Transcript Ice Age introduction

The Ice Age and Last Glacial
Maximum (LGM)
Lesson 4 Starter
Slides
Key facts about the Ice Age
• The Earth entered its most recent ‘Ice Age’ phase
2.6 million years ago, after hundreds of millions
of years when the Earth had a warmer climate.
• Geologists call this time frame (between 2.6
million years ago and the present) the
Quaternary Period.
• Deep in Earth’s past there have been earlier Ice
Age times (for instance around 700 million years
ago so much of the Earth was covered in ice that
the nickname for this episode is ‘Snowball
Earth’).
Formation
of the
Earth
http://commons.wikimedia.org/wiki/File:Geological_time_spiral.png
USGS
Notice the Quaternary Period as the most recent phase of this diagram of geological time.
Key facts about the Quaternary Period
• The Quaternary Period has been a time when
Earth’s climate has been colder than normal
compared with most of Earth’s history.
• In addition to being colder, during the Quaternary
Period climate has also been fluctuating more
than normal for Earth’s history.
• The relatively colder times during the Quaternary
are called glacials and the relatively warmer
times are called interglacials.
• We are currently living during an interglacial
phase.
Colder
Warmer
This diagram shows how the average surface air temperature
of Earth has changed over the last 5 million years (‘kyr’ refers
to thousand year cycles of fluctuating temperature).
http://upload.wikimedia.org/wikipedia/commons/f/f7/Five_Myr_Clim
ate_Change.svg?uselang=en-gb
•
•
•
Notice how temperature has cooled while also fluctuating more.
During the coldest times, glaciers spread their furthest, causing sea level to drop to
lower levels.
This is because water that evaporated from oceans fell as snow and became part
of glaciers on land.
During colder times of the Quaternary Period landscapes in
Europe and North America looked like this.
commons.wikimedia.org/wiki/Image:
Mauricio Antón.jpg Ice age fauna of northern Spain
Now extinct animals, such as these mammoths and
woolly rhinos, ranged across the cold plains of
Europe south of the ice sheets
During warmer times (interglacials) areas like this returned to forest.
Key facts about the Last Glacial Maximum
• The Last Glacial Maximum (LGM) represents the latest glacial phase
during the Quaternary Period when the planet’s average
temperature reached a minimum and the area of land covered by
glaciers and ice sheets reached a maximum.
NASA
During the LGM, (between 26,000 and 18,000 years ago), there was about three times
more glacier ice on the planet than there is now.
•
Notice the difference in the extent of ice sheets and sea ice in the Northern and Southern
Hemispheres between the Last Glacial Maximum and the present day.
Mark McCaffrey , NGDC/NOAA
Source: http://www.ncdc.noaa.gov/paleo/slides/slideset/11/11_178_slide.html
Alpine glaciers like this were much bigger in many mountainous
regions of the world during the Last Glacial Maximum.
Glacier in Baffin Island, Canada (John T. Andrews,
INSTAAR and Department of Geological Sciences, University of Colorado,Boulder.)
http://www.ncdc.noaa.gov/paleo/slides/slideset/11/11_176_slide.html
www.geocities.com/reginheim/europeiceage.gif
Source http://www.earth4567.com/talks/ice.html
• This illustrates what
Europe was like
during the Last
Glacial Maximum.
• Most of Britain and
much of northern
Europe was covered
by an ice sheet.
• Forests could only
grow in areas of
southern Europe.
• The sea level was
about 120 metres
lower than now, so
the English Channel
and North Sea did not
exist!
• Notice other
differences in the
coastline at that time.
This photo taken in Iceland near the edge of an ice cap is how it would have
looked in the midlands of England near the edge of the British Ice Sheet
during the Last Glacial Maximum (without the houses of course!).
DEA
The Last Glacial Maximum and present day
compared
• Ice cover:
– Glaciers cover about 10% of Earth’s land area today (c. 15 mill km2).
– During the LGM, about 30% of land area was covered (over 40 mill km2).
• Different distribution of ice cover:
– Today 85% of the world’s area covered by glacier ice is accounted for by Antarctica,
11% by Greenland. (Just 4% by everywhere else!)
– During the LGM, Antarctica accounted for over 30% of the total area and
Greenland about 5%.
– The Laurentide Ice Sheet over north-east North America accounted for about 30%,
and the Scandinavian Ice Sheet over northern Europe about 15%.
• Remember that glacier ice is not the same as sea ice.
• The average global temperature was about 6⁰C colder
than today.
– Temperature dropped more than this at high latitudes, but
not as much at lower latitudes nearer to the Equator.
Useful websites to follow up
• To view the extent of glacier ice cover across the
globe during the LGM and at other times visit:
– http://www.ncdc.noaa.gov/cgi-bin/paleo/peltice.pl
• To view animations of changing ice cover since
the LGM visit:
– http://www.youtube.com/watch?v=C3Jwnp-Z3yE (Blue Marble 3000)
– http://www.youtube.com/watch?v=wbsURVgoRD0 (Laurentide ice sheet)
• To learn more about the LGM and the Ice Ages in
general visit:
– http://www.earth4567.com/talks/ice.html
– http://www.museum.state.il.us/exhibits/ice_ages/