
Archaeology is the scientific study of historic people and their cultures by excavation and analysis of
their material remains, such as artifacts, inscriptions, monuments, artworks, and human, floral and
faunal remains. An archaeologist studies these remains to discover how people lived in the past.
Why is Pompeii such an important archaeological site?
Pompeii provides a unique learning experience for archaeologists because it is so remarkably well
preserved. A single day is essentially “frozen in time”. Houses and other buildings were preserved
under layers of ash and stone, though the body shells found at Pompeii are what has made this site
so well known. They provide information about clothing and hairstyles, in addition to more personal
information about the people who lived, worked, played, and died suddenly on that fateful day.
Why is Pompeii so well preserved?
When Vesuvius began to erupt, it sent an enormous amount of porous pumice stone and fine ash
high into the sky. As that material fell back to earth, it formed what is called a pyroclastic surge of hot
gases and ash that rolled down the side
of the volcano and rushed southeast
toward Pompeii like a tsunami. While
other towns were either blasted with
extreme heat (such as Herculaneum) or
covered with pumice stone, Pompeii
was covered predominantly in
superfine heated ash. This ash rolled
into the city in stages (see timeline
above), but the third and fourth surges
were the most deadly to anyone
remaining in Pompeii. With a decrease
in pumice fall around 6:30 am, many
people attempted to escape and were
knocked down by the third surge which
rushed in, completely covering many people, killing them almost instantly. This ash was so fine and
so thick that it filled every crevice surrounding the body, including clothing and hair detail. As the ash
cooled, it hardened, forming a rock shell around the body. Eventually the bodies decayed, but the
shell remained. This means that during excavation, if a hole is uncovered and suspected to be a body
shell, it can be filled with plaster, allowed to dry, and chipped away. This leaves a cast behind that is
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exactly the shape of the original body, often including facial features and clothing details.
Was all of Pompeii preserved this way?
No, some areas were covered in mostly larger pumice stones, so no body shell was ever formed.
When and how was Pompeii rediscovered?
Walls and frescoes of Pompeii were rediscovered accidentally in 1599 when underground tunnels
were being dug to divert the river Sarno, however they were covered over again. The town wasn’t
truly rediscovered until 1748 by the Spanish military engineer Rocque Joaquin de Alcubierre, though
the first excavations were led by Karl Weber who was followed in 1764 by military engineer Franscisco
la Vega. It wasn’t until nearly 100 years later that Giuseppe Fiorelli took charge of the excavations in
1863. It was Fiorelli who realized that holes found in the ash with small amounts of human remains
were truly spaces left by the decomposed bodies. He was the one who devised the technique of
injecting plaster into them to recreate the forms of Vesuvius's victims. This technique is still in use
today, with a clear resin now used instead of plaster because it is more durable, and does not destroy
the bones, allowing further analysis.
Can we make plaster casts in other archaeological sites?
Theoretically yes, but the conditions found at Pompeii are quite unique. There may be several
sites where bodies were preserved in this way, but not many.
How are the casts different from fossils?
A fossil is formed when a living thing is buried in a material like mud or sand. Usually flesh
decays over time; but if undisturbed, the bones can remain packed in that material. If that layer
gets covered over and compacted, it can begin to solidify into rock. Very slowly minerals from
the surrounding rock leach into the bones and replace the bones as they decay. This leaves a
hard mineral imprint where the bone once was. Fossils take millions of years to form, whereas
the body shells at Pompeii formed as soon as the ash cooled, and the hole formed in the few
years it took for the bodies to decay.
How are the casts different from mummies?
A mummy is a carefully preserved body. There are no bodies preserved at Pompeii, they
decayed away long ago. All that was left was a shell, an imprint, where the body once was. The
cast is simply plaster that was poured into that imprint.
What do I say when a guest asks how the people of Pompeii died?
Warning: This conversation can get graphic, so please read your audience before responding.
There is evidence that most people evacuated during the early stages of the eruption (of about
20,000 inhabitants, approximately 2000 bodies have been recovered or are predicted to be
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recovered) but those who stayed behind suffered for it. Some people were killed by stone falling
from the sky or from buildings collapsing, but that was not how most of the people met their
end. As the pyroclastic surges rolled through the city, they brought with them hot poisonous
gasses (above 200 degrees C) and thick ash. There has been a fair amount of debate about
whether it was the heat, the poison, or asphyxiation on the ash that was cause of death, but
regardless, one or several of these conditions certainly ended the lives of these victims of
Vesuvius.
Activities:
Activity #1: Frog Cast
Goals: Visitors will learn how body shells are formed and how plaster casts of bodies are made.
Materials: Three clear cases. #1 has the plastic frog in it, #2 has the impression left by the frog, and #3
is the plaster cast of the frog.
Procedure:
- Place the three cases on the table in numerical order for the visitors.
- Walk visitors through the cases explaining along the way:
#1- The body is completely buried in fine ash, filling in all crevices. Eventually ash cools and
hardens.
#2- The body decomposes, leaving a hard shell with a few bones in the bottom.
#3- Archeologists uncover an opening to the shell in #2, fill the cavity with plaster, then chip
away the shell to produce a plaster cast of the body that was once there.
Explanation:
Please see the section above for an explanation of how these body casts were formed.
Activity #2: Make an Impression
Goals: Visitors will experience how the surrounding medium can affect cast formation. They will learn
why Pompeii is such a unique archaeological site and why most other sites are not preserved in the
same way.
Materials: Two plastic trays: one filled with small pebbles, the other with Kinetic Sand. Alternative
impression items. Proscope images. Please do not allow guests to remove pebbles or sand from their
boxes!
Procedure:
- Place the two trays on the table within visitors’ reach.
- Ask visitor to make impression of their hand in each tray. Compare the impressions and discuss why
they are different. (Alternative: if they don’t want to use their hand, allow them to use an alternative
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impression item)
Explanation:
In order to make a shell like those found at Pompeii, a body must be encased in a very fine material.
The small pebbles are much too large, so it is difficult to leave a visible impression. Also, they roll
past each other and fill in any impression you try to leave. The sand is much finer, and so it holds a
much more detailed impression. The ash that fell on Pompeii was much finer than this sand and was
also very hot. It made a very detailed impression, and then cooled and hardened, making the
impression permanent.
The laminated images that accompany this activity have magnified images of different media. The
first shows three images: pebbles, sand, and ash. These images were taken using a proscope (a
hand-held microscope) with a 30x magnification. They can more clearly show the difference in
particle size between these three media. The pebbles look enormous and cannot pack together to
form a detailed impression. The sand has a much smaller particle size and you can see that the sand
makes a pretty good impression when you press your hand into it. The ash has a particle size so small
that you can’t differentiate particles at 30x magnification. The second laminated image has another
image of a single particle of ash. Note that the scale for this image is in micrometers (a micrometer is
one millionth of a meter or one thousandth of a millimeter). The ash is so fine, that it can penetrate
even the tiniest crevice that we can see. It is because of thise particle size and that these particles
fastened together as they cooled that the body shells found at Pompeii have such striking details.
What is Kinetic Sand?
Kinetic sand is sand held together with a small amount (roughly 2% by weight) of a polymer similar to
that found in putty. It allows the sand to stick together better than regular sand so we can hopefully
make less of a mess. It also makes it a lot of fun to play with. This is a product that is available online
under the name Kinetic Sand if guests are interested in purchasing it. We do not carry it at the Sci
Store.
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Sources:
Summit crater of Vesuvius: http://apetcher.wordpress.com/2010/03/25/sorrento-vesuvius/
http://www.flickr.com/photos/7909459@N03/8356102564/sizes/c/in/photostream/
Jordan, T. H. (1979). "Structural geology of the Earth's interior." Proceedings National Academy of
Science 76 (9): 4192–4200.
Monnereau, Marc; Calvet, Marie; Margerin, Ludovic; Souriau, Annie (May 21, 2010). "Lopsided Growth
of Earth's Inner Core". Science 328 (5981): 1014–1017.
Barrel, J.(1914) ”The strength of the crust, Part VI. Relations of isostatic movements to a sphere of
weakness - the astenosphere [sic].” J. Geol. 22, 655-683.
Dutch, Steven. "Faults and Earthquakes." University of Wisconsin - Green Bay, 15 Jan. 1997. Retrieved
14 Oct. 2013 from https://www.uwgb.edu/dutchs/EarthSC202Notes/quakes.htm.
Thorkelson, Derek J (1996). “Subduction of diverging plates and the principles of slab window
formation.” Tectonophysics v. 255, p. 47-63.
“USGS Photo Glossary of volcanic terms" US Geological Survey, 17 Nov. 2011. Retrieved 21 Oct. 2013
from http://volcanoes.usgs.gov/images/pglossary/.
“VEI (Volcanic Explosivity Index).” Global Volcanism Program, Smithsonian National Museum of
Natural History Retrieved 21 Sept. 2013 from
http://www.volcano.si.edu/world/eruptioncriteria.cfm.
Tarbuck, E. J., Lutgens, F. K. (1984). The Earth: An Introduction to Physical Geology. Second Edition.
Merrill Publishing Company, Columbus OH.
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