The Ice Age and Last Glacial Maximum (LGM)

Lesson 4 StarterSlides

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’).

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.

Formationof theEarth

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.

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).

• 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.

http://upload.wikimedia.org/wikipedia/commons/f/f7/Five_Myr_Climate_Change.svg?uselang=en-gb

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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 andwoolly rhinos, ranged across the cold plains ofEurope 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.

During the LGM, (between 26,000 and 18,000 years ago), there was about three timesmore glacier ice on the planet than there is now.

NASA

Mark McCaffrey , NGDC/NOAA Source: http://www.ncdc.noaa.gov/paleo/slides/slideset/11/11_178_slide.html

• 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.

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

• 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.

Source http://www.earth4567.com/talks/ice.html

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/