After another one of my trademark hiatuses, I am now back and hopefully more composed, motivated and ready to post with more frequency. Forgoing anymore excuse ridden sentences let’s jump right into the geology.
It’s time for the next installment of “Do You See What I See?”. This time I’ll give you two pictures two consider; both of the same feature but taken at slightly different angles. Careful though, this is not going to be hard rock geology (big hint).
This feature was found at high elevations in the Alps Mountains while I was traversing this past July. My friends and I had just hit the summit and were now on the arduous decent into town miles and thousands of meters in elevation away. Where this picture was taken though was along a relatively nice and flat portion of the trail (another big hint). What we stumbled upon here were a couple of recessional moraines created by sediment accumulation at the edge of a preexisting glacier. Here are some annotated pictures to help visualize. The numbers on the moraines dictate the order in which they were deposited.
The name moraine actually originated in the Alps to describe ridges of debris found at the edge of glaciers. As the glacier that was previously here retreated during melting, the sediments within the glacier were transported and dumped along the terminal edge from meltwater within the ice. These sediments, described generically as till, are various in grain size and if the moraine was cut open it would be seen that the sediments are unstratified. There are a few types of moraines that also include terminal and lateral. All moraines are found along the edges, but the different varieties describe where or when they were deposited there. Lateral moraines are found along the lateral edges of the glacier since debris flows there as well. Terminal moraines are found along the downstream edge like recessional moraines, but are deposited on the front of advancing glaciers. Because of the advancing glacier the terminal moraines are often eroded away by the very feature that put them there in the first place.
If you had stood where this picture was taken and looked back towards the summit you would see that the trail takes you down through a large cirque where the depositing glacier originated.