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Talk outline Part 1: How was the Ice Age first discovered? Investigation: Beetles as evidence of past climate Part 2: What causes Ice Ages? Investigation: The Day After Tomorrow? Presenter notes: In this talk we will discover more about Ice Age Earth. In Part 1, we will investigate how geologists first discovered that the Earth had been in the grip of an Ice Age until recently. In the investigation that follows we will learn about how fossil beetles can provide information about the climate of the Ice Age. In Part 2, we will think about what causes Ice Ages. In particular we will see how little wobbles in the Earth’s orbit around the Sun are the most likely trigger. In the investigation that follows we will watch the movie, The Day After Tomorrow, which deals with the start of a new Ice Age. We will discuss how much of this movie is fact and how much is fiction. In Part 3, we will explore what Europe was like at the height of the Last Ice Age. We will understand how this Ice Age completely changed the kind of animals and plants present and even the shape of the coastline. Part 3: What was Europe like in the Last Ice Age?
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The Ice Ages Presenter notes: Its hard to believe that only
20,000 years ago, the Earth was in the grip of a Great Ice Age.
Most of the British Isles were covered by an ice sheet up to three
kilometres thick. Southern England lay just south of the ice and
was a treeless tundra inhabited by herds of woolly mammoths.
However, this Great Ice Age was only the most recent of a series of
ice ages that have occurred over the past 2.5 million years. In
this talk we will learn more about the Last Ice Age, how it was
discovered and what caused it and earlier ice ages. NSA Howard
Falcon-Lang Talk outline Part 1: How was the Ice Age first
discovered?
Investigation: Beetles as evidence of past climate Part 2: What
causes Ice Ages? Investigation: The Day After Tomorrow? Presenter
notes: In this talk we will discover more about Ice Age Earth. In
Part 1, we will investigate how geologists first discovered that
the Earth had been in the grip of an Ice Age until recently. In the
investigation that follows we will learn about how fossil beetles
can provide information about the climate of the Ice Age. In Part
2, we will think about what causes Ice Ages. In particular we will
see how little wobbles in the Earths orbit around the Sun are the
most likely trigger. In the investigation that follows we will
watch the movie, The Day After Tomorrow, which deals with the start
of a new Ice Age. We will discuss how much of this movie is fact
and how much is fiction. In Part 3, we will explore what Europe was
like at the height of the Last Ice Age. We will understand how this
Ice Age completely changed the kind of animals and plants present
and even the shape of the coastline. Part 3: What was Europe like
in the Last Ice Age? Discovery (1): The Flood
boulder Presenter notes: So, onto our first topic, how was the Ice
Age first discovered? Throughout the eighteenth century early
geologists noticed a thick layer of sticky clay across much of
Europe. Elsewhere giant boulders were found scattered across the
landscape. How had these rocks reached their final resting place?
Many believed that this was clear evidence for Noahs Flood in the
Bible. After all it would have required incredible power to move
the giant boulders around. But was there an alternative
explanation? Early geologists noticed a layer of sticky clay with
boulders over much of Europe. Had it been deposited by a
catastrophic flood like Noahs Flood in the Bible? Discovery (2):
The Alps In the early 1800s Jean de Charpentier observed the
advance and retreat of glaciers in the Alps and studied the kind of
deposits they left behind. 1820s 1850s Presenter notes: Scientists
had the first inkling that the boulder clay may not been deposited
by Noahs Flood in the early 1800s. At that time, the worlds climate
was a bit colder than now. Glaciers in the French Alps started to
advance threatening towns and villages. Later they retreated
leaving behind a big pile of rocky debris. Jean de Charpentier was
one of the first people to study such glacial deposits. Glacial
retreat en.wikipedia.org/wiki/Image:Johann_von_Charpentier.jpg
Discovery (3): Scotland
In 1840, Louis Agassiz observed similar glacial features in
Scotland. He found scratches on a rocky hillside near Edinburgh
like those made by glaciers. He argued that Scotland had recently
been covered in a thick ice sheet. Presenter notes: De Charpentier
showed his glacial deposits to a young Swiss geologist called Louis
Agassiz. In 1840, Agassiz toured around Scotland and saw tell-tale
signs that the Scottish landscape had earlier been shaped by ice
like those examples hed seen in the Alps. One bit of evidence that
particularly excited him were glacial scratches on a rocky hillside
near Edinburgh. Agassiz argued that Scotland had once been covered
by a thick ice sheet. ice scratches
en.wikipedia.org/wiki/Image:Louis_Agassiz-2.jpg Discovery (4): Ice
Age landforms
Parallel marks show former level of an ice-dammed lake Presenter
notes: Agassiz spent much of his life touring round the world
searching for more evidence to support his idea of a Great Ice Age
in the recent past. In Scotland he found grand U-shaped valleys
which had been cut by glaciers thousands of years earlier. He also
found the mounds of rocky debris left behind when they melted. At
Glen Roy, he saw parallel marks on the hillside and realized that
these indicated the former levels of a lake that had become
temporarily dammed by ice sheets. Glen Roy, Scotland Agassiz
amassed more evidence from landforms and boulder clays to support
his idea of a Great Ice Age in recent times. Discovery (5): Fossils
Fossil discoveries also
Fossil discoveries also suggested that climate had recently been
much colder. Beetles and pollen grains found in sediments
associated with the boulder clays were identified as types known
only from the Arctic tundra today. Woolly mammoths found deep
frozen in Siberia had fur adapted to tundra life. Pollen Presenter
notes: At time when on, the evidence for a Great Ice Age got
stronger and stronger. Fossil remains of beetles and pollen grains
were found in sediments associated with the boulder clay across
Britain and North America. These were of a type that are only found
in the Arctic today. The remains of giant woolly mammoths and
woolly rhinos were also uncovered deep frozen in Siberian glaciers,
the evidence of their thick shaggy hair suggest that they were
adapted to chilly weather. Here was clear fossil evidence that the
climate had been much colder in the recent past. Beetles Mammoth
en.wikipedia.org/wiki/Image:Mammoth_mg_2791.jpg Discovery (6):
Chemical studies
In the 1960s, chemical studies offered more evidence for an Ice
Age. They showed that the amount of heavy oxygen in seawater was
controlled by the size of the polar ice cap. When polar icecaps
were bigger there was more heavy oxygen in the sea and vice-versa.
Howard Falcon-Lang More ice Presenter notes: In the 1960s chemical
studies offered more evidence for a recent Ice Age. It had long
been known that oxygen came in two main types heavy and light. It
was also known that the amount of heavy oxygen in seawater was
controlled by the size of the polar icecaps. So when the icecaps
were really big, there was more heavy oxygen in the sea, and when
icecaps were small, there was less heavy oxygen in the sea. As we
will see in the next slide, this was soon to provide further
evidence for a recent Ice Age. More heavy oxygen in sea Discovery
(7): Microscopic animals
Foraminifera In 1967, Shackleton used this fact to learn more about
the Ice Age. He studied heavy oxygen in bugs called foraminifera
fossilized in deep sea mud. The bugs proved that the icecaps had
been bigger at certain times in the past. Presenter notes: In 1967,
a Cambridge geologist called Nick Shackleton used this fact to
learn more about the Ice Ages. He studied heavy oxygen in the
fossil shells of microscopic animals called foraminifera found in
deep sea muds. This showed him how heavy oxygen levels had changed
in the sea over the last million years. The bugs showed that the
icecaps had been much bigger in the recent past and the Earth had
been gripped by Ice Ages at various times.
nj.usgs.gov/nawc/images/68brcore.jpg Borehole core Discovery (8):
Ice Archive
en.wikipedia.org/wiki/Image:GISP2_1855m_ice_core_layers.png In the
early 1980s, there was another major breakthrough. Cores were
drilled in the polar icecaps revealing annual layers of snow going
back thousands of years. Presenter notes: In the 1980s another
exciting discovery came to light. Scientist started to drill deep
cores down into the ice sheets of Greenland and Antarctica. They
discovered that the ice contained annual layers, each layer
representing one years snow fall. The ice cores provided a record
of snowfall going back many thousands of years. Drilling cores Sepp
Kipfstuhl, Alfred-Wegener-Institut Annual layers in ice Discovery
(9): Air bubbles
Scientists found air bubbles in the ice that had got trapped when
the snow had first fallen. Bubbles showed how much greenhouse gas
there had once been in the atmosphere. As we will see later this
was important for understanding what causes Ice Ages. Presenter
notes: Most exciting of all was the fact that tiny air bubbles were
locked up in the ice. These had become trapped when the snow had
first fallen. By analyzing the air it became possible to work out
the make-up of the atmosphere back through time. This work showed
how the amount of greenhouse gases in the air had changed over
time. As we will see later this was really important for
understanding what causes Ice Ages. CSIRO Air bubbles in ice
en.wikipedia.org/wiki/Image:GISP2_1855m_ice_core_layers.png
Investigation 1 Using beetles as evidence of past climate
Presenter notes: Before we go on to look at what causes Ice Ages,
lets first think a little more about how we know that there was an
Ice Age in recent times. In this first investigation we will study
fossil remains of beetles and see what they can tell us about the
climate of the recent past. Cause (1): Introduction
Presenter notes: When the Last Ice Age was at its maximum, 20,000
years ago, ice sheets spread over much of Europe and North America.
In this second part, we will investigate what causes Ice Ages. NASA
When the Last Ice Age was at its maximum, ice sheets covered much
of Europe and North America. So what caused it? Cause (2): Many Ice
Ages Ice age layers
Ian and Tanya West Ice age layers Presenter notes: For a very long
time, geologists had known that there hadnt been just one Ice Age.
By studying the layers of gravel left behind by ice sheets, they
knew that there had been many ice ages over the past 2.5 million
years, each separated by a short warm period. By studying the
layers of gravel left behind by the ice, geologists figured out
that there hadnt been just one Great Ice Age. Rather, over the last
two and a half million years, there had been many ice ages each
separated by a short warmer period. Cause (3): Orbital
wobbles
en.wikipedia.org/wiki/Milutin_Milankovi
commons.wikimedia.org/wiki/Image:Milankovitch-cycles_hg.png
Presenter notes: In the 1940s, a Yugoslavian mathematician came up
with a great idea to explain why the Earth seemed to flip in and
out of ice ages. He worked out that as the Earth orbited the Sun it
wobbled on its axis. Although these wobbles were tiny, they had
huge effects on the amount of heat reaching the Earth. Could this
be enough to push the Earth in and out of Ice Ages? Milutin
Milankovi ( ) In the 1940s, Milankovi wondered whether wobbles in
the Earths orbit around the Sun could explain multiple Ice Ages by
changing the amount of heating reaching the Earth Cause (4): Cycles
en.wikipedia.org/wiki/Image:Milankovitch_Variations.png Presenter
notes: There were lots of different wobbles in the Earths orbit.
When Milankovic had added them all up (a difficult sum!) he
predicted that they would cause Ice Ages in a regular cycle, say
once every 100,000 years Milankovi added up all the orbital wobbles
and predicted that ice ages should occur in regular cycles -
probably happening every hundred thousand years or so. Cause (5):
Suns pacemaker
The Oil Drum cold hot 1000s of years before present Presenter
notes: Now youll remember that in the 1960s, Nick Shackleton had
figured out a way to see how the polar icecaps had contracted and
expanded through time using heavy oxygen in microscopic marine
animals. In 1976 Shackleton further showed that ice ages happened
every 100,000 years just as Milankovic had predicted. Here was
crucial evidence that wobbles in the Earths orbit around the Sun
were acting like a sort of pacemaker, causing the planet to flip in
and out of Ice Ages. In 1960s, deep sea records showed that
Milankovi was right! The Earths climate had repeatedly blown hot
and cold with ice age cycles happening every hundred thousand years
just as Milankovi had predicted. Cause (6): The Big Question
But one big question remained: Exactly how did changes in the
amount of solar energy reaching the Earth trigger Ice Age cycles?
Presenter notes: But one big question remained: Exactly how did
changes in the amount of solar energy reaching the Earth trigger
Ice Ages? So far, this is a question that scientists have been
unable to answer. However, we have three good ideas. So far there
are no firm answers but three good ideas Cause (7): Colour of the
Poles
Absorbs energy: Warming The first idea is that as the Earth cooled,
green forests in the far north were replaced by white ice. Ice
reflects back more of the suns energy, so this would have caused
further cooling, leading to an Ice Age. Presenter notes: The first
idea concerns the colour of the poles. If the Earth started to cool
down, we can imagine that green forests in the far north would
eventually get replaced by white ice. Ice reflects back more of the
suns energy so this would cause further cooling. In turn this would
result in more ice at poles. We call this kind of process a
positive feedback loop. Once the Earth starts to cool, changes lead
to further cooling, and a downward spiral into an Ice Age. Reflects
energy: Cooling en.wikipedia.org/wiki/Image:AntarcticaDomeCSnow.jpg
Cause (8): Greenhouse Gases
The second idea is that changes in greenhouse gas levels were to
blame. Greenhouse gases help to soak up sunlight and keep the Earth
warm. Air bubbles in ice cores show that levels fell during Ice
Ages so this may have sped up cooling. NOAA Greenhouse Gas levels
dropped during Ice Ages Presenter notes: A second idea is that
changes in greenhouse gas levels in the atmosphere were to blame
for the Ice Ages. The sun heats the Earth and the Earth re-radiates
some of this heat. Greenhouse gases absorb this re-radiated heat
keeping the Earth warm. Youll remember how scientists found air
bubbles in polar ice cores. This tells us that the amount of
greenhouse gas in the atmosphere dropped during Ice Ages. This
would have sped up the cooling of the Earth. Last Ice Age = Low
Greenhouse Gas Cause (9): Ocean Currents
Gulf Stream warms the Arctic The third idea is that ocean currents
like the Gulf Stream were important. This current helps warm up the
Arctic. If it switched off this would cool the Arctic further and
increase the likelihood of an Ice Age Presenter notes: A third idea
is that ocean currents like the Gulf Stream were important. Today,
this current carries heat from the equator and heats up the Arctic.
If it wasnt for the Gulf Stream, Britain would have a cold climate
like Newfoundland! If the Gulf Stream ever switched off for some
reason, this would cool the Arctic further and increase the
likelihood of an Ice Age. 800/le-gulf-stream.jpg Practical Exercise
2 The Day After Tomorrow?
Presenter notes: And that leads us nicely onto our next
investigation. In this exercise we will watch the Hollywood
blockbuster movie, The Day After Tomorrow (2004). This movie deals
with the scenario weve just discussed, i.e. the idea that if the
Gulf Stream switched off it would increase the likelihood of an Ice
Age. But how realistic is the film? How much is fact and how much
is fiction? You decide.
commons.wikimedia.org/wiki/Image:Perito_Moreno_Glacier_Patagonia_Argentina_Luca_Galuzzi_2005.JPG
Ice Age Europe (1): Geography
20,000 years ago Europe was very different at the height of the
Last Ice Age. Thick ice sheets in north Frozen tundra in centre
Presenter notes: In this final section, we are going to explore
what Europe was like at the height of the Last Ice Age about 20,000
years ago. At this time, northern Europe was covered by an ice
sheet more than three kilometres thick. However, we will focus our
attention on southern England, which evidence shows was a frozen
and treeless tundra just south of the ice sheets. Conifer forests
in south We will focus on the tundra region of southern England.
Ice Age Europe (2): Coasts
With so much water locked up as ice, sea level was much lower in
the Last Ice Age and Britain was attached to mainland Europe. This
allowed humans, animals and plants to migrate far and wide. Ice
sheet Presenter notes: With so much water locked up as ice, sea
level was much lower at the height of the Last Ice Age. In fact you
could have walked from Germany to England across land where the
North Sea is today. Consequently, it was fairly easy for Ice Age
animals and human hunters to migrate between Britain and Europe.
Tundra Ice Age Europe (3): Plants
en.wikipedia.org/wiki/Mountain_Avens Fossil pollen show that
southern England was a mostly treeless tundra. The main plants were
grass and sedge. Together with the arctic willow, dwarf birch,
juniper and the mountain avens, these plants formed a low growing
carpet. Presenter notes: It was so cold in the Last Ice Age that
almost no trees could survive in southern England. Evidence from
fossil pollen show that the main plants were grasses and sedge in
addition to a few stunted trees such as the arctic willow, dwarf
birch and dwarf juniper. All these plants probably only grew a few
centimetres high as they do today. They covered the landscape with
a springy carpet of vegetation. We find pollen from one common
flower, the mountain avens (Dryas), so this would have brought a
bit of colour on the tundra landscape. The mountain avens (Dryas)
was common in the Ice Age tundra Ice Age Europe (4): Mammals
commons.wikimedia.org/wiki/Image:Woolly_mammoth_siberian_tundra.jpg
Presenter notes: Although cold and inhospitable, many large animals
survived on the tundra of southern England. Best known is the
woolly mammoth whose shaggy coat was well adapted to these harsh
conditions. Some complete mammoths have even been found, deep
frozen in the ice of Siberia. In fact there are several stories of
explorers having eaten mammoth meat after stumbling over the frozen
carcasses! Other animals that lived on the tundra included woolly
rhinos, reindeer, horses, musk ox, and even lions and spotted
hyaenas. Today we think of lions and hyaenas as exotic animals
characteristic of the African savannas. However, this distribution
is a result of human hunting and competition. Without humans, lions
would be a normal part of the British fauna! Many large animals
lived on the tundra south of the ice sheet. Fossil bones of the
woolly mammoth, woolly rhino, reindeer, horse, musk ox, lion, and
spotted hyaena have been found. Ice Age Europe (5):
Neanderthals
en.wikipedia.org/wiki/Image:Neanderthal_2D.jpg Early humans like
Neanderthal Man also survived on the tundra where they hunted herds
of mammoth. Their fossils show they had thickset bodies, which were
adapted to the extreme cold. They were probably wiped out by
competition with our modern human ancestors who arrived on the
scene about thirty thousand years ago. Presenter notes: Europe
during the Last Ice Age was also the hunting ground of early humans
like the Neanderthal Man. This is an extinct species of human whose
fossil bones show a thickset body that was very well adapted to
life on the ice. Neanderthals got wiped out near the end of the
Last Ice Age. No one is quite sure why this happened. Maybe when
modern humans arrived, they ate the Neanderthal foods and the
Neanderthals couldnt compete. Although our brain sizes are similar
in size, modern humans had the edge over Neanderthals because of
cultural and social abilities (eg. fully developed speech, art, a
more complex toolkit). This helped them to survive and thrive
during the Last Ice Age when the Neanderthals failed.
en.wikipedia.org/wiki/Image:Homo_sapiens_neanderthalensis.jpg Ice
Age Europe (6): Our ancestors
Fossils show that our modern ancestors arrived in Europe right at
the end of the Last Ice Age. They left spectacular artwork on cave
walls across the continent. The most famous cave art is in the
Lascaux Cave of France Presenter notes: Fossil evidence shows that
our modern human ancestors arrived in Europe right at the end of
the Last Ice Age. They left spectacular artwork in caves that tell
us what life was like at that time. The most famous cave art is in
the Lascaux Cave in France and shows many of the animals which were
hunted for food. Ice Age hunters also lived in southern Britain.
Burial chambers have been found in South Wales and some cave art
has even been found in Derbyshire recently.
en.wikipedia.org/wiki/Lascaux Art in the Lascaux Cave, France Ice
Age Europe (7): Melt water
en.wikipedia.org/wiki/Image:Gordale_scar_from_bottom.jpg
wikimedia.org/wiki/Image:Malham_Cove.jpg ancient waterfall
Presenter notes: As the Last Ice Age came to end about 14,000 years
ago, huge volumes of melt waters flooded over northern Europe. In
many part of England you can still see the effects of these
catastrophe floods. For example in Derbyshire, the deep gorge at
Goredale Scar was cut by floodwater. As this flowed downstream it
formed a colossal waterfall at Malham Cove! Goredale Scar and
Malham Cove in Derbyshire As the Last Ice Age came to an end,
gorges and waterfalls were cut by melt water floods across northern
Europe Ice Age Europe (8): Sea Level
As ice sheets melted, sea level rose by 120 metres reaching present
levels about eight thousand years ago. Presenter notes: Another
effect of the melting ice was to significantly raise sea level.
Over a period of about seven thousand years, there is evidence from
around the world that sea level rose by an amazing 120 metres (more
than twice the height of Nelsons column). The English Channel and
North Sea flooded and Britain became an island. Fishing boats
trawling the North Sea bottom today occasionally find mammoth tusks
left behind from the animals that used to graze on these Ice Age
lands. en.wikipedia.org/wiki/Image:Post-Glacial_Sea_Level.png Ice
Age Europe (9): Rebound
Those areas that had been pressed down by the weight of thick ice
sheets then rebounded upwards. This left beaches and sea-cliffs
around the Scottish coast high and dry. Presenter notes: The huge
weight of the ice sheets over northern Britain pressed it down into
the crust. When the ice completely melted, Britain started to
rebound upwards, in much the same way that a rubber duck will bob
back to the surface of a bath when released but much more slowly!
We can observe the effects of this rebound in Scotland today. On
the Isle of Arran we can find old sea caves which are now high and
dry and well above sea level. This rebound is still going on today
with Scotland rising by a few millimetres each year. Sea caves left
high and dry on Arran The Ice Ages Presenter notes: So that brings
us to the end of our exploration of the Ice Ages. Weve looked at
how geologists first got an inkling that there had been an Ice Age
in the recent past. Weve discussed what causes Ice Ages and weve
explored what Europe was like at the height of the Last Ice Age.
Its hard to imagine a thick ice sheet lying over the top of
Manchester just 20,000 years ago. But what the ice age tells us is
that climate can change dramatically over only a few hundred years.
As we close, here are some questions to think about and discuss: So
what about the Day after the Day After Tomorrow? Could the Earth
continue to warm due to greenhouse gas emissions, and if so, what
would this mean for the sea level of the UK? What would it mean for
us? Or could Earths orbital wobble trigger another Ice Age in near
future? as scientists thought was happening just 30 years ago. If
so, what would this mean for the sea level and climate of the UK?
What would it mean for us? NSA Howard Falcon-Lang