Tuesday, May 28, 2013

Author's Ridge

The top of the kame delta (you can use the headstones as a reference for scale)


Hello everyone!


    Yesterday Tessie and I went to Author’s Ridge in Concord, Ma to look at the kame delta that is located there.
   
 If you would like to learn about how a kame delta forms in general, please head on over to this post that I wrote awhile ago.
  
 This kame delta in particular formed when the Laurentide Ice sheet reached to just north of Massachusetts Route 2. There, meltwater flowed off of the glacier into Lake Sudbury, which was just south of there, creating this feature. We know that the glacier was located north of the Author’s Ridge due to the direction of the layers of sediment. The layers are parallel to the southwestern, steeper side of the ridge, which means that the meltwater from the glacier that deposited the sediment flowed down that side. This means the ice contact slope was the other (northerneastern side). That then tells us that Glacial Lake Concord was southwest of the kame delta, since the meltwater ran down the southwestern slope into the lake.

This map shows the direction of the layers of sediment on the Kame Delta.


The view down the side of the delta that the sediment is parallel to. 

The view down the ice contact slope of the kame delta.

We also know that the glacier was moving northeast to southwest due to the direction the ridge is running. The kame delta runs southeast to northwest. These features always form parallel to the snout of the glacier, so the snout must have been running east-west. Glaciers always more perpendicular to the snout, so the glacier moved northeast to southwest.

Here's a little map that I made showing the relative location of the delta, the lake and the glacier.

Have a fantastic day!


Image Citations:

Formation of Walden Pond. Digital image. Geology of Middlesex County. N.p., n.d. Web. 26 May 2013. <http://middlesexgeology.weebly.com/uploads/2/3/8/5/2385615/3232311.jpg?345x383>.


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