Figure 1. 'Kames' in the 'Kettle' lake at GZ in winter
Once at GZ, you may have noticed that the higher elevation of the land around emerged from the surrounding plains almost imperceptibly. The differentiation is due to the 'hummocky' and ridged 'ground moraines.' These uplands are known geologically as part of the 'Minichinas Moraines' which were deposited during the last ice age.1 After the last glacial retreat, this area was left as an 'end moraine complex,' characterized by its hummocky terrain, dead ice, and locally 'kettled' lacustrine deposits.
If you park at the posted coordinates on the south side of the intersection and look to the west, in the midst of the 'kettle' lake, you can observe a landform called a 'kame.' A 'kame' can best be described as a conical landform composed of roughly sorted sand and gravel deposited by meltwater, in association with glacial ice. They are mounded in shape and represent the deposits of glacial till that accumulated in lakes and depressions on the remains of a glacier. Kames most often occur in hummocky moraines, and are sometimes refered to as 'till knobs.' They often occur in clusters as evident here. Many other kames may be observed from the short roadway to the north of the nearby intersection with the east/west grid. To simplify its construction, the road to the west curves around the base of the large kame, pictured below in winter.
Figure 2. Roadway around the 'Kame' at GZ in winter
Imagine being here some 12,000 years ago when this area would have been covered by a layer of glacial ice, hundreds of feet thick. As the glaciers initially formed and advanced, they actually moved across the landscape scouring the earth and rocks ahead and underneath them with material refered to as 'glacial till.' When the glaciers stopped advancing, the eroded glacial till was deposited in ridges known as 'moraines' such as the range of hills around you.
As the climate warmed, the glaciers began to melt in place. This process is usually referred to as 'receding,' even though there was no actual reverse movement of the ice sheet. Over the next several hundreds of years, the glaciers fluctuated from periods of growth and advancement, to periods of melting and recession. During the periods of recession, great slabs of ice would have been calved off as orphaned remnants of the main ice sheet. When the glacier next advanced, those large chunks would have become buried by the 'drift' or 'till' being pushed along in front of the advancing ice sheet. Some 10,000 years ago, as the climate continued to warm, the great ice sheets eventually receded to the northeast and over the next few centuries, those large slabs of ice buried under the layer of till, began to melt.
The glacial meltwater flowed across the top surface of the great slab towards depressions in the surface of the ice. Much like a small creek, the flowing water carried with it sediments from the ice sheet's overburden of roughly-sorted 'glaciofluvial till' and deposited it in the depression.
Figure 3. Water accumulates in a depression atop the glacier. Coarse sediments are accumulated after being carried into the depression by meltwater.2
As the calved-off blocks of orphan ice melted away, either the sediments settled through holes in the ice sheet, or the ice sheet collapsed, depositing the till in a pile directly below the hole or collapsed depression.
Figure 4. When the ice melts away, sediments drop through the ice and remain as a conical mound, or Kame, amid the Kettle Lake.2
The falling till created these near-perfectly shaped conical hills, as sand or gravel would when dropping off the end of a conveyer belt. These steep-sided, conical-shaped mounds of roughly-layered glacial till are geologically refered to as 'kames,' and the meltwater in the surrounding closed-drainage basin is refered to as a 'kettle lake,' hence the term 'kame and kettle' topography. The steepness or gradient of kames is dependant on the texture of original eroded material, i.e. finer sediments would form a more gentle gradient as they flowed outwards, while more coarse materials would form cones with a much steeper gradient as they dropped much faster.
Figure 5. 'Kame' in 'Kettle' lake amid the wooded, hummocky moraine uplands surrounding GZ.
Logging Requirements:
To log this Earth Cache as a "Found," please message me your answers to the following questions:
1. On the day of your visit, estimate the height of the large kame to the south west of GZ above the level of the water in the kettle lake?
2. Looking south and west from GZ, what are three visual indicators that this kettle lake is a closed-drainage basin? (Note: Three indicators may be difficult to ascertain in winter, in which case a photo from GZ featuring a personal item, such as a geocaching nametag or GPS, indicating your visit will suffice.)
3. If you travel about a hundred metres up the short road to the north, how many kames can you spot in the distance from this vantage point?
4. Bonus question, why do you suppose the trees only grow on the north side of the kames?
5. Although not a requirement, photos of your visit are always an interesting addition to your log!
References:
1. Richards, J.H., Fung K.I., Atlas of Saskatchewan,University of Saskatchewan, 1969, p 40.
2. Rowe, J.S., Landscapes: A Guide to the Landforms and Ecology of Southern Saskatchewan, Saskatchewan Environment, 1980, p 35.