The most recent ice age peaked about 23,000 years ago. Glaciers covered approximately 1/3 of all land on earth. All of these glaciers were formed by snow that turned into ice through compaction and recrystallization. Because of all the snow used to created these giant ice masses, nearly 5% of the earth’s water was trapped in the glaciers, which is over 10 million cubic miles of water. This caused the sea levels to fall eustatically, so the coasts then extended 100 miles farther out to sea than they do today. During the ice ages, the earth was a different planet.
Today we are going to talk a little bit about the geologic history of Massachusetts and New England. As you probably know, in Earth’s past, the planet has experienced periods of cooling called ice ages for the past 2.6 million years during the Quaternary period. In these ice ages, large, moving ice masses, called glaciers were a prevalent feature of the topography. Even today, there are glaciers left over from our last ice age, although they are much less common.
|This is just an example of the types of glaciers that were common during the last ice age.|
|This is an image of what the coastlines of the world would have looked like during the last ice age.|
In North America, an ice sheet covered a large portion of the continent. It was called the Laurentide Ice Sheet and it stretched from northern Canada to Long Island, a total of more than 5 million square miles. The reason that this ice sheet was able to become so large was because at that time there was a positive glacial budget. More snow was being added than was melting, so the glacier was able to advance. Since it was an ice sheet, it did not carve out the land the way an alpine glacier would, instead, it blanketed the land as it spread out from its center. This spreading was caused by the intense weight and pressure that the ice was subjected to as more snow and ice was added above it. Although a continental ice sheet like the Laurentide does not form erosional features such as cirques and aretes, it does leave behind depositional features when it retreats. Many of these features are still visible today in the Massachusetts area, and they serve as a constant reminder of our impressive geologic past.
|This is the location of the Laurentide ice sheet as well as the other, smaller ice sheets that covered North America at this time.|
In the next few weeks, I plan on visiting some of these depositional features near me, but in the meantime I’ll continue to fill you in about the history and features of the Laurentide ice sheet and the Massachusetts area.
Have a fantastic day!
Lougheed, Stephen C., and Natalie Morrill. The location of the Laurentide Ice Sheet. Digital image. Opinicon Natural History. Queen's University, n.d. Web. 25 May 2013. <http://opinicon.files.wordpress.com/2012/04/laurentide-ice-sheet.jpg>.
National Geophysical Data Center. Sea Levels in the Last Ice Age. Digital image. Not by Fire but by Ice THE NEXT ICE AGE - NOW! N.p., 11 July 2011. Web. 25 May 2013. <http://www.iceagenow.com/SeaLevel_LastIceAge.gif>.
Nygren, Harley D. Antarctica. Digital image. Phys.org. Phys.org, 1 May 2013. Web. 25 May 2013. <http://cdn.physorg.com/newman/gfx/news/hires/2013/howtheiceage.jpg>.