Geog 1400 – Jan. 7 th
Stratification/Water Movement Within Lakes (Last class)
- Different layers, top is warmer, bottom is colder. Highest density at the bottom, lower at
- Epilimnion: Top Layer of warm water.
- Hypolumnion: High density
- Thermocline: Temperature changes more rapidly in between the top and bottom layer.
- In winter everything switches. So the warm part is at the bottom, cool part at the top.
- The wind will trigger mixing of the lake, strong mixing and the top will get colder.
- This tends to be more specific in larger lakes.
- Alpine glacier, google image. At the bottom is the valley and lots of debris. Downslope,
- Rivers and glaciers the two most significant.
8. Glacier formation and movement
- Today just about formation and movement.
a) Glaciers – Intro
- Three categories:
Past continental ice sheets.
Current major ice sheets.
- Over the geological time there have been many glaciations. About 15000 years ago there
was a huge glacier covering a big part of North America and Europe.
- If you are in a zone that was once glaciated there are usually a lot of debris, and things
that was created during that time.
- That ice sheet was referred to as the Laurentide Ice Sheet.
- This was the last glaciation.
Maximum Glaciations North America
- Area covered by the Laurentide ice sheet.
- Plastic because the glaciation deforms, moves and changes shape.
- How does this work?
- Accumulation of snow happens, you have compaction of the snow layers, the
consequence is that there is change in density, light or heavy. The density of the snow
varies between temperatures and distance, etc. - As you have accumulation, physical compaction takes place, takes away the air bubbles,
and there is a gradual increase in density.
- Transition stage between snow and ice, related to compaction of the snow and the
- As the process of this continues you get a glacier.
- Change in density is the main part of the definition.
Transformation – Snow to Ice
- If you have cold temperatures but low snow accumulations, it will take longer, same with
dry places that are very cold.
- Snow accumulation rates and time is important.
c) Alpine Glaciers
- This diagram of the glacier is important, the terms will be defined in this lecture and the
- Movement due to gravitational flow and sliding of the bedrock. Internal flow is always
Athabasca Glacier (Rockies, AB)
- Comes from the Colombia ice fields which sits on top the of the rockies.
- From that ice field there are valley glaciers flowing down.
Franz Josef Glacier, NZ
- Valley glacier.
- South island of New Zealand.
- Even more spectacular.
- Bottom is a few meters above sea level and not very cold.
- A lot of precipitation, and it is a dynamic system.
- Valley glaciers originate from a depression in the bedrock where snow accumulates, and
when it reaches a certain point it flows out off the cirque and the formation of the entire
ice mass begins. (zone where is feeds the glacier – accumulation zone)
- Once large enough it flows slowly from the upslope (zone of