1.      Ice age is the decrease in the temperature of the Earth's exterior and atmosphere for long periods giving rise to mainland and polar ice sheets and mountainous glaciers

2.      Discrete pulses of cold climate called glacial advances / glacials and intermittent warm periods – interglacials are part of ice ages.

3.      Proofs for ice ages:

a.       Geological - rock scouring, mass of rocks / sediment transmitted and dumped by a glacier, drumlins, valley cutting, and the deposition of till. Glaciations distort and remove geological evidence.

b.      Chemical - noting the ratios of isotopes in fossils in deposits and sedimentary rocks and ocean cores. Water with heavier isotopes has a more heat of evaporation and its percentage reduce with colder conditions

c.       Paleontological- studying variations in the geographical dispersal of fossils as cold adapted organisms go into lower latitudes during glacial period while other organisms become extinct

4.      At least five major ice ages were in the Earth's history:

a.        Huronian- ( 2.4 to 2.1 Ga (billion years) ago /early Proterozoic Eon). It was triggered by the removal of atmospheric methane during the Great Oxygenation Event.

b.      Cryogenian (720 to 630 million years ago / the Cryogenian period) . It was the most severe which ended by the buildup of greenhouse gases from volcanoes

c.        Andean-Saharan (460 to 420 million years ago / Late Ordovician) marked by several sequences of glacials and interglacials lasting several million years.

d.      Karoo Ice Age (360 to 260 million years ago / Devonian period ) The evolution of land plants resulted in increase in planetary oxygen levels. Widespread polar ice caps covered mountain tops in South Africa, Argentina during the Carboniferous

e.       Quaternary Ice Age (2.58 million years ago) marked by sequences of glacial advances, and interglacial periods/ glacial retreats of average 70000 years The earth is presently in an interglacial (Holocene epoch) as about 11,700 years ago the last glacial period ended and Greenland and Antarctic ice sheets are the remains. 18,000 years ago it reached peak conditions when the ice grew more than 12,000 feet thick spreading across Canada, Russia, South America and Scandinavia with 400 feet high sea and temperature of -10 to -40 F. Pine forests and prairie grasses grew in North America. Humans survived as they adapted by creating tools like bone needle to sew warm clothing and they travelled to spread to new regions by ice land bridges. With the advent of Holocene epoch, humans started agriculture and domestication

5.      There has been no ice in high latitudes when ice age is not prevalent

6.      An ice age results in huge change in Earth’s surface as glaciers by gathering rocks and soil and corroding hills restyle the landscape and intense drip in sea levels causes rivers to cut out deeper valleys creating large inland lakes

7.      Causes:

a.       atmospheric composition of carbon dioxide and methane

b.      variations in the earth's orbit around the Sun

c.       volcanic eruptions of supervolcanoes

d.      the tectonic plates movement affecting wind and ocean currents

e.       differences in solar output

f.        the effect of huge meteorites

g.      plate tectonics elevate mountain ranges exposing new rock which gets weathered and broken into oceans absorbing carbon dioxide

1) In biology who discovered nucleus?

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