Download - Des Withanimation
-
7/31/2019 Des Withanimation
1/22
-
7/31/2019 Des Withanimation
2/22
-
7/31/2019 Des Withanimation
3/22
-
7/31/2019 Des Withanimation
4/22
An ice age, is a period of long-term reduction inthe temperature of the Earth's surface and atmosphere,resulting in the presence or expansion of continental ice
sheets, polar ice sheets and alpine glaciers. Within a long-term ice age, individual pulses of cold climate are termed
"glacial periods" and intermittent warm periods are called"interglacials".
-
7/31/2019 Des Withanimation
5/22
-
7/31/2019 Des Withanimation
6/22
Agassiz amassed more evidence from landforms and boulder clays to support his idea of a Great Ice Age in recent times.
Glen Roy, Scotland
Parallel marks showformer level of anice-dammed lake
-
7/31/2019 Des Withanimation
7/22
Pollen
MammothBeetles
Fossil discoveries alsosuggested that climate hadrecently been much colder .
Beetles and pollen grainsfound in sediments associatedwith the boulder clays wereidentified as types known only
from the Arctic tundra today.
Woolly mammoths founddeep frozen in Siberia hadfur adapted to tundra life.
-
7/31/2019 Des Withanimation
8/22 Annual layers in ice
Drilling cores
In the early 1980s, therewas another majorbreakthrough.
Cores were drilled in thepolar icecaps revealingannual layers of snow going
back thousands of years.
-
7/31/2019 Des Withanimation
9/22
When the Last Ice Age was at its maximum, ice sheets coveremuch of Europe and North America.
So what actually caused it?
-
7/31/2019 Des Withanimation
10/22
In the 1940s, Milankovi wondered whether wobbles in theEarths orbit around the Sun could explain multiple Ice Ages by
changing the amount of heating reaching the Earth
Milutin Milankovi (1879-1958)
-
7/31/2019 Des Withanimation
11/22
Milankovi added up all the orbital wobbles and predicted thatice ages should occur in regular cycles - probably happening
every hundred thousand years or so.
-
7/31/2019 Des Withanimation
12/22
In 1960s, deep sea records showed that Milankovi was right!
c o
l d
h o
t
1000s of years before present
The Oil Drum
The Earths climate had repeatedly blown hot and cold withice age cycles happening every hundred thousand years just
as Milankovi had predicted.
-
7/31/2019 Des Withanimation
13/22
NOAA
Greenhouse Gas levelsdropped during Ice Ages
Last Ice Age =
Low Greenhouse Gas
The second idea is thatchanges in greenhousegas levels were to blame.
Greenhouse gases help tosoak up sunlight and keepthe Earth warm.
Air bubbles in ice coresshow that levels fell duringIce Ages so this mayhave sped up cooling.
-
7/31/2019 Des Withanimation
14/22
Gulf Stream warms the Arctic Some scientists believethat ocean currents likethe Gulf Stream
were important.
This current helpswarm up the Arctic. If itswitched off thiswould cool the Arcticfurther andincrease the likelihood ofan Ice Age
-
7/31/2019 Des Withanimation
15/22
Much of the worlds water from seas and oceans got frozen. As aresult , sea level droppedPlaces that had been under water become dry landMany plants and animals adapt to these changes but many died
-
7/31/2019 Des Withanimation
16/22
-
7/31/2019 Des Withanimation
17/22
-
7/31/2019 Des Withanimation
18/22
-
7/31/2019 Des Withanimation
19/22
-
7/31/2019 Des Withanimation
20/22
The next ice age is more than 15,000 years away, according to
evidence from an Antarctic ice core, the deepest and oldest ever extracted.
The core gives us a 740,000-year record of the planet's climate,including the past eight ice ages, and interglacials in between.
The core was more than 3 km long and measured to be 740,000years old at its farthest end.
The core gives a picture of the Earth's cycles of warm and cold,reflected in the different thicknesses of ice that fell on Antarcticaas snow.
-
7/31/2019 Des Withanimation
21/22
-
7/31/2019 Des Withanimation
22/22