As stated before, there are four definite Ice Ages in the history of the world; however, there is the potential that one more may have existed. The potential Ice Age would have started 1.7 to 2.3 billion years ago during the Precambrian Era. Due to the large amount of time that has passed since then it is hard to provide undisputed physical evidence of its existence (Source 2).
While nothing is definite, the four commonly accepted Ice Ages occurred during the Proterozoic Era, Ordovician Period, Permian Glaciation (Pennsylvanian), and Pleistocene Glaciation (Quaternary period) (Source 1).
Proterozoic Era- This Ice Age occurred from 800 to 600 million years ago. During this time it is believed that the earth was covered completely in ice that could be up to one kilometer thick.
Ordovician Period- This Ice Age lasted from 460 to 430 million years ago. Evidence shows that during that time, the continents were in extremely different locations, placing the South Pole near present day Africa.
Permian Glaciation Pennsylvanian)- This glaciation (Glacial period of an Ice Age) lasted from 350 to 250 million years ago. It occurred over the southern portion of Pangaea called Gonwandaland, which includes present day Australia, New Zealand, Antarctica, South America, Africa, Arabia, and India.
Pleistocene Glaciation ( Quaternary period)- This started around 3 million years ago and ended around 20,000 years ago. An ice sheet that started in Antarctica and spread through Europe and North America ultimately covering around half the planet, characterized this particular Ice Age.
When combined, the total time in the history of the earth spent in a Glacial Period of an Ice Age is 50 to 200 million years, only about one to four percent of the world's history (Source 2).
While the causes of Ice Ages are disputed, one thing that is known is how they progress. When the summers are not warm enough to melt all of the snow from the winter, it builds up over centuries and forms sheets of ice. The weight of the ice eventually throws off the earth's orbit. This orbital change creates seasonal extremes at both poles, which take millions of years to re-align (Source 5). The remnants of Ice Ages however, can last much longer. In fact, some snow and ice from the last ice age ending over 20,000 years ago can still be found today (Source 6).
Subscribe to:
Post Comments (Atom)
7 comments:
I did not realize that Ice Ages lasted that long. It is really weird to think that we are currently in an Ice Age. Do you view the climate change as being a large problem for the world? What can we do to fix it?
Megan, Great job on your blog. I especially like how you gave a reliable background on each of the eras which were very interesting. Your very last part about the ice ages in the different seasons was engaging. This ties in nicely with my topic about weather changes. Great!
As you previously said that we have been in an Interglacial period for only 10,000 years, is it plausible to say that the current temperature increase is largely based on Ice Ages? And has this theory been studied in depth?
Very interesting stuff. I never knew that the ice during an ice age could actually change the orbit of Earth. That could have catastrophic implications! What if Earth moved so far away from the Sun that it left the habitable zone (where water can exist as water).
The fact that an Ice Age throws off the Earth's orbit is very interesting. Did you find out how the orbit realigns?
This is an excellent summary of the Ice Ages. I am very interested to find out more about how global warming could lead to another ice age. Have you found out how scientists can tell how old ice is? I think it's very facinating that there is 20,000 year old ice out there.
All of your research is very well presented in your blog, nice job!
if organisms did not inhabit Earth, and we were viewing the Earth from another home planet, do you think that we would think of these weather changes to be so terrible oris it because of the effects on living things that we are looking at the fears of past and future ice ages as terrible?
Post a Comment