1) The study of glaciation is a relatively new field that began in the 1830s when Louis Agassiz discovered evidence of past glaciation in the Swiss Alps. 2) Ice core records from Greenland and Antarctica provide evidence of climate cycles over the past 800,000 years through analyzing trapped air bubbles and CO2 concentrations. 3) We are currently in the Quaternary period which began 2 million years ago, and the most recent ice age termed the Pleistocene epoch ended approximately 11,500 years ago at the conclusion of the Younger Dryas stadial period.

1. History of Glaciation
AS Geography

2. What we’ll learn today
1. That the idea of glaciation as a science is
a relatively new phenomena
2. That we know they existed due to ice
cores
3. That the age of the earth can be broken
down into different timescales
4. That we are looking at once specific
epoch of time
5. That there are potential reasons for ice
ages to begin
6. The last stadial finished approximately
11,500 years ago

3. • Ice ages were first
discovered in 1830s by
Louis Agassiz in the Swiss
Alps
• He identified that they had
occurred all over Europe.
• He id this by seeing that
certain areas had similar
features

4. Ice Cores
• Ice cores have helped to determine this is
the case
• Scientific research into Greenland and the
Antarctic has provided us with a record of
climate over the last 800,000 years.
Bubbles trapped in the ice contain CO2
From the atmosphere showing low
concentrations in glacial periods and high
concentrations in interglacial periods

5. Geological Time
• We currently live in the QUARTERNARY
epoch which began 2 million years ago
• The previous TERTIARY period ended
with global cooling and ice-house
conditions.
• What are Epochs:
• They are periods of geological time

6. Geological Time
• These relate to times of the past where
geological strata were laid down
• The earth is around 4.5 billion years old
• Epochs denote changes with this such as
mass extinctions,

7. The Epochs

8. The Quaternary Period
• This is broken down into two epochs
• Holocene and Pleistocene
• Pleistocene – covers the beginning of the
period - 2,588,000 to about 11,700 years
ago (THIS IS THE AGE WE ARE
INTERESTED IN)
• Holocene
• Interglacial – the age of man

9. The Pleistocene
• Though considered a single period in time
• In reality it is it has multiple periods of
glacial and interglacial periods
• These glacial periods have left evidence in
the landscape in terms of erosional and
depositional features
• Each time a glacial period occurs the
previous features and landforms are
remoulded and shaped
• making it complex to reconstruct the past.

10. • The graph above highlights the different glacial periods
with each one being harder to detect in the landscape
that the next.
• Even the most recent (UK Devensian) is being modified
by geomorphological processes

11. • Smaller fluctuations and shorter periods of intense cold
are called stadial periods, followed by shorter periods of
relative warmth known as interstadials
• Recent ice core analysis show these to be sometimes
quite abrupt changes

12. TASK
• In pairs try to come up with reasons for
long term climate change:

13. Causes of longer term glacial and
interglacial cycles.
• Long term changes in the earths orbit are
seen as the current primary cause of
oscillations between glacial and
interglacial periods.
• Milankovitch Theory
– Eccentricity of orbit
Changes from Elliptical to a
More circular orbit and back
Again approx. 100,000 years

14. Axial Tilt
• This varies from between 21.8o
to 24.4o (Currently at 23.5o)
• Does this over 41,000yr
timescale
• This impacts on the intensity of
light received at the poles and
therefore seasonality of the
earth

15. Wobble
• Known as precession the earth
Wobbles on its axis changing the point
In time the earth is nearest the sun (Over
a 21,000 year cycle)
This causes long term changes to when
different seasons occur along the earths
orbit path

16. Time line of long term change
ECCENTRICITY
100,000 years
AXIAL TILT
41,000 years
WOBBLE
21,000 years

17. • The three cycles can come together to
minimise the amount of solar energy
reaching the northern hemisphere during
summer (Leading to cooler summers
overall)
• Milankovitch’s theory is supported by
glacial periods occurring approx. 100,000
years. Though the impact is considered to
be small, only about 1 – 1. 5o

18. Ice needs more
• For vast amounts of ice to form a 5o
change would be necessary or melt, the
answer to this lies in climate feedback
• Milankovitch cycles may trigger change
however it is these feedback mechanisms
that can magnify them and lead us into or
out of glacial periods

19. FEEDBACK MECHANISMS
• Climatic feedbacks can either amplify a
small change (Positive feedback)
• Or diminish the change and make it
smaller (Negative feedback)

20. Positive Feedback
Increased Global Warming
Small
increases to
snow and ice
cover can
raise surface
albedo
1
More solar
radiation is
reflected
back into
space
2 Could lead to
more snow
and ice cover3
Alternatively increased melting could lead to decrease in albedo
releasing more CO2 and methane leading to increased global
warming

21. Negative Feedback
Decreased global Warming
Increased
global warming
and industry
leads to more
evaporation
which
increases cloud
cover
1
Increased cloud
cover reflects
solar energy
back into space2 Reducing the
intensity of
global warming3
OR
Ice sheet
dynamics
disrupt THC1
Warming
waters in the
Arctic
disrupts
ocean
currents
2
Less warm
water from
the gulf
stream
creating
global cooling
in N. Europe
3

22. Short term Fluctuations
• There are other factors that cause climate
change:
• Solar forcing
• Volcanic Causes

23. Solar Forcing
• Energy emitted by the sun varies due to
sunspots. Cycling every 11 years which
we have reliable records dating back
400yrs (Some going back further)
• 1645-1715 – Maunder Minimum at the
height of the little Ice Age Temperatures
were around 1 degree lower than today
• 950 to 1250 - Medieval Warm Period –
Occurred before this where temperature
was about 1 degree hotter than today
• Solar forcing is seen as attributing 20% of
warming in the 20th century

24. Volcanic Causes
• There are many past examples where volcanic
eruptions have altered temperature
• Highly explosive volcanoes (VEI 7+) eject
huge amounts of ash Sulphur Dioxide CO2
and water vapour into the atmosphere.
• These spread around the globe blocking out
sunlight
• 1815 – Tambora in Indonesia caused
temperatures to drop by 0.4-0.7 degrees for
two to three years
• ENSO cycles are also capable of changing
climate in the short term

25. Issues
• None of these could cause the amount of
cause stadial or interstadial fluctuations
• Again it brings us back to feedback
mechanisms
• Ice masses are definitely impacted upon
by both internal and external factors such
as global ocean circulation and GHG
concentrations

26. Loch Lomond Stadial
(Younger Dryas Event)
• Ice sheets began melting 18,000 yrs. ago
• Rapid deglaciation 15,000 yrs. ago Due to
similar temperatures as today
• 12,500 yrs. ago glacial conditions
reoccurred and by 11,500 yrs. ago temps.
Were 6-7 degrees lower than today
• Glaciers readvanced all over the world
including Scotland, Lake District and
Snowdonia
• Reason: Believed to be due to the draining
of Lake Agassiz (Glacial lake in N.
America) into Atlantic disrupting the THC
(Thermoholine Circulation) by cutting off
the poleward heat from the gulf stream

27. Known Ice Ages

28. The Little Ice Age
• Proxy records tell us that between 1350 – 1900 perhaps
between 1 – 2 degrees between 1550 – 1750 there was
a trough of cold temperatures having many impacts

29. • Abandonment of many hill farms in
northern Europe
• Glaciers advanced down valleys
• Arctic sea ice spread further south with
Polar bears found in Iceland
• Rivers froze in UK, lowland Europe and
New York
• Curling developed as a sport in Scotland!
• It is argued it never developed into a full
blown stadial due to the onset of the
industrial revolution GHGs creating a
warming effect.

30. • Winter was a very different
proposition back then!