when did the first ice age start?

Answer 1

This is something that there is still some uncertainty about. The further back in geologic history we go, the harder it is to find reliable indications of past climate. One of the most common methods of identifying past glaciation is the presence of diamictite deposits. This is a type of sedimentary rock that is deposited by glaciers. Here is a photo of glacial till, which becomes diamictite when preserved as sedimentary rock.
http://www-geology.ucdavis.edu/~GEL109/SedStructures/Lg/GlacialMoraine.jpg


There is a hypothesis that the earliest ice age refered to as a 'Snowball Earth' was about 2.2 billion years ago. That is because glacial deposits have been found in rockof that age that was probably near the equator when it was deposited. Earlier periods of regional glaciation preceeded this as far back as 2.7 billion years ago. Here is an excellent explanation and a graph that shows the early Snowball Earth periods:
http://www.snowballearth.org/when.html

Another Snowball Earth occurred about 710 Million years before present. Deposits from this period, called the 'Sturtian' have been found on every continent, suggesting that glaciation was common over most of Rodinia, as the continental land mass from that time is called. Here is a map of Rodinia:
http://www.scotese.com/precambr.htm

To see a graph of global temperature change over the past 600 million years go here:
http://www.scotese.com/climate.htm
You can see that during the late Ordovician (440 Mybp), the Early Permian (280 Mybp), and the more recent Pleistocene were all periods of cooler climate that had periodic ice ages.

The most recent ice age, the Wisconsinian glaciation, was between 10,000 and 70,000 years ago. Before that was the Illinioian betweeen 125,000 and 200,000 years, the Kansan (240-455 kybp), and the Nebraskan from 620-680 kybp. Other periods of glaciation in the Pleistocene preceeded those, and date back to the Pre-Pastonian from 800-1300 kybp. Here is some further information:
http://www.ngdc.noaa.gov/paleo/ctl/clisci100k.html

Answer 2

The earliest hypothesized ice age is believed to have occurred around 2.7 to 2.3 billion years ago during the early Proterozoic Age.

The earliest well-documented ice age occurred from 800 to 600 million years ago (the Cryogenian period) and it has been suggested that it produced a Snowball Earth in which permanent sea ice extended to or very near the equator.

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Answer 3

with the first snowflake